Patent Application
20250233150
The present invention relates generally to graphite particles and, in particular, to a graphite pulverulent body which is aggregate of graphite particles suited for use as an electrode material.
In the declaration of “Carbon Neutrality by 2050” announced by the Japanese government in 2020, realization of a decarbonized society by 2050 and net zero emissions of greenhouse effect gas are their goals. It is difficult to achieve these goals only by reduction of carbon dioxide, which forces suppression in economic activity, and technology which promotes the economic activity by recycling of the carbon dioxide and effective utilization thereof is required.
As a method for recycling the carbon dioxide, a method in which the carbon dioxide is converted into a carbonate to be utilized in cement and the like and a method in which the carbon dioxide is utilized as a raw material of polycarbonate as well as also technology which immobilizes carbon from the carbon dioxide have been attracting attention. The immobilized carbon is utilized as a raw material of graphite particles and the like.
As to the immobilization of the carbon dioxide, for example, in Japanese Patent Application Laid-Open Publication No. 2010-53425 (Patent Literature 1), an immobilization method of the carbon in the carbon dioxide by an electrochemical process using molten salt is described. In this method, a cathode and an anode are arranged in an electrolytic bath made of molten salt containing carbonate ions, the carbon dioxide is injected into the electrolytic bath and also a voltage by which the carbonate ions are reduced is applied between the cathode and the anode to pass electric current therebetween, and the carbon dioxide is decomposed and is immobilized on a surface of the cathode as the carbon.
On the other hand, as to manufacturing of the graphite particles, described in Japanese Patent Application Laid-Open Publication No. 2014-103095 (Patent Literature 2) is a method in which carbon powder as a raw material and a carbon precursor binder are melt-mixed; thereafter, a pressurized compact is prepared; the pressurized compact is changed into a graphitized compact by heat treatment; thereafter, the graphitized compact is pulverized; and graphite powder is thereby manufactured from the carbon powder.
However, in the immobilization method of the carbon dioxide described in Patent Literature 1, a method in which functionality is imparted to the carbon immobilized on the surface of the cathode is not described, and for example, the immobilization method is not a method for manufacturing a carbon material which can be utilized as an electrode material of a battery.
In addition, in the method for manufacturing graphite particles described in Patent Literature 2, the generated graphite powder receives influence of components of the carbon precursor binder.
Therefore, an object of the present invention is to provide graphite particles, in which carbon dioxide can be used as a raw material and the graphite particles can be used as an electrode material.
The present inventors have devoted themselves to earnest research. As a result, the present inventors have found out that by locating a cathode in the vicinity of a surface of an electrolytic bath which includes molten salt containing carbonate ions, locating an anode in the electrolytic bath, and generating electric discharge between the cathode and the anode and reducing the carbonate ions, carbon particles can be generated in the molten salt and by subjecting the carbon particles to heat treatment, graphite particles which can be used as an electrode material can be obtained. Since the carbonate ions in the molten salt can be generated by injecting the carbon dioxide into the molten salt, the graphite particles can be manufactured with the carbon dioxide as a raw material. In addition, since upon subjecting the carbon particles obtained by this method to the heat treatment, it is not required to melt and mix a binder, the obtained graphite particles do not receive any influence of the binder.
Graphite particles according to the present invention obtained on the basis of the above-described findings is constituted as follows.
As to graphite particles according to the present invention, an interplanar spacing d 002 based on a diffraction peak corresponding to a lattice plane (002) being measured by a powder X-ray diffraction method is 0.3355 nm or more and 0.3370 nm or less, a primary particle diameter is 50 nm or more and 500 nm or less, a value of 50% of an integrated value in number base particle diameter distribution (a mean particle diameter) is a secondary particle diameter (d50), the secondary particle diameter (d50) is 0.15 μm or more and 1.6 μm or less, and a specific surface area (BET) being calculated from a nitrogen-adsorption amount at 77 K is 10 m2/g or more and 400 m2/g or less.
Thus, the carbon dioxide can be used as a raw material and the graphite particles which can be used as an electrode material can be provided.
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that in the present description, unless otherwise specified, a “primary particle diameter” means an arithmetic mean particle diameter obtained by visual measurement using an electron microscope (SEM), a “secondary particle diameter (d50)” means that an integrated value in number base particle diameter distribution is a value of 50%, and a “specific surface area” is a BET specific surface area calculated from a nitrogen-adsorption amount at 77 K.
As to graphite particles according to the present invention, an interplanar spacing d002 based on a diffraction peak corresponding to a lattice plane (002) measured by employing a powder X-ray diffraction method is 0.3355 nm or more and 0.3370 nm or less, a primary particle diameter is 50 nm or more and 500 nm or less, a secondary particle diameter (d50) is 0.15 μm or more and 1.6 μm or less, and a specific surface area (BET) is 10 m2/g or more and 400 m2/g or less.
The graphite particles according to the present invention are, as described later, manufactured by manufacturing carbon particles with carbon dioxide as a raw material and subjecting the obtained carbon particles to heat treatment. Hereinafter, first, a method in which the carbon particles are manufactured with the carbon dioxide as the raw material will be described.
<A Principle of a Method for Manufacturing Carbon Particles with Carbon Dioxide as a Raw Material>
As shown in
When the carbon dioxide is externally supplied to the molten salt in which the oxide ions (O2−) are contained, carbonate ions (CO32−) are generated according to a formula (1) and the carbon dioxide is absorbed into the molten salt.
In molten salt: CO2 (externally supplied)+O2−→CO32− (1)
When this CO32− is reduced by discharge electrolysis at the cathode, minute carbon particles 40 are generated in the electrolytic bath according to a formula (2).
Cathode reaction: CO32−+4e−→C (minute particles)+3O2− (2)
In a case where the anode is an oxygen-generating anode, a part of O2− generated at the cathode is oxidized according to a formula (3), thereby generating oxygen gas.
Anode reaction: 2O2−→O2+4e− (3)
On the other hand, in a case where as the anode, a carbon electrode is used, carbon monoxide or carbon dioxide is generated as shown below.
Anode reaction: C+O2−→CO+2e− or C+2O2−→CO2+4e− (4)
Since O2− which has not been oxidized at the anode and has remained is utilized for CO2 absorption reaction in the formula (1), as the entire reaction, carbon minute particles and oxygen are obtained by electrolysis of the carbon dioxide as shown in the following formula.
CO2 (externally supplied)→C (minute particles)+O2 (5)
As the molten salt, an alkali metal halide, an alkali earth metal halide, an alkali metal carbonate, and an alkali earth metal carbonate can be used.
As the alkali metal halide, a compound of LiF, NaF, KF, RbF, CsF, LiCl, NaCl, KCl, RbCl, CsCl, LiBr, NaBr, KBr, RbBr, CsBr, LiI, NaI, KI, RbI, CsI, or the like can be used.
As the alkali earth metal halide, a compound of MgF2, CaF2, SrF2, BaF2, MgCl2, CaCl2), SrCl2, BaCl2, MgBr2, CaBr2, SrBr2, BaBr2, MgI2, Cal2, SrI2, BaI2 or the like can be used.
As the alkali metal carbonate, a carbonate of Li2CO3, Na2CO3, K2CO3, or the like can be used.
As the alkali earth metal carbonate, a carbonate of MgCO3, CaCO3, BaCO3, or the like can be used.
The oxide ion (O2−) source is previously supplied in the electrolytic bath. As the oxide ion (O2−) source, an alkali metal oxide and an alkali earth metal oxide can be used. As the alkali metal oxide, an oxide of Li2O, Na2O, K2O, or the like can be used. As the alkali earth metal oxide, an oxide of MgO, CaO, BaO, or the like can be used.
