Patent Application
20230331556
The present invention relates to a method for manufacturing a positive electrode active material. Alternatively, the present invention relates to a method for manufacturing a secondary battery. Alternatively, the present invention relates to an electronic device, a vehicle, and the like each including a secondary battery.
The present invention relates to an object, a method, or a manufacturing method. Alternatively, the present invention relates to a process, a machine, manufacture, or a composition of matter. In particular, one embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, a driving method thereof, a manufacturing method thereof, or an evaluation method thereof. In particular, one embodiment of the present invention relates to a power storage device and a manufacturing method thereof or an evaluation method thereof. Alternatively, the present invention relates to a composite oxide and a manufacturing method thereof. Alternatively, the present invention relates to a positive electrode active material and a manufacturing method thereof Alternatively, the present invention relates to a lithium ion battery. Alternatively, the present invention relates to a battery management unit and an electronic device.
Note that in this specification, a semiconductor device refers to any device that can function by utilizing semiconductor characteristics, and an electro-optical device, a semiconductor circuit, and an electronic device are all semiconductor devices.
Note that an electronic device in this specification refers to any device including a positive electrode active material, a secondary battery, or a power storage device; an electro-optical device including a positive electrode active material, a secondary battery, or a power storage device, an information terminal device including a power storage device, and the like are all electronic devices.
Note that in this specification, a power storage device refers to every element and device having a function of storing power. For example, a power storage device (also referred to as a secondary battery) such as a lithium-ion secondary battery, a lithium-ion capacitor, and an electric double layer capacitor are included.
In recent years, a variety of power storage devices such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries have been actively developed. In particular, demand for lithium-ion secondary batteries with high output and high energy density has rapidly grown with the development of the semiconductor industry, for portable information terminals such as mobile phones, smartphones, and laptop computers, portable music players, digital cameras, medical equipment, next-generation clean energy vehicles such as hybrid electric vehicles (HVs), electric vehicles (EVs), and plug-in hybrid electric vehicles (PHVs), and the like, and the lithium-ion secondary batteries are essential as rechargeable energy supply sources for today's information society.
An example of such a power storage device includes a power storage device including an electrode using LiFePO4 (lithium iron phosphate), which is a composite oxide, as an active material. The power storage device including the electrode using LiFePO4 has high thermal stability and favorable cycle performance.
The solubility in a solution at high temperature and under high pressure is higher than at normal temperature and under normal pressure. Furthermore, by controlling the pH of a solution, dissolution and precipitation of a material can be controlled (Patent Document 1). An example of a reaction at high temperature and under high pressure is a hydrothermal method.
As a method for generating a composite oxide such as LiFePO4, a hydrothermal method is used, for example (Patent Document 2).
With the use of a hydrothermal method, even a material that is less likely to be dissolved in water at normal temperature and under normal pressure can be dissolved, thereby achieving synthesis or crystal growth of a substance that is difficult to obtain by a production method at normal temperature and under normal pressure. Moreover, the use of a hydrothermal method can easily synthesize single crystal microparticles of a target substance.
In a hydrothermal method, for example, a desired compound can be generated by putting a solution containing a raw material in a pressure-resistant container, performing treatment with pressure application and heating, and then filtering the solution that has been subjected to the treatment with pressure application and heating.
[Patent Document 1] PCT International Publication No. 2008/091578
[Patent Document 2] Japanese Published Patent Application No. 2004-95385
Since a positive electrode active material is a high-cost material in a lithium-ion secondary battery, higher performance (e.g., increase in capacity, improvement in cycle performance, and increase in reliability or safety) has been in high demand. In particular, one of objects for higher performance is a demand for increasing the purity of a positive electrode active material to increase the capacity.
In view of the above, an object of one embodiment of the present invention is to provide a method for manufacturing a highly purified positive electrode active material. Another object is to provide a method for manufacturing a positive electrode active material whose crystal structure is not easily broken even when charge and discharge are repeated. Another object is to provide a method for manufacturing a positive electrode active material with excellent charge and discharge cycle performance. Another object is to provide a method for manufacturing a positive electrode active material with high charge and discharge capacity. Another object is to provide a secondary battery with high reliability or safety.
Another object of one embodiment of the present invention is to provide a novel substance, novel active material particles, a novel secondary battery, a novel power storage device, or a manufacturing method thereof. Another object of one embodiment of the present invention is to provide a method for manufacturing a secondary battery having one or more characteristics selected from high purity, high performance, and high reliability or to provide the secondary battery.
Note that the description of these objects does not preclude the existence of other objects. In one embodiment of the present invention, there is no need to achieve all these objects. Other objects are apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.
One embodiment of the present invention is a method for manufacturing a positive electrode active material containing lithium and a transition metal, including a first step of preparing a lithium compound, a phosphorus compound, and water; a second step of forming a first mixture by mixing the lithium compound, the phosphorus compound, and the water; a third step of forming a second mixed solution by adding a first aqueous solution to a first mixed solution to adjust a pH; a fourth step of forming a third mixed solution by mixing an iron(II) compound with the second mixed solution; a fifth step of forming a fourth mixed solution by heating the third mixed solution; and a sixth step of obtaining a composite oxide by filtering, washing, and drying the fourth mixed solution. In the first step, a material having a purity higher than or equal to 99.99% is prepared as the lithium compound, a material having a purity higher than or equal to 99% is prepared as the phosphorus compound, and pure water having a resistivity higher than or equal to 15 MΩ·cm is prepared as the water. In the fourth step, a material having a purity higher than or equal to 99.9% is used as the iron(II) compound. In the fourth step, a pH of the third mixed solution is greater than or equal to 3.5 and less than or equal to 5.0. The heating in the fifth step is performed under a pressure higher than or equal to 0.11 MPa and lower than or equal to 2 MPa at a temperature higher than or equal to 150° C. and lower than or equal to 250° C. for longer than or equal to 1 hour and shorter than or equal to 10 hours.
In the above embodiment, it is preferred that lithium chloride be used as the lithium compound, phosphoric acid be used as the phosphorus compound, and iron(II) chloride tetrahydrate be used as the iron(II) compound.
In the above embodiments, it is preferred that pure water having a resistivity higher than or equal to 15 MΩ·cm be used for the washing.
According to one embodiment of the present invention, a method for manufacturing a highly purified positive electrode active material can be provided. A method for manufacturing a positive electrode active material whose crystal structure is not easily broken even when charge and discharge are repeated can be provided. A method for manufacturing a positive electrode active material with excellent charge and discharge cycle performance can be provided. A method for manufacturing a positive electrode active material with high charge and discharge capacity can be provided. A secondary battery with high reliability or safety can be provided.
According to one embodiment of the present invention, a novel substance, novel active material particles, a novel secondary battery, a novel power storage device, or a manufacturing method thereof can be provided. According to one embodiment of the present invention, a method for manufacturing a secondary battery having one or more characteristics selected from high purity, high performance, and high reliability or the secondary battery can be provided.
Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not need to have all these effects. Other effects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.
Embodiments of the present invention are described in detail below with reference to the drawings. Note that the present invention is not limited to the following description, and it is readily understood by those skilled in the art that modes and details of the present invention can be modified in various ways. In addition, the present invention should not be construed as being limited to the description of the embodiments below.
A secondary battery includes a positive electrode and a negative electrode, for example. A positive electrode active material is a material included in the positive electrode. The positive electrode active material is a material that performs a reaction contributing to the charge and discharge capacity, for example. Note that the positive electrode active material may partly include a material that does not contribute to the charge and discharge capacity.
In this specification and the like, the positive electrode active material of one embodiment of the present invention is expressed as a positive electrode material, a secondary battery positive electrode material, a composite oxide, or the like in some cases. In this specification and the like, the positive electrode active material of one embodiment of the present invention preferably includes a compound. In this specification and the like, the positive electrode active material of one embodiment of the present invention preferably includes a composition. In this specification and the like, the positive electrode active material of one embodiment of the present invention preferably includes a composite.
In this specification and the like, particles are not necessarily spherical (with a circular cross section). Other examples of the cross-sectional shapes of particles include an ellipse, a rectangle, a trapezoid, a triangle, a quadrilateral with rounded corners, and an asymmetrical shape, and a particle may have an indefinite shape.
In this specification and the like, a secondary battery having characteristics of high purity means that a material of one or more selected at least from a positive electrode, a negative electrode, a separator, and an electrolyte has high purity. A highly purified positive electrode active material means that a material included in the positive electrode active material has high purity. Regarding the purity of a material that can be used as the material of the positive electrode active material of one embodiment of the present invention, for example, the purity of Li2CO3 is higher than or equal to 3N (99.9%), preferably higher than or equal to 4N (99.99%), further preferably higher than or equal to 4N5 (99.995%), still further preferably higher than or equal to 5N (99.999%). The purity of LiCl is higher than or equal to 3N (99.9%), preferably higher than or equal to 4N (99.99%), further preferably higher than or equal to 4N5 (99.995%), still further preferably higher than or equal to 5N (99.999%). The purity of NH4H2PO4 is higher than or equal to 2N (99%), preferably higher than or equal to 3N (99.9%), further preferably higher than or equal to 4N (99.99%), still further preferably higher than or equal to 4N5 (99.995%). The purity of FeCl is higher than or equal to 3N (99.9%), preferably higher than or equal to 4N (99.99%), further preferably higher than or equal to 4N5 (99.995%), still further preferably higher than or equal to 5N (99.999%). In the case of H3PO4, the content of impurity elements other than H, P, and O in an aqueous solution is less than 1%, preferably less than 0.1%, further preferably less than 0.01%, still further preferably less than 0.005%. In other words, the purity of H3PO4 is higher than or equal to 2N (99%), preferably higher than or equal to 3N (99.9%), further preferably higher than or equal to 4N (99.99%), still further preferably higher than or equal to 4N5 (99.995%).
