Positive electrode active material, positive electrode material, battery, and method for producing positive electrode active material

Abstract

The positive electrode active material of the present disclosure is a composite oxide represented by formula (1): LiNi x Me 1‑ x O2 as a main component, and the water content is 2.9 mass ppm or more and 44.7 mass ppm or less. Here, x satisfies 0.5 ≤ x ≤ 1, and Me is at least one element selected from Mn, Co, and Al.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a positive electrode active material, a positive electrode material, a battery, and a method for manufacturing a positive electrode active material. BACKGROUND

[0002] Patent Literature 1 discloses an all-solid battery using a composite active material particle having an active material particle and a covering layer covering at least part of the surface of the active material particle, and a sulfide solid electrolyte, and a moisture amount of 2.9 mass ppm or less. Patent Literature 1 discloses that a lithium ion conductive oxide such as lithium niobate, lithium titanate, lithium zirconate, lithium tantalate, lithium tungstate is used as a covering material, and lithium niobate is particularly preferable.

[0003] PRIOR ART DOCUMENTS

[0004] Patent Literature 1: Japanese Patent Application Publication No. 2018-125214 SUMMARY

[0005] The present disclosure provides a battery having a low internal resistance.

[0006] The positive electrode active material of the present disclosure,

[0007] The composite oxide represented by the following formula (1) is used as a main component, and the amount of moisture generated at 180°C is 2.9 mass ppm or more and 44.7 mass ppm or less, as measured by Karl Fischer titration.

[0008] LiNi x Me 1-x O2(1)

[0009] wherein x satisfies 0.5≤x≤1, and Me is at least one element selected from Mn, Co, and Al.

[0010] According to the present disclosure, a battery having a low internal resistance can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a cross-sectional view showing the schematic structure of the positive electrode material 1000 and the battery 2000 in Embodiments 1 and 2.

[0012] Figure 2 is a Nyquist plot showing an example of evaluation results of reaction resistance obtained by AC impedance measurement. DETAILED DESCRIPTION

[0013] (Insight underlying the present disclosure)

[0014] The present inventors have conducted intensive studies on factors that increase the battery resistance of an all-solid lithium ion battery. As a result, the present inventors have found that trace amounts of moisture contained in an active material react with a halide solid electrolyte to deteriorate the halide, thereby increasing the resistance of the all-solid lithium ion battery. Based on this insight, the present inventors have recognized the need to implement a process that significantly reduces the amount of moisture in the active material when the active material is manufactured, and have further conducted studies. As a result, it has been found that the amount of moisture contained in the active material can be significantly reduced by drying the active material under predetermined conditions when the active material is manufactured. When an all-solid lithium ion battery is manufactured using the active material thus manufactured, an all-solid lithium ion battery having a low battery resistance can be obtained.

[0015] (SUMMARY)

[0016] The positive electrode active material of the first aspect of the present disclosure,

[0017] The composite oxide represented by the following formula (1) is used as a main component, and the amount of moisture generated when heated at 180°C, as measured by Karl Fischer titration, is 2.9 mass ppm or more and 44.7 mass ppm or less.

[0018] LiNi x Me 1-x O2(1)

[0019] wherein x satisfies 0.5≤x≤1, and Me is at least one element selected from Mn, Co, and Al.

[0020] The positive electrode active material of the first aspect has a small amount of moisture. Therefore, a battery using the positive electrode active material of the first aspect can achieve a reduction in internal resistance.

[0021] The second aspect of the present disclosure, for example, in the positive electrode active material of the first aspect, can further include a covering material that covers the surface of the positive electrode active material, the covering material containing lithium (Li) and at least one element selected from oxygen (O), fluorine (F), and chlorine (Cl).

[0022] The positive electrode active material of the second aspect can achieve a reduction in battery internal resistance.

[0023] The third aspect of the present disclosure, for example, in the positive electrode active material of the second aspect, the covering material can be at least one selected from lithium niobate, lithium phosphate, lithium titanate, lithium tungstate, lithium fluorozirconate, lithium fluoroaluminate, lithium fluorotitanate, and lithium fluoromagnesium.

[0024] The positive electrode active material of the third aspect can achieve a reduction in battery internal resistance.

[0025] The fourth aspect of the present disclosure includes the positive electrode active material of any one of the first aspect to the third aspect and a solid electrolyte.

[0026] The positive electrode material of the fourth aspect can achieve a reduction in battery internal resistance.

[0027] The fifth aspect of the present disclosure, for example, in the positive electrode material of the fourth aspect, the solid electrolyte is represented by the following formula (2).

[0028] Li α M β X γ (2)

[0029] wherein α, β, and γ are each independently a value greater than 0,

[0030] M contains at least one selected from metal elements and metalloid elements other than Li,

[0031] X contains at least one selected from F, Cl, Br, and I.

[0032] The positive electrode material of the fifth aspect can achieve a reduction in battery internal resistance.

[0033] The sixth aspect of the present disclosure, for example, in the positive electrode material of the fifth aspect, the M can contain yttrium.

[0034] The positive electrode material of the sixth aspect can achieve a reduction in battery internal resistance.