A treatment temperature (a bath temperature of an electrolytic cell) is not particularly limited. However, because in a high temperature range exceeding 900° C., thermal decomposition of the carbonate itself becomes noticeable, a material of the electrolytic cell which can be used is limited, and handling is difficult, a treatment temperature of 250° C. or more and 800° C. or less is preferable.
In the method for manufacturing graphite particles according to the present invention, as shown in
In addition, the electrode is not immersed in the electrolytic bath, whereby impurities derived from a cathode base material are hardly mixed into the electrolytic bath. Furthermore, because all formed carbon particles are present in the electrolytic bath, collection of the carbon particles is facilitated.
As a material of the cathode, kinds of metal such as iron, nickel, molybdenum, tantalum, and tungsten; alloys thereof; a carbon material such as glass-like carbon and a conductive diamond; conductive ceramics; semiconductive ceramics, or the like can be used. In addition, a cathode obtained by forming each of these on a different kind of a material can also be used as the cathode.
As a material of the anode, an electrode material which can oxidize O2− generated by the reduction reaction of the carbonate ions (CO32−) shown in the formula (2) is used. As one example, carbon or an inert anode is mainly used.
As the inert anode, an insoluble electrode whose base body surface formed of metal such as Ti is coated with RuO2, IrO2, RhO2, or Ta2O5; a conductive ceramics electrode formed of nickel ferrite represented by NiXFe3-XO4 (X=0.1 to 2.0) or of a nickel cobalt oxide represented by a composition formula: NiXCo1-XO (X=0.1 to 0.5 or a formula: NiXCo3-XO4 (X=0.3 to 1.5); a conductive diamond electrode; or the like can be used.
The carbon particles formed in the above-described electrolytic bath are present in the following two states in the molten salt. One is a state in which the carbon particles are dispersed in the bath of the molten salt and become muddy (hereinafter, referred to as “muddy carbon”) (
In a step of collecting the carbon particles, an electrolytic bath containing the muddy carbon and an electrolytic bath containing the aggregated carbon are separated, are carried out of the electrolytic cell, and are made into solidified salt at a room temperature. The solidified salt of each of the electrolytic baths is individually dissolved in water or warm water whose temperature is 50° C. or less and while ultrasonic is applied thereto, carbon particles are suspended in an aqueous solution. The obtained suspension is filtered by a membrane filter and carbon particles deposited on the filter are dried, thereby obtaining a carbon pulverulent body.
As shapes of the carbon particles finally obtained in the above-described collecting step, in addition to a spherical shape, there are a sheet shape, a ribbon shape, and a cube shape. It is considered that the carbon particles having the various shapes as mentioned above can be obtained because the reduction of the carbonate ions is utilized to generate the carbon particles. Note that the carbon particles may be manufactured by employing other method and the carbon particles may be constituted of particles each having a single shape.
Since a temperature of the electrolytic bath immediately beneath the electric discharge is approximately 3000° C., formation of the carbon particles and the heat treatment concurrently proceed, and as shown in
The carbon particles obtained as described above are subjected to the heat treatment, thereby graphitizing the carbon particles. It is preferable that a heat treatment temperature is 2800° C. or more. Since it is not required to add a carbon precursor binder to the carbon particles, any influence of binder components is not received.
<Characteristics of Generated Graphite Particles (after Heat Treatment)>
An interplanar spacing d 002 of the graphite particles according to the present invention based on a diffraction peak corresponding to a lattice plane (002), which is measured by a powder X-ray diffraction method, is 0.3355 nm or more and 0.3370 nm or less. A primary particle diameter of the graphite particles is 50 nm or more and 500 nm or less, an integrated value in number base particle diameter distribution of the graphite particles which is a value (a mean particle diameter) of 50% is defined as a secondary particle diameter (d50), and the secondary particle diameter (d50) is 0.15 μm or more and 1.6 μm or less. A specific surface area (BET) of the graphite particles, which is calculated from a nitrogen-adsorption amount at 77 K is 10 m2/g or more and 400 m2/g or less and preferably, 50 m2/g or more and 70 m2/g or less.
The graphite pulverulent body which is aggregate of the graphite particles includes variously shaped graphite particles. Representative shapes of the carbon particles included in the carbon pulverulent body before the heat treatment are a sheet shape, a ribbon shape, and a cube shape. Also in the graphite particles obtained by subjecting the carbon particles including variously shaped carbon particles to the heat treatment, variously shaped graphite particles are included. It is preferable that the graphite particles include graphite particles each having a sheet shape, a ribbon shape, and a cube shape. The graphite particles may be constituted of graphite particles each having a single shape.
A graphite pulverulent body which is aggregate of graphite particles according to the present invention functions as an electrode material of a nonaqueous secondary battery.
In the present disclosure, a nonaqueous secondary battery is a device, an element, or the like which has at least a positive electrode, a negative electrode, and a nonaqueous electrolyte, takes out, in a form of electric power, chemically stored energy by carriers, and can be recharged. The carriers are ions which assume electric conduction and for example, lithium ions, sodium ions, potassium ions, magnesium ions, calcium ions, aluminum ions, fluoride ions, chloride ions, iodide ions, and the like are cited. In other words, the nonaqueous secondary battery is a collectively called battery system as a lithium-ion battery, a sodium-ion battery, a potassium-ion battery, a magnesium-ion battery, a calcium-ion battery, an aluminum-ion battery, a fluoride-ion battery, a chloride-ion battery, an iodide-ion battery, the later-described dual-ion battery, and the like.
In addition, an electrode material refers to an active material which can reversibly insert and desorb anions or cations. In other words, in a case where the present electrode material inserts and desorbs the anions, the electrode material functions as a positive electrode and in case where the present electrode material inserts and desorbs the cations, the electrode material functions as a negative electrode.
The anions in the present disclosure refer to, for example, a negatively charged atom group such as PF6−, BF4−, ClO4−, TiF4−, VF5−, AsF6−, SbF6−, CF3SO2−, (CF3SO2)2N−, B(C2O4)2−, B10Cl10−, B12Cl12−, CF3COO−, S2O42−, NO3−, SO42−, PF3(C2F5)3−, (FSO2)2N−, CF3SO3−, and FeCl4−. It is preferable that an atom group of these anions is an atom group which includes halogen such as F, Cl, Br, and I and among these, from a point of view that a battery voltage is high, it is preferable that the atom group thereof is an atom group which includes F.
Note that in the present description, in a case where in the electrode of the present invention is used as the positive electrode and in a battery system which is charged when this positive electrode inserts the anions and is discharged when the anions are desorbed, and the group of the anions is the atom group which includes F, irrespective of a counter-electrode, the battery system is referred to as a fluoride-ion battery. Similarly, in a case where the group of the anions is the atom group which includes Cl, the battery system is referred to as a chloride-ion battery; in a case where the group of the anions is the atom group which includes Br, the battery system is referred to as a bromide-ion battery; and in a case where the group of the anions is the atom group which includes I, the battery system is referred to as an iodide-ion battery.
