WO2023037769A1 - 正極材料、正極および電池 - Google Patents
正極材料、正極および電池 Download PDFInfo
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- WO2023037769A1 WO2023037769A1 PCT/JP2022/028285 JP2022028285W WO2023037769A1 WO 2023037769 A1 WO2023037769 A1 WO 2023037769A1 JP 2022028285 W JP2022028285 W JP 2022028285W WO 2023037769 A1 WO2023037769 A1 WO 2023037769A1
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- Prior art keywords
- solid electrolyte
- positive electrode
- active material
- coating layer
- battery
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Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
- H01M10/0562—Solid materials
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/14—Sulfur, selenium, or tellurium compounds of phosphorus
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G23/00—Compounds of titanium
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G53/00—Compounds of nickel
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
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- H—ELECTRICITY
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- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0065—Solid electrolytes
- H01M2300/0068—Solid electrolytes inorganic
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- H—ELECTRICITY
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- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0065—Solid electrolytes
- H01M2300/0068—Solid electrolytes inorganic
- H01M2300/008—Halides
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0088—Composites
- H01M2300/0094—Composites in the form of layered products, e.g. coatings
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the present disclosure relates to cathode materials, cathodes and batteries.
- Patent Document 1 describes a method of manufacturing a composite active material by coating a positive electrode active material with an oxide solid electrolyte and further coating it with a sulfide solid electrolyte.
- This disclosure is a positive electrode active material; a coating layer containing a first solid electrolyte and covering at least part of the surface of the positive electrode active material; a second solid electrolyte; with the first solid electrolyte contains Li, Ti, M, and X; M is at least one selected from the group consisting of metal elements and metalloid elements other than Li and Ti, X is at least one selected from the group consisting of F, Cl, Br, and I;
- the second solid electrolyte is in contact with the positive electrode active material through the coating layer,
- the ratio of the volume of the first solid electrolyte to the total volume of the first solid electrolyte and the second solid electrolyte is 4% or more and 45% or less.
- a cathode material is provided.
- FIG. 1 is a cross-sectional view showing a schematic configuration of a positive electrode material according to Embodiment 1.
- FIG. FIG. 2 is a cross-sectional view showing a schematic configuration of a positive electrode material according to a modification.
- FIG. 3 is a cross-sectional view showing a schematic configuration of a battery according to Embodiment 2.
- FIG. 4A is a graph showing a Cole-Cole plot obtained from electrochemical impedance measurements of the battery of Example 1 before charge-discharge cycles.
- FIG. 4B is a graph showing a Cole-Cole plot obtained from electrochemical impedance measurements of the battery of Example 1 after charge-discharge cycles.
- Oxygen may be generated from the positive electrode active material when the battery using the solid electrolyte is repeatedly charged and discharged.
- the generated oxygen oxidizes the solid electrolyte and increases the internal resistance of the battery.
- An increase in internal resistance causes various problems such as a decrease in output voltage, heat generation of the battery, and a decrease in discharge capacity. Therefore, a technique suitable for suppressing an increase in internal resistance of a battery using a solid electrolyte is desired.
- the positive electrode material according to the first aspect of the present disclosure is a positive electrode active material; a coating layer containing a first solid electrolyte and covering at least part of the surface of the positive electrode active material; a second solid electrolyte; with the first solid electrolyte contains Li, Ti, M, and X; M is at least one selected from the group consisting of metal elements and metalloid elements other than Li and Ti, X is at least one selected from the group consisting of F, Cl, Br, and I;
- the second solid electrolyte is in contact with the positive electrode active material through the coating layer, A ratio of the volume of the first solid electrolyte to the total volume of the first solid electrolyte and the second solid electrolyte is 4% or more and 45% or less.
- the positive electrode material of the first aspect it is possible to suppress an increase in the internal resistance of the battery.
- the ratio may be 4.8% or more. With such a configuration, it is possible to further suppress an increase in the internal resistance of the battery.
- the ratio may be 41.2% or less. With such a configuration, it is possible to further suppress an increase in the internal resistance of the battery.
- the ratio may be 8% or more. With such a configuration, it is possible to further suppress an increase in the internal resistance of the battery.
- the ratio may be 30% or less. With such a configuration, it is possible to further suppress an increase in the internal resistance of the battery.
- the second solid electrolyte may contain Li and S.
- a sulfide solid electrolyte has high ionic conductivity and can improve the charge-discharge efficiency of a battery.
- sulfide solid electrolytes may be inferior in oxidation resistance.
- M is at least one selected from the group consisting of Ca, Mg, Al, Y, and Zr may contain
- M includes at least one selected from the group consisting of Ca, Mg, Al, Y, and Zr, the halide solid electrolyte exhibits high ionic conductivity.
- M may contain Al.
- the halide solid electrolyte exhibits high ionic conductivity.
- the first solid electrolyte may be represented by the following compositional formula (1), ⁇ , ⁇ , ⁇ and ⁇ may each independently be a value greater than zero.
- the output characteristics of the battery can be improved.
- the coating layer includes a first coating layer containing the first solid electrolyte and a first coating layer containing a base material. and two coating layers, and the first coating layer may be located outside the second coating layer. According to such a configuration, it is possible to improve the charging and discharging efficiency of the battery.
- the base material may contain an oxide solid electrolyte having lithium ion conductivity.
- an oxide solid electrolyte By using an oxide solid electrolyte as the base material, the charge/discharge efficiency of the battery can be further improved.
- the base material may contain lithium niobate. According to such a configuration, it is possible to improve the charging and discharging efficiency of the battery.
- a positive electrode according to the thirteenth aspect of the present disclosure includes the positive electrode material according to any one of the first to twelfth aspects. According to such a configuration, an increase in internal resistance of the battery can be suppressed.
- a battery according to the fourteenth aspect of the present disclosure includes the positive electrode of the thirteenth aspect. According to the present disclosure, it is possible to suppress an increase in the internal resistance of the battery.
- FIG. 1 is a cross-sectional view showing a schematic configuration of a positive electrode material according to Embodiment 1.
- the positive electrode material 10 has a positive electrode active material 101 , a coating layer 102 containing a first solid electrolyte, and a second solid electrolyte 105 .
- the coating layer 102 covers at least part of the surface of the positive electrode active material 101 .
- the coating layer 102 may cover only part of the surface of the positive electrode active material 101 , or may cover the surface of the positive electrode active material 101 uniformly.
- the positive electrode active material 101 and the coating layer 102 constitute the coated active material 100 .
- the second solid electrolyte 105 is in contact with the positive electrode active material 101 via the coating layer 102 .
- the first solid electrolyte contains Li, Ti, M, and X.
- M is at least one selected from the group consisting of metal elements and metalloid elements other than Li and Ti.
- X is at least one selected from the group consisting of F, Cl, Br and I;
- the ratio V1/Vt of the volume V1 of the first solid electrolyte to the total volume Vt of the first solid electrolyte and the second solid electrolyte 105 is 4% or more and 45% or less, expressed as a percentage. be.
- “Semimetallic elements” include B, Si, Ge, As, Sb, and Te.