In this embodiment, a method for manufacturing a positive electrode active material of one embodiment of the present invention is described.
The positive electrode active material of one embodiment of the present invention is manufactured using a liquid phase method, preferably a hydrothermal method.
A method for manufacturing a positive electrode active material of one embodiment of the present invention is described using
In Step S21a, a lithium compound 803 is prepared. In Step S21b, a phosphorus compound 804 is prepared.
Here, the atomic ratio of lithium to a transition metal M and phosphorus of a composite oxide that is preferably obtained as an after-mentioned positive electrode active material 100 is x:y:z. In order to obtain LiMPO4, for example, x:y:z=1:1:1 is satisfied.
Typical examples of the lithium compound include lithium chloride (LiCl), lithium acetate (CH3COOLi), lithium oxalate ((COOLi)2), lithium carbonate (Li2CO3), and lithium hydroxide monohydrate (LiOH·H2O).
Typical examples of the phosphorus compound include phosphoric acid such as orthophosphoric acid (H3PO4), and ammonium hydrogen phosphate such as diammonium hydrogen phosphate ((NH4)2HPO4) and ammonium dihydrogen phosphate (NH4H2PO4).
Next, in Step S21c, a solvent 805 is prepared. Water is preferably used as the solvent 805. Alternatively, a mixed solution of water and another liquid may be used as the solvent 805. For example, water and alcohol may be mixed. Here, the lithium compound 803 and the phosphorus compound 804 or a reaction product of the lithium compound 803 and the phosphorus compound 804 may have different solubilities in water and alcohol. Using alcohol makes the grain size of formed particles smaller in some cases. Furthermore, by using alcohol, which has a lower boiling point than water, pressure can be easily increased in some cases in Step S53 described later.
Note that in the case where water is used as the solvent 805, it is preferably pure water that includes few impurities and preferably has a resistivity of 1 MΩ·cm or higher, further preferably has a resistivity of 10 MΩ·cm or higher, and still further preferably has a resistivity of 15 MΩ·cm or higher. The use of a high-purity material can increase the capacity of a secondary battery and/or increase the reliability of a secondary battery.
Next, in Step S31, the lithium compound 803, the phosphorus compound 804, and the solvent 805 are mixed, whereby a mixture 811 of Step S32 is obtained. The mixing in Step S31 can be performed in an atmosphere of air, an inert gas, or the like. As the inert gas, nitrogen is used, for example. Here, as an example, the lithium compound 803 prepared in Step S21a, the phosphorus compound 804 prepared in Step S21b, and the solvent 805 prepared in Step S21c are mixed in an air atmosphere. For example, the lithium compound 803 prepared in Step S21a and the phosphorus compound 804 prepared in Step S21b are put in the solvent 805 prepared in Step S21c, whereby the mixture 811 of Step S32 is formed.
In the mixture 811 of Step S32, the lithium compound 803, the phosphorus compound 804, and the reaction product of the lithium compound 803 and the phosphorus compound 804 are precipitated in the mixture 811 in some cases; however, they are partly dissolved in the solvent without being precipitated, i.e., they partly exist as ions in the mixture 811. Here, when the mixture 811 has a low pH, the reaction product and the like may be easily dissolved in the solvent; when the mixture 811 has a high pH, the reaction product and the like may be easily precipitated.
Note that instead of forming the mixture 811 of Step S32 by mixing the lithium compound 803 and the phosphorus compound 804, the mixture 811 of Step S32 may be formed by preparing a compound containing phosphorus and lithium, such as Li3PO4, Li2HPO4, or LiH2PO4, and adding the compound to a solvent.
Here, in the case where the mixture 811 of Step S32 is an aqueous solution, the pH of the mixture 811 depends on the kind and dissociation degree of the salt included in the mixture 811. Accordingly, the pH of the mixture 811 changes depending on the lithium compound 803 and the phosphorus compound 804 used as the source materials. For example, in the case of using lithium chloride as the lithium compound 803 and orthophosphoric acid as the phosphorus compound 804, the mixture 811 of Step S32 is likely to be a strong acid. As another example, in the case of using lithium hydroxide monohydrate as the lithium compound 803, the mixture 811 of Step S32 is likely to be alkaline.
Next, in Step S33, a solution P 812 is prepared. Then, in Step S35, the mixture 811 of Step S32 and the solution P 812 prepared in Step S33 are mixed, whereby a mixture 821 of Step S41 is formed. Here, by adjusting the amount or concentration of the solution P 812 to be added, the pH of the obtained mixture 821 of Step S41 and a subsequently obtained mixture 831 of Step S52 can be adjusted. In Step S35, for example, the solution P 812 is dropped while the pH of the mixture 811 of Step S32 is measured. As the solution P 812, an alkaline solution or an acidic solution is used in accordance with the pH of the mixture 811 of Step S32. Here, by using a slightly alkaline or slightly acidic solution, the pH is easily adjusted in some cases. For example, the pH of the alkaline solution is greater than or equal to 8 and less than or equal to 12. Furthermore, the pH of the acidic solution is greater than or equal to 2 and less than or equal to 6. As the alkaline solution, ammonia water is used, for example. The pH and mixed amount of the solution P 812 are preferably determined so that the mixture 831 of Step S52, which is described later, becomes acidic or neutral.
Next, in Step S42, a transition metal M source 822 is prepared. As the transition metal M source 822, one or more of an iron(II) compound, a manganese(II) compound, a cobalt(II) compound, and a nickel(II) compound (hereinafter referred to as an M(II) compound) can be used.
Note that a high-purity material is preferably used as the transition metal M source used for the synthesis. Specifically, the purity of the material is higher than or equal to 3N (99.9%), preferably higher than or equal to 4N (99.99%), further preferably higher than or equal to 4N5 (99.995%), still further preferably higher than or equal to 5N (99.999%). The use of a high-purity material can increase the capacity of a secondary battery and/or increase the reliability of a secondary battery.
In addition, it is preferred that the transition metal M source here have high crystallinity. For example, the transition metal M source preferably includes single crystal grains. To evaluate the crystallinity of the transition metal M source, for example, the crystallinity can be judged by a TEM (transmission electron microscope) image, an STEM (scanning transmission electron microscope) image, a HAADF-STEM (high-angle annular dark field scanning transmission electron microscope) image, an ABF-STEM (annular bright-field scan transmission electron microscope) image, and the like. For evaluation of the crystallinity of the transition metal M source, X-ray diffraction (XRD), electron diffraction, neutron diffraction, and the like can also be used for judging. Note that the above-described crystallinity evaluation can be applied not only to the transition metal M source but also to a primary particle or a secondary particle.
Typical examples of the iron(II) compound include iron chloride tetrahydrate (FeCl2·4H2O), iron sulfate heptahydrate (FeSO4·7H2O), and iron acetate (Fe(CH3COO)2).
Typical examples of the manganese(II) compound include manganese chloride tetrahydrate (MnCl2·4H2O), manganese sulfate monohydrate (MnSO4H2O), and manganese acetate tetrahydrate (Mn(CH3COO)2·4H2O).
Typical examples of the cobalt(II) compound include cobalt chloride hexahydrate (CoCl2·6H2O), cobalt sulfate heptahydrate (CoSO4·7H2O), and cobalt acetate tetrahydrate (Co(CH3COO)2·4H2O).
Typical examples of the nickel(II) compound include nickel chloride hexahydrate (NiCl2·6H2O), nickel sulfate hexahydrate (NiSO4·6H2O), and nickel acetate tetrahydrate (Ni(CH3COO)2·4H2O).
Note that in Step S42, an aqueous solution of any of the above compounds may be prepared as the transition metal M source 822. In the case of preparing an aqueous solution of the compound, water to be used is preferably pure water that includes few impurities and preferably has a resistivity of 1 MΩ·cm or higher, further preferably has a resistivity of 10 MΩ·cm or higher, and still further preferably has a resistivity of 15 MΩ·cm or higher.
Next, in Step S51, the mixture 821 of Step S41 and the transition metal M source 822 are mixed, whereby the mixture 831 of Step S52 is obtained.
Here, in Step S51, the concentration of the mixture 831 of Step S52 can be reduced by addition of a solvent. For example, in Step S51, the mixture 821 of Step S41, the transition metal M source 822, and a solvent are mixed, whereby the mixture 831 of Step S52 can be manufactured.
Next, in Step S53, the mixture 831 of Step S52 is put into a heat- and pressure-resistant container such as an autoclave; then, heating is performed at a temperature higher than or equal to 100° C. and lower than or equal to 350° C., preferably higher than 100° C. and lower than 200° C. under a pressure higher than or equal to 0.11 MPa and lower than or equal to 100 MPa, preferably higher than or equal to 0.11 MPa and lower than or equal to 2 MPa for longer than or equal to 0.5 hours and shorter than or equal to 24 hours, preferably longer than or equal to 1 hour and shorter than or equal to 10 hours, further preferably longer than or equal to 1 hour and shorter than 5 hours; after that, cooling is performed. Then, in Step S54, the solution in the heat- and pressure-resistant container is filtered, followed by washing with water. Next, in Step S55, drying and subsequent collection are performed, whereby the positive electrode active material 100 of Step S56 is obtained.