It is preferable that as to the anions used for the battery, an ion radius is within a range of 0.23 nm or more and 0.29 nm or less. This is because if the ion radius is less than 0.23 nm, anions which are inserted by the carbon material are hardly desorbed and if the ion radius exceeds 0.29 nm, the carbon material hardly inserts the anions. In addition, it is preferable that as to the anions, a van der Waals volume is within a range of 0.04 nm3 or more and 0.10 nm3 or less. This is because if the van der Waals volume thereof is less than 0.04 nm3, the anions which are inserted by the carbon material are hardly desorbed and if the van der Waals volume thereof exceeds 0.10 nm3, the carbon material hardly inserts the anions. For example, PF6−, BF4−, AsF6−, SbF6−, or CF3SO3− is preferable and from a point of view of a cycle life and a discharge capacity, PF6− is preferable.
The cations in the present disclosure refer to, for example, positively charged ions such as Li+, Na+, K+, Mg2+, Ca2+, and Al3+. Because the graphite of the present invention exhibits excellent input-output characteristics and a high electric capacity, as compared with the conventional graphite, it is preferable that the ions are alkali metal ions such as Na+ or K+.
Although general graphite can insert and desorb Li+ or K+, the general graphite cannot insert and desorb ions of Na+, Mg2+, Ca2+, Al3+, and the like in a large amount.
However, the graphite of the present invention can insert and desorb ions of Li+, Na+, K+, Mg2+, Ca2+, Al3+ and the like in a large amount, as compared with the conventional graphite.
In addition, because a specific surface area is large, an electrode for the nonaqueous secondary battery which can exhibit excellent input-output characteristics can be made.
Note that in the present description, in a case where the electrode of the present invention is used as the negative electrode and in a battery system which is charged when the negative electrode inserts the cations and is discharged when the cations are desorbed, in a case where the cations are Li+, irrespective of a counter-electrode, the battery system is referred to as a lithium-ion battery. Similarly, in a case where the cations are Na+, the battery system is referred to as a sodium-ion battery; in a case where the cations are K+, the battery system is referred to as a potassium-ion battery; in a case where the cations are Mg2+, the battery system is referred to as a magnesium-ion battery; in a case where the cations are Ca2+, the battery system is referred to as a calcium-ion battery; and in a case where the cations are Al3+, the battery system is referred to as an aluminum-ion battery.
Note that a battery in which the electrode of the present invention is used as the positive electrode and the negative electrode, the positive electrode inserts and desorbs the anions and the negative electrode inserts and desorbs the cations, thereby allowing the battery to be charged and discharged, is referred to as a dual-ion battery. This battery system has a characteristic that a salt concentration in the nonaqueous electrolyte decreases.
In other words, a material of a secondary battery which uses both of cations and anions in an electrolytic bath as carriers involved in oxidation and reduction reaction (Toshihiro Nakabo: NISSIN ELECTRIC Co., Ltd. Technical Report, Vol. 57(2) 28-31 (2012)), for example, a carbon-based material is known as an active material which can reversibly insert and desorb Li+ which are cations and in addition thereto, PF6− which are anions (Japanese Patent Application Laid-Open Publication No. 2013-054987).
The above-described graphite pulverulent body is formed on a current collector in a deposited manner, whereby any electrode for the nonaqueous secondary battery, of the positive electrode, the negative electrode, and the later-described bipolar electrode which are related to the present invention can be obtained.
Forming in the deposited manner is fixing with the current collector in contact with the electrode material of the present invention. Specifically, filling of the electrode material, fixing the electrode material by a metal net which is the current collector, or the like corresponds to forming in the deposited manner. A method for forming in the deposited manner is not particularly limited, and for example, a pressure bonding, a slurry method (a paste method), an electrophoresis method, a dipping method, a spin-coat method, an aerosol deposition method, and the like are cited.
Since in the electrode for the nonaqueous secondary battery according to the present invention, the present carbon material itself has a conductive property, in order to further enhance the conductive property, a conductive assistant may be contained as needed though the conductive assistant is not essential. A kind of the conductive assistant is not particularly limited, and for example, a carbon-based conductive assistant such as acetylene black, furnace black, vapor-phase grown carbon fiber, carbon nanotube, graphene, and carbon nanohorn can be adopted.
The electrode for the nonaqueous secondary battery according to the present invention may include a binder. A kind of the binder is not particularly limited, and for example, a binder often used in general such as polyvinylidene fluoride (PVDF), carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), acrylic resin, and polyimide can be adopted.
Besides the above-mentioned materials, the electrode for the nonaqueous secondary battery according to the present invention may include an active material which can reversibly insert and desorb the anions or the cations. For example, Li, Na, K, Mg, Ca, Al, graphite, non-crystalline carbon, Si, SiO, Sn, SnO, SnO2, Li4Ti5O12, V2O5, S8, a sulfur compound, LiFePO4, LiMnPO4, LiCoPO4, Li2FeSiO4, Li2Mn2SiO4, Li3Fe2SiPO4, Li3Mn2SiPO4, LiV2O5, Li3V2(PO4)3, LiCoO2, LiNiO2, LiFeO2, LiCrO2, LiMnO2, LiMn2O4, LiNi0.5Mn0.5O2, LiCo1/3Ni1/3Mn1/3O2, NaFePO4, NaMnPO4, NaCoPO4, Na2FeSiO4, Na2Mn2SiO4, Na3Fe2SiPO4, Na3Mn2SiPO4, NaV2O5, Na3V2(PO4)3, NaCoO2, NaNiO2, NaFeO2, NaCrO2, NaMnO2, NaMn2O4, NaNi0.5Mn0.5O2 and NaCo1/3Ni1/3Mn1/3O2, KFePO4, KMnPO4, KCoPO4, K2FeSiO4, K2Mn2SiO4, K3Fe2SiPO4, K3Mn2SiPO4, KV2O5, K3V2(PO4)3, KCoO2, KNiO2, KFeO2, KCrO2, KMnO2, KMn2O4, KNi0.5Mn0.5O2, KCo1/3Ni1/3Mn1/3O2, CaV2O5, CaV4O9, CaV3O7, MaV2O5, MgV4O9, MgV3O7, AlV2O5, AlMoO3, AlWO3, AlCl2O3, AlFe2O5, AlNi2O3, AlCuO, AlSiO2, AlZnO, and the like are cited.
As the current collector used for the electrode for the nonaqueous secondary battery of the present invention, in a case where the electrode is used as a negative electrode of a lithium-ion battery, Cu, Ni, stainless steel, carbon, or the like can be used.
In a case where the electrode is used as a negative electrode of a sodium-ion battery or a potassium-ion battery, Cu, Ni, Al, Cr, Ti, Co, W, WC, stainless steel, carbon, or the like can be used.
In a case where the electrode is used as a positive electrode of any of a fluoride-ion battery, a chloride-ion battery, a bromide-ion battery, and an iodide-ion battery, Al, Cr, Ti, Co, W, WC, stainless steel, carbon, or the like can be used.
In the dual-ion battery, as the above-described positive electrode and negative electrode, respective current collectors can be used.
Although a shape of the current collector is not particularly limited, for example, a foil shape, a platy shape, a mesh shape, a woven cloth shape, an unwoven cloth shape, a foam shape, an expand shape, a punching metal shape, and the like are cited.
However, in a case where the current collector is used for a bipolar electrode, a shape having no through-hole (for example, the foil shape or the platy shape) is preferable.
In a battery system in which as cations, Na+ or K+ is selected, Al can be used for current collectors of a positive electrode and a negative electrode in common. The Al is metal which is lightweight, is excellent in conductivity, and is inexpensive. By forming a current collector constituted of one piece of Al foil and by providing a positive electrode layer and a negative electrode layer on front and back sides of this current collector, a bipolar electrode can be obtained.