- Metallic element means all elements contained in Groups 1 to 12 of the periodic table, except hydrogen, and B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. Including all elements contained in Groups 13 to 16, except That is, the metal element is a group of elements that can become cations when forming an inorganic compound with a halogen compound.
- the first solid electrolyte can be a halogen-containing solid electrolyte, a so-called halide solid electrolyte.
- Halide solid electrolytes have excellent oxidation resistance. Therefore, by coating the positive electrode active material 101 with the first solid electrolyte, oxidation of the second solid electrolyte 105 can be suppressed. Thereby, an increase in the internal resistance of a battery using the positive electrode material 10 can be suppressed.
- the positive electrode active material 101 may be insufficiently covered with the first solid electrolyte, and the above effect may not be obtained sufficiently. If the above ratio V1/Vt is too high, there is concern that the positive electrode material 10 may have insufficient electronic conductivity or insufficient ionic conductivity.
- the ratio V1/Vt may be 4.8% or more, or 8% or more.
- the ratio V1/Vt may be 41.2% or less, or may be 30% or less.
- the total volume Vt of the first solid electrolyte and the second solid electrolyte 105 is the sum of the volume V1 of the first solid electrolyte and the volume V2 of the second solid electrolyte 105.
- the volume V1 of the first solid electrolyte is the total volume of the first solid electrolyte in the positive electrode material 10 powder.
- the volume V2 of the second solid electrolyte 105 is the total volume of the second solid electrolyte 105 in the positive electrode material 10 powder. That is, the above ratio V1/Vt is a value obtained from a certain amount of powder of the positive electrode material 10 as a whole.
- the above ratio V1/Vt can be calculated from the charged amount of materials, and can also be calculated by the method described below. That is, a cross section of a positive electrode using the positive electrode material 10 is observed with a scanning electron microscope (SEM-EDX) to obtain a two-dimensional mapping image of elements.
- the measurement conditions of the scanning electron microscope for acquiring the two-dimensional mapping image are, for example, a magnification of 1000 times to 3000 times and an acceleration voltage of 5 kV.
- a two-dimensional mapping image is acquired at a resolution of 1280 ⁇ 960.
- the second solid electrolyte 105 and the coated active material 100 may be in contact with each other. At this time, the first solid electrolyte and the second solid electrolyte 105 are in contact with each other.
- the positive electrode material 10 may contain a plurality of particles of the second solid electrolyte 105 and a plurality of particles of the coated active material 100 .
- the ratio "v1:100-v1" between the volume of the positive electrode active material 101 and the volume of the solid electrolyte may satisfy 30 ⁇ v1 ⁇ 95.
- 30 ⁇ v1 the energy density of the battery is sufficiently ensured.
- v1 ⁇ 95 the battery can operate at high power.
- “Volume of solid electrolyte” is the total volume of the first solid electrolyte and the second solid electrolyte 105 .
- the positive electrode active material 101 includes a material that has the property of intercalating and deintercalating metal ions (for example, lithium ions).
- metal ions for example, lithium ions.
- As the positive electrode active material 101 lithium-containing transition metal oxides, transition metal fluorides, polyanion materials, fluorinated polyanion materials, transition metal sulfides, transition metal oxysulfides, transition metal oxynitrides, and the like can be used.
- a lithium-containing transition metal oxide when a lithium-containing transition metal oxide is used as the positive electrode active material 101, the manufacturing cost of the battery can be reduced and the average discharge voltage can be increased.
- Lithium-containing transition metal oxides include Li(NiCoAl)O 2 , Li(NiCoMn)O 2 and LiCoO 2 .
- the positive electrode active material 101 has, for example, a particle shape.
- the shape of the particles of the positive electrode active material 101 is not particularly limited.
- the shape of the particles of the positive electrode active material 101 can be spherical, oval, scaly, or fibrous.
- the median diameter of the coated active material 100 may be 0.1 ⁇ m or more and 100 ⁇ m or less.
- the coated active material 100 and the second solid electrolyte 105 can form a good dispersion state in the positive electrode material 10 .
- the charge/discharge characteristics of the battery are improved.
- the median diameter of coated active material 100 is 100 ⁇ m or less, the diffusion rate of lithium inside coated active material 100 is sufficiently ensured. Therefore, the battery can operate at high output.
- the median diameter of the coated active material 100 may be larger than the median diameter of the second solid electrolyte 105 . Thereby, the coated active material 100 and the second solid electrolyte 105 can form a good dispersion state.
- volume diameter means the particle diameter when the cumulative volume in the volume-based particle size distribution is equal to 50%.
- the volume-based particle size distribution is measured by, for example, a laser diffraction measurement device or an image analysis device.
- Coating layer 102 contains a first solid electrolyte.
- the first solid electrolyte has ionic conductivity.
- the ionic conductivity is typically lithium ion conductivity.
- a coating layer 102 is provided on the surface of the positive electrode active material 101 .
- Coating layer 102 may contain the first solid electrolyte as a main component, or may contain only the first solid electrolyte.
- a “main component” means the component contained most in mass ratio. "Containing only the first solid electrolyte” means that materials other than the first solid electrolyte are not intentionally added except for unavoidable impurities.
- raw materials of the first solid electrolyte, by-products generated when manufacturing the first solid electrolyte, and the like are included in the unavoidable impurities.
- the mass ratio of the inevitable impurities to the total mass of the coating layer 102 may be 5% or less, 3% or less, 1% or less, or 0.5% or less.
- the first solid electrolyte is a material containing Li, Ti, M, and X. M and X are as described above. Such materials have good ionic conductivity and oxidation resistance. Therefore, the coated active material 100 having the coating layer 102 of the first solid electrolyte improves the charge/discharge efficiency of the battery and the thermal stability of the battery.
- M may contain at least one selected from the group consisting of Ca, Mg, Al, Y, and Zr. With such a configuration, the halide solid electrolyte exhibits high ionic conductivity.
- M may be Al.
- a halide solid electrolyte as the first solid electrolyte is represented, for example, by the following compositional formula (1).
- composition formula (1) ⁇ , ⁇ , ⁇ and ⁇ are each independently a value greater than 0.
- the halide solid electrolyte represented by the compositional formula (1) has higher ionic conductivity than a halide solid electrolyte such as LiI, which consists only of Li and a halogen element. Therefore, when the halide solid electrolyte represented by the compositional formula (1) is used in a battery, the charge/discharge efficiency of the battery can be improved.
- the halide solid electrolyte may consist essentially of Li, Ti, Al and X.
- the halide solid electrolyte consists essentially of Li, Ti, Al and X means that Li, Ti, Al and X means that the total molar ratio (ie, molar fraction) of the amount of substances is 90% or more. As an example, the molar ratio (ie, mole fraction) may be 95% or greater.
- the halide solid electrolyte may consist of Li, Ti, Al and X only.
- the ratio of the amount of Li to the total amount of Ti and Al is 1.12 or more and 5.07 or less.
- the halide solid electrolyte as the first solid electrolyte may be represented by the following compositional formula (2).