[0035] The seventh aspect of the present disclosure, for example, in the positive electrode material of the fifth aspect or the sixth aspect, the formula (2) can satisfy 2.5 ≤ α ≤ 3, 1 ≤ β ≤ 1.1, and γ = 6.

[0036] The positive electrode material of the sixth aspect can achieve a reduction in battery internal resistance.

[0037] The eighth aspect of the present disclosure, for example, in the positive electrode material of any one of the fifth aspect to the seventh aspect, the X can contain at least one selected from Cl and Br.

[0038] The positive electrode material of the eighth aspect can achieve a reduction in battery internal resistance.

[0039] The ninth aspect of the present disclosure is a battery comprising:

[0040] a positive electrode,

[0041] a negative electrode, and

[0042] an electrolyte layer disposed between the positive electrode and the negative electrode,

[0043] the positive electrode contains the positive electrode material of any one of the fourth aspect to the eighth aspect.

[0044] The battery of the ninth aspect can achieve a low internal resistance.

[0045] The electrolyte layer of the battery according to the 10th aspect of the present disclosure may, for example, contain the solid electrolyte in the battery according to the 9th aspect.

[0046] The battery according to the 10th aspect can achieve a low internal resistance.

[0047] The electrolyte layer of the battery according to the 11th aspect of the present disclosure may, for example, contain a halide solid electrolyte different from the solid electrolyte in the battery according to the 9th aspect or the 10th aspect.

[0048] The battery according to the 11th aspect can achieve a low internal resistance.

[0049] The electrolyte layer of the battery according to the 12th aspect of the present disclosure may, for example, contain a sulfide solid electrolyte in the battery according to any one of the 9th aspect to the 11th aspect.

[0050] The battery according to the 12th aspect can achieve a low internal resistance.

[0051] The manufacturing method of the positive electrode active material according to the 13th aspect of the present disclosure is a method of manufacturing the positive electrode active material according to any one of the 1st aspect to the 3rd aspect,

[0052] The manufacturing method includes a drying step of drying a material constituting the positive electrode active material,

[0053] The drying step satisfies (A) or (B) below.

[0054] (A) The drying step includes only a step of drying the material constituting the positive electrode active material at 70°C or higher and lower than 120°C for 12 hours or more and 500 hours or less.

[0055] (B) The drying step includes a step of drying the material constituting the positive electrode active material at 70°C or higher and lower than 120°C for 12 hours or more and 500 hours or less, and at least one step selected from the group consisting of a step of drying the material constituting the positive electrode active material at a temperature of 150°C or higher and lower than 500°C for 0.5 hours or more, and a step of drying the material constituting the positive electrode active material at a temperature of 600°C or higher and 850°C or lower for 0.5 hours or more.

[0056] According to the manufacturing method according to the 13th aspect, a positive electrode active material with a small amount of moisture can be manufactured. Thus, a reduction in internal resistance of a battery can be achieved.

[0057] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0058] (Embodiment 1)

[0059] Figure 1 is a cross-sectional view showing a schematic structure of the positive electrode material 1000 of Embodiment 1.

[0060] The positive electrode material 1000 in Embodiment 1 includes a solid electrolyte 100 and a positive electrode active material 110. As shown in FIG. 1, the positive electrode active material 110 and the solid electrolyte 100 are, for example, granular. Figure 1

[0061] Here, the positive electrode active material 110 includes, as a main component, a composite oxide represented by the following formula (1), and the amount of water generated at 180°C, which is determined by Karl Fischer titration, is 2.9 mass ppm or more and 44.7 mass ppm or less.

[0062] LiNi x Me 1-x O2(1)

[0063] x satisfies 0.5≤x≤1, and Me is at least one element selected from Mn, Co, and Al.

[0064] According to the above structure, the battery resistance can be reduced.

[0065] Here, the "main component" refers to a component contained in the largest amount in terms of mass ratio.

[0066] The amount of water of the positive electrode active material 110 is determined by Karl Fischer titration of the amount of water generated at 180°C. It is presumed that the water generated at 180°C is mainly water physically adsorbed on the positive electrode active material 110 and water of hydration combined with surface impurities and the like.

[0067] The positive electrode active material 110 can include, in addition to the composite oxide represented by formula (1), a material that can be used as an active material for a full solid lithium ion battery.

[0068] Examples of the material that can be used as an active material for a full solid lithium ion battery are LiCoO2, LiNi x Co 1-x O2(0 < x < 0.5), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMnO2, a hetero-element-substituted Li-Mn spinel (for example, LiMn 1.5 Ni 0.5 O4, LiMn 1.5 Al 0.5 O4, LiMn 1.5 Mg 0.5 O4, LiMn 1.5 Co 0.5 O4, LiMn 1.5 Fe 0.5 O4, or LiMn 1.5 Zn 0.5 ​O4), lithium titanate (e.g., Li4Ti5O12), lithium metal phosphate (e.g., LiFePO4, LiMnPO4, LiCoPO4, or LiNiPO4), transition metal oxide (e.g., V2O5, MoO3). 12 ), lithium metal phosphate (e.g., LiFePO4, LiMnPO4, LiCoPO4, or LiNiPO4), transition metal oxide (e.g., V2O5, MoO3).