As a method for manufacturing the electrode for the nonaqueous secondary battery, according to the present invention, cited is a method in which the electrode material for the nonaqueous secondary battery, of the present invention, a binder, and a conductive assistant added as needed are mixed and made into slurry, the slurry is applied to the current collector, temporary drying is performed, and thereafter, heat treatment is performed, thereby obtaining an electrode.
A method for the temporary drying is not particularly limited as long as the method therefor is a method which allows the solvent in the slurry can be volatilized and removed, and for example, a method in which the heat treatment is performed under an atmosphere at a temperature of 50° C. or more and 300° C. or less in the atmosphere can be cited. The above-mentioned heat treatment can be performed by retaining under reduced pressure at 50° C. or more and 300° C. or less for one hour or more and 50 hours or less.
In a case where the electrode for the nonaqueous secondary battery, of the present invention, is used as the positive electrode, it is preferable that charging and discharging are performed with a lower limit electric potential of 2.0 V or more of the electrode (vs. a lithium electric potential) and an upper limit electric potential of 5.5 V or less (vs. a lithium electric potential). Even if discharging is performed with less than 2 V, not only a capacity cannot be obtained and it is useless, but also it is highly likely that the negative electrode is oxidized. Charging exceeding 5.5 V easily decomposes the electrolytic bath. It is more preferable that the lower limit electric potential is 2.0 V and it is further preferable that the lower limit electric potential is 2.5 V. In addition, it is more preferable that the upper limit electric potential is 5.0 V.
In a case where the electrode for the nonaqueous secondary battery, of the present invention, is used as the negative electrode, it is preferable that charging and discharging are performed with a lower limit electric potential of 0.0 V or more of the battery (vs. a lithium electric potential) and an upper limit electric potential of 2.0 V or less thereof (vs. a lithium electric potential). If the electric potential is less than 0 V, the negative electrode is overcharged and the cations become metal, thereby increasing likelihood of deposition thereof on the electrode. It is more preferable that the lower limit electric potential is 0.001 V and it is further preferable that the lower limit electric potential is 0.01 V. In addition, it is more preferable that the upper limit electric potential is 1.5 V.
The electrode (the positive electrode or the negative electrode) obtained as described above is joined to a counter-electrode with a separator interposed and the electrode is sealed in a state in which the electrode is immersed in the nonaqueous electrolyte (an electrolytic bath), thereby becoming a secondary battery. In addition, in a case where the bipolar electrode is used, the bipolar electrodes are joined with a separator interposed and the electrodes are sealed in a state in which the electrodes are immersed in the nonaqueous electrolyte (the electrolytic bath), thereby becoming a secondary battery.
Since it is required for the nonaqueous secondary battery obtained by using the electrode of the present invention to include both of the anions and the cations, as electrolyte salt, salt which includes the above-described anions and cations is suitable. For example, LiPF6, NaPF6, KPF6, Mg(PF6)2, Ca(PF6)2, Al(PF6)3, LiBF4, NaBF4, KBF4, Mg(BF4)2, Ca(BF4)2, Al(BF4)3, LiClO4, NaClO4, KClO4, Mg(ClO4)2, Ca(ClO4)2, Al(ClO4)3, LiTiF4, NaTiF4, KTiF4, Mg(TiF4)2, Ca(TiF4)2, Al(TiF4)3, LiVF5, NaVF5, KVF5, Mg(VF5)2, Ca(VF5)2, Al(VF5)3, LiAsF6, NaAsF6, KAsF6, Mg(AsF6)2, Ca(AsF6)2, Al(AsF6)3, LiSbF6, NaSbF6, KSbF6, Mg(SbF6)2, Ca(SbF6)2, Al(SbF6)3, LiCF3SO2, NaCF3SO2, KCF3SO2, Mg(CF3SO2)2, Ca(CF3SO2)2, Al(CF3SO2)3, Li (CF3SO2)2N, Na (CF3SO2)2N, K (CF3SO2)2N, Mg((CF3SO2)2N)2, Ca((CF3SO2)2N)2, AI ((CF3SO2)2N)3, LiB10Cl10, NaB10Cl10, KB10Cl10, Mg(B10Cl10)2, Ca(B10Cl10)2, Al(B10Cl10)3, and the like are cited, and one kind or two kinds or more among these can be used. Amount these, from a point of view that a battery whose battery voltage is high and capacity is high and which is excellent in input-output characteristics can be obtained, salt which is sodium salt or potassium salt and is an atom group including F is preferable.
In addition, as a solvent of the above-described electrolyte, a propylene carbonate, an ethylene carbonate, a dimethyl carbonate, a diethyl carbonate, γ-butyrolactone, and the like are cited, and one kind or two kinds or more can be used. Among these, a simple substance of the propylene carbonate and a mixture of the ethylene carbonate and the diethyl carbonate are suitable. Note that a mixture ratio of the above-mentioned mixture of the ethylene carbonate and diethyl carbonate can be optionally adjusted in a range of 10% or more and 90% or less.
The nonaqueous secondary battery having the above-described structure can function as a secondary battery whose electric potential is high and which is excellent in input-output characteristics.
In a case where the electrode of the present invention is used as the positive electrode or the negative electrode, a structure of the nonaqueous secondary battery is not particularly limited, and a configuration or a structure of the existing battery such as a pouch-type battery and a wound-type battery can be adopted.
However, in a case where the electrode of the present invention is the bipolar electrode, a configuration or a structure thereof is the configuration or the structure of the pouch-type battery. Accordingly, the battery using the bipolar electrode has a structure in which a plurality of bipolar electrodes, in each of which on one surface of a current collector, a positive electrode layer is provided and on the other surface thereof, a negative electrode layer is provided, are laminated with separators respectively interposed therebetween, each of the separators including an electrolyte. Since single cells are arranged in series in a lamination direction inside the battery, a current flows in a thickness direction of the battery. Since the above-mentioned battery has advantages such as a short path of the battery and a small current loss, a battery having high output characteristics and high energy density can be made. Note that in order to prevent an ionic short circuit, an insulation material (polyolefin, fluorine resin, or the like) may be provided for peripheral portions and end surfaces the electrodes of each of the positive electrode layers and each of the negative electrode layers.
The bipolar electrode is an electrode formed by providing a positive electrode layer and a negative electrode layer on both surfaces of one current collector, and a positive electrode material (a positive electrode active material) and a negative electrode material (a negative electrode active material) of a general bipolar electrode are different from each other. (For example, refer to Japanese Patent Application Laid-Open Publication No. 2012-129095, Japanese Patent Application Laid-Open Publication No. 2021-150106, and the like). Therefore, active material layers whose properties are different from each other had been forced to be provided on the front and back surfaces of the current collector. However, since the electrode material (an active material) of the present invention can operate as a positive electrode active material and a negative electrode active material, layers formed of the same material can be provided on the front and back surfaces of the current collector. Thus, a number of steps of manufacturing the battery and a number of parts required to configure the battery can be reduced.
In particular, in the dual-ion battery which can be charged and discharged by inserting and desorbing Na+ as the cations and PF6− as the anions, electric capacities of the negative electrode and the positive electrode, each of which is formed of the electrode material (the active material) of the present invention, are equivalent to each other. Therefore, as to electrodes whose basis weights (applied amounts) are the same as each other, a capacity difference between the positive electrode and the negative electrode is hardly caused and efficient charging and discharging can be made.
As to the electrodes whose basis weights on the front and back surfaces are different from each other, in a drying process or a press process in manufacturing the electrodes, a difference of stresses exerted on the front and back surface is caused, whereby drawbacks such as electrode bending and exfoliation of the active material layers are easily caused. In other words, as long as the basis weights on the front and back surfaces are equivalent to each other, the above-mentioned problems are hardly caused.