Note that the water used in Step S54 is preferably pure water that includes few impurities and preferably has a resistivity of 1 MΩ·cm or higher, further preferably has a resistivity of 10 MΩ·cm or higher, and still further preferably has a resistivity of 15 MΩ·cm or higher. The washing with high-purity pure water makes it possible to obtain the high-purity positive electrode active material 100, and can increase the capacity of a secondary battery and/or increase the reliability of a secondary battery.
Here, a composite oxide, for example, LiMPO4 (M is one or more of Fe(II), Ni(II), Co(II), and Mn(II)) is preferably obtained as the positive electrode active material 100. Depending on the kind of the M(II) compound, any of the following is obtained as appropriate, for example: LiFePO4, LiNiPO4, LiCoPO4, LiMnPO4, LiFeaNibPO4, LiFeaCobPO4, LiFeaMnbPO4, LiNiaCobPO4, LiNiaMnbPO4 (a+b is 1 or less, 0<a<1, and 0<b<1), LiFecNidCoePO4, LiFecNiaMnePO4, LiNicCodMnePO4 (c+d+e is 1 or less, 0<c<1, 0<d<1, and 0<e<1), and LiFejNigCohMniPO4 (f+g+h+i is 1 or less, 0<f<1, 0<g<1, 0<h<1, and 0<i<1). The composite oxide obtained according to this embodiment may be a single crystal grain.
By performing crystal analysis such as XRD or electron diffraction, for example, on the positive electrode active material 100, the crystal structure can be identified. By performing crystal analysis on the positive electrode active material 100, a crystal structure belonging to a space group Pnma can be obtained in some cases. Here, LiMPO4 having an olivine crystal structure belongs to the space group Pnma, for example.
As described above, in one embodiment of the present invention, high-purity materials are used as raw materials used in the synthesis, and a positive electrode active material is manufactured in a process where impurities are less likely to be mixed during the synthesis. The positive electrode active material obtained by such a method for manufacturing a positive electrode active material is a material having a low impurity concentration, that is, a highly purified material. Moreover, the positive electrode active material obtained by such a method for manufacturing a positive electrode active material is a material having high crystallinity. With the positive electrode active material obtained by the method for manufacturing the positive electrode active material of one embodiment of the present invention, the capacity of a secondary battery can be increased and/or the reliability of a secondary battery can be increased.
This embodiment can be used in appropriate combination with any of the other embodiments.
In this embodiment, a method for manufacturing a positive electrode active material of one embodiment of the present invention is described.
The positive electrode active material of one embodiment of the present invention is manufactured using a liquid phase method, preferably a hydrothermal method.
A method for manufacturing a positive electrode active material of one embodiment of the present invention is described using
In Step S21a, a lithium-containing solution 806 is prepared. In Step S21b, a phosphorus-containing solution 807 is prepared.
The lithium-containing solution 806 can be formed by dissolving a lithium compound in a solvent. As the lithium compound, any one or more of lithium hydroxide monohydrate (LiOH·H2O), lithium chloride (LiCl), lithium carbonate (Li2CO3), lithium acetate (CH3COOLi), and lithium oxalate ((COOLi)2) can be used. Water can be used as the solvent in which the lithium compound is dissolved. In the case where water is used as the solvent, it is preferably pure water that includes few impurities and preferably has a resistivity of 1 MΩ·cm or higher, further preferably has a resistivity of 10 MΩ·cm or higher, and still further preferably has a resistivity of 15 MΩ·cm or higher. The use of a high-purity material can increase the capacity of a secondary battery and/or increase the reliability of a secondary battery.
The phosphorus-containing solution 807 can be formed by dissolving a phosphorus compound in a solvent. As the phosphorus compound, any one or more of phosphoric acid such as orthophosphoric acid (H3PO4) and ammonium hydrogen phosphate such as diammonium hydrogen phosphate ((NH4)2HPO4) and ammonium dihydrogen phosphate (NH4H2PO4) can be used. Water can be used as the solvent in which the phosphorus compound is dissolved. In the case where water is used as the solvent, it is preferably pure water that includes few impurities and preferably has a resistivity of 1 MΩ·cm or higher, further preferably has a resistivity of 10 MΩ·cm or higher, and still further preferably has a resistivity of 15 MΩ·cm or higher. The use of a high-purity material can increase the capacity of a secondary battery and/or increase the reliability of a secondary battery.
Next, in Step S31, the lithium-containing solution 806 and the phosphorus-containing solution 807 are mixed, whereby the mixture 811 of Step S32 is obtained. The mixing in Step S31 can be performed in an atmosphere of air, an inert gas, or the like. As the inert gas, nitrogen is used, for example. Here, as an example, the lithium-containing solution 806 prepared in Step S21a and the phosphorus-containing solution 807 prepared in Step S21b are mixed in an air atmosphere.
Note that instead of forming the mixture 811 of Step S32 by mixing the lithium-containing solution 806 and the phosphorus-containing solution 807, the mixture 811 of Step S32 may be formed by preparing a compound containing phosphorus and lithium, such as Li3PO, Li2HPO4, or LiH2PO4, and adding the compound to a solvent.
Next, in Step S33, a solution 813 containing the transition metal M is prepared.
The solution 813 containing the transition metal M can be formed by dissolving a transition metal M compound in a solvent. As the transition metal M compound, one or more of an iron(II) compound, a manganese(II) compound, a cobalt(II) compound, and a nickel(II) compound (hereinafter referred to as an M(II) compound) can be used. Water can be used as the solvent in which the transition metal M compound is dissolved. In the case where water is used as the solvent, it is preferably pure water that includes few impurities and preferably has a resistivity of 1 MΩ·cm or higher, further preferably has a resistivity of 10 MΩ·cm or higher, and still further preferably has a resistivity of 15 MΩ·cm or higher. The use of a high-purity material 0 can increase the capacity of a secondary battery and/or increase the reliability of a secondary battery.
Note that a high-purity material is preferably used as the transition metal M compound used for the synthesis. Specifically, the purity of the material is higher than or equal to 3N (99.9%), preferably higher than or equal to 4N (99.99%), further preferably higher than or equal to 4N5 (99.995%), still further preferably higher than or equal to 5N (99.999%). The use of a high-purity material can increase the capacity of a secondary battery and/or increase the reliability of a secondary battery.
In addition, it is preferred that the transition metal M compound here have high crystallinity. For example, the transition metal compound preferably includes single crystal grains. To evaluate the crystallinity of the transition metal compound, for example, the crystallinity can be judged by a TEM (transmission electron microscope) image, an STEM (scanning transmission electron microscope) image, a HAADF-STEM (high-angle annular dark field scanning transmission electron microscope) image, an ABF-STEM (annular bright-field scan transmission electron microscope) image, and the like. For evaluation of the crystallinity of the transition metal M compound, X-ray diffraction (XRD), electron diffraction, neutron diffraction, and the like can also be used for judging. Note that the above-described crystallinity evaluation can be applied not only to the transition metal M compound but also to a primary particle or a secondary particle.
Typical examples of the iron(II) compound include iron chloride tetrahydrate (FeCl2·4H2O), iron sulfate heptahydrate (FeSO4·7H2O), and iron acetate (Fe(CH3COO)2).
Typical examples of the manganese(II) compound include manganese chloride tetrahydrate (MnCl2·4H2O), manganese sulfate monohydrate (MnSO4H2O), and manganese acetate tetrahydrate (Mn(CH3COO)2·4H2O).
Typical examples of the cobalt(II) compound include cobalt chloride hexahydrate (CoCl2·6H2O), cobalt sulfate heptahydrate (CoSO4·7H2O), and cobalt acetate tetrahydrate (Co(CH3COO)2·4H2O).
Typical examples of the nickel(II) compound include nickel chloride hexahydrate (NiCl2·6H2O), nickel sulfate hexahydrate (NiSO4·6H2O), and nickel acetate tetrahydrate (Ni(CH3COO)2·4H2O).
Next, in Step 35, the mixture 811 of Step S32 and the solution 813 containing the transition metal M are mixed, whereby a mixture 823 of Step S41 is obtained.
Here, the atomic ratio of lithium to the transition metal M and phosphorus of the composite oxide preferably obtained as the positive electrode active material 100 described later is x:y:z. In order to obtain LiMPO4, for example, x:y:z=1:1:1 is satisfied.
In a method for the mixing in Step S35, the solution 813 containing the transition metal M is dropped little by little into the mixture 811 of Step S32 that is put in a container, whereby the mixture 823 of Step S41 can be manufactured. In the mixing, it is preferred that the solution in the container and the solution used for the mixing be being stirred, and it is also preferred that dissolved oxygen be removed by N2 bubbling.
Alternatively, in a method for the mixing in Step S35, the mixture 811 of Step S32 is dropped little by little into the solution 813 containing the transition metal M that is put in a container, whereby the mixture 823 of Step S41 can be manufactured. In the mixing, it is preferred that the solution in the container and the solution used for the mixing be being stirred, and it is also preferred that dissolved oxygen be removed by N2 bubbling.
Here, in Step S35, the concentration of the mixture 823 of Step S41 can be adjusted by addition of a solvent. For example, in Step S35, the mixture 811 of Step S32, the solution 813 containing the transition metal M, and a solvent are mixed, whereby the mixture 823 of Step S41 can be manufactured. In the case where water is used as the solvent, it is preferably pure water that includes few impurities and preferably has a resistivity of 1 MΩ·cm or higher, further preferably has a resistivity of 10 MΩ·cm or higher, and still further preferably has a resistivity of 15 MΩ·cm or higher.