[0069] Among the above materials, LiCoO2, LiNi x Co 1-x O2(0 < x < 0.5), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMnO2, Li-Mn spinel with hetero-element substitution, lithium metal phosphate, and the like.

[0070] The amount of water in the positive electrode active material 110 is 2.9 mass ppm or more and 44.7 mass ppm or less. By inhibiting the amount of water in the positive electrode active material 110 to be 44.7 mass ppm or less, in the case of being applied to a full solid lithium ion battery, it is possible to inhibit the case where the solid electrolyte 100 described later is deteriorated due to the water contained in the positive electrode active material 110, and to maintain the high conductivity of the solid electrolyte 100. Therefore, by using the positive electrode active material 110, a battery with low battery resistance can be obtained. In addition, by setting the amount of water in the positive electrode active material 110 to be 2.9 ppm or more, it is possible to inhibit the case where the solid electrolyte 100 is oxidatively decomposed in contact with the positive electrode active material 110 accompanying battery charging, and a battery with low battery resistance can be obtained.

[0071] LiNi x Me 1-x When the composition of LiNi0.5-xCo2xO2 is 0.5 ≤ x ≤ 1, there is a concern that the physical adsorption water reacts with the active material to cause deterioration at the time of high-temperature drying, and thus it is desirable to sufficiently remove the physical adsorption water at a low temperature.

[0072] For example, the positive electrode active material 110 is dried by being heated at 70°C or higher and lower than 120°C for 12 hours or more and 500 hours or less before being used to constitute a positive electrode material. Alternatively, the positive electrode active material 110 is dried, for example, by being heated at 70°C or higher and lower than 120°C for 12 hours or more and 500 hours or less before being used to constitute a positive electrode material, and at least one selected from the following steps: a step of heating at a temperature of 150°C or higher and lower than 500°C for 0.5 hours or more, and a step of heating at a temperature of 600°C or higher and 850°C or lower for 0.5 hours or more.

[0073] The atmosphere at the time of drying can be an atmosphere of vacuum or normal pressure and a dew point of -60°C or lower. The dew point can be -60°C or lower in nitrogen or oxygen. The positive electrode active material 110 after drying is measured for the amount of water generated at the time of heating at 180°C by a Karl Fischer moisture meter.

[0074] The heating in the range of 70°C or higher and lower than 120°C can be 12 hours or more and 350 hours or less, further can be 24 hours or more and 350 hours or less.

[0075] The at least one selected from the heating at a temperature of 150°C or higher and lower than 500°C and the heating at a temperature of 600°C or higher and 850°C or lower can be 0.5 hours or more and 24 hours or less, further can be 1 hour or more and 12 hours or less.

[0076] The amount of water generated at the time of heating at 180°C of the positive electrode active material 110 measured by the Karl Fischer titration method can be 30 mass ppm or less, further can be 20 mass ppm or less. That is, the amount of water generated at the time of heating at 180°C measured by the Karl Fischer titration method can be 2.9 mass ppm or more and 30 mass ppm or less, or can be 2.9 mass ppm or more and 20 mass ppm or less.

[0077] The positive electrode active material 110 can have the covering material 120 on the surface. Further, the covering material 120 can cover the entire surface of the positive electrode active material 110, or can partially cover the surface.

[0078] The covering material 120 can contain Li and at least one element selected from O, F, and Cl.

[0079] The covering material 120 can contain at least one selected from lithium niobate, lithium phosphate, lithium titanate, lithium tungstate, lithium fluorozirconate, lithium fluoroaluminate, lithium fluorotitanate, and lithium fluoromagnesite.

[0080] Figure 1 The structure of the positive electrode material 1000 is schematically shown. As shown in Figure 1 the positive electrode material 1000 includes the positive electrode active material 110 and the solid electrolyte 100.

[0081] As the solid electrolyte material contained in the solid electrolyte 100, a halide solid electrolyte can be used.

[0082] The solid electrolyte 100 can be a compound represented by the following formula (2).

[0083] Li α M β X γ (2)

[0084] wherein a, β, and γ are values greater than 0. M contains at least one selected from metal elements and metalloid elements other than Li. X is at least one element selected from F, Cl, Br, and I.

[0085] Here, the metalloid element is B, Si, Ge, As, Sb, or Te. The metal element is all elements contained in Groups 1 to 12 of the periodic table other than hydrogen, and all elements contained in Groups 13 to 16 other than the aforementioned metalloid elements, C, N, P, O, S, and Se. That is, the metal element is a group of elements that can become a cation when forming halogen compounds and inorganic compounds.

[0086] As the solid electrolyte 100, for example, Li3YX6, Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, Li3(Al, Ga, In)X6, or the like can be used. Here, X is at least one selected from F, Cl, Br, and I.

[0087] In the present disclosure, "(A, B, C)" means "at least one selected from A, B, and C".

[0088] According to the above structure, the battery resistance can be reduced.

[0089] The formula (2) can satisfy 2.5 ≤ a ≤ 3, 1 ≤ β ≤ 1.1, and γ = 6.

[0090] In the formula (2), X can contain at least one selected from Cl and Br.

[0091] In the formula (2), M can contain yttrium (Y).