Since the nonaqueous secondary battery which includes the electrodes of the present invention and whose active materials contain no rare metal exhibits high input-output characteristics, the nonaqueous secondary battery can be utilized as a power source for various electric appliances (including vehicles which use electricity).
As the electric appliances, for example, cited are an air conditioner, a washing machine, a television set, a refrigerator, a freezer, a cooling unit, a notebook computer, a personal computer keyboard, a display for a personal computer, a desktop type personal computer, a notebook-type personal computer, a CRT monitor, a personal computer rack, a printer, an all-in-one personal computer, a mouse, a hard disk, a personal computer peripheral device, a clothes iron, a clothing drying machine, a window fan, a transceiver, an air blower, a ventilation fan, a television, a music recorder, a music player, an oven, a cooking range, a toilet seat with a washing function, a warm air heater, a car component, a car navigation system, an electric torch, a humidifying device, a mobile karaoke device, an extractor fan, a drier machine, a dry cell battery, an air freshener unit, a mobile telephone, an emergency electric light, a gaming machine, a blood-pressure gauge, a coffee mill, a coffee maker, a Japanese foot warmer, a copying machine, a disk changer, a radio, a shaver, a juicer, a shredder, a water purifier, a lighting apparatus, a dehumidifier, a tableware dryer, a rice cooker, a stereo, a stove, a speaker, a trouser press, a flying car, a sweeper, a body fat meter, a weight scale, a bathroom scale, a movie player, an electrically heated carpet, an electric rice-cooker, a rice cooker, an electric shaver, a desk lamp, an electric pot, an electronic gaming machine, a portable gaming machine, an electronic dictionary, an electronic notebook, a microwave oven, an electromagnetic cooking device, an electronic calculator, an electric cart, an electric wheelchair, an electric tool, an electric toothbrush, a footwarmer, a haircut device, a telephone, a clock, an intercommunication phone, an air circulator, an electric intersect killer, a duplicating machine, a hot plate, a toaster, a dryer, an electric drill, a hot water dispenser, a panel heater, a pulverizing machine, a soldering iron, a video camera, a videocassette recorder, an electrograph, a fan heater, a food processor, a bedding dryer, headphones, an electric pot, an electric carpet, a microphone, a massage machine, a miniature bulb, a mixer, a sewing machine, a rice cake making machine, a floor heating panel, a lantern, a remote controller, a cold-hot storage, a water cooler, a freezing stocker, a cold air blower, a word processor, a whisk, an electronic musical instrument, a motorcycle, toys, a lawn mower, a float, a bicycle, an automobile, a hybrid automobile, a plug-in hybrid automobile, an electric automobile, a railroad, a ship, an airplane, a storage battery for emergency, and the like.
With reference to Examples, the present invention will be further specifically described. Note that the present invention is not limited by these Examples at all.
As molten salt, 900 g to 3100 g of eutectic salt of LiCl and KCl (eutectic composition is 58.5:41.5 mol %) was melted under an argon atmosphere at atmospheric pressure and was retained at 450° C. As a carbonate ion source, an amount of K2CO3 whose salt concentration is 2 mol % was added into the molten salt, and by injecting argon gas thereto, an electrolytic bath was agitated, thereby conducting suspension and dispersion in the electrolytic bath. As an anode, a carbon plate was located in the electrolytic bath. In the vicinity of a surface of the electrolytic bath outside the electrolytic bath, as a cathode which was a discharge electrode, a tungsten rod was located. Discharge electrolysis was performed for the above-described electrolytic bath with an electrolytic current of 2 A to 4 A and a quantity of electricity of 107208 C to 450000 C (coulomb).
In Examples 1 to 7, weights of the molten salts, electrolytic currents, and quantities of electricity are different. In Example 1, a weight of the molten salt was 900 g, an electrolytic current was 3 A, and a quantity of electricity was 107208 C; in each of Examples 2 to 5, a weight of the molten salt was 1350 g, an electrolytic current was 2 A, and a quantity of electricity was 200000 C; and in each of Examples 6 to 7, a weight of the molten salt was 3100 g, an electrolytic current was 2 A, and a quantity of electricity was 450000 C.
After the electrolysis, in all of Examples, the muddy carbon and the aggregated carbon were formed in the electrolytic bath. The muddy carbon and the aggregated carbon were moved outside the electrolytic cell and were made into the solidified salt at a room temperature. The solidified salt containing the muddy carbon and the solidified salt containing the aggregated carbon were individually dissolved in warm water at a temperature of 50° C. or less or water, and carbon particles were suspended in the aqueous solutions while ultrasonic was applied thereto. Each of the obtained aqueous solutions was filtered by a membrane filter and carbon particles deposited on the filter were dried. Hereinafter, as to Examples 1 to 7, the muddy carbon is shown as Examples 1A to 7A and the aggregated carbon is shown as Examples 1B to 7B.
An interplanar spacing d (002) (nm), a crystallite size (Lc (002) (nm), La (110) nm), a mean secondary particle diameter (d50) (nm), and a specific surface area of the carbon particles collected in each of Examples 1A to 7A (muddy carbon) and each of Examples 1B to 7B (aggregated carbon) were measured. A result of the measurement in Examples 1A to 7A (muddy carbon) is shown in Table 1.
The interplanar spacing d (002) (nm), the crystallite size (Lc (002) (nm), and La (110) nm) of the carbon particles were measured by the XRD (X-ray diffractometry) Gakushin method.
The mean secondary particle diameter (d50) (nm) was measured by using a particle diameter distribution measurement apparatus: Nanotrac UPA, model: UPA-EX, manufactured by MicrotracBEL Corp.
The specific surface area was measured by the BET method in which a specific surface area was calculated from a nitrogen-adsorption amount at 77 K.
As shown in Table 1, the interplanar spacing (d (002)) of the carbon particles in each of Examples 1A to 7A (muddy carbon) was 0.3360 nm or more and 0.3373 nm or less, and particles having crystallinity which was equivalent to that of graphite were included.
As shown in
A BET specific surface area of the carbon particles was 200 m2/g or more and 500 m2/g or less.
As impurities of the collected carbon particles in Example 4, contained a mounts of potassium and chlorine of molten salt components were measured. T he impurities were measured by an EDX method. A result of the measurement is shown in Table 2.
Carbon particles of each of Examples 2A and 2B were observed by a SEM (manufactured by JEOL Ltd., JSM-6010PLUS/LA). As shown in
Carbon particles in each of Examples 1 to 7 were subjected to heat treatment at 2800° C. for one hour, thereby obtaining graphite particles. An interplanar spacing d (002) (nm), a crystallite size (Lc (002) (nm) and La (110) (nm)), a mean secondary particle diameter (d50) (nm), and a specific surface area of the obtained graphite particles were measured in a manner similar to the manner in which the measurement for the carbon particles before the heat treatment was conducted. A result thereof is shown in Table 3.
As shown in Table 3, the interplanar spacing d (002) based on a diffraction peak corresponding to the d (002) of the graphite particles in each of Examples 1 to 7 was 0.3355 nm or more and 0.3365 nm or less.
In general, the higher crystallinity of graphite is, the more excellent characteristics such as thermal conductivity, electrical conductivity, slidability, lubricity, and heat resistance are exhibited. However, since where it is often the case that definition of the graphite is ambiguous in documents, the crystallinity of the graphite particles generated by employing the above-mentioned method was evaluated.