- composition formula (2) 0 ⁇ x ⁇ 1 and 0 ⁇ b ⁇ 1.5 are satisfied.
- a halide solid electrolyte having such a composition has high ionic conductivity.
- composition formula (2) 0.1 ⁇ x ⁇ 0.7 may be satisfied.
- the upper and lower limits of the range of x in the composition formula (2) are 0.1, 0.3, 0.4, 0.5, 0.6, 0.67, 0.7, 0.8, and It can be defined by any combination of values selected from 0.9.
- the upper and lower limits of the range of b in the composition formula (2) are selected from numerical values of 0.8, 0.9, 0.94, 1.0, 1.06, 1.1, and 1.2 It can be defined by any combination.
- the halide solid electrolyte may be crystalline or amorphous.
- the thickness of the coating layer 102 is, for example, 1 nm or more and 500 nm or less. If the thickness of coating layer 102 is appropriately adjusted, contact between positive electrode active material 101 and second solid electrolyte 105 can be sufficiently suppressed.
- the thickness of the coating layer 102 can be specified by thinning the coated active material 100 by a method such as ion milling and observing the cross section of the coated active material 100 with a transmission electron microscope. An average value of thicknesses measured at a plurality of arbitrary positions (for example, 5 points) can be regarded as the thickness of the coating layer 102 .
- the halide solid electrolyte may be a solid electrolyte that does not contain sulfur. In this case, generation of sulfur-containing gas such as hydrogen sulfide gas from the solid electrolyte can be avoided.
- a solid electrolyte containing no sulfur means a solid electrolyte represented by a composition formula containing no elemental sulfur. Therefore, a solid electrolyte containing a very small amount of sulfur, for example a solid electrolyte having a sulfur content of 0.1% by mass or less, belongs to the solid electrolyte containing no sulfur.
- the halide solid electrolyte may further contain oxygen as an anion other than the halogen element.
- the shape of the halide solid electrolyte is not particularly limited.
- the shape of the halide solid electrolyte may be, for example, acicular, spherical, ellipsoidal, or the like.
- the shape of the halide solid electrolyte may be particulate.
- the halide solid electrolyte When the shape of the halide solid electrolyte is, for example, particulate (eg, spherical), the halide solid electrolyte may have a median diameter of 0.01 ⁇ m or more and 100 ⁇ m or less.
- a halide solid electrolyte can be produced by the following method.
- a method for producing the halide solid electrolyte represented by the compositional formula (1) will be exemplified.
- Raw material powders of halides are prepared according to the desired composition.
- a halide may be a compound consisting of three elements including a halogen element.
- LiF, TiF 4 and AlF 3 are prepared as raw material powders at a molar ratio of about 2.7:0.3:0.7.
- the element species of "M” and "X" in the composition formula (1) can be determined.
- the values of " ⁇ ", " ⁇ ", “ ⁇ ” and “ ⁇ ” in the composition formula (1) can be adjusted by adjusting the type of raw material powder, the mixing ratio of the raw material powder and the synthesis process.
- the raw material powders may be mixed in pre-adjusted molar ratios to compensate for possible compositional changes in the synthesis process.
- the mechanochemical milling method is used to react the raw material powders with each other to obtain a reactant.
- the reactants may be fired in vacuum or in an inert atmosphere.
- raw material powders may be mixed and pulverized and then fired in a vacuum or in an inert atmosphere to obtain a reactant. Firing is performed, for example, under conditions of 100° C. or higher and 400° C. or lower for 1 hour or longer.
- the raw material powder may be fired in a sealed container such as a quartz tube in order to suppress compositional changes that may occur during firing. A halide solid electrolyte is obtained through these steps.
- composition of the crystal phase (that is, the crystal structure) of the halide solid electrolyte can be adjusted and determined by the reaction method and reaction conditions between the raw material powders.
- Second solid electrolyte 105 may contain at least one selected from the group consisting of halide solid electrolytes, sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, and complex hydride solid electrolytes.
- halide solid electrolyte examples include the materials previously described as the first solid electrolyte. That is, the composition of the second solid electrolyte 105 may be the same as or different from the composition of the first solid electrolyte.
- An oxide solid electrolyte is a solid electrolyte containing oxygen.
- the oxide solid electrolyte may further contain anions other than sulfur and halogen elements as anions other than oxygen.
- oxide solid electrolytes examples include NASICON solid electrolytes typified by LiTi 2 (PO 4 ) 3 and element-substituted products thereof, (LaLi)TiO 3 -based perovskite solid electrolytes, Li 14 ZnGe 4 O 16 , Li LISICON solid electrolytes typified by 4 SiO 4 , LiGeO 4 and elemental substitutions thereof, garnet type solid electrolytes typified by Li 7 La 3 Zr 2 O 12 and elemental substitutions thereof, Li 3 PO 4 and its N Glass or glass-ceramics obtained by adding materials such as Li 2 SO 4 and Li 2 CO 3 to base materials containing Li—BO compounds such as substitutes, LiBO 2 and Li 3 BO 3 may be used.
- a compound of a polymer compound and a lithium salt can be used.
- the polymer compound may have an ethylene oxide structure.
- a polymer compound having an ethylene oxide structure can contain a large amount of lithium salt. Therefore, the ionic conductivity can be further increased.
- Lithium salts include LiPF6 , LiBF4 , LiSbF6 , LiAsF6 , LiSO3CF3 , LiN( SO2F )2, LiN(SO2CF3)2 , LiN ( SO2C2F5 ) 2 , LiN ( SO2CF3 ) ( SO2C4F9 ), LiC( SO2CF3 ) 3 etc. are mentioned .
- One lithium salt selected from these may be used alone, or a mixture of two or more lithium salts selected from these may be used.
- LiBH 4 --LiI LiBH 4 --P 2 S 5 or the like
- LiBH 4 --LiI LiBH 4 --P 2 S 5 or the like
- the second solid electrolyte 105 may contain Li and S.
- the second solid electrolyte 105 may contain a sulfide solid electrolyte.
- a sulfide solid electrolyte has high ionic conductivity and can improve the charge-discharge efficiency of a battery.
- sulfide solid electrolytes may be inferior in oxidation resistance.
- Examples of sulfide solid electrolytes include Li 2 SP 2 S 5 , Li 2 S—SiS 2 , Li 2 S—B 2 S 3 , Li 2 S—GeS 2 , Li 3.25 Ge 0.25 P 0.75 S 4 , Li 10 GeP 2 S 12 and the like can be used.
- LiX, Li2O , MOq , LipMOq , etc. may be added to these.
- X in “LiX” is at least one selected from the group consisting of F, Cl, Br and I.
- the element M in “MO q " and “Li p MO q " is at least one selected from the group consisting of P, Si, Ge, B, Al, Ga, In, Fe, and Zn.
- p and q in "MO q " and "Li p MO q " are each independently natural numbers.
- the second solid electrolyte 105 may contain two or more of the materials listed as solid electrolytes.
- the second solid electrolyte 105 may contain, for example, a halide solid electrolyte and a sulfide solid electrolyte.
- the second solid electrolyte 105 may have lithium ion conductivity higher than that of the first solid electrolyte.