Next, in Step S53, the mixture 823 of Step S41 is put into a heat- and pressure-resistant container such as an autoclave; then, heating is performed at a temperature higher than or equal to 100° C. and lower than or equal to 350° C., preferably higher than 100° C. and lower than 200° C. under a pressure higher than or equal to 0.11 MPa and lower than or equal to 100 MPa, preferably higher than or equal to 0.11 MPa and lower than or equal to 2 MPa for longer than or equal to 0.5 hours and shorter than or equal to 24 hours, preferably longer than or equal to 1 hour and shorter than or equal to 10 hours, further preferably longer than or equal to 1 hour and shorter than 5 hours; after that, cooling is performed. Then, in Step S54, the solution in the heat- and pressure-resistant container is filtered, followed by washing with water. Next, in Step S55, drying and subsequent collection are performed, whereby the positive electrode active material 100 of Step S56 is obtained.
Note that the water used in Step S54 is preferably pure water that includes few impurities and preferably has a resistivity of 1 MΩ·cm or higher, further preferably has a resistivity of 10 MΩ·cm or higher, and still further preferably has a resistivity of 15 MΩ·cm or higher. The washing with high-purity pure water makes it possible to obtain the high-purity positive electrode active material 100, and can increase the capacity of a secondary battery and/or increase the reliability of a secondary battery.
Here, a composite oxide, for example, LiMPO4 (M is one or more of Fe(II), Ni(II), Co(II), and Mn(II)) is preferably obtained as the positive electrode active material 100. Depending on the kind of the M(II) compound, any of the following is obtained as appropriate, for example: LiFePO4, LiNiPO4, LiCoPO4, LiMnPO4, LiFeaNibPO4, LiFeaCobPO4, LiFeaMnbPO4, LiNiaCobPO4, LiNiaMnbPO4 (a+b is 1 or less, 0<a<1, and 0<b<1), LiFecNidCoePO4, LiFecNidMnePO4, LiNicCodMnePO4 (c+d+e is 1 or less, 0<c<1, 0<d<1, and 0<e<1), and LiFejNigCohMniPO4 (f+g+h+i is 1 or less, 0<f<1, 0<g<1, 0<h<1, and 0<i<1). The composite oxide obtained according to this embodiment may be a single crystal grain.
By performing crystal analysis such as XRD or electron diffraction, for example, on the positive electrode active material 100, the crystal structure can be identified. By performing crystal analysis on the positive electrode active material 100, a crystal structure belonging to a space group Pnma can be obtained in some cases. Here, LiMPO4 having an olivine crystal structure belongs to the space group Pnma, for example.
As described above, in one embodiment of the present invention, high-purity materials are used as raw materials used in the synthesis, and a positive electrode active material is manufactured in a process where impurities are less likely to be mixed during the synthesis. The positive electrode active material obtained by such a method for manufacturing a positive electrode active material is a material having a low impurity concentration, that is, a highly purified material. Moreover, the positive electrode active material obtained by such a method for manufacturing a positive electrode active material is a material having high crystallinity. With the positive electrode active material obtained by the method for manufacturing the positive electrode active material of one embodiment of the present invention, the capacity of a secondary battery can be increased and/or the reliability of a secondary battery can be increased.
This embodiment can be used in appropriate combination with any of the other embodiments.
In this embodiment, examples of a secondary battery of one embodiment of the present invention are described using
Hereinafter, a secondary battery in which a positive electrode, a negative electrode, and and electrolyte are wrapped in an exterior body is described as an example.
The positive electrode includes a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, and may include a conductive additive and a binder. As the positive electrode active material, any one or more of the positive electrode active materials 100 manufactured by the manufacturing methods described in the above embodiments can be used.
The positive electrode active material 100 described in the above embodiments and another positive electrode active material may be mixed to be used.
As another positive electrode active material, it is preferable to mix lithium nickel oxide (LiNiO2 and/or LiNi1−xMxO2 (0<x<1) (M=Co, Al, or the like)) with a lithium-containing material that has a spinel crystal structure and contains manganese, such as LiMn2O4. This composition can improve the performance of the secondary battery.
As another positive electrode active material, a lithium-manganese composite oxide that can be represented by a composition formula LiaMnbMcOd can be used. Here, the element M is preferably silicon, phosphorus, or a metal element other than lithium and manganese, and is further preferably nickel. In the case where the whole particles of a lithium-manganese composite oxide are measured, it is preferable to satisfy the following at the time of discharging: 0<a/(b+c)<2; c>0; and 0.26 (b+c)/d<0.5. Note that the proportions of metals, silicon, phosphorus, and the like in the whole particles of a lithium-manganese composite oxide can be measured with, for example, an ICP-MS (inductively coupled plasma mass spectrometer). The proportion of oxygen in the whole particles of a lithium-manganese composite oxide can be measured by, for example, EDX (energy dispersive X-ray spectroscopy). Alternatively, the proportion of oxygen can be measured by ICPMS combined with fusion gas analysis and valence evaluation of XAFS (X-ray absorption fine structure) analysis. Note that a lithium-manganese composite oxide is an oxide containing at least lithium and manganese, and may contain at least one kind of element selected from chromium, cobalt, aluminum, nickel, iron, magnesium, molybdenum, zinc, indium, gallium, copper, titanium, niobium, silicon, phosphorus, and the like.
A cross-sectional structure example of an active material layer 200 using a graphene compound as a conductive additive is described below.
The graphene compound 201 in this specification and the like refers to graphene, multilayer graphene, multi graphene, graphene oxide, multilayer graphene oxide, multi graphene oxide, reduced graphene oxide, reduced multilayer graphene oxide, reduced multi graphene oxide, graphene quantum dots, and the like. The graphene compound 201 contains carbon, has a plate-like shape, a sheet-like shape, or the like, and has a two-dimensional structure formed of a six-membered ring composed of carbon atoms. The two-dimensional structure formed of the six-membered ring composed of carbon atoms may be referred to as a carbon sheet. The graphene compound 201 may include a functional group. The graphene compound 201 preferably has a bent shape. The graphene compound 201 may be rounded like carbon nanofiber.
In this specification and the like, graphene oxide contains carbon and oxygen, has a sheet-like shape, and includes a functional group, in particular, an epoxy group, a carboxy group, or a hydroxy group.
In this specification and the like, reduced graphene oxide contains carbon and oxygen, has a sheet-like shape, and has a two-dimensional structure formed of a six-membered ring composed of carbon atoms. The reduced graphene oxide may be referred to as a carbon sheet. The reduced graphene oxide functions by itself and may have a stacked-layer structure. The reduced graphene oxide preferably includes a portion where the carbon concentration is higher than 80 atomic % and the oxygen concentration is higher than or equal to 2 atomic % and lower than or equal to 15 atomic %. With such a carbon concentration and such an oxygen concentration, the reduced graphene oxide can function as a conductive additive having high conductivity even with a small amount. In addition, the intensity ratio G/D of a G band to a D band of the Raman spectrum of the reduced oxide graphene oxide is preferably 1 or more. The reduced graphene oxide with such an intensity ratio can function as a conductive additive having high conductivity even with a small amount.
Reducing graphene oxide can form a vacancy in the graphene compound 201 in some cases.
A material obtained by terminating an end portion of the graphene compound 201 with fluorine may be used.
The graphene compound 201 preferably includes a vacancy in part of a carbon sheet. When a vacancy through which carrier ions such as lithium ions can pass is provided in part of the carbon sheet of the graphene compound 201, insertion and extraction of carrier ions are facilitated on the surface of an active material covered with the graphene compound 201, thereby increasing the rate performance of a secondary battery. The vacancy provided in part of the carbon sheet is referred to as a pore, a defect, or a gap in some cases.
The graphene compound 201 preferably includes a vacancy formed with a plurality of carbon atoms. The plurality of carbon atoms are preferably bonded to each other in a ring, and one or more of the plurality of carbon atoms bonded to each other in a ring are preferably terminated by a fluorine atom. Fluorine has high electronegativity and is easily negatively charged. Approach of positively-charged lithium ions causes interaction, whereby energy is stable and the barrier energy in passage of lithium ions through a vacancy can be lowered. Thus, a fluorine atom contained in a vacancy in the graphene compound 201 makes it possible to obtain the graphene compound 201 having excellent conductivity in which a lithium ion passes easily through even a small vacancy.
The longitudinal cross section of the active material layer 200 in
Here, the plurality of graphene compounds can be bonded to each other to form a net-like graphene compound sheet (hereinafter referred to as a graphene compound net or a graphene net). A graphene net that covers the active material can function as a binder for bonding the active materials. Accordingly, the amount of the binder can be reduced, or the binder does not have to be used. This can increase the proportion of the active material in the electrode volume and/or the electrode weight. That is, the capacity of the secondary battery can be increased.
Here, it is preferable to perform reduction after a layer to be the active material layer 200 is formed in such a manner that graphene oxide is used as the graphene compound 201 and mixed with an active material. That is, the formed active material layer preferably contains reduced graphene oxide. When graphene oxide with extremely high dispersibility in a polar solvent is used for the formation of the graphene compound 201, the graphene compound 201 can be substantially uniformly dispersed in the active material layer 200. The solvent is removed by volatilization from a dispersion medium in which graphene oxide is uniformly dispersed, and the graphene oxide is reduced; hence, the graphene compounds 201 remaining in the active material layer 200 partly overlap with each other and are dispersed such that surface contact is made, thereby forming a three-dimensional conductive path. Note that graphene oxide may be reduced by heat treatment or with the use of a reducing agent, for example.