[0092] As the solid electrolyte containing Y, for example, a compound represented by the composition formula Li a M' b Y c X6. Here, a + mb + 3c = 6 and c > 0 are satisfied. M' is at least one selected from metal elements and metalloid elements other than Li and Y. m represents the valence of M'. X is at least one selected from F, Cl, Br, and I.

[0093] As M', at least one selected from Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb can be used.

[0094] Specifically, as the solid electrolyte containing Y, Li3YF6, Li3YCl6, Li3YBr6, Li3YI6, Li3YBrCl5, Li3YBr3Cl3, Li3YBr5Cl, Li3YBr5I, Li3YBr3I3, Li3YBrI5, Li3YClI5, Li3YCl3I3, Li3YCl5I, Li3YBr2Cl2I2, Li3YBrCl4I, Li 2.7 Y 1.1 Cl6, Li 2.5 Y 0.5 Zr 0.5 Cl6, Li 2.5 Y 0.3 Zr 0.7 Cl6, and the like.

[0095] According to the above structure, the battery resistance can be further reduced.

[0096] Further, the halide solid electrolyte can not contain sulfur. In addition, the shape of the solid electrolyte 100 and the positive electrode active material 110 in Embodiment 1 is not particularly limited, and can be, for example, needle-shaped, spherical, oval spherical, or the like. For example, the shape of the solid electrolyte 100 and the positive electrode active material 110 can be granular.

[0097] For example, in a case where the shape of the solid electrolyte 100 in Embodiment 1 is granular (for example, spherical), the median diameter can be 100 μm or less.

[0098] In a case where the median diameter of the solid electrolyte 100 is 100 μm or less, the positive electrode active material 110 and the solid electrolyte 100 can form a good dispersion state in the positive electrode material 1000. Thus, the charge-discharge characteristics of the battery are improved.

[0099] In addition, in Embodiment 1, the median diameter of the solid electrolyte 100 can be 10 μm or less.

[0100] According to the above structure, the positive electrode active material 110 and the solid electrolyte 100 can form a good dispersion state in the positive electrode material 1000.

[0101] In addition, in Embodiment 1, the median diameter of the solid electrolyte 100 can be smaller than the median diameter of the positive electrode active material 110.

[0102] According to the above structure, the solid electrolyte 100 and the positive electrode active material 110 can form a further good dispersion state in the positive electrode material 1000.

[0103] The median diameter of the positive electrode active material 110 can be 0.1 μm or more and 100 μm or less.

[0104] In a case where the median diameter of the positive electrode active material 110 is 0.1 μm or more, the positive electrode active material 110 and the solid electrolyte 100 can form a good dispersion state in the positive electrode material 1000. As a result, the charge-discharge characteristics of the battery are improved.

[0105] In addition, in a case where the median diameter of the positive electrode active material 110 is 100 μm or less, the lithium diffusion speed within the positive electrode active material 110 can be sufficiently ensured. Therefore, the battery can operate at a high output.

[0106] In the present disclosure, the "median diameter" refers to a particle diameter at which the cumulative volume in a particle size distribution on a volume basis is equal to 50%. The particle size distribution on a volume basis is measured, for example, using a laser diffraction type measuring device or an image analysis device.

[0107] Further, in the positive electrode material 1000 of Embodiment 1, as shown in FIG. 1, the particles of the solid electrolyte 100 and the particles of the positive electrode active material 110 can be in contact with each other. At this time, the covering material 120 and the positive electrode active material 110 are in contact with each other. Figure 1

[0108] In addition, the positive electrode material 1000 in Embodiment 1 can include a plurality of particles of the solid electrolyte 100 and a plurality of particles of the positive electrode active material 110.

[0109] In addition, the content of the solid electrolyte 100 and the content of the positive electrode active material 110 in the positive electrode material 1000 of Embodiment 1 can be the same as or different from each other.

[0110] (Embodiment 2)

[0111] Hereinafter, Embodiment 2 will be described. Descriptions repeated in Embodiment 1 described above are appropriately omitted.

[0112] Figure 1 is a cross-sectional view showing the schematic structure of the battery 2000 in Embodiment 2.

[0113] The battery 2000 in Embodiment 2 includes a positive electrode 201, an electrolyte layer 202, and a negative electrode 203.

[0114] The positive electrode 201 includes the positive electrode material 1000.

[0115] The electrolyte layer 202 is disposed between the positive electrode 201 and the negative electrode 203.

[0116] According to the above structure, the discharge voltage of the battery can be improved.

[0117] ​The volume ratio "v1:100-v1" of the positive electrode active material 110 contained in the positive electrode 201 to the first solid electrolyte 100 can satisfy 30 ≤ v1 ≤ 95. In a case where 30 ≤ v1 is satisfied, the energy density of the battery 2000 can be sufficiently ensured. In addition, in a case where v1 ≤ 95 is satisfied, the battery can be operated at a high output.

[0118] The thickness of the positive electrode 201 can be 10 μm or more and 500 μm or less. In a case where the thickness of the positive electrode 201 is 10 μm or more, the energy density of the battery 2000 can be sufficiently ensured. In a case where the thickness of the positive electrode 201 is 500 μm or less, the battery can be operated at a high output.