In general, as graphite peaks, a peak having low crystallinity, which is a turbostratic structure component (a T component), is exhibited at a diffraction angle (20) of 26° and a peak having high crystallinity, which is a graphitic structure component (a G component), is exhibited at a diffraction angle (20) of 26.5°. As shown in
In order to quantify a degree of progress of graphitizing, a graphitization degree P1 was obtained by the following formula.
A result thereof is shown in Table 4. It is indicated by P1 that the more proximate to one P1 is, the more progressing the graphitizing is, and it turned out that in each of Examples, the graphitization degree of the graphite particles was high.
Next, an interplanar spacing d (002) of each of the carbon particles before the heat treatment and the graphite particles after the heat treatment was examined. A theoretical value of d (002) of the graphite is 0.3354 nm. Values of the interplanar spacing d (002) of the carbon particles after graphitizing in Examples 1 to 7 were in a range of 0.3355 nm or more and 0.3368 nm or less and were equivalent to values of synthetic graphite and natural graphite. As shown in
As shown in Table 3 and
As general synthetic graphite, Lc (002) of synthetic graphite manufactured by SEC CARBON, Ltd. is 117 nm, La (110) thereof is 284.6 nm. Both of Lc (002) and La (110) of the graphite particles in each of Examples 1 to 7 are ⅓ or less of those of the general synthetic graphite.
Means and standard deviations of La and Lc before and after the heat treatment in Examples 1A to 7A (muddy carbon) are shown in Table 5.
As shown in Table 5, the standard deviations of La (110) and Lc (002) after the heat treatment were decreased from those before the heat treatment, and it is seen that variation in the crystallite sizes can be reduced.
As shown in Table 3, the secondary particle diameter of the graphite particles is 0.15 μm or more and 1.6 μm or less. In Examples 1 to 5, a particle diameter of the graphite particles after the heat treatment at 2800° C. became drastically larger than a particle diameter of the carbon particles before the heat treatment. For example, in Example 4, while a carbon particle diameter of the carbon particles as the raw material was 180 nm (d50), a graphite particle diameter was 1600 nm (d50). As shown in
On the other hand, in Examples 6 and 7, a particle diameter after graphitizing was substantially the same as a particle diameter of the carbon particles as the raw material. As shown in
The reason why further minute graphite particles were obtained without the occurrence of the aggregation due to the heat treatment in Examples 6 and 7 is because it is considered that increasing a generated amount of the carbon particles as the raw material caused concurrently the following two phenomena.
As a primary particle diameter of the graphite particles in Examples 1 to 7, as shown in
A specific surface area (BET) of the graphite particles in Examples 1 to 7 obtained from the nitrogen-adsorption amount at 77 K was 50 m2/g or more and 60 m2/g or less.
As shown in
The graphite pulverulent body was observed by a SEM (manufactured by JEOL Ltd., JSM-6010PLUS/LA). As to shapes of the graphite particles, particles each having not only a structure of a spherical shape but also a sheet shape, a ribbon shape, and a cube shape were also present, and particles having various shapes were included. As these results of the SEM observation, it was found that not only the spherical shape particles but also the sheet shape particles, the ribbon shape particles, and the cube shape particles were present in a mixed manner and particles having various shapes were included. The reason why the graphite particles having the above-mentioned various shapes were formed is because in the stage of the carbon particles as the raw material, the shapes of the particles have already been diversified. As described above, it is considered that the carbonate ions were subjected to the cathode discharge electrolysis, thereby obtaining the carbon particles having the various shapes, and various shapes of also the graphite particles obtained by subjecting the obtained carbon particles to the heat treatment were exhibited.
Furthermore, in TEM photographs of the graphite particles each having the ribbon shape, stacking of graphene sheets was confirmed, and it can be said that the graphite particles even having the various shapes have graphitic nature.
As impurities of the graphite particles in Example 4A, contained amounts of potassium and chlorine of molten salt components were measured. The impurities were measured by an EDX method. A result is shown in Table 6.
As shown in Table 6, it was confirmed that by increasing the heat treatment temperature, the impurities decreased and at 2800° C., the impurities substantially vanished. Accordingly, it is preferable that the treatment temperature of graphitizing is 2800° C. or more.
<Manufacturing of Graphite Particles with Carbon Dioxide Gas as a Raw Material>
Hereinafter, carbon particles generated from an electrolytic bath prepared by injecting carbon dioxide gas into the electrolytic bath which includes molten salt containing oxide ions and graphite particles manufactured by performing the heat treatment will be described.
Under an argon atmosphere at atmospheric pressure, 400 g of eutectic salt (eutectic composition was 58.5:41.5 mol %) of LiCl and KCl as the molten salt was melted and was retained at 450° C. Added into the molten salt was an amount of Li2O as an oxide ion source, which made a concentration 1 mol %, and by injecting argon gas thereto, the electrolytic bath was agitated, thereby making suspension and dispersion in the electrolytic bath. Thereafter, argon gas containing 10 vol % of carbon dioxide was injected into the electrolytic bath at a flow rate of 100 mL/minute for 24 hours. In order to confirm that carbonate ions were generated, cyclic voltammetry was performed in such a way that a Ni wire was used as a cathode, a glass-like carbon rod was used as an anode, an Ag(I)/Ag electrode which included LiCl—KCl eutectic salt containing 1 mol % of AgCl and an Ag wire was used as a reference electrode, and a scan rate was 10 mV/s. As a comparison target, measurement was similarly made in such a way that molten salt which contained K2CO3 having approximately 2.0 mol % was used and a scan rate was 100 mV/s.
Thereafter, discharge electrolysis was performed for the above-mentioned molten salt into which the carbon dioxide was injected in such a way that an anode and a cathode which were similar to those used in Examples 1 to 7 were used, an electrolytic current was 2 A, and a quantity of electricity was 10000 C.
As shown in
Next, as a result of performing the discharge electrolysis, the muddy carbon was formed in the electrolytic bath after the electrolysis. The muddy carbon was moved outside the electrolytic cell and was made to the solidified salt at a room temperature. The solidified salt including the muddy carbon was dissolved in warm water whose temperature was 50° C. or less or water, and while ultrasonic was applied thereto, carbon particles were suspended in the aqueous solution. The obtained aqueous solution was filtered by a membrane filter and carbon particles deposited on the filter were dried.
An interplanar spacing d (002) (nm) of the collected carbon particles in Example 8, a crystallite size (Lc (002) (nm) and La (110) (nm)) thereof, a mean secondary particle diameter (d50) (nm) thereof, and a specific surface area thereof were measured. A result in Example 8 is shown in Table 7. Note that a measurement method of these is similar to that in Examples 1 to 7.
As shown in Table 7, the interplanar spacing (d (002)) of the carbon particles in Example 8 was 0.3362 nm, and as in Examples 1 to 7, particles having crystallinity equivalent to that of the graphite were included.
As shown in
The BET specific surface area of the carbon particles was 523 m2/g and was equivalent to that in each of Examples 1 to 7.
As impurities of the carbon particles in Example 8, contained amounts of potassium and chlorine of molten salt components were measured. Note that a measurement method of these is similar to that in each of Examples 1 to 7. A result is shown in Table 8.
The carbon particles in Example 8 were observed by a SEM. As shown in
The carbon particles in Example 8 were subjected to heat treatment at 2800° C. for one hour, thereby obtaining graphite particles. An interplanar spacing d (002) (nm), a crystallite size (Lc (002) (nm), and La (110) (nm)), a mean secondary particle diameter (d50) (nm), and a specific surface area of the obtained graphite particles were measured in a manner similar to the manner in which the measurement for the carbon particles before the heat treatment was conducted. A result thereof is shown in Table 9.