- the second solid electrolyte 105 may contain unavoidable impurities such as starting materials, by-products, and decomposition products used when synthesizing the solid electrolyte. This also applies to the first solid electrolyte.
- the positive electrode material 10 may contain a binder for the purpose of improving adhesion between particles.
- a binder is used to improve the binding properties of the material forming the positive electrode.
- Binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polyacrylic acid methyl ester, polyacrylic acid ethyl ester, poly Acrylate hexyl ester, polymethacrylic acid, polymethacrylic acid methyl ester, polymethacrylic acid ethyl ester, polymethacrylic acid hexyl ester, polyvinyl acetate, polyvinylpyrrolidone, polyether, polycarbonate, polyether sulfone, polyether ketone, polyether Ether ketone, polyphenylene sulfide, hexafluoropolypropylene
- tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, butadiene, styrene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid ester, acrylic acid , and hexadiene may also be used.
- One selected from these may be used alone, or two or more may be used in combination.
- the binder may be an elastomer because it has excellent binding properties. Elastomers are polymers that have rubber elasticity.
- the elastomer used as the binder may be a thermoplastic elastomer or a thermosetting elastomer.
- the binder may contain a thermoplastic elastomer.
- thermoplastic elastomers styrene-ethylene-butylene-styrene (SEBS), styrene-ethylene-propylene-styrene (SEPS), styrene-ethylene-ethylene-propylene-styrene (SEEPS), butylene rubber (BR), isoprene rubber (IR) , chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), styrene-butylene rubber (SBR), styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), hydrogenated isoprene rubber (HIR), hydrogenated Butyl rubber (HIIR), hydrogenated nitrile rubber (HNBR), hydrogenated styrene-butylene rubber (HSBR), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE) and
- the coating layer 102 may contain a conductive aid for the purpose of increasing electronic conductivity.
- conductive aids include graphites such as natural graphite or artificial graphite, carbon blacks such as acetylene black and Ketjen black, conductive fibers such as carbon fiber or metal fiber, carbon fluoride, and metal powder such as aluminum.
- conductive whiskers such as zinc oxide or potassium titanate, conductive metal oxides such as titanium oxide, conductive polymer compounds such as polyaniline, polypyrrole, polythiophene, and the like. Cost reduction can be achieved when a carbon conductive aid is used.
- the positive electrode material 10 may contain the above conductive aid for the purpose of increasing electronic conductivity.
- the coated active material 100 can be manufactured by the following method.
- a powder of the positive electrode active material 101 and a powder of the first solid electrolyte are mixed at an appropriate ratio to obtain a mixture.
- the mixture is milled and mechanical energy is imparted to the mixture.
- a mixing device such as a ball mill can be used for the milling treatment.
- the milling process may be performed in a dry and inert atmosphere to suppress oxidation of the material.
- the coated active material 100 may be produced by a dry particle compounding method.
- the treatment by the dry particle compounding method includes applying at least one mechanical energy selected from the group consisting of impact, compression and shear to the positive electrode active material 101 and the first solid electrolyte.
- the positive electrode active material 101 and the first solid electrolyte are mixed at an appropriate ratio.
- the device used to manufacture the coated active material 100 is not particularly limited, and may be a device capable of imparting mechanical energy such as impact, compression, and shear to the mixture of the positive electrode active material 101 and the first solid electrolyte.
- Apparatuses capable of imparting mechanical energy include compression shear processing apparatuses (particle compounding apparatuses) such as ball mills, "Mechanofusion” (manufactured by Hosokawa Micron Corporation), and "Nobiruta” (manufactured by Hosokawa Micron Corporation).
- Mechanisms is a particle compounding device that uses dry mechanical compounding technology by applying strong mechanical energy to multiple different raw material powders.
- mechanofusion mechanical energies of compression, shear, and friction are imparted to raw material powder placed between a rotating container and a press head. This causes particle compositing.
- Nobilta is a particle compounding device that uses dry mechanical compounding technology, which is an advanced form of particle compounding technology, in order to compound nanoparticles from raw materials. Nobilta manufactures composite particles by subjecting multiple types of raw powders to mechanical energy of impact, compression and shear.
- the rotor which is arranged in a horizontal cylindrical mixing vessel with a predetermined gap between it and the inner wall of the mixing vessel, rotates at high speed, forcing the raw material powder to pass through the gap. This process is repeated multiple times. Thereby, composite particles of the positive electrode active material 101 and the first solid electrolyte can be produced by applying impact, compression, and shear forces to the mixture.
- the thickness of the coating layer 102, the coverage of the positive electrode active material 101 with the first solid electrolyte, and the like can be controlled by adjusting the conditions such as the rotational speed of the rotor, the treatment time, and the amount of charge.
- the coated active material 100 may be manufactured by mixing the positive electrode active material 101 and the first solid electrolyte using a mortar, mixer, or the like.
- the first solid electrolyte may be deposited on the surface of the positive electrode active material 101 by various methods such as a spray method, a spray dry coating method, an electrodeposition method, an immersion method, and a mechanical mixing method using a disperser.
- Cathode material 10 is obtained by mixing coated active material 100 and second solid electrolyte 105 .
- a method for mixing the coated active material 100 and the second solid electrolyte 105 is not particularly limited.
- the coated active material 100 and the second solid electrolyte 105 may be mixed using a tool such as a mortar, or the coated active material 100 and the second solid electrolyte 105 may be mixed using a mixing device such as a ball mill. .
- FIG. 2 is a cross-sectional view showing a schematic configuration of a positive electrode material 20 according to a modification.
- Cathode material 20 has a coating active material 110 and a second solid electrolyte 105 .
- Coating active material 110 has positive electrode active material 101 and coating layer 104 .
- the covering layer 104 has a first covering layer 102 and a second covering layer 103 .
- the first coating layer 102 is a layer containing a first solid electrolyte.
- the second coating layer 103 is a layer containing a base material.
- the first coating layer 102 is positioned outside the second coating layer 103 . With such a configuration, it is possible to further suppress an increase in the internal resistance of the battery.
- the first coating layer 102 is a layer corresponding to the coating layer 102 described with reference to FIG.
- the second coating layer 103 is located between the first coating layer 102 and the positive electrode active material 101 .
- the second coating layer 103 is in direct contact with the positive electrode active material 101 .
- the second coating layer 103 may contain, as a base material, a material with low electronic conductivity such as an oxide material or an oxide solid electrolyte.
- oxide materials include SiO 2 , Al 2 O 3 , TiO 2 , B 2 O 3 , Nb 2 O 5 , WO 3 and ZrO 2 .
- oxide solid electrolytes include Li—Nb—O compounds such as LiNbO 3 , Li—B—O compounds such as LiBO 2 and Li 3 BO 3 , Li—Al—O compounds such as LiAlO 2 , Li 4 SiO 4 and the like.
- the base material may be one selected from these or a mixture of two or more.
- the underlying material may be a solid electrolyte having lithium ion conductivity.
- the underlying material is typically an oxide solid electrolyte with lithium ion conductivity.