[0119] The electrolyte layer 202 is a layer containing an electrolyte material. The electrolyte material is, for example, a solid electrolyte material. That is, the electrolyte layer 202 can be a solid electrolyte layer. As the solid electrolyte, the material exemplified as the material of the solid electrolyte 100 in Embodiment 1 can be used. That is, the electrolyte layer 202 can contain a solid electrolyte having the same composition as the solid electrolyte 100 contained in the positive electrode material 1000.

[0120] The electrolyte layer 202 can also contain a halide solid electrolyte having a different composition from the solid electrolyte 100 contained in the positive electrode material 1000.

[0121] The electrolyte layer 202 can contain a sulfide solid electrolyte.

[0122] The electrolyte layer 202 can contain only one kind of solid electrolyte selected from the above-described solid electrolytes, or can contain two or more kinds of solid electrolytes selected from the above-described solid electrolytes. The compositions of the plurality of solid electrolytes are different from each other. For example, the electrolyte layer 202 can contain a halide solid electrolyte and a sulfide solid electrolyte.

[0123] The thickness of the electrolyte layer 202 can be 1 μm or more and 300 μm or less. In a case where the thickness of the electrolyte layer 202 is 1 μm or more, the positive electrode 201 and the negative electrode 203 are less likely to be short-circuited. In a case where the thickness of the electrolyte layer 202 is 300 μm or less, the battery can be operated at a high output.

[0124] The negative electrode 203 contains a material having a property of occluding and releasing metal ions (for example, lithium ions). The negative electrode 203 contains, for example, a negative electrode active material.

[0125] As the negative electrode active material, a metal material, a carbon material, an oxide, a nitride, a tin compound, a silicon compound, or the like can be used. The metal material can be a single metal. Alternatively, the metal material can be an alloy. As examples of the metal material, lithium metal, lithium alloy, or the like can be given. As examples of the carbon material, natural graphite, coke, semi-graphitized carbon, carbon fiber, spherical carbon, artificial graphite, amorphous carbon, or the like can be given. From the viewpoint of capacity density, it is preferable to use silicon (Si), tin (Sn), a silicon compound, or a tin compound.

[0126] The negative electrode 203 can contain a solid electrolyte material. According to the above structure, the lithium ion conductivity inside the negative electrode 203 can be improved, and the battery can be operated at high output. As the solid electrolyte, the material exemplified in Embodiment 1 can be used. That is, the negative electrode 203 can contain a solid electrolyte having the same composition as the solid electrolyte contained in the positive electrode material 1000.

[0127] The median diameter of the negative electrode active material can be 0.1 μm or more and 100 μm or less.

[0128] In a case where the median diameter of the negative electrode active material is 0.1 μm or more, the negative electrode active material and the solid electrolyte material can form a good dispersion state. As a result, the charge and discharge characteristics of the battery are improved.

[0129] In addition, in a case where the median diameter of the negative electrode active material is 100 μm or less, the lithium diffusion speed inside the negative electrode active material can be sufficiently ensured. Therefore, the battery can be operated at high output.

[0130] The median diameter of the negative electrode active material can be larger than the median diameter of the solid electrolyte material. Thereby, the negative electrode active material and the solid electrolyte material can form a good dispersion state.

[0131] With respect to the volume ratio "v2: 100-v2" of the negative electrode active material to the solid electrolyte material contained in the negative electrode 203, 30 ≤ v2 ≤ 95 can be satisfied. In a case where 30 ≤ v2 is satisfied, the energy density of the battery 2000 can be sufficiently ensured. In addition, in a case where v2 ≤ 95 is satisfied, the battery can be operated at high output.

[0132] The thickness of the negative electrode 203 can be 10 μm or more and 500 μm or less. In a case where the thickness of the negative electrode 203 is 10 μm or more, the energy density of the battery 2000 can be sufficiently ensured. In a case where the thickness of the negative electrode 203 is 500 μm or less, the battery can be operated at high output.

[0133] For the purpose of improving the adhesion of the particles to each other, at least one selected from the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 can include a binder. The binder is used for the purpose of improving the adhesion of the materials constituting the electrode. As the binder, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aromatic polyamide resin, polyamide, polyimide, polyamide-imide, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluorinated polypropylene, styrene butadiene rubber, carboxymethyl cellulose, and the like can be given. In addition, as the binder, a copolymer of two or more materials selected from tetrafluoroethylene, hexafluoroethylene, hexafluorinated propylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluorinated propylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene can be used. In addition, two or more selected from among them can be mixed and used as the binder.

[0134] For the purpose of improving the electron conductivity, at least one selected from the positive electrode 201 and the negative electrode 203 can include a conductive aid. As the conductive aid, for example, graphite such as natural graphite or artificial graphite, carbon black such as acetylene black or ketjen black, conductive fiber such as carbon fiber or metal fiber, metal powder such as fluorinated carbon or aluminum, conductive whisker such as zinc oxide or potassium titanate, conductive metal oxide such as titanium oxide, conductive high molecular compound such as polyaniline, polypyrrole, polythiophene, and the like can be used. In the case of using a carbon conductive aid, cost reduction can be achieved.

