Patent Application
20240145691
The present invention relates to a positive electrode active material for lithium-ion battery, and more specifically, to a positive electrode active material for lithium-ion battery with novel chemical composition.
With the development of technology and the increasing demand for mobile devices, the demand for secondary batteries as a source of energy is also increasing rapidly. Among these secondary batteries, commercially available lithium secondary batteries have high energy density and high voltage, long life and low self-charging characteristics, making them widely used.
Lithium-containing cobalt oxide (LiCoO2) is commonly used as the positive electrode active material in lithium secondary batteries. Lithium-containing manganese oxides, such as LiMnO2 with a layered crystal structure and LiMn2O4 with a spinel crystal structure, and lithium-containing nickel oxides (LiNiO2) can also be used. Among the above-mentioned positive electrode active materials, LiCoO2 is the most commonly used due to its superior physical properties (e.g., excellent cycling characteristics). However, LiCoO2 is unstable and is expensive due to the resource limitation of raw material cobalt.
Lithium manganese oxides, such as LiMnO2 and LiMnO4, are alternatively used because manganese is abundant and environmentally friendly as a raw material, therefore making it a candidate for replacing LiCoO2 as a positive electrode active material. However, these lithium-manganese oxides have the disadvantage of low capacitance and poor cycling characteristics.
Lithium-nickel oxides (e.g., LiNiO2) are cheaper than cobalt oxides and have a higher discharge capacitance after charging to a certain state. Therefore, despite the lower average discharge voltage and bulk density, research has been widely devoted to develop high-capacity batteries, so the energy density of commercially available batteries including LiNiO2 as the positive electrode active material has been improved in recently years. In this respect, conventional technologies focus on the properties of LiNiO2-based negative electrode active materials and the improvement of LiNiO2 processes. However, the disadvantages of LiNiO2-based negative electrode active materials are high cost, the volume expansion caused by the gas generated from the cell, low chemical stability, and high pH manufacturing condition. These shortcomings are not yet overcome and unsatisfactory to current demands. In related fields, there are suggestions proposed to coat specific materials (e.g., LiF, Li2SO4, Li3PO4) on the surface of lithium-nickel-manganese-cobalt oxides in an attempt to improve the performance of the cells. In these circumstances, the addition of other elements to the lithium battery though brings some advantages in one hand, but also creates drawbacks in another hand (e.g., complicated process etc.). Manufacturers are committed to developing better lithium battery compositions.
Nevertheless, there is still a need to develop a lithium containing material with satisfactory performance as the positive electrode material for lithium-ion batteries.
The present invention therefore provides a positive electrode active material for lithium-ion battery, which has excellent electrical performance.
According to one embodiment of the present invention, a positive electrode active material for lithium-ion battery is provided. Said positive electrode active material has an average composition expressed by the following formula: Li1.2NixMn0.8-x-yZnyO2, wherein x and y satisfy 0<x≤0.8 and 0<y≤0.1.
According to another embodiment of the present invention, a lithium-ion battery is provided. Said lithium-ion battery comprises an positive electrode active material having an average composition expressed by the following formula: Li1.2NixMn0.8-x-yZnyO2, wherein x and y satisfy 0<x≤0.8 and 0<y≤0.1.
According to another embodiment of the present, a method of manufacturing a positive electrode active material for lithium-ion battery is provided. First, a first solution is provided, wherein the first solution includes a manganese salt solution, a nickel salt solution and a zinc salt solution. Next, a second solution is provided, wherein the second solution includes a chelating agent and a buffer solution. Then, the first solution is titrated into the second solution under a predetermined condition to produce a precipitation reaction, thereby forming a precursor material. Following by adding a lithium-containing compound into the precursor material, a heat process is performed to obtain the positive electrode active material.
By using the positive electrode active material and the lithium-ion battery using said positive electrode active material set forth in the present invention, a superior battery performance can be obtained.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
In order to overcome the aforementioned problems of the conventional art, as well as to avoid using the rare cobalt as the raw material, the present invention relates to a positive electrode active material for a lithium-ion battery, which can be represented by the following formula (I):
Li1.2NixMn0.8-x-yZnyO2 (I)
wherein the range of x is 0<x≤0.8 and the range of y is 0<y≤0.1. In one embodiment of the present invention, the range of x is 0.1≤x≤0.2, and the range of y is 0<y≤0.02. In one preferred embodiment of the present invention, the range of x is 0.2≤x≤0.3, and the range of y is 0<y≤0.02.