- the oxide solid electrolyte has high ionic conductivity and excellent high potential stability. By using an oxide solid electrolyte as the base material, the charge/discharge efficiency of the battery can be improved.
- the underlying material may be a material containing Nb.
- the underlying material typically includes lithium niobate (LiNbO 3 ). According to such a configuration, it is possible to improve the charging and discharging efficiency of the battery. It is also possible to use the materials described above as the oxide solid electrolyte, which is the underlying material.
- the ionic conductivity of the halide solid electrolyte included in the first coating layer 102 is higher than the ionic conductivity of the underlying material included in the second coating layer 103 .
- oxidation of the second solid electrolyte 105 can be further suppressed without sacrificing ionic conductivity.
- the thickness of the first coating layer 102 is, for example, 1 nm or more and 500 nm or less.
- the thickness of the second covering layer 103 is, for example, 1 nm or more and 500 nm or less. If the thicknesses of first coating layer 102 and second coating layer 103 are appropriately adjusted, contact between positive electrode active material 101 and second solid electrolyte 105 can be sufficiently suppressed.
- the thickness of each layer can be specified in the manner previously described.
- the coated active material 110 can be manufactured by the following method.
- the second coating layer 103 is formed on the surface of the positive electrode active material 101 .
- a method for forming the second coating layer 103 is not particularly limited. Methods for forming the second coating layer 103 include a liquid phase coating method and a vapor phase coating method.
- a precursor solution of the base material is applied to the surface of the positive electrode active material 101 .
- the precursor solution can be a mixed solution (sol solution) of solvent, lithium alkoxide and niobium alkoxide.
- Lithium alkoxides include lithium ethoxide.
- Niobium alkoxides include niobium ethoxide.
- Solvents are, for example, alcohols such as ethanol. The amounts of lithium alkoxide and niobium alkoxide are adjusted according to the target composition of the second coating layer 103 . Water may be added to the precursor solution, if desired.
- the precursor solution may be acidic or alkaline.
- the method of applying the precursor solution to the surface of the positive electrode active material 101 is not particularly limited.
- the precursor solution can be applied to the surface of the positive electrode active material 101 using a tumbling fluidized granulation coating apparatus.
- the precursor solution can be sprayed onto the positive electrode active material 101 while rolling and flowing the positive electrode active material 101 to apply the precursor solution to the surface of the positive electrode active material 101 . .
- a precursor film is formed on the surface of the positive electrode active material 101 .
- the positive electrode active material 101 coated with the precursor coating is heat-treated. The heat treatment promotes gelation of the precursor coating to form the second coating layer 103 .
- the vapor phase coating method includes a pulsed laser deposition (PLD) method, a vacuum deposition method, a sputtering method, a thermal chemical vapor deposition (CVD) method, a plasma chemical vapor deposition method, and the like.
- PLD pulsed laser deposition
- CVD thermal chemical vapor deposition
- a plasma chemical vapor deposition method and the like.
- an ion-conducting material as a target is irradiated with a high-energy pulse laser (eg, KrF excimer laser, wavelength: 248 nm) to deposit sublimated ion-conducting material on the surface of the positive electrode active material 101 .
- a high-energy pulse laser eg, KrF excimer laser, wavelength: 248 nm
- high-density sintered LiNbO 3 is used as a target.
- the method of forming the second coating layer 103 is not limited to the above.
- the second coating layer 103 may be formed by various methods such as a spray method, a spray dry coating method, an electrodeposition method, an immersion method, and a mechanical mixing method using a disperser.
- the first coating layer 102 is formed by the method described above. Thereby, the coated active material 110 is obtained.
- FIG. 3 is a cross-sectional view showing a schematic configuration of a battery according to Embodiment 2.
- Battery 200 includes positive electrode 201 , separator layer 202 and negative electrode 203 .
- a separator layer 202 is arranged between the positive electrode 201 and the negative electrode 203 .
- Positive electrode 201 includes at least one of positive electrode material 10 and positive electrode material 20 described in the first embodiment. With such a configuration, an increase in internal resistance of battery 200 can be suppressed.
- each of the positive electrode 201 and the negative electrode 203 may be 10 ⁇ m or more and 500 ⁇ m or less. When the thickness of the positive electrode 201 and the negative electrode 203 is 10 ⁇ m or more, sufficient energy density of the battery can be ensured. When the thickness of the positive electrode 201 and the negative electrode 203 is 500 ⁇ m or less, the battery 200 can operate at high output.
- the separator layer 202 is a layer containing an electrolyte material. Separator layer 202 may contain at least one solid electrolyte selected from the group consisting of sulfide solid electrolytes, oxide solid electrolytes, halide solid electrolytes, polymer solid electrolytes, and complex hydride solid electrolytes. Details of each solid electrolyte are as described in the first embodiment.
- the thickness of the separator layer 202 may be 1 ⁇ m or more and 300 ⁇ m or less. When the thickness of the separator layer 202 is 1 ⁇ m or more, the positive electrode 201 and the negative electrode 203 can be separated more reliably. When the separator layer 202 has a thickness of 300 ⁇ m or less, the battery 200 can operate at high output.
- the negative electrode 203 contains, as a negative electrode active material, a material that has the property of absorbing and releasing metal ions (for example, lithium ions).
- Metal materials, carbon materials, oxides, nitrides, tin compounds, silicon compounds, etc. can be used as negative electrode active materials.
- the metal material may be a single metal.
- the metallic material may be an alloy.
- metal materials include lithium metal and lithium alloys.
- Examples of carbon materials include natural graphite, coke, ungraphitized carbon, carbon fiber, spherical carbon, artificial graphite, and amorphous carbon. From the viewpoint of capacity density, silicon (Si), tin (Sn), silicon compounds, tin compounds, etc. can be preferably used.
- the median diameter of the particles of the negative electrode active material may be 0.1 ⁇ m or more and 100 ⁇ m or less.
- the negative electrode 203 may contain other materials such as a solid electrolyte.
- a solid electrolyte the material described in Embodiment 1 can be used.
- Example 1 [Production of first solid electrolyte]
- These were pulverized in a mortar and mixed to obtain a mixture.
- the mixed powder was milled using a planetary ball mill for 12 hours at 500 rpm.
- a powder of a halide solid electrolyte was obtained as the first solid electrolyte of Example 1.
- the halide solid electrolyte of Example 1 had a composition represented by Li2.5Ti0.5Al0.5F6 (hereinafter referred to as "LTAF").
- NCA Li(NiCoAl)O 2
- LTAF a coating layer made of LTAF
- the coating layer was formed by compressive shearing treatment using a particle compounding device (NOB-MINI, manufactured by Hosokawa Micron Corporation).
- NCA and LTAF were weighed so as to have a volume ratio of 98:2, and treated under the conditions of blade clearance: 2 mm, number of revolutions: 6000 rpm, and treatment time: 50 minutes.
- NOB-MINI particle compounding device
- Example 2 A coated active material of Example 2 was obtained in the same manner as in Example 1, except that the volume ratio of NCA and LTAF was changed to 97:3.