Unlike conductive additive particles that make point contact with an active material, such as acetylene black, the graphene compound 201 is capable of making low-contact-resistance surface contact; accordingly, the electric conduction between the particles of the positive electrode active material 100 and the graphene compounds 201 can be improved with a smaller amount of the graphene compound 201 than that of a normal conductive additive. Thus, the proportion of the positive electrode active material 100 in the active material layer 200 can be increased. Hence, the discharge capacity of the secondary battery can be increased.
With a spray dry apparatus, a graphene compound serving as a conductive additive can be formed in advance as a coating film to cover the entire surface of the active material, and a conductive path can be formed between the active materials using the graphene compound.
As the binder, a rubber material such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, or ethylene-propylene-diene copolymer is preferably used, for example. Alternatively, fluororubber can be used as the binder.
As the binder, for example, water-soluble polymers are preferably used. As the water-soluble polymers, a polysaccharide or the like can be used, for example. As the polysaccharide, starch, a cellulose derivative such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, or regenerated cellulose, or the like can be used. It is further preferred that such water-soluble polymers be used in combination with any of the above-described rubber materials.
Alternatively, as the binder, it is preferable to use a material such as polystyrene, poly(methyl acrylate), poly(methyl methacrylate) (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene-propylene-diene polymer, polyvinyl acetate, or nitrocellulose.
Two or more of the above-described materials may be used in combination for the binder.
For example, a material having a significant viscosity modifying effect and another material may be used in combination. For example, a rubber material or the like has high adhesion and high elasticity but may have difficulty in viscosity modification when mixed in a solvent. In such a case, a rubber material or the like is preferably mixed with a material having a significant viscosity modifying effect, for example. As a material having a significant viscosity modifying effect, for instance, a water-soluble polymer is preferably used. As a water-soluble polymer having a significant viscosity modifying effect, it is possible to use the above-mentioned polysaccharide, for instance, a cellulose derivative such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, or regenerated cellulose, or starch.
Note that a cellulose derivative such as carboxymethyl cellulose obtains a higher solubility when converted into a salt such as a sodium salt or an ammonium salt of carboxymethyl cellulose, and thus easily exerts an effect as a viscosity modifier. A high solubility can also increase the dispersibility of an active material and other components in the formation of slurry for an electrode. In this specification, cellulose and a cellulose derivative used as a binder of an electrode include salts thereof.
A water-soluble polymer stabilizes the viscosity by being dissolved in water and allows stable dispersion of the active material or another material combined as a binder, such as styrene-butadiene rubber, in an aqueous solution. Furthermore, a water-soluble polymer is expected to be easily and stably adsorbed onto an active material surface because it has a functional group. Many cellulose derivatives, such as carboxymethyl cellulose, have a functional group such as a hydroxyl group or a carboxyl group. Because of functional groups, polymers are expected to interact with each other and cover an active material surface in a large area.
In the case where the binder that covers the active material surface or is in contact with the surface forms a film, the film is expected to serve also as a passivation film to inhibit the decomposition of an electrolyte. Here, a passivation film refers to a film without electric conductivity or a film with extremely low electric conductivity, and can inhibit the decomposition of an electrolyte at a battery reaction potential when the passivation film is formed on the active material surface, for example. It is preferred that the passivation film can conduct lithium ions while suppressing electrical conduction.
The current collector can be formed using a material that has high conductivity, such as a metal like stainless steel, gold, platinum, aluminum, or titanium, or an alloy thereof. It is preferred that a material used for the positive electrode current collector not dissolve at the potential of the positive electrode. It is also possible to use an aluminum alloy to which an element that improves heat resistance, such as silicon, titanium, neodymium, scandium, or molybdenum, is added. A metal element that forms silicide by reacting with silicon may be used. Examples of the metal element that forms silicide by reacting with silicon include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, and nickel. The current collector can have a foil-like shape, a plate-like shape, a sheet-like shape, a net-like shape, a punching-metal shape, an expanded-metal shape, or the like as appropriate. The current collector preferably has a thickness greater than or equal to 5 μm and less than or equal to 30 μm.
The negative electrode includes a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer may contain a conductive additive and a binder.
As the negative electrode active material, for example, an alloy-based material and/or a carbon-based material can be used.
As the negative electrode active material, an element that enables charge and discharge reactions by an alloying reaction and a dealloying reaction with lithium can be used. For example, a material containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, and the like can be used. Such elements have higher capacity than carbon. In particular, silicon has a high theoretical capacity of 4200 mAh/g. For this reason, silicon is preferably used as the negative electrode active material. Alternatively, a compound containing any of the above elements may be used. Examples of the compound include SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, and SbSn. Here, an element that enables charge and discharge reactions by an alloying reaction and a dealloying reaction with lithium, a compound containing the element, and the like may be referred to as an alloy-based material.
In this specification and the like, SiO refers, for example, to silicon monoxide. Note that SiO can alternatively be expressed as SiOx. Here, x preferably has an approximate value of 1. For example, x is preferably greater than or equal to 0.2 and less than or equal to 1.5, further preferably greater than or equal to 0.3 and less than or equal to 1.2.
As the carbon-based material, graphite, graphitizing carbon (soft carbon), non-graphitizing carbon (hard carbon), carbon nanotube, graphene, carbon black, or the like can be used.
Examples of graphite include artificial graphite and natural graphite. Examples of artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. As artificial graphite, spherical graphite having a spherical shape can be used. For example, MCMB is preferable because it may have a spherical shape. Moreover, MCMB may be preferable because it can relatively easily have a small surface area. Examples of natural graphite include flake graphite and spherical natural graphite.
Graphite has a low potential substantially equal to that of a lithium metal (greater than or equal to 0.05 V and less than or equal to 0.3 V vs. Li/Li+) when lithium ions are inserted into graphite (while a lithium-graphite intercalation compound is formed). For this reason, a lithium-ion secondary battery can have a high operating voltage. In addition, graphite is preferred because of its advantages such as a relatively high capacity per unit volume, relatively small volume expansion, low cost, and a higher level of safety than that of a lithium metal.
As the negative electrode active material, an oxide such as titanium dioxide (TiO2), lithium titanium oxide (Li4Ti5O12), a lithium-graphite intercalation compound (LixC6), niobium pentoxide (Nb2O5), tungsten oxide (WO2), or molybdenum oxide (MoO2) can be used.
As the negative electrode active material, Li3−xMxN (M=Co, Ni, or Cu) with a Li3N structure, which is a composite nitride of lithium and a transition metal, can be used. For example, Li2.6Co0.4N3 is preferable because of high charge and discharge capacity (900 mAh/g and 1890 mAh/cm3).
A composite nitride of lithium and a transition metal is preferably used, in which case lithium ions are contained in the negative electrode active material and thus the negative electrode active material can be used in combination with a material for a positive electrode active material that does not contain lithium ions, such as V2O5 or Cr3O8. Note that in the case of using a material containing lithium ions as a positive electrode active material, the composite nitride of lithium and a transition metal can be used as the negative electrode active material by extracting the lithium ions contained in the positive electrode active material in advance.
Alternatively, a material that causes a conversion reaction can be used as the negative electrode active material. For example, a transition metal oxide that does not form an alloy with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), or iron oxide (FeO), may be used as the negative electrode active material. Other examples of the material that causes a conversion reaction include oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3, sulfides such as CoS0.89, NiS, and CuS, nitrides such as Zn3N2, Cu3N, and Ge3N4, phosphides such as NiP2, FeP2, and CoP3, and fluorides such as FeF3 and BiF3.
For the conductive additive and the binder that can be included in the negative electrode active material layer, materials similar to those for the conductive additive and the binder that can be included in the positive electrode active material layer can be used.
For the negative electrode current collector, a material similar to that of the positive electrode current collector can be used. Note that a material that is not alloyed with carrier ions of lithium or the like is preferably used for the negative electrode current collector.
As one mode of the electrolyte, an electrolyte solution containing a solvent and an electrolyte dissolved in the solvent can be used. As the solvent of the electrolyte solution, an aprotic organic solvent is preferable. For example, one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, and sultone can be used, or two or more of these solvents can be used in an appropriate combination at an appropriate ratio.
The use of one or more ionic liquids (room temperature molten salts) that are unlikely to burn and volatize as the solvent of the electrolyte solution can prevent a secondary battery from exploding or catching fire even when the secondary battery internally shorts out and/or the internal temperature increases owing to overcharging or the like. An ionic liquid contains a cation and an anion, specifically, an organic cation and an anion. Examples of the organic cation used for the electrolyte solution include aliphatic onium cations such as a quaternary ammonium cation, a tertiary sulfonium cation, and a quaternary phosphonium cation, and/or aromatic cations such as an imidazolium cation and a pyridinium cation. Examples of the anion used for the electrolyte solution include a monovalent amide-based anion, a monovalent methide-based anion, a fluorosulfonate anion, a perfluoroalkylsulfonate anion, a tetrafluoroborate anion, a perfluoroalkylborate anion, a hexafluorophosphate anion, and a perfluoroalkylphosphate anion.
As the electrolyte dissolved in the above-described solvent, one of lithium salts such as LiPF6, LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, Li2B10Cl10, Li2B12Cl12, LiCF3SO3, LiC4F9SO3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), and LiN(C2F5SO2)2 can be used, or two or more of these lithium salts can be used in an appropriate combination at an appropriate ratio.