As shown in Table 9, the interplanar spacing d (002) based on a diffraction peak corresponding to the lattice plane (002) of the graphite particles in Example 8 was 0.3369 nm.
Crystallinity of the graphite particles generated by the above-mentioned manufacturing method was evaluated in a manner similar to the manner in which the crystallinity of the graphite particles in each of Examples 1 to 7 was evaluated. As shown in
A graphitization degree Pl representing a degree of progress of graphitizing was obtained and a result is shown in Table 10. It is indicated by Pl that the more proximate to one Pl is, the more progressing the graphitizing is, and it turned out that the high graphitization degree was represented though the graphitization degree did not reach that in each of Examples 1 to 7.
In addition, an interplanar spacing d (002) based on a diffraction peak corresponding to d (002) of the graphite particles in Example 8 was 0.3369 nm and was a value equivalent to that of each of the synthetic graphite and the natural graphite.
As shown in Table 9, Lc (002) of the graphite particles after graphitizing was 12.2 nm and La (110) thereof was 58.7 nm.
As general synthetic graphite, Lc (002) of synthetic graphite manufactured by SEC CARBON, Ltd. is 117 nm, La (110) thereof is 284.6 nm. Both of Lc (002) and La (110) of the graphite particles in Example 8 as a crystallite size are ¼ or less of those of the general synthetic graphite.
As shown in Table 9, a secondary particle diameter of the graphite particles was 0.1684 μm, and a particle diameter after graphitizing was substantially the same as the particle diameter of the carbon particles as the raw material. As shown in
It is considered that it was made possible to obtain further minute graphite particles without the occurrence of the aggregation due to the heat treatment because the crystal structure of the carbon particles before the heat treatment had already approached to that of the graphite since the peak higher than the peak shown in
A primary particle diameter of the graphite particles in Example 8, which was visually measured by a SEM (electron microscope), as shown in
As to the graphite particles in Example 8, a specific surface area (BET) calculated from the nitrogen-adsorption amount at 77 K was 68.6 m2/g.
A graphite pulverulent body in Example 8 was observed by a SEM. As a result, as in Examples 1 to 7, as to shapes of the graphite particles, particles each having a structure of not only a spherical shape but also a sheet shape, a cube shape, and a ribbon shape were present, and the graphite particles had various shapes. In
As impurities of the carbon particles in Example 8, contained amounts of potassium and chlorine of molten salt components were measured. Note that a measurement method of these is similar to that in each of Examples 1 to 7. A result is shown in Table 11.
As shown in Table 11, it was confirmed that by performing the heat treatment at 2800° C., the impurities substantially vanished.
Hereinafter, a form of a battery for embodying the present invention will be described.
A graphite pulverulent body which was aggregate of graphite particles of the present invention (Example 2A, a particle diameter: 1200 nm (d50)) was used as a positive electrode active material; a positive electrode active material whose mass percent was 83%, acetylene black whose mass percent was 2%, and polyvinylidene fluoride whose mass percent was 15% were mixed, thereby preparing a mixture agent in a slurry state; the mixture agent was applied onto an aluminum foil current collector whose thickness was 12 μm; and thereafter, heat treatment (under a reduced pressure, at 150° C., for 10 or more hours) was performed, thereby obtaining a test electrode whose basis weight per one surface was 1.1 mg/cm2. As a counter-electrode, metal lithium foil whose thickness was 500 μm was used; a separator obtained by overlaying a glass filter (manufactured by ADVANTEC CO., LTD: GA-100) and a polyolefin-based microporous membrane was used; and as an electrolytic bath, a mixture of lithium hexafluorophosphate (LiPF6) whose salt concentration was 1 mol/L, ethylene carbonate (EC), and diethyl carbonate (DEC) was included, thereby preparing a battery in Example B1.
As a counter-electrode, metal sodium foil whose thickness was 500 μm was used; as an electrolytic bath, a mixture of sodium hexafluorophosphate (NaPF6) whose salt concentration was 1 mol/L, EC, and DEC was used; and others were similar to those in Example B1, thereby preparing a battery in Example B2.
As a counter-electrode, metal potassium foil whose thickness was 500 μm was used; as an electrolytic bath, a mixture of potassium bis(trifluoromethane) sulfonamide (KTFSA) whose salt concentration was 0.5 mol/L and 1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl) amide (Pyr13TFSA) was used; and others were similar to those in Example B1, thereby preparing a battery in Example B3.
As a positive electrode active material, natural graphite (manufactured by Sigma-Aldrich Co. LLC; 496596 graphite powder;-325mesh shape; and hereinafter, referred to as “natural graphite”) whose maximum particle diameter was 44 μm (FISHER diameter: 3.5 μm) was used; and others were similar to those of the battery in Example B1, thereby preparing a battery in Comparative Example B1.
As a positive electrode active material, natural graphite was used; and others were similar to those of the battery in Example B2, thereby preparing a battery in Comparative Example B2.
As a positive electrode active material, natural graphite was used; and others were similar to those of the battery in Example B3, thereby preparing a battery in Comparative Example B3.
As a negative electrode active material, the graphite pulverulent body in Example 2A of the present invention was used; the negative electrode active material whose mass percent was 83%, polyvinylidene fluoride whose mass percent was 15%, and acetylene black whose mass percent was 2% were mixed, thereby preparing a mixture agent in a slurry state; the mixture agent was applied onto a copper foil current collector whose thickness was 10 μm; and others were similar to those of the battery in Example B1, thereby preparing a battery in Example B4.
As a negative electrode active material, natural graphite was used; and others were similar to those of the battery in Example B4, thereby preparing a battery in Comparative Example B4.
As a current collector of a test electrode, aluminum foil whose thickness was 12 μm was used; as a counter-electrode, metal sodium foil whose thickness was 500 μm was used; as an electrolytic bath, a mixture of NaPF6 whose salt concentration was 1 mol/L, EC, and DEC was used; and others were similar to those in Example B4, thereby preparing a battery in Example B5.
As a negative electrode active material, natural graphite was used; and others were similar to those of the battery in Example B5, thereby preparing a battery in Comparative Example B5.
As a counter-electrode, metal potassium foil whose thickness was 500 μm was used; as an electrolytic bath, a mixture of potassium bis(fluorosulfonyl) amide (KFSA) whose salt concentration was 1 mol/L and 1-methyl-1-propylpyrrolidinium bis (fluorosulfonyl) amide (Pyr13FSA) was used; others were similar to those of the battery in Example B5, thereby preparing a battery in Example B6.
As a negative electrode active material, natural graphite was used; and others were similar to those of the battery in Example B6, thereby preparing a battery in Comparative Example B6.
As to a battery in each of Examples B1 to B6 and Comparative Examples B1 to B6, 0.1C-rate charge and discharge was performed under the environment at 30° C. in a predetermined voltage range, and a reversible capacity of an active material was calculated from a quotient of a reversible capacity of the battery and active material mass. In other words, the reversible capacity of the active material is a reversible electric capacity per unit mass of the active material.
In Table 12, reversible capacities of active materials in Examples B1 to B6 and Comparative Examples B1 to B6 are shown.
In a case where each of the test electrodes was used as the positive electrode for the fluoride-ion battery or the negative electrode for the lithium-ion battery, in Examples (Examples B1 to B4), reversible capacities were equal to or smaller than those in Comparative Examples (Comparative Examples B1 to B4). However, in a case where each of the test electrodes was used as the negative electrode for the sodium-ion battery or the negative electrode for the potassium-ion battery, capacities in Examples (Examples B5 and B6) were higher than those in Comparative Examples (Comparative Examples B5 and B6).