- Example 3 A coated active material of Example 3 was obtained in the same manner as in Example 1, except that the volume ratio of NCA and LTAF was changed to 95.4:4.6.
- Example 4 A coated active material of Example 4 was obtained in the same manner as in Example 1, except that the volume ratio of NCA and LTAF was changed to 93:7.
- Example 5 A coated active material of Example 5 was obtained in the same manner as in Example 1, except that the volume ratio of NCA and LTAF was changed to 90:10.
- Example 6 A coated active material of Example 6 was obtained in the same manner as in Example 1, except that the volume ratio of NCA and LTAF was changed to 85:15.
- the positive electrode materials of Examples 2 to 6 and Reference Example 1 were produced by the same method as in Example 1.
- the ratio V1/Vt of the volume V1 of the first solid electrolyte to the total volume Vt of the first solid electrolyte (LTAF) and the second solid electrolyte (LPS) is expressed as a percentage and is shown in Table 1. It was as shown.
- the cathode material was weighed to contain 14 mg of NCA.
- LPS and a positive electrode material were laminated in this order in an insulating outer cylinder.
- the resulting laminate was pressure molded at a pressure of 720 MPa.
- metallic lithium was arranged so as to be in contact with the LPS layer, and pressure molding was performed again at a pressure of 40 MPa.
- stainless steel current collectors were arranged above and below the laminate.
- a current collecting lead was attached to each current collector.
- the inside of the outer cylinder was isolated from the outside atmosphere by sealing the outer cylinder with an insulating ferrule. Batteries of Examples 1 to 6 and Reference Example 1 were produced through the above steps.
- a surface pressure of 150 MPa was applied to the battery by restraining the battery from above and below with four bolts.
- Electrochemical impedance measurements were performed by Charging refers to a state in which current flows in the direction in which lithium ions move from the NCA-containing positive electrode to the Li metal (ie, negative electrode).
- a potentiostat (VMP300, manufactured by Biologic) equipped with a frequency response analyzer was used for the measurement. The measurement temperature was 25°C.
- Discharge refers to a state in which current flows in the direction that lithium ions move from the Li metal (ie, the negative electrode) to the positive electrode containing the NCA.
- the internal temperature of the constant temperature bath was changed to 60°C, and charging/discharging was performed for 60 cycles at a current value of 5.88 mA, which is a 2C rate (1/2 time rate).
- the internal temperature of the constant temperature bath is returned to 25° C., and the battery is charged at a constant current of 147 ⁇ A, which is 0.05 C rate (20 hour rate) with respect to the theoretical capacity of the battery, until the voltage reaches 4.3 V.
- Electrochemical impedance measurements were performed by applying an amplitude of 10 mV at frequencies from 1 MHz to 0.01 Hz.
- the battery was discharged at a constant current of 147 ⁇ A, which is 0.05C rate (20 hour rate) with respect to the theoretical capacity of the battery, until the voltage reached 2.5V.
- FIG. 4A is a graph showing a Cole-Cole plot obtained by electrochemical impedance measurement of the battery of Example 1 before charge-discharge cycles.
- FIG. 4B is a graph showing a Cole-Cole plot obtained from electrochemical impedance measurements of the battery of Example 1 after charge-discharge cycles. 4A and 4B, the vertical axis represents the imaginary part of impedance and the horizontal axis represents the real part of impedance.
- the resistance component can be roughly divided into the following three. resistance up to point R1 (bulk resistance), resistance between points R1 and R2 (charge transfer resistance), and resistance between points R2 and R3 (ion diffusion resistance). .
- the resistance between points R 1 and R 2 ie the difference between the real values of points R 1 and R 2 is taken as the resistance of the battery. From the Cole-Cole plots of each of the examples and reference examples, using the real values of the points R 1 and R 2 , using the following formula (1), the battery before the charge-discharge cycle and after the charge-discharge cycle A resistance value R was calculated. Table 1 shows the results.
- the internal resistance decreased. That is, when the ratio V1/Vt of the volume of the first solid electrolyte (LTAF) and the second solid electrolyte (LPS) to the total volume of the first solid electrolyte (LTAF) and the second solid electrolyte (LPS) is 8% or more and 30% or less, Decreased internal resistance. It is presumed that this is because the positive electrode active material 101 was sufficiently covered with the first solid electrolyte when the ratio V1/Vt was 8% or more. Further, it is presumed that the above ratio V1/Vt of 40% or less ensures sufficient electronic conductivity and ionic conductivity of the positive electrode material.
- At least one selected from the group consisting of metal elements and metalloid elements other than Li and Ti for example, Ca, Mg, Al, Y, or Zr, halogen
- compound solid electrolytes exhibit similar ionic conductivity (for example, Japanese Patent Application No. 2020-048461 filed by the applicant of the present application). Therefore, instead of Al or together with Al, a halide solid electrolyte containing at least one selected from the group consisting of these elements can be used. Even in this case, the battery can be charged and discharged, and the effect of suppressing the oxidation reaction of the sulfide solid electrolyte and suppressing the increase in resistance can be obtained.
- oxidation of the sulfide solid electrolyte mainly occurs when the sulfide solid electrolyte comes into contact with the positive electrode active material and electrons are extracted from the sulfide solid electrolyte. Therefore, according to the technology of the present disclosure, the effect of suppressing oxidation of the sulfide solid electrolyte can be obtained even when an active material other than NCA is used.
- the technology of the present disclosure is useful, for example, for all-solid lithium secondary batteries.