The electrolyte solution used for a secondary battery is preferably highly purified and contains a small number of dust particles and/or elements other than the constituent elements of the electrolyte solution (hereinafter also simply referred to as impurities). Specifically, the weight ratio of impurities to the electrolyte solution is preferably less than or equal to 1%, further preferably less than or equal to 0.1%, still further preferably less than or equal to 0.01%. Furthermore, an additive agent such as vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate)borate (LiBOB), or a dinitrile compound such as succinonitrile or adiponitrile may be added to the electrolyte solution. The concentration of the material to be added in the solvent in which the electrolyte is dissolved is, for example, higher than or equal to 0.1 wt % and lower than or equal to 5 wt %.
Alternatively, a polymer gel electrolyte obtained in such a manner that a polymer is swelled with an electrolyte solution may be used.
When a polymer gel electrolyte is used, safety against liquid leakage and the like is improved. Moreover, a secondary battery can be thinner and more lightweight.
As a polymer that undergoes gelation, a silicone gel, an acrylic gel, an acrylonitrile gel, a polyethylene oxide-based gel, a polypropylene oxide-based gel, a fluorine-based polymer gel, or the like can be used.
As the polymer, it is possible to use, for example, a polymer having a polyalkylene oxide structure, such as polyethylene oxide (PEO); PVDF; polyacrylonitrile; and/or a copolymer containing any of them. For example, PVDF-HFP, which is a copolymer of PVDF and hexafluoropropylene (HFP), can be used. The formed polymer may be porous.
As the electrolyte, a solid electrolyte including an inorganic material such as a sulfide-based or oxide-based inorganic material, or a solid electrolyte including a polymer material such as a PEO (polyethylene oxide)-based polymer material can alternatively be used. When the solid electrolyte is used, a separator and/or a spacer are not necessary. Furthermore, the battery can be entirely solidified; therefore, there is no possibility of liquid leakage and thus the safety of the battery is dramatically improved.
The secondary battery preferably includes a separator. The separator can be formed using, for example, paper, nonwoven fabric, glass fiber, ceramics, or synthetic fiber containing nylon (polyamide), vinylon (polyvinyl alcohol-based fiber), polyester, acrylic, polyolefin, or polyurethane. The separator is preferably formed to have an envelope-like shape to wrap one of the positive electrode and the negative electrode.
The separator may have a multilayer structure. For example, an organic material film of polypropylene, polyethylene, or the like can be coated with a ceramic-based material, a fluorine-based material, a polyamide-based material, a mixture thereof, or the like. Examples of the ceramic-based material include aluminum oxide particles and silicon oxide particles. Examples of the fluorine-based material include PVDF and polytetrafluoroethylene. Examples of the polyamide-based material include nylon and aramid (meta-based aramid and para-based aramid).
When the separator is coated with the ceramic-based material, the oxidation resistance is improved; hence, deterioration of the separator in charging and discharging at a high voltage can be suppressed and thus the reliability of the secondary battery can be improved. When the separator is coated with the fluorine-based material, the separator is easily brought into close contact with an electrode, resulting in high output characteristics. When the separator is coated with the polyamide-based material, in particular, aramid, the safety of the secondary battery is improved because heat resistance is improved.
For example, both surfaces of a polypropylene film may be coated with a mixed material of aluminum oxide and aramid. Alternatively, a surface of a polypropylene film that is in contact with the positive electrode may be coated with a mixed material of aluminum oxide and aramid, and a surface of the polypropylene film that is in contact with the negative electrode may be coated with the fluorine-based material.
With the use of a separator having a multilayer structure, the capacity per volume of the secondary battery can be increased because the safety of the secondary battery can be maintained even when the total thickness of the separator is small.
For an exterior body included in the secondary battery, a metal material such as aluminum and/or a resin material can be used, for example. A film-like exterior body can also be used. As the film, for example, it is possible to use a film having a three-layer structure in which a highly flexible metal thin film of aluminum, stainless steel, copper, nickel, or the like is provided over a film formed of a material such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and an insulating synthetic resin film of a polyamide-based resin, a polyester-based resin, or the like is provided as the outer surface of the exterior body over the metal thin film.
A structure of a secondary battery including a solid electrolyte layer is described below as another structure example of a secondary battery.
As illustrated in
The positive electrode 410 includes a positive electrode current collector 413 and a positive electrode active material layer 414. The positive electrode active material layer 414 includes a positive electrode active material 411 and a solid electrolyte 421. As the positive electrode active material 411, the positive electrode active material formed by the manufacturing method described in the above embodiments is used. The positive electrode active material layer 414 may also include a conductive additive and a binder.
The solid electrolyte layer 420 includes the solid electrolyte 421. The solid electrolyte layer 420 is positioned between the positive electrode 410 and the negative electrode 430 and is a region that includes neither the positive electrode active material 411 nor a negative electrode active material 431.
The negative electrode 430 includes a negative electrode current collector 433 and a negative electrode active material layer 434. The negative electrode active material layer 434 includes the negative electrode active material 431 and the solid electrolyte 421. The negative electrode active material layer 434 may also include a conductive additive and a binder. Note that when metal lithium is used for the negative electrode 430, the negative electrode 430 that does not include the solid electrolyte 421 can be formed, as illustrated in
As the solid electrolyte 421 included in the solid electrolyte layer 420, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a halide-based solid electrolyte can be used, for example.
Examples of the sulfide-based solid electrolyte include a thio-LISICON-based material (e.g., Li10GeP2S12 and Li3.25Ge0.25P0.75S4), sulfide glass (e.g., 70Li2S·30P2S5, 30Li2S·26B2S3·44LiI, 63Li2S·36SiS2·1Li3PO4, 57Li2S·38SiS2·5Li4SiO4, and 50Li2S·50GeS2), and sulfide-based crystallized glass (e.g., Li7P3S11 and Li3.25Po0.95S4). The sulfide-based solid electrolyte has advantages such as high conductivity of some materials, low-temperature synthesis, and ease of maintaining a path for electrical conduction after charging and discharging because of its relative softness. Note that the sulfide-based solid electrolyte may generate hydrogen sulfide by a reaction with water. Therefore, diligent attention to safety is required. For example, in order to improve the safety, the hermeticity of an exterior body included in the secondary battery and/or a housing in which the secondary battery is held is preferably high.
Examples of the oxide-based solid electrolyte include a material with a perovskite crystal structure (e.g., La2/3−xLi3xTiO3), a material with a NASICON crystal structure (e.g., Li1+xAlxTi2−xPO4)3), a material with a garnet crystal structure (e.g., Li7La3Zr2O12), a material with a LISICON crystal structure (e.g., Li14ZnGe4O16), oxide glass (e.g., Li3PO4—Li4SiO4 and 50Li4SiO4·50Li3BO3), and oxide-based crystallized glass (e.g., Li1.07Al0.69Ti1.46(PO4)3 and Li1.5Al0.5Ge1.5(PO4)3). The oxide-based solid electrolyte has an advantage of stability in the air. Note that in this specification and the like, a material with a NASICON crystal structure refers to a compound that is represented by M2(XO4)3 (M: transition metal; X: S, P, As, Mo, W, or the like) and has a structure in which MO6 octahedrons and XO4 tetrahedrons that share common corners are arranged three-dimensionally.
Examples of the halide-based solid electrolyte include LiAlCl4, Li3InBr6, LiF, LiCl, LiBr, and LiI. Moreover, a composite material in which pores of porous aluminum oxide or porous silica are filled with such a halide-based solid electrolyte can be used as the solid electrolyte.
Alternatively, different solid electrolytes may be mixed and used.
An exterior body of the secondary battery 400 of one embodiment of the present invention can employ a variety of materials and shapes, and preferably has a function of applying pressure to the positive electrode, the solid electrolyte layer, and the negative electrode.
The evaluation material is placed on an electrode plate 751, surrounded by an insulating tube 752, and pressed from above by the electrode plate 753.
A stack of a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c is shown here as an example of the evaluation material, and its cross section is shown in
The electrode plate 751 and the lower component 761 that are electrically connected to the positive electrode 750a correspond to a positive electrode terminal. The electrode plate 753 and the upper component 762 that are electrically connected to the negative electrode 750c correspond to a negative electrode terminal. The electric resistance or the like can be measured while pressure is applied to the evaluation material through the electrode plate 751 and the electrode plate 753.
The exterior body of the secondary battery of one embodiment of the present invention is preferably a package having excellent airtightness. For example, a ceramic package or a resin package can be used. The exterior body is sealed preferably in a closed atmosphere where the outside air is blocked, for example, in a glove box.
The external electrode 771 is electrically connected to the positive electrode 750a through the electrode layer 773a and functions as a positive electrode terminal. The external electrode 772 is electrically connected to the negative electrode 750c through the electrode layer 773b and functions as a negative electrode terminal.
This embodiment can be used in appropriate combination with any of the other embodiments.
In this embodiment, examples of a shape of a secondary battery including the positive electrode described in the above embodiment are described. For the materials used for the secondary battery described in this embodiment, the description of the above embodiment can be referred to.
First, an example of a coin-type secondary battery is described.
In a coin-type secondary battery 300, a positive electrode can 301 doubling as a positive electrode terminal and a negative electrode can 302 doubling as a negative electrode terminal are insulated from each other and sealed by a gasket 303 made of polypropylene or the like. A positive electrode 304 includes a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with the positive electrode current collector 305. A negative electrode 307 includes a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact with the negative electrode current collector 308.