The present invention further provides a method of manufacturing a positive electrode active material for lithium-ion battery. First, a first solution is provided. The first solution includes a manganese salt solution (e.g., manganese acetate, manganese nitrate, or manganese sulfate, and is not limited thereto), a nickel salt solution (e.g., nickel acetate, nickel nitrate, or nickel sulfate, and is not limited thereto) and a zinc salt solution (e.g., zinc acetate, zinc nitrate, or zinc sulfate, and is not limited thereto). Next, a second solution is provided. The second solution includes a chelating agent (e.g., urea, acetylacetonate nickel, ethylenediamine, 2,2′-bipyridine, 1,10-phthalodiazepine, oxalic acid, 1,2-di(dimethylarsenyl) benzene or ethylenediaminetetraacetic acid, and is not limited thereto) and a buffer solution (e.g., sodium carbonate, sodium acetate, sodium hydroxide or sodium bicarbonate, and is not limited thereto). Then, the first solution is titrated into the second solution under a predetermined condition to produce a precipitation reaction, thereby forming a precursor material. In one embodiment, the predetermined condition refers to: titrating the first solution and the second solution into one container/beaker for the precipitation reaction, in which the first solution is titrated at a rate of, for example, 50 ml per minute, and the second solution is titrated at a controlled rate to maintain a pH range of 7 to 8, with a temperature maintained at 70° C. and stirring speed is approximately 1000 rpm for 24 hours to completely conduct the precipitation reaction. The precipitated solution is then washed by centrifugation to remove redundant ions to obtain a salt precipitate (namely, the precursor material). The precursor material is baked until being completely dry. Next, a lithium-containing compound (e.g., lithium carbonate, lithium acetate, or lithium hydroxide, but not limited to) is added to the material precursor according to predetermined chemical proportions. Lastly, after a heat treatment, e.g., at 800° C. to 950° C. for at least 10 hours (e.g., 12 hours), the positive electrode active material for a lithium electronic battery is obtained.
According to the above embodiment, the present invention further provides a lithium-ion battery having a positive electrode including the above-mentioned positive electrode active material. The lithium-ion battery (also referred to as “secondary battery”) according to the present embodiment includes a positive electrode containing the positive electrode active material described above, a negative electrode, and a non-aqueous electrolyte. The secondary battery may be any secondary battery which is charged and discharged by desorption and insertion of lithium ions and may be, for example, a non-aqueous electrolyte solution secondary battery or an all-solid-state lithium secondary battery. Note that, the embodiments described below are merely examples, and the lithium-ion secondary battery can be implemented in various modified and improved forms based on the knowledge of those skilled in the art including the following embodiments. Furthermore, the use of the secondary battery is not particularly limited.
Referring to the positive electrode, it can be prepared by using the positive electrode active material according to one embodiment of the present invention described above. An example of a method for producing the positive electrode will be described below. First, the above positive electrode active material (powder shape), a conductive material, and a binder are mixed, activated carbon and a solvent for viscosity adjustment or the like are further added as necessary, and the resulting mixture is kneaded to prepare a positive electrode mixture paste. The mixing ratio of the respective materials in the positive electrode mixture is a factor that determines the performance of the lithium-ion battery and thus can be adjusted according to the use. The mixing ratio of the materials can be similar to that of the positive electrode of any known lithium-ion battery, and for example, when the entire mass of the solids in the positive electrode mixture excluding the solvent is 100% by mass, the positive electrode active material can be contained at 60% to 95% by mass, the conductive material can be contained at 1% to 20% by mass, and the binder can be contained at 1% to 20% by mass. The obtained positive electrode mixture paste is applied to, for example, a surface of an aluminum foil current collector and dried to scatter the solvent, and a sheet-like positive electrode is thereby prepared. Pressurization may be performed by roll press or the like in order to increase an electrode density as necessary. The sheet-like positive electrode thus obtained can be cut into a proper size according to an intended battery and used in preparation of a battery. However, a method for preparing the positive electrode is not limited to the above-exemplified method, and other methods may be used. As the conductive material, for example, graphite (natural graphite, artificial graphite, expanded graphite, and the like), and a carbon black-based material such as acetylene black or ketjen black can be used. The binder plays a role of connecting active material particles together, and for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluororubber, ethylene propylene diene rubber, styrene butadiene, a cellulose-based resin, polyacrylic acid, and the like can be used. A solvent which disperses the positive electrode active material, the conductive material, and the activated carbon and dissolves the binding agent is added to the positive electrode mixture as necessary. As the solvent, specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used. Furthermore, the activated carbon can be added to the positive electrode mixture in order to increase electric double layer capacity. The method of making the positive electrode is not limited to the method illustrated above, thus other methods may be used as well. For example, the positive electrode mixture can be pressure formed and then manufactured by drying under vacuum.