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Abstract
Description
正極活物質と、
第1固体電解質を含み、前記正極活物質の表面の少なくとも一部を被覆する被覆層と、
第2固体電解質と、
を備え、
前記第1固体電解質は、Li、Ti、M、およびXを含み、
Mは、LiおよびTi以外の金属元素および半金属元素からなる群より選択される少なくとも1つであり、
Xは、F、Cl、Br、およびIからなる群より選択される少なくとも1つであり、
前記第2固体電解質は前記被覆層を介して前記正極活物質と接しており、
前記第1固体電解質と前記第2固体電解質との合計体積に対する前記第1固体電解質の体積の比率が4%以上、かつ、45%以下である、
正極材料を提供する。
固体電解質を用いた電池の充放電を繰り返すと、正極活物質から酸素が発生することがある。発生した酸素は、固体電解質を酸化させ、電池の内部抵抗を増加させる。内部抵抗の増加は、出力電圧の低下、電池の発熱、放電容量の低下などの諸問題を引き起こす。したがって、固体電解質を用いた電池の内部抵抗の増加を抑制するのに適した技術が望まれている。
本開示の第1態様に係る正極材料は、
正極活物質と、
第1固体電解質を含み、前記正極活物質の表面の少なくとも一部を被覆する被覆層と、
第2固体電解質と、
を備え、
前記第1固体電解質は、Li、Ti、M、およびXを含み、
Mは、LiおよびTi以外の金属元素および半金属元素からなる群より選択される少なくとも1つであり、
Xは、F、Cl、Br、およびIからなる群より選択される少なくとも1つであり、
前記第2固体電解質は前記被覆層を介して前記正極活物質と接しており、
前記第1固体電解質と前記第2固体電解質との合計体積に対する前記第1固体電解質の体積の比率が4%以上、かつ、45%以下である。
LiαTiβMγXδ・・・式(1)
図1は、実施の形態1に係る正極材料の概略構成を示す断面図である。正極材料10は、正極活物質101、第1固体電解質を含む被覆層102、および第2固体電解質105を有する。被覆層102は、正極活物質101の表面の少なくとも一部を被覆している。被覆層102は、正極活物質101の表面の一部のみを被覆していてもよく、正極活物質101の表面を一様に被覆していてもよい。正極活物質101および被覆層102は、被覆活物質100を構成している。第2固体電解質105は、被覆層102を介して正極活物質101と接している。
正極活物質101は、金属イオン(例えば、リチウムイオン)を吸蔵および放出する特性を有する材料を含む。正極活物質101として、リチウム含有遷移金属酸化物、遷移金属フッ化物、ポリアニオン材料、フッ素化ポリアニオン材料、遷移金属硫化物、遷移金属オキシ硫化物、遷移金属オキシ窒化物などが使用されうる。特に、正極活物質101として、リチウム含有遷移金属酸化物を用いた場合には、電池の製造コストを安くでき、平均放電電圧を高めることができる。リチウム含有遷移金属酸化物としては、Li(NiCoAl)O2、Li(NiCoMn)O2、LiCoO2などが挙げられる。
被覆層102は、第1固体電解質を含む。第1固体電解質は、イオン伝導性を有する。イオン伝導性は、典型的には、リチウムイオン伝導性である。正極活物質101の表面上に被覆層102が設けられている。被覆層102は、第1固体電解質を主成分として含んでいてもよく、第1固体電解質のみを含んでいてもよい。「主成分」は、質量比で最も多く含まれる成分を意味する。「第1固体電解質のみを含む」とは、不可避不純物を除き、第1固体電解質以外の材料が意図的に添加されていないことを意味する。例えば、第1固体電解質の原料、第1固体電解質を作製する際に生じる副生成物などは、不可避不純物に含まれる。被覆層102の全体の質量に対する不可避不純物の質量の比率は、5%以下であってもよく、3%以下であってもよく、1%以下であってもよく、0.5%以下であってもよい。
ハロゲン化物固体電解質は、下記の方法によって製造されうる。ここでは、組成式(1)で表されるハロゲン化物固体電解質の製造方法について例示する。
第2固体電解質105は、ハロゲン化物固体電解質、硫化物固体電解質、酸化物固体電解質、高分子固体電解質、および錯体水素化物固体電解質からなる群より選択される少なくとも1つを含んでいてもよい。
正極材料10には、粒子同士の密着性を向上する目的で、結着剤が含まれていてもよい。結着剤は、正極を構成する材料の結着性を向上するために用いられる。結着剤としては、ポリフッ化ビニリデン、ポリテトラフルオロエチレン、ポリエチレン、ポリプロピレン、アラミド樹脂、ポリアミド、ポリイミド、ポリアミドイミド、ポリアクリルニトリル、ポリアクリル酸、ポリアクリル酸メチルエステル、ポリアクリル酸エチルエステル、ポリアクリル酸ヘキシルエステル、ポリメタクリル酸、ポリメタクリル酸メチルエステル、ポリメタクリル酸エチルエステル、ポリメタクリル酸ヘキシルエステル、ポリ酢酸ビニル、ポリビニルピロリドン、ポリエーテル、ポリカーボネート、ポリエーテルサルフォン、ポリエーテルケトン、ポリエーテルエーテルケトン、ポリフェニレンサルファイド、ヘキサフルオロポリプロピレン、スチレンブタジエンゴム、カルボキシメチルセルロース、エチルセルロースなどが挙げられる。また、テトラフルオロエチレン、ヘキサフルオロエチレン、ヘキサフルオロプロピレン、パーフルオロアルキルビニルエーテル、フッ化ビニリデン、クロロトリフルオロエチレン、エチレン、プロピレン、ブタジエン、スチレン、ペンタフルオロプロピレン、フルオロメチルビニルエーテル、アクリル酸エステル、アクリル酸、およびヘキサジエンからなる群より選択される2つ以上のモノマーの共重合体も使用されうる。これらから選択される1つが単独で使用されてもよく、2つ以上が組み合わされて使用されてもよい。
被覆活物質100は、下記の方法によって製造されうる。
正極材料10は、被覆活物質100と第2固体電解質105とを混合することによって得られる。被覆活物質100と第2固体電解質105とを混合する方法は特に限定されない。乳鉢などの器具を用いて被覆活物質100と第2固体電解質105とを混合してもよく、ボールミルなどの混合装置を用いて被覆活物質100と第2固体電解質105とを混合してもよい。
図2は、変形例に係る正極材料20の概略構成を示す断面図である。正極材料20は、被覆活物質110および第2固体電解質105を有する。被覆活物質110は、正極活物質101および被覆層104を有する。被覆層104は、第1被覆層102および第2被覆層103を有する。第1被覆層102は、第1固体電解質を含む層である。第2被覆層103は、下地材料を含む層である。第1被覆層102は、第2被覆層103の外側に位置している。このような構成によれば、電池の内部抵抗の増加を更に抑制することができる。
被覆活物質110は、下記の方法によって製造されうる。
図3は、実施の形態2に係る電池の概略構成を示す断面図である。電池200は、正極201、セパレータ層202、および負極203を含む。セパレータ層202は、正極201と負極203との間に配置されている。正極201は、実施の形態1で説明した正極材料10および正極材料20の少なくとも1つを含む。このような構成によれば、電池200の内部抵抗の増加を抑制することができる。
[第1固体電解質の作製]
露点-60℃以下のアルゴングローブボックス内で、原料粉末であるLiF、TiF4、およびAlF3をLiF:TiF4:AlF3=2.5:0.5:0.5のモル比で秤量した。これらを乳鉢で粉砕して混合して混合物を得た。混合粉は、遊星型ボールミルを用い、12時間、500rpmの条件でミリング処理した。これにより、実施例1の第1固体電解質として、ハロゲン化物固体電解質の粉末を得た。実施例1のハロゲン化物固体電解質は、Li2.5Ti0.5Al0.5F6(以下、「LTAF」と記載する)により表される組成を有していた。
正極活物質として、Li(NiCoAl)O2(以下、NCAと表記する)の粉末を用意した。次に、NCAの表面上にLTAFでできた被覆層を形成した。被覆層は、粒子複合化装置(NOB-MINI,ホソカワミクロン社製)を用いた圧縮せん断処理により形成した。具体的には、NCAとLTAFとを98:2の体積比率となるように秤量し、ブレードクリアランス:2mm、回転数:6000rpm、処理時間:50minの条件で処理した。これにより、実施例1の被覆活物質を得た。