It is known that as to the graphite, irrespective of the synthetic graphite or the natural graphite, it is difficult to insert the sodium ions into a graphene layer and electrochemical activity is hardly exhibited (for example, Akira Kano, et al., Panasonic Technical Journal, Vol. 63(1), 55-59 (2017)). However, in a case where the electrode using the graphite pulverulent body, of the present invention, was used as the negative electrode for the sodium ion battery, the above-mentioned electrode realized 2.8 times higher capacity than that of the conventional natural graphite.
As to a ratio (N/P) of a negative electrode capacity (N) and a positive electrode capacity (P), in a combination of Example B1 (a positive electrode) and Example B4 (a negative electrode), N/P=8.26; in a combination of Example B2 (a positive electrode) and f Example B5 (a negative electrode), N/P=1.12; in a combination of Example B3 (a positive electrode) and Example B6 (a negative electrode), N/P=6.48; in a combination of Comparative Example B1 (a positive electrode) and Comparative Example B4 (a negative electrode), N/P=5.81; in a combination of Comparative Example B2 (a positive electrode) and Comparative Example B5 (a negative electrode), N/P=0.20; and in a combination of Comparative Example B3 (a positive electrode) and Comparative Example B6 (a negative electrode), N/P=2.26.
In each of the nonaqueous secondary batteries constituted of these electrodes, in a case where N/P is less than one, since alkali metal precipitates on a negative electrode surface in the process of charging, a short-circuit risk of the battery increases. Therefore, it is preferable that N/P is 1.0 or more. However, in a case where N/P exceeds 2.0, since there are many negative electrode active materials not involved in charging and discharging and an irreversible capacity of the negative electrode with respect to a reversible capacity of the positive electrode is large, a factor of reducing an energy density of the battery results.
A reversible capacity in Example B5 was slightly larger than that in Example B2 and reversible capacities of these electrodes were substantially the same as each other. By using a current collector which can be used for the positive electrode and the negative electrode (for example, Al, an Al alloy, W, stainless steel, carbon, or the like), while the electrodes are exactly the same as each other, the electrode can be used as the positive electrode and negative electrode. In other words, it is made possible to reduce a number of parts required to configure the battery.
As to each of batteries in Example B1 and Comparative Example B1, a high-rate dischargeability test was conducted. As conditions thereof, the high-rate dischargeability test was conducted: under the environment at 30° C.; with a cut-off voltage of 2.0 V to 5.0 V (vs. Li+/Li); and under 0.1 C-rate charge, by changing an electric discharge rate to a 0.1 C rate, a 0.2 C rate, a 0.5 C rate, a 1 C rate, a 2 C rate, and a 3 C rate, thereby obtaining a utilization ratio of each of the batteries. Note that the utilization ratio represents a capacity ratio of each of the discharge rates with a discharge capacity obtained in 0.1C-rate charge and discharge as 100%. In other words, it is shown that the larger a value is, the higher in output a battery is (that a battery can discharge electricity with a large current).
In
As to each of batteries in Example B2 and Comparative Example B2, a high-rate dischargeability test was conducted. As conditions thereof, the high-rate dischargeability test was conducted: under the environment at 30° C.; with a cut-off voltage of 2.0 V to 5.0 V (vs. Na+/Na); and under 0.1C-rate charge, by changing a discharge rate to a 0.1C rate, a 0.2C rate, a 0.5C rate, and a 1C rate, thereby obtaining a utilization ratio of each of the batteries. Note that the utilization ratio represents a capacity ratio of each of the discharge rates with a discharge capacity obtained in 0.1C-rate charge and discharge as 100%.
In
As to each of batteries in Example B1 and Comparative Example B1, a high-rate chargeability test was conducted. As conditions thereof, the high-rate chargeability test was conducted: under the environment at 30° C.; with a cut-off voltage of 2.0 V to 5.0 V (vs. Li+/Li); and under 0.1C-rate electric discharge, by changing a charge rate to a 0.1C rate, a 0.2C rate, a 0.5C rate, a 1C rate, a 2C rate, a 3C rate, and a 6C rate, thereby obtaining a charging rate of each of the batteries. Note that the charging rate represents a capacity ratio of each of the charge rates with a capacity obtained in 0.1C-rate charging and discharging as 100%. In other words, it is shown that the larger a value is, the more excellent in input characteristics a battery is (that a battery can be fully charged for a short period of time).
In
As to each of batteries in Example B4 and Comparative Example B4, a high-rate dischargeability test was conducted. As conditions thereof, the high-rate dischargeability test was conducted: under the environment at 30° C.; with a cut-off voltage of 0.001 V to 1.5 V (vs. Li+/Li); and under 0.1C-rate charge, by changing a discharge rate to a 0.1C rate, a 0.2C rate, a 0.5C rate, a 1C rate, a 2C rate, a 3C rate, a 6C rate, a 10C rate, a 20C rate, and a 30C rate, thereby obtaining a utilization ratio of each of the batteries. Note that the utilization ratio represents a capacity ratio of each of the discharge rates with a discharge capacity obtained in 0.1C-rate charge and discharge as 100%. In other words, it is shown that the larger a value is, the higher in output a battery is.
In
As to each of batteries in Example B6 and Comparative Example B6, a high-rate dischargeability test was conducted. As conditions thereof, the high-rate dischargeability test was conducted: under the environment at 30° C.; with a cut-off voltage of 0.001 V to 1.5 V (vs. K+/K); and under 0.05C-rate charge, by changing a discharge rate to a 0.05C rate, a 0.1C rate, a 0.2C rate, a 0.5C rate, and a 1C rate, thereby obtaining a utilization ratio of each of the batteries. Note that the utilization ratio represents a capacity ratio of each of the discharge rates with a discharge capacity obtained in 0.05C-rate charge and discharge as 100%. In other words, it is shown that the larger a value is, the higher in output a battery is.
In
As to each of batteries in Example B6 and Comparative Example B6, a high-rate chargeability test was conducted. As conditions thereof, the high-rate chargeability test was conducted: under the environment at 30° C.; with a cut-off voltage of 0.001 V to 1.5 V (vs. K+/K); and under 0.05C rate discharge, by changing a charge rate to a 0.05C rate, a 0.1C rate, a 0.2C rate, a 0.5C rate, and a 1C rate, thereby obtaining a charging rate of each of the batteries. Note that the charging rate represents a capacity ratio of each of the charge rates with a charging capacity obtained in 0.05C rate charge and discharge as 100%. In other words, it is shown that the larger a value is, more excellent in input characteristics a battery is.
In
The invention of the present application is summarized as follows.
As described above, with reference to the accompanying drawings, the preferred embodiment of the present invention is described. However, various addition, modification, or deletion can be made without departing from the purport of the present invention. For example, the nonaqueous secondary battery obtained by the present invention is not limited to the carriers contributing to battery reaction in the above-described embodiment. In addition, the scope of the present invention is not limited to that of the above-described embodiment, and granulation, pulverization, classification, or the like may be conducted. Accordingly, those obtained by conducting the granulation, the pulverization, the classification, or the like are embraced within the scope of the present invention.
The described embodiment and examples are to be considered in all respects only as illustrative and not restrictive. It is intended that the scope of the invention is, therefore, indicated by the appended claims rather than the foregoing description of the embodiment and examples and that all modifications coming within the meaning and equivalency range of the appended claims are embraced within their scope.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-166267 | Oct 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/037738 | 10/7/2022 | WO |