As the negative electrode, metal lithium, a lithium alloy, and the like can be used. Furthermore, as the negative electrode, a negative electrode may be used which is formed by mixing a binding agent with a negative electrode active material which can insert and de-insert lithium ions, adding a proper solvent thereto to form a paste-like negative electrode mixture, applying the paste-like negative electrode mixture to the surface of a metal foil current collector such as copper, drying the negative electrode mixture, and compressing the negative electrode mixture in order to increase the electrode density as necessary. Examples of the negative electrode active material include natural graphite, artificial graphite, a fired organic compound such as a phenol resin, and a powdery carbon material such as coke. In this case, as a negative electrode binding agent, a fluorine-containing resin such as PVDF can be used as in the positive electrode, and as a solvent for dispersing the active material and the binding agent, an organic solvent such as N-methyl-2-pyrrolidone can be used.
Referring to the separator, it is configured by being interposed between the positive electrode and the negative electrode. The separator separates the positive electrode and the negative electrode from each other and retains the electrolyte. A conventional separator can be used, and for example, a thin film such as polyethylene or polypropylene having a large number of minute pores can be used.
As to the non-aqueous electrolyte, for example, a non-aqueous electrolyte solution can be used. The non-aqueous electrolyte solution is obtained by dissolving a lithium salt as a supporting salt in an organic solvent. Furthermore, as the non-aqueous electrolyte solution, a solution obtained by dissolving a lithium salt in an ionic liquid may be used. It is noted that, the ionic liquid refers to a salt including a cation other than a lithium ion and an anion, and being in a liquid state even at room temperature. As the organic solvent, one selected from the group consisting of cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate, further, ether compounds such as tetrahydrofuran, 2-methyltetrahydrofuran, and dimethoxyethane, sulfur compounds such as ethyl methyl sulfone and butane sultone, and phosphorus compounds such as triethyl phosphate and trioctyl phosphate can be used singly, or two or more of these can be used in mixture.
As the supporting salt, LiPF6, LiBF4, LiClO4, LiAsF6, LiN(CF3SO2)2, a composite salt thereof, and the like can be used. Further, the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like. Furthermore, as the non-aqueous electrolyte, a solid electrolyte may be used. The solid electrolyte has a property capable of withstanding a high voltage. Examples of the solid electrolyte include an inorganic solid electrolyte and an organic solid electrolyte. Examples of the inorganic solid electrolyte include an oxide-based solid electrolyte and a sulfide solid electrolyte. The oxide-based solid electrolyte is not particularly limited, and for example, one that contains oxygen (O) and exhibits lithium ion conductivity and electron insulating property can be suitably used. As the oxide-based solid electrolyte, for example, one or more selected from the group consisting of lithium phosphate (Li3PO4), Li3PO4Nx, LiBO2Nx, LiNbO3, LiTaO3, Li2SiO3, Li4SiO4-Li3PO4, Li4SiO4-Li3VO4, Li2O—B2O3—P2O5, Li2O—SiO2, Li2O—B2O3—ZnO, Li1+XAlXTi2-X(PO4)3(0≤X≤1), Li1+XAlXGe2-X(PO4)3 (0≤X≤1), LiTi2(PO4)3, Li3XLa2/3-XTiO3 (0≤X≤2/3), Li5La3Ta2O12, Li7La3Zr2O12, Li6BaLa2Ta2O12, and Li3.6Si0.6P0.4O4 can be used. The sulfide solid electrolyte is not particularly limited, and for example, one that contains sulfur (S) and exhibits lithium-ion conductivity and electron insulating property can be suitably used. As the sulfide solid electrolyte, for example, one or more selected from the group consisting of Li2S—P2S5, Li2S—SiS2, LiI—Li2S—SiS2, LiI—Li2S—P2S5, LiI—Li2S—B2S3, Li3PO4-Li2S—Si2S, Li3PO4-Li2S—SiS2, LiPO4-Li2S—SiS, LiI—Li2S—P2O5, and LiI—Li3PO4—P2S5 can be used. Note that, as the inorganic solid electrolyte, an inorganic solid electrolyte other than those described above may be used, and for example, Li3N, LiI, Li3N—LiI—LiOH, and the like may be used. The organic solid electrolyte is not particularly limited as long as it is a polymer compound exhibiting ionic conductivity, and for example, polyethylene oxide, polypropylene oxide, and copolymers of these can be used. Furthermore, the organic solid electrolyte may contain a supporting salt (lithium salt).
The shape of the secondary battery is not particularly limited, and the secondary battery can be formed into various shapes such as a cylindrical shape and a stacked shape. For example, when the secondary battery is a non-aqueous electrolyte solution secondary battery, a positive electrode and a negative electrode are stacked with a separator interposed therebetween to form an electrode body, the obtained electrode body is impregnated with a non-aqueous electrolyte solution, a positive electrode collector is connected to a positive electrode terminal communicating with the outside using a current collecting lead or the like, a negative electrode collector is connected to a negative electrode terminal communicating with the outside using a current collecting lead or the like, and the resulting product is sealed in a battery case to complete the secondary battery. Note that, the secondary battery according to the present embodiment is not limited to a form in which a non-aqueous electrolyte solution is used as a non-aqueous electrolyte but can be formed into, for example, a secondary battery using a solid non-aqueous electrolyte, that is, an all-solid-state battery. When the secondary battery according to the present embodiment is formed into the all-solid-state battery, the components other than the positive electrode active material can be changed as necessary.
The secondary battery according to the present embodiment can be used in any fields, due to its realized high thermal stability and low cost. In particular, the secondary battery is suitable for a power source of a small portable electronic device (such as a notebook personal computer or a mobile phone terminal) that is required to have a high capacity all the time. Also, the secondary battery is suitably used as a power source for electric cars that are restricted in a mounting space since microminiaturization and capacity enlargement thereof are possible. Note that, the secondary battery can be used not only as a power source for an electric car driven purely by electric energy but also as a power source for a so-called hybrid car used together with a combustion engine such as a gasoline engine or a diesel engine.
Please refer to Table 1 and Table, which show the compositions of the positive electrode active material of lithium-ion battery according to each embodiment of the present invention. As shown in Table 1, Comparative Embodiment 1 and Comparative Embodiment 2 show the positive electrode active material without Zn doping, Embodiment 1 and Embodiment 2 are positive electrode active material doped with increased Zn, Embodiment 3 and Embodiment 4 are positive electrode active material doped with increased Zn. Furthermore, Embodiment 1 and Embodiment 2 exhibit lower Ni/Mn ratio and Embodiment 3 and Embodiment 4 exhibit higher Ni/Mn ratio.
Referring to the manufacturing method, Comparative Embodiment 1 and Comparative Embodiment 2 are formed by a precipitation method (“co-precipitation”). First, two solutions are prepared according to the composition in Comparative Embodiment 1 and 2, respectively. One solution contains a manganese salt (such as manganese acetate, manganese nitrate, or manganese sulfate) and a nickel salt (such as nickel acetate, nickel nitrate, or nickel sulfate), and the other solution contains urea and sodium carbonate (both with a concentration of 1M). The two solutions are titrated into another beaker to conduct the co-precipitation interaction under a condition where the metal salt solution (manganese salt and nickel salt) is titrated in a speed of 50 ml/min, the other solution (urea and sodium carbonate) is titrated with a pH between 7˜8, and the titration temperature is maintained at approximate 70° C. and the stirring speed is about 1000 rpm for 24 hours to completely conduct the precipitation interaction. Next, the precipitation is washed by centrifugation to remove redundant ions to obtain a salt precipitate (the precursor material). The precursor material is baked until being completely dried. Subsequently, lithium carbonate is added to the material precursor according to the predetermined proportions and is mixed properly. Lastly, after a 800° C.-950° C. heat treatment for 12 hours, the powders of positive electrode active material of Comparative Embodiment 1 and Comparative Embodiment 2 can therefore be obtained.
Likewise, Embodiment 1, Embodiment 2, Embodiment 3 and Embodiment 4 are formed by the co-precipitation method. First, two solutions are prepared according to the composition in Embodiment 1, Embodiment 2, Embodiment 3 and Embodiment 4, respectively. One solution contains a manganese salt (such as manganese acetate, manganese nitrate, or manganese sulfate), a nickel salt (such as nickel acetate, nickel nitrate, or nickel sulfate) and a zinc salt (such as zinc acetate, zinc nitrate, or zinc sulfate), and the other solution contains urea and sodium carbonate (both with a concentration of 1M). The two solutions are titrated into another beaker to conduct the co-precipitation interaction under a condition where the metal salt solution (manganese salt, nickel salt and zinc salt) is titrated in a speed of 50 ml/min, the other solution (urea and sodium carbonate) is titrated with a pH between 7˜8, and the titration temperature is maintained at approximate 70° C. and the stirring speed is about 1000 rpm for 24 hours to completely conduct the precipitation interaction. Next, the precipitation is washed by centrifugation to remove redundant ions to obtain a salt precipitate (the precursor material). The precursor material is baked until completely dried. Subsequently, lithium carbonate is added to the material precursor according to the predetermined proportions and is mixed properly. Lastly, after a 800° C.-950° C. heat treatment for 12 hours, the powders of positive electrode active material in Embodiment 1, Embodiment 2, Embodiment 3 and Embodiment 4 can therefore be obtained respectively.
Please refer to
Please refer to
Electricity of the Material
For the electricity performance of the positive electrode active material according to the above-motioned Comparative Embodiment 1, Embodiment 1 and Embodiment 2 (that is, the “low Ni/Mn ratio” group), please refer to
Please refer to
In comparison, for the electricity performance of the positive electrode active material according to the Comparative Embodiment 2, Embodiment 3 and Embodiment 4 (that is, the “high Ni/Mn ratio” group), please refer to
Please refer to
As demonstrated by the above FIGS. and Tables, the present invention provides a novel positive electrode active material for lithium-ion battery, which is expressed by the following formula (I):
Li1.2NixMn0.8-x-yZnyO2 (I)
wherein x and y satisfy 0<x≤0.8 and 0<y≤0.1. According to the above-mention embodiments, as a positive electrode active material, in either the “low Ni/Mn ratio” group (Embodiment 1 and Embodiment 2, in which in formula (I) x and y satisfy 0.1≤x≤0.2 and 0<y≤0.02) or the “high Ni/Mn ratio” group (Embodiment 3 and Embodiment 4, in which in formula (I), x and y satisfy 0.2≤x≤0.3 and 0<y≤0.02), it can exhibit superior discharge capacity and energy density, whether in the 1st cycle or in even up to the 50th cycle. It is noted that in the “low Ni/Mn ratio” group, comparing to embodiment without doping zinc, the active material with doped zinc can dramatically increase the discharge capacity and the energy density, where the upgrade level is superior to the “high Ni/Mn ratio” group, indicating that the addition of zinc ion in positive electrode active material can help to stabilize the structure, especially in low Ni/Mn ratio.
In summary, the present invention provides a novel positive electrode active material for lithium-ion battery, which is feature by incorporating zinc ion. By using the manufacturing method for the positive electrode active material, a uniform and stable laminar structure can be produced. a superior battery performance can be obtained, which has been experimentally proven to have good electrical performance and is suitable for application in various electronic products.
| Number | Date | Country | Kind |
|---|---|---|---|
| 111141275 | Oct 2022 | TW | national |