NCAとLTAFとの体積比率を97:3に変更したことを除き、実施例1と同じ方法で実施例2の被覆活物質を得た。
NCAとLTAFとの体積比率を95.4:4.6に変更したことを除き、実施例1と同じ方法で実施例3の被覆活物質を得た。
NCAとLTAFとの体積比率を93:7に変更したことを除き、実施例1と同じ方法で実施例4の被覆活物質を得た。
NCAとLTAFとの体積比率を90:10に変更したことを除き、実施例1と同じ方法で実施例5の被覆活物質を得た。
NCAとLTAFとの体積比率を85:15に変更したことを除き、実施例1と同じ方法で実施例6の被覆活物質を得た。
LTAFを被覆していないNCAを参考例1の活物質として用いた。
露点-60℃以下のアルゴングローブボックス内で、原料粉末であるLi2SとP2S5とを、モル比でLi2S:P2S5=75:25となるように秤量した。これらを乳鉢で粉砕および混合して混合物を得た。その後、遊星型ボールミル(P-7型,フリッチュ社製)を用い、10時間、510rpmの条件で混合物をミリング処理した。これにより、ガラス状の固体電解質を得た。ガラス状の固体電解質について、不活性雰囲気中、270℃、2時間の条件で熱処理した。これにより、実施例1の第2固体電解質として、ガラスセラミックス状の硫化物固体電解質であるLi2S-P2S5(以下、「LPS」と記載する)を得た。
アルゴングローブボックス内で、NCAと固体電解質との体積比率が70:30、第1固体電解質(LTAF)と第2固体電解質(LPS)との体積比率が4.8:95.2となるように、実施例1の被覆活物質および第2固体電解質を秤量した。これらをメノウ乳鉢で混合することで、実施例1の正極材料を作製した。NCAと固体電解質との体積比率において、「固体電解質」は、第1固体電解質(LTAF)および第2固体電解質(LPS)の合計体積を意味する。
14mgのNCAが含まれるように正極材料を秤量した。絶縁性を有する外筒の中にLPSと正極材料とをこの順に積層した。得られた積層体を720MPaの圧力で加圧成形した。次に、LPS層に接するように金属リチウムを配置し、再度40MPaの圧力にて加圧成形した。これにより、正極、セパレータ層および負極からなる積層体を作製した。次に、積層体の上下にステンレス鋼製の集電体を配置した。各集電体に集電リードを取り付けた。次に、絶縁性フェルールを用いて外筒を密閉することで外筒の内部を外気雰囲気から遮断した。以上の工程を経て、実施例1から6および参考例1の電池を作製した。4本のボルトで電池を上下から拘束することで、電池に面圧150MPaの圧力を印加した。
実施例および参考例のそれぞれの電池について、以下の条件で充放電試験を実施し、充放電サイクル前の抵抗値に対する充放電サイクル後の抵抗値の比率の評価を行った。
まず、電池を25℃の恒温槽に配置した。
充放電サイクル前および充放電サイクル後の電気化学インピーダンス測定の結果について、以下に示す方法により、充放電サイクル前および充放電サイクル後の電池の抵抗値を算出した。
表1に示すように、正極活物質に対しハロゲン化物固体電解質が被覆された実施例1から6では、充放電サイクル前の抵抗値に対する充放電サイクル後の抵抗値の比率が抑制された。これは、ハロゲン化物固体電解質の被覆層によって、正極活物質から放出される酸素と硫化物固体電解質との反応が抑制されたことが原因と推測される。このように、実施例1から6では、電池の内部抵抗の増加が抑制された。
100,110 被覆活物質
101 正極活物質
102 第1被覆層
103 第2被覆層
104 被覆層
105 第2固体電解質
200 電池
201 正極
202 セパレータ層
203 負極
Claims (14)
- 正極活物質と、
第1固体電解質を含み、前記正極活物質の表面の少なくとも一部を被覆する被覆層と、
第2固体電解質と、
を備え、
前記第1固体電解質は、Li、Ti、M、およびXを含み、
Mは、LiおよびTi以外の金属元素および半金属元素からなる群より選択される少なくとも1つであり、
Xは、F、Cl、Br、およびIからなる群より選択される少なくとも1つであり、
前記第2固体電解質は前記被覆層を介して前記正極活物質と接しており、
前記第1固体電解質と前記第2固体電解質との合計体積に対する前記第1固体電解質の体積の比率が4%以上、かつ、45%以下である、
正極材料。 - 前記比率が4.8%以上である、
請求項1に記載の正極材料。 - 前記比率が41.2%以下である、
請求項1または2に記載の正極材料。 - 前記比率が8%以上である、
請求項1に記載の正極材料。 - 前記比率が30%以下である、
請求項1または2に記載の正極材料。 - 前記第2固体電解質は、LiおよびSを含む、
請求項1から5のいずれか1項に記載の正極材料。 - Mは、Ca、Mg、Al、Y、およびZrからなる群より選択される少なくとも1つを含む、
請求項1から6のいずれか1項に記載の正極材料。 - Mは、Alを含む、
請求項1から7のいずれか1項に記載の正極材料。 - 前記第1固体電解質は、下記の組成式(1)により表され、
LiαTiβMγXδ・・・式(1)
ここで、α、β、γおよびδは、それぞれ独立して、0より大きい値である、
請求項1から8のいずれか1項に記載の正極材料。 - 前記被覆層は、前記第1固体電解質を含む第1被覆層と、下地材料を含む第2被覆層とを含み、
前記第1被覆層は、前記第2被覆層の外側に位置している、
請求項1から9のいずれか1項に記載の正極材料。 - 前記下地材料がリチウムイオン伝導性を有する酸化物固体電解質を含む、
請求項10に記載の正極材料。 - 前記下地材料がニオブ酸リチウムを含む、
請求項10または11に記載の正極材料。 - 請求項1から12のいずれか1項に記載の正極材料を備えた、正極。
- 請求項13に記載の正極を備えた、電池。
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WO2019135322A1 (ja) * | 2018-01-05 | 2019-07-11 | パナソニックIpマネジメント株式会社 | 正極材料、および、電池 |
WO2019146236A1 (ja) * | 2018-01-26 | 2019-08-01 | パナソニックIpマネジメント株式会社 | 正極材料、および、電池 |
JP2020048461A (ja) | 2018-09-26 | 2020-04-02 | 旭化成株式会社 | 高濃度タンパク飲料 |
WO2021157361A1 (ja) * | 2020-02-05 | 2021-08-12 | パナソニック株式会社 | 正極材料および電池 |
WO2021187391A1 (ja) * | 2020-03-18 | 2021-09-23 | パナソニックIpマネジメント株式会社 | 正極材料、および、電池 |
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WO2019135322A1 (ja) * | 2018-01-05 | 2019-07-11 | パナソニックIpマネジメント株式会社 | 正極材料、および、電池 |
WO2019146236A1 (ja) * | 2018-01-26 | 2019-08-01 | パナソニックIpマネジメント株式会社 | 正極材料、および、電池 |
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WO2021157361A1 (ja) * | 2020-02-05 | 2021-08-12 | パナソニック株式会社 | 正極材料および電池 |
WO2021187391A1 (ja) * | 2020-03-18 | 2021-09-23 | パナソニックIpマネジメント株式会社 | 正極材料、および、電池 |
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