Note that only one surface of each of the positive electrode 304 and the negative electrode 307 used for the coin-type secondary battery 300 is provided with an active material layer.
For the positive electrode can 301 and the negative electrode can 302, a metal having corrosion resistance to an electrolyte, such as nickel, aluminum, or titanium, an alloy of such a metal, or an alloy of such a metal and another metal (e.g., stainless steel) can be used. Alternatively, the positive electrode can 301 and the negative electrode can 302 are preferably covered with nickel, aluminum, and/or the like in order to prevent corrosion due to the electrolyte.
The positive electrode can 301 and the negative electrode can 302 are electrically connected to the positive electrode 304 and the negative electrode 307, respectively.
The negative electrode 307, the positive electrode 304, and a separator 310 are immersed in the electrolyte. Then, as illustrated in
When the positive electrode active material described in the above embodiment is used in the positive electrode 304, the coin-type secondary battery 300 with high capacity and excellent cycle performance can be obtained.
Here, a current flow in charging a secondary battery is described using
Two terminals illustrated in
Next, an example of a cylindrical secondary battery is described with reference to
Inside the battery can 602 having a hollow cylindrical shape, a battery element in which a strip-like positive electrode 604 and a strip-like negative electrode 606 are wound with a separator 605 located therebetween is provided. Although not illustrated, the battery element is wound around a center pin. One end of the battery can 602 is close and the other end thereof is open. For the battery can 602, a metal having corrosion resistance to an electrolyte, such as nickel, aluminum, or titanium, an alloy of such a metal, or an alloy of such a metal and another metal (e.g., stainless steel) can be used. Alternatively, the battery can 602 is preferably covered with nickel, aluminum, and/or the like in order to prevent corrosion due to the electrolyte. Inside the battery can 602, the battery element in which the positive electrode, the negative electrode, and the separator are wound is provided between a pair of insulating plates 608 and 609 that face each other. The inside of the battery can 602 provided with the battery element is filled with an electrolyte (not illustrated). An electrolyte similar to that for the coin-type secondary battery can be used.
Since a positive electrode and a negative electrode that are used for a cylindrical storage battery are wound, active materials are preferably formed on both surfaces of a current collector. A positive electrode terminal (positive electrode current collecting lead) 603 is connected to the positive electrode 604, and a negative electrode terminal (negative electrode current collecting lead) 607 is connected to the negative electrode 606. Both the positive electrode terminal 603 and the negative electrode terminal 607 can be formed using a metal material such as aluminum. The positive electrode terminal 603 and the negative electrode terminal 607 are resistance-welded to a safety valve mechanism 612 and the bottom of the battery can 602, respectively. The safety valve mechanism 612 is electrically connected to the positive electrode cap 601 through a PTC element (Positive Temperature Coefficient) 611. The safety valve mechanism 612 cuts off electrical connection between the positive electrode cap 601 and the positive electrode 604 when the internal pressure of the battery exceeds a predetermined threshold value. The PTC element 611, which serves as a thermally sensitive resistor whose resistance increases as temperature rises, limits the amount of current by increasing the resistance, in order to prevent abnormal heat generation. Barium titanate (BaTiO3)-based semiconductor ceramics or the like can be used for the PTC element.
Alternatively, as shown in
When the positive electrode active material described in the above embodiment is used in the positive electrode 604, the cylindrical secondary battery 600 with high capacity and excellent cycle performance can be obtained.
Other structure examples of a secondary battery are described using
The circuit board 900 includes a terminal 911 and a circuit 912. The terminal 911 is connected to the terminal 951, the terminal 952, the antenna 914, and the circuit 912. Note that a plurality of terminals 911 may be provided to serve as a control signal input terminal, a power supply terminal, and the like.
The circuit 912 may be provided on the rear surface of the circuit board 900. Note that the shape of the antenna 914 is not limited to a coil shape and may be a linear shape or a plate shape, for example. An antenna such as a planar antenna, an aperture antenna, a traveling-wave antenna, an EH antenna, a magnetic-field antenna, or a dielectric antenna may be used. Alternatively, the antenna 914 may be a flat-plate conductor. The flat-plate conductor can serve as one of conductors for electric field coupling. That is, the antenna 914 may serve as one of two conductors of a capacitor. Thus, electric power can be transmitted and received not only by an electromagnetic field or a magnetic field but also by an electric field.
The battery pack includes a layer 916 between the antenna 914 and the secondary battery 913. The layer 916 has a function of blocking an electromagnetic field by the secondary battery 913, for example. As the layer 916, for example, a magnetic body can be used.
Note that the structure of the battery pack is not limited to that in
For example, as illustrated in
As illustrated in
With the above structure, both the antenna 914 and the antenna 918 can be increased in size. The antenna 918 has a function of communicating data with an external device, for example. An antenna with a shape that can be used for the antenna 914, for example, can be used as the antenna 918. As a system for communication using the antenna 918 between the secondary battery and another device, a response method that can be used between the secondary battery and another device, such as NFC (near field communication), can be employed.
Alternatively, as illustrated in
The display device 920 may display, for example, an image showing whether charge is being carried out, an image showing the amount of stored power, or the like. As the display device 920, electronic paper, a liquid crystal display device, an electroluminescent (EL) display device, or the like can be used. For example, the use of electronic paper can reduce power consumption of the display device 920.
Alternatively, as illustrated in
The sensor 921 has a function of measuring, for example, displacement, position, speed, acceleration, angular velocity, rotational frequency, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, electric power, radiation, flow rate, humidity, gradient, oscillation, odor, or infrared rays. With the sensor 921, for example, data on an environment (e.g., temperature) where the secondary battery is placed can be detected and stored in a memory inside the circuit 912.
Furthermore, structure examples of the secondary battery 913 are described using
The secondary battery 913 illustrated in
Note that as illustrated in
For the housing 930a, an insulating material such as an organic resin can be used. In particular, when a material such as an organic resin is used for the side on which an antenna is formed, blocking of an electric field from the secondary battery 913 can be inhibited. When an electric field is not significantly blocked by the housing 930a, an antenna such as the antenna 914 may be provided inside the housing 930a. For the housing 930b, a metal material can be used, for example.
The negative electrode 931 is connected to the terminal 911 illustrated in
When the positive electrode active material described in the above embodiment is used in the positive electrode 932, the secondary battery 913 with high capacity and excellent cycle performance can be obtained.
Next, an example of a laminated secondary battery is described with reference to
A laminated secondary battery 980 is described using
Note that the number of stacks each including the negative electrode 994, the positive electrode 995, and the separator 996 is designed as appropriate depending on required capacity and element volume. The negative electrode 994 is connected to a negative electrode current collector (not illustrated) through one of a lead electrode 997 and a lead electrode 998. The positive electrode 995 is connected to a positive electrode current collector (not illustrated) through the other of the lead electrode 997 and the lead electrode 998.
As illustrated in
For the film 981 and the film 982 having a depressed portion, a metal material such as aluminum and/or a resin material can be used, for example. With the use of a resin material for the film 981 and the film 982 having a depressed portion, the film 981 and the film 982 having a depressed portion can be changed in their forms when external force is applied; thus, a flexible storage battery can be manufactured.
Although
When the positive electrode active material described in the above embodiment is used in the positive electrode 995, the secondary battery 980 with high capacity and excellent cycle performance can be obtained.
A laminated secondary battery 500 illustrated in
In the laminated secondary battery 500 illustrated in
As the exterior body 509 of the laminated secondary battery 500, for example, a laminate film having a three-layer structure can be employed in which a highly flexible metal thin film of aluminum, stainless steel, copper, nickel, or the like is provided over a film formed of a material such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and an insulating synthetic resin film of a polyamide-based resin, a polyester-based resin, or the like is provided as the outer surface of the exterior body over the metal thin film.
In
Here, an example of a method for manufacturing the laminated secondary battery whose external view is shown in
First, the negative electrode 506, the separator 507, and the positive electrode 503 are stacked.
Then, the negative electrodes 506, the separators 507, and the positive electrodes 503 are placed over the exterior body 509.
Subsequently, the exterior body 509 is folded along a portion shown by a dashed line, as illustrated in
Next, the electrolyte 508 (not illustrated) is introduced into the exterior body 509 from the inlet of the exterior body 509. The electrolyte 508 is preferably introduced in a reduced pressure atmosphere or in an inert atmosphere. Lastly, the inlet is bonded. In this manner, the laminated secondary battery 500 can be manufactured.
When the positive electrode active material described in the above embodiment is used in the positive electrode 503, the secondary battery 500 with high capacity and excellent cycle performance can be obtained.
Next, an example of a bendable secondary battery is described with reference to
The positive electrode 211a and the negative electrode 211b that are included in the secondary battery 250 are described using
As illustrated in
The positive electrodes 211a and the negative electrodes 211b are stacked so that surfaces of the positive electrodes 211a on each of which the positive electrode active material layer is not formed are in contact with each other and surfaces of the negative electrodes 211b on each of which the negative electrode active material layer is not formed are in contact with each other.
The separator 214 is provided between the surface of the positive electrode 211a on which the positive electrode active material layer is formed and the surface of the negative electrode 211b on which the negative electrode active material layer is formed. In
As illustrated in
Next, the exterior body 251 is described using
The exterior body 251 has a film-like shape and is folded in half so as to sandwich the positive electrodes 211a and the negative electrodes 211b. The exterior body 251 includes a folded portion 261, a pair of seal portions 262, and a seal portion 263. The pair of seal portions 262 are provided with the positive electrodes 211a and the negative electrodes 211b positioned therebetween and can also be referred to as side seals. The seal portion 263 includes portions overlapping with the lead 212a and the lead 212b and can also be referred to as a top seal.