[0135] Further, the battery in Embodiment 2 can be configured as a battery of various shapes such as a coin type, a cylindrical type, a square type, a sheet type, a button type, a flat type, a stacked type, and the like.

[0136] Example

[0137] Hereinafter, the present disclosure will be described in more detail with reference to Examples.

[0138] Example 1

[0139] [Production of positive electrode active material]

[0140] The positive electrode active material LiNi 0.8 (Co,Mn) 0.2 After the positive electrode active material LiNi 0.8 (Co,Mn) 0.2 O2 is dried in a vacuum at 100°C for 2 weeks, and is taken out in a dry atmosphere with a dew point of -20°C or lower. Hereinafter, the positive electrode active material LiNi

[0141] In the present example, for the positive electrode active material, it was confirmed that the physically adsorbed water was sufficiently removed by vacuum drying at 100°C for 2 weeks. Specifically, for the positive electrode active material of the present example, it was confirmed that the water content determined at 120°C using the Karl Fischer titration method became 1 ppm or less.

[0142] [Measurement of water content]

[0143] The water content of the positive electrode active material of Example 1 produced was measured using a Karl Fischer moisture meter (CA-310 manufactured by Mitsubishi Chemical Analytics). The heating temperature of the measurement sample was set to 180°C. The water content of the positive electrode active material of Example 1 was 44.7 mass ppm.

[0144] [Production of halide solid electrolyte]

[0145] In an argon glove box in which the dew point was -60°C or less, the raw material powders LiCl, LiBr, and YCl3 were weighed in a molar ratio of LiCl:LiBr:YCl3 = 1:2:1. They were crushed and mixed using a mortar. Then, using a planetary ball mill, they were ground at 600 rpm for 12 hours.

[0146] As described above, a halide solid electrolyte powder represented by the composition formula Li3YBr2Cl4 was obtained.

[0147] [Production of positive electrode material]

[0148] In an argon glove box in which the dew point was -60°C or less, Li3YBr2Cl4 and the positive electrode active material of Example 1 were weighed in a mass ratio of 20:80. By mixing them using an agate mortar, a positive electrode material of Example 1 was produced.

[0149] [Production of sulfide solid electrolyte]

[0150] In an argon glove box in which the dew point was -60°C or less, Li2S and P2S5 were weighed in a molar ratio of Li2S:P2S5 = 75:25. They were crushed and mixed using a mortar. Then, using a planetary ball mill (P-7 manufactured by Fritsch), they were ground at 510 rpm for 10 hours, thereby obtaining a glassy solid electrolyte. For the glassy solid electrolyte, heat treatment was performed at 270°C for 2 hours in an inert atmosphere. Thereby, a glass-ceramic sulfide solid electrolyte was obtained.

[0151] [Production of battery]

[0152] The following procedures were performed using Li3YBr2Cl4, the positive electrode material of Example 1, and the sulfide solid electrolyte, respectively.

[0153] First, 80 mg of a sulfide solid electrolyte, 40 mg of Li3YBr2Cl4, and 12 mg of the positive electrode material of Example 1 were sequentially stacked in the insulating outer cylinder. This was press-formed at a pressure of 720 MPa, whereby a positive electrode and a solid electrolyte layer were obtained.

[0154] Next, a metal Li (thickness 200 μm) was stacked on the side opposite to the side in contact with the positive electrode of the solid electrolyte layer, and this was press-formed at a pressure of 80 MPa, whereby a laminate including the positive electrode, the solid electrolyte layer, and the negative electrode was produced.

[0155] Next, stainless steel current collectors were arranged above and below the laminate, and current collecting leads were attached to the current collectors.

[0156] Finally, the inside of the insulating outer cylinder was sealed from the outside atmosphere by sealing the insulating outer cylinder with an insulating sleeve, whereby the battery of Example 1 was produced.

[0157] [Electrochemical Test]

[0158] A charge-discharge test was performed using the battery of Example 1 under the following conditions.

[0159] The battery was placed in a thermostat set to 25°C and connected to a potentiostat (manufactured by Solartron) equipped with a frequency response analyzer.

[0160] Constant current charging was performed at a current value of 96 μA, which is 0.05 C rate (20 hour rate) with respect to the theoretical capacity of the battery, and the charging was ended at a voltage of 4.3 V.

[0161] Next, the reaction resistance of the battery at room temperature was measured by electrochemical impedance spectroscopy.

[0162] Figure 2 is a Nyquist plot showing an example of the evaluation results of the reaction resistance obtained by impedance spectroscopy.

[0163] In Figure 2 , the semicircular arc waveform shown in the Nyquist plot obtained belongs to the resistance of the positive electrode and the negative electrode In, and the value of the resistance of the positive electrode was calculated by performing a fitting analysis. In Example 1, the reaction resistance of the positive electrode of the battery was 49 Ω.

[0164] Examples 2 to 4

[0165] [Production of Positive Electrode Active Material]

[0166] The NCM was vacuum-dried at 100°C for 2 weeks, and then fired at 300°C for 1 hour in a nitrogen atmosphere. Then, it was taken out in a dry atmosphere with a dew point of -20°C or lower. In this way, the positive electrode active material of Example 2 was obtained.

[0167] The NCM was vacuum-dried at 100°C for 2 weeks, and then fired at 400°C for 1 hour in a nitrogen atmosphere. Then, it was taken out under a dry atmosphere with a dew point of -20°C or less. In this way, the positive electrode active material of Example 3 was obtained.

[0168] The NCM was vacuum-dried at 100°C for 2 weeks, and then fired at 800°C for 1 hour in a nitrogen atmosphere. Then, it was taken out under a dry atmosphere with a dew point of -20°C or less. In this way, the positive electrode active material of Example 4 was obtained.

[0169] [Measurement of the moisture content]

[0170] The moisture content of the positive electrode active material of Examples 2 to 4 was measured in the same manner as in Example 1. The moisture content of the positive electrode active material of Examples 2 to 4 is shown in Table 1.

[0171] [Production of the positive electrode material]

[0172] The positive electrode material of Examples 2 to 4 was produced in the same manner as in Example 1, except that the positive electrode active material of Examples 2 to 4 was used as the positive electrode active material, respectively.

[0173] [Production of the battery]

[0174] The battery of Examples 2 to 4 was produced in the same manner as in Example 1, except that the positive electrode material of Examples 2 to 4 was used as the positive electrode material, respectively.

[0175] [Electrochemical test]

[0176] The charge-discharge test was performed in the same manner as in Example 1 using the battery of Examples 2 to 4. The reaction resistance of the positive electrode of the battery of Examples 2 to 4 is shown in Table 1 below.

[0177] [Examples 5 to 8]

[0178] [Production of the positive electrode active material]

[0179] The positive electrode active material of Example 5 was obtained in the same manner as in Example 2.

[0180] The positive electrode active material of Example 6 was obtained in the same manner as in Example 3.

[0181] The NCM was vacuum-dried at 100°C for 2 weeks, and then fired at 450°C for 1 hour in a nitrogen atmosphere. Then, it was taken out under a dry atmosphere with a dew point of -20°C or less. In this way, the positive electrode active material of Example 7 was obtained.

[0182] The positive electrode active material of Example 8 was obtained in the same manner as in Example 4.

[0183] [Measurement of the moisture content]

[0184] The moisture content of the positive electrode active material of Examples 5 to 8 thus produced was measured in the same manner as in Example 1. The moisture content of the positive electrode active material of Examples 5 to 8 is shown in Table 1.

[0185] [Production of halide solid electrolyte]

[0186] In an argon glove box in which the dew point was -60°C or less, the raw material powders LiCl and YCl3 were weighed in a molar ratio of LiCl:YCl3 = 3:1. They were pulverized and mixed using a mortar. Then, using a planetary ball mill, they were ground at 600 rpm for 12 hours.

[0187] As described above, a powder of the halide solid electrolyte represented by the composition formula Li3YCl6 was obtained.

[0188] [Production of positive electrode material]

[0189] In an argon glove box in which the dew point was -60°C or less, Li3YCl6 and the positive electrode active material of Example 5 were weighed in a weight ratio of 20:80. By mixing them using an agate mortar, the positive electrode material of Example 5 was produced.

[0190] The positive electrode materials of Examples 6 to 8 were produced in the same manner as in Example 5, except that the positive electrode active material of Example 6 to 8 was used as the positive electrode active material, respectively.

[0191] [Production of battery]

[0192] The battery of Example 5 was produced in the same manner as in Example 1, except that Li3YCl6, the positive electrode material of Example 5, and the sulfide solid electrolyte were used, respectively.

[0193] The batteries of Examples 6 to 8 were produced in the same manner as in Example 5, except that the positive electrode material of Example 6 to 8 was used as the positive electrode material, respectively.

[0194] [Electrochemical test]

[0195] The charge-discharge test was performed in the same manner as in Example 1, using the batteries of Examples 5 to 8. The reaction resistance of the positive electrode of the batteries of Examples 5 to 8 is shown in Table 1 below.

[0196] [Comparative Example 1]

[0197] [Production of positive electrode active material]

[0198] The NCM managed in a dry atmosphere in which the dew point was -20°C or less was used as the positive electrode active material of Comparative Example 1.

[0199] [Measurement of moisture content]

[0200] The water content of the positive electrode active material of Comparative Example 1 was measured in the same manner as in Example 1. The water content of the positive electrode active material of Comparative Example 1 was 274.8 mass ppm.

[0201] [Production of positive electrode material]

[0202] Li3YBr2Cl4and the positive electrode active material of Comparative Example 1 were weighed in a weight ratio of 20:80 in an argon glove box in which the dew point was -60°C or lower. The positive electrode material of Comparative Example 1 was produced by mixing them with an agate mortar.

[0203] [Production of battery]

[0204] The battery of Comparative Example 1 was produced in the same manner as in Example 1 using Li3YBr2Cl4, the positive electrode material of Comparative Example 1, and the sulfide solid electrolyte, respectively.

[0205] [Electrochemical test]

[0206] The charge-discharge test was performed in the same manner as in Example 1 using the battery of Comparative Example 1. The reaction resistance of the positive electrode of the battery of Comparative Example 1 is shown in Table 1 below.

[0207] Comparative Example 2

[0208] [Production of positive electrode active material]

[0209] The NCM was vacuum-dried at 100°C for 2 weeks, and then fired at 500°C for 1 hour in a nitrogen atmosphere. Then, it was taken out under a dry atmosphere in which the dew point was -20°C or lower. In this way, the positive electrode active material of Comparative Example 2 was obtained.

[0210] [Measurement of water content]

[0211] The water content of the produced positive electrode active material of Comparative Example 2 was measured in the same manner as in Example 1. The heating temperature of the measurement sample was set to 180°C. The water content of the positive electrode active material of Comparative Example 2 was 2.5 mass ppm.

[0212] [Production of positive electrode material]

[0213] Li3YBr2Cl4and the positive electrode active material of Comparative Example 2 were weighed in a weight ratio of 20:80 in an argon glove box in which the dew point was -60°C or lower. The positive electrode material of Comparative Example 2 was produced by mixing them with an agate mortar.

[0214] [Production of battery]

[0215] The battery of Comparative Example 2 was produced in the same manner as in Example 1 using Li3YBr2Cl4, the positive electrode material of Comparative Example 2, and the sulfide solid electrolyte, respectively.

[0216] [Electrochemical test]

[0217] A charge-discharge test was performed using the battery of Comparative Example 2, in the same manner as in Example 1. The reaction resistance of the positive electrode of the battery of Comparative Example 2 is shown in Table 1 below.

[0218] [Table 1]

[0219]

[0220] Investigation

[0221] As shown in the results of Example 1, it was found that the reaction resistance of the battery was low when the amount of moisture generated at 180°C, as measured by Karl Fischer titration, of the positive electrode active material was 2.9 mass ppm or more and 44.7 mass ppm or less. This is because the hydration and hydrolysis of the halide solid electrolyte Li3YBr2Cl4was suppressed by reducing the water content of the positive electrode active material.

[0222] On the other hand, as shown in the results of Comparative Example 1, it was found that the reaction resistance of the battery was high when the amount of moisture of the positive electrode active material was large. This is because the halide solid electrolyte Li3YBr2Cl4contacted with the moisture on the surface of the positive electrode active material and thus hydration and hydrolysis occurred.

[0223] As shown in the results of Comparative Example 2, it was found that the reaction resistance of the battery was high when the amount of moisture at 180°C, as measured by Karl Fischer titration, of the positive electrode active material was less than 2.9 mass ppm. This is because the hydration and hydrolysis of the halide solid electrolyte Li3YBr2Cl4was suppressed too much, and thus the positive electrode active material powder contacted with the halide solid electrolyte Li3YBr2Cl4and oxidatively decomposed as the battery was charged.

[0224] In addition, as shown in the results of Comparative Example 2, it was found that the reaction resistance of the battery was high when the temperature at which the positive electrode active material was dried was 500°C. This is because the temperature affects the surface state of the active material. For example, it is considered that when the temperature at which the active material is dried reaches 500°C, the surface of the active material becomes a state in which the reaction resistance increases. In addition, it is considered that if the temperature at which the active material is dried is a higher temperature of 600°C or more, the surface of the active material becomes a state in which the reaction resistance decreases.

[0225] As shown in the above examples, according to the present disclosure, it is possible to reduce the internal resistance of a battery when the battery is charged.

[0226] Industrial Applicability

[0227] The battery of the present disclosure can be used as, for example, a full solid battery or the like.

[0228] Explanation of Reference Signs

[0229] 1000 positive electrode material

[0230] 100 solid electrolyte

[0231] 110 positive electrode active material

[0232] 120 coating material

[0233] 2000 battery

[0234] 201 positive electrode

[0235] 202 electrolyte layer

[0236] 203 negative electrode

Claims

1. A positive electrode material comprising a positive electrode active material and a solid electrolyte, The positive electrode active material uses a composite oxide represented by the following formula (1) as its main component. The water content produced when heated to 180°C, as determined by Karl Fischer titration, is above 2.9 ppm by mass and below 44.7 ppm by mass. LiNi x Along with 1-x O2(1) in, x satisfies 0.5 ≤ x ≤ 1, and Me is at least one element selected from Mn, Co, and Al. The solid electrolyte is represented by the following formula (2), Li α M β X γ (2) Where α, β, and γ are each an independent value greater than 0. M contains at least one selected from metallic elements and metalloids other than Li. X contains at least one selected from F, Cl, Br and I.

2. The cathode material according to claim 1, It also includes a covering material that covers the surface of the positive electrode active material. The covering material contains lithium (Li) and at least one element selected from oxygen (O), fluorine (F) and chlorine (Cl).

3. The cathode material according to claim 2, The covering material contains at least one selected from lithium niobate, lithium phosphate, lithium titanate, lithium tungstate, lithium fluorozirconate, lithium fluoroaluminate, lithium fluorotitanate, and lithium fluoromagnesium fluorooxide.

4. The cathode material according to any one of claims 1 to 3, The M contains yttrium.

5. The positive electrode material according to claim 1, Equation (2) satisfies 2.5≤α≤3, 1≤β≤1.1 and γ=6.

6. The cathode material according to claim 1, The X contains at least one selected from Cl and Br.

7. A battery comprising: positive electrode, Negative electrode, and An electrolyte layer