Part of the exterior body 251 that overlaps with the positive electrodes 211a and the negative electrodes 211b preferably has a wave shape in which crest lines 271 and trough lines 272 are alternately arranged. The seal portions 262 and the seal portion 263 of the exterior body 251 are preferably flat.
Here, the distance between end portions of the positive electrode 211a and the negative electrode 211b in the width direction and the seal portion 262, that is, the distance between the end portions of the positive electrode 211a and the negative electrode 211b and the seal portion 262 is referred to as a distance La. When the secondary battery 250 changes in shape, for example, is bent, the positive electrode 211a and the negative electrode 211b change in shape such that the positions thereof are shifted from each other in the length direction as described later. At the time, if the distance La is too short, the exterior body 251 and the positive electrode 211a and the negative electrode 211b are rubbed hard against each other, so that the exterior body 251 is damaged in some cases. In particular, when a metal film of the exterior body 251 is exposed, the metal film might be corroded by the electrolyte. Therefore, the distance La is preferably set as long as possible. However, if the distance La is too long, the volume of the secondary battery 250 is increased.
Furthermore, the distance La between the positive electrode 211a and the negative electrode 211b, and the seal portion 262 is preferably increased as the total thickness of the positive electrode 211a and the negative electrode 211b that are stacked is increased.
Specifically, when the total thickness of the stacked positive electrodes 211a, negative electrodes 211b, and separators 214 (not illustrated) is t, the distance La is preferably 0.8 times or more and 3.0 times or less, further preferably 0.9 times or more and 2.5 times or less, still further preferably 1.0 times or more and 2.0 times or less as large as the thickness t. When the distance La is in the above range, a compact battery highly reliable for bending can be obtained.
When the distance between the pair of seal portions 262 is referred to as a distance Lb, it is preferred that the distance Lb be sufficiently longer than the widths of the positive electrode 211a and the negative electrode 211b (here, a width Wb of the negative electrode 211b). In that case, even if the positive electrode 211a and the negative electrode 211b come into contact with the exterior body 251 when deformation such as repeated bending of the secondary battery 250 is conducted, parts of the positive electrode 211a and the negative electrode 211b can be shifted in the width direction; thus, the positive electrode 211a and the negative electrode 211b can be effectively prevented from being rubbed against the exterior body 251.
For example, the difference between the distance Lb, which is the distance between the pair of seal portions 262, and the width Wb of the negative electrode 211b is preferably 1.6 times or more and 6.0 times or less, further preferably 1.8 times or more and 5.0 times or less, still further preferably 2.0 times or more and 4.0 times or less as large as the thickness t of the positive electrode 211a and the negative electrode 211b.
In other words, the distance Lb, the width Wb, and the thickness t preferably satisfy the relation of Formula 1 below.
Here, a satisfies 0.8 or more and 3.0 or less, preferably 0.9 or more and 2.5 or less, further preferably 1.0 or more and 2.0 or less.
When the secondary battery 250 is bent, a part of the exterior body 251 positioned on the outer side in bending is unbent and the other part positioned on the inner side changes its shape as it shrinks. More specifically, the part of the exterior body 251 positioned on the outer side changes its shape such that the wave amplitude becomes smaller and the length of the wave period becomes larger. In contrast, the part of the exterior body 251 positioned on the inner side changes its shape such that the wave amplitude becomes larger and the length of the wave period becomes smaller. When the exterior body 251 changes its shape in this manner, stress applied to the exterior body 251 due to bending is relieved, so that a material itself of the exterior body 251 does not need to expand or contract. Thus, the secondary battery 250 can be bent with weak force without damage to the exterior body 251.
Furthermore, as illustrated in
The space 273 is included between the positive electrode 211a and the negative electrode 211b, and the exterior body 251, whereby the positive electrode 211a and the negative electrode 211b can be shifted relatively while the positive electrode 211a and the negative electrode 211b located on the inner side in bending do not come into contact with the exterior body 251.
In the secondary battery 250 illustrated in
In an all-solid-state battery, the contact state of the inside interfaces can be kept favorable by applying a predetermined pressure in the direction of stacking positive electrodes and/or negative electrodes. By applying a predetermined pressure in the direction of stacking the positive electrodes and/or the negative electrodes, expansion in the stacking direction due to charge and discharge of the all-solid-state battery can be suppressed, and the reliability of the all-solid-state battery can be improved.
This embodiment can be used in appropriate combination with any of the other embodiments.
In this embodiment, examples of electronic devices each including the secondary battery of one embodiment of the present invention are described.
A semiconductor display device such as a liquid crystal display device, a light-emitting device in which a light-emitting element such as an organic EL element is provided in each pixel, an electrophoresis display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), or an FED (Field Emission Display) can be used for the display portion 8002.
Note that the display device includes, in its category, all of information display devices for personal computers, advertisement displays, and the like besides information display devices for TV broadcast reception.
In
Note that although the installation lighting device 8100 provided in the ceiling 8104 is illustrated in
As the light source 8102, an artificial light source that emits light artificially by using electric power can be used. Specifically, an incandescent lamp, a discharge lamp such as a fluorescent lamp, and light-emitting elements such as an LED and/or an organic EL element are given as examples of the artificial light source.
In
Note that although the split-type air conditioner including the indoor unit and the outdoor unit is illustrated in
In
Note that among the electronic devices described above, a high-frequency heating apparatus such as a microwave oven and an electronic device such as an electric rice cooker require high power in a short time. Accordingly, the tripping of a breaker of a commercial power supply in use of the electronic device can be prevented by using the secondary battery of one embodiment of the present invention as an auxiliary power supply for supplying electric power that cannot be supplied enough by a commercial power supply.
In a time period when electronic devices are not used, particularly when the proportion of the amount of electric power that is actually used to the total amount of electric power that can be supplied from a commercial power supply source (such a proportion is referred to as a usage rate of electric power) is low, electric power is stored in the secondary battery, whereby an increase in the usage rate of electric power can be inhibited in a time period other than the above time period. For example, in the case of the electric refrigerator-freezer 8300, electric power is stored in the secondary battery 8304 in night time when the ambient temperature is low and the refrigerator door 8302 and the freezer door 8303 are not opened or closed. Moreover, in daytime when the ambient temperature rises and the refrigerator door 8302 and the freezer door 8303 are opened and closed, the usage rate of electric power in daytime can be kept low by using the secondary battery 8304 as an auxiliary power supply.
According to one embodiment of the present invention, the secondary battery can have excellent cycle performance and improved reliability. Furthermore, according to one embodiment of the present invention, a secondary battery with high capacity can be obtained; thus, the secondary battery itself can be made more compact and lightweight as a result of improved characteristics of the secondary battery. Thus, the secondary battery of one embodiment of the present invention is used in the electronic device described in this embodiment, whereby a more lightweight electronic device with a longer lifetime can be obtained.
This embodiment can be implemented in appropriate combination with any of the other embodiments.
In this embodiment, examples of vehicles each including the secondary battery of one embodiment of the present invention are described.
The use of secondary batteries in vehicles enables production of next-generation clean energy vehicles such as hybrid electric vehicles (HVs), electric vehicles (EVs), and plug-in hybrid electric vehicles (PHVs).
The secondary battery can also supply electric power to a display device included in the automobile 8400, such as a speedometer or a tachometer. Furthermore, the secondary battery can supply electric power to a semiconductor device included in the automobile 8400, such as a navigation system.
An automobile 8500 illustrated in
Although not illustrated, the vehicle may include a power receiving device so that it can be charged by being supplied with electric power from an above-ground power transmitting device in a contactless manner. In the case of the contactless power feeding system, by fitting a power transmitting device in a road or an exterior wall, charging can be performed not only when the vehicle stops but also when moves. In addition, the contactless power feeding system may be utilized to perform transmission and reception of electric power between vehicles. Furthermore, a solar cell may be provided in the exterior of the vehicle to charge the secondary battery when the vehicle stops and/or moves. To supply electric power in such a contactless manner, an electromagnetic induction method and/or a magnetic resonance method can be used.
In the motor scooter 8600 illustrated in
According to one embodiment of the present invention, the secondary battery can have improved cycle performance and the capacity of the secondary battery can be increased. Thus, the secondary battery itself can be made more compact and lightweight. The compact and lightweight secondary battery contributes to a reduction in the weight of a vehicle, and thus increases the mileage. Furthermore, the secondary battery included in the vehicle can be used as a power source for supplying electric power to products other than the vehicle. In such a case, the use of a commercial power supply can be avoided at peak time of electric power demand, for example. Avoiding the use of a commercial power supply at peak time of electric power demand can contribute to energy saving and a reduction in carbon dioxide emissions. Moreover, the secondary battery with excellent cycle performance can be used over a long period; thus, the use amount of rare metals typified by cobalt can be reduced.
This embodiment can be implemented in appropriate combination with the any of other embodiments.
100: positive electrode active material, 200: active material layer, 201: graphene compound, 803: lithium compound, 804: phosphorus compound, 805: solvent, 806: lithium-containing solution, 807: phosphorus-containing solution, 811: mixture, 812: solution P, 813: solution containing transition metal M, 821: mixture, 822: transition metal M source, 823: mixture, 831: mixture
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-149330 | Sep 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2021/057661 | 8/20/2021 | WO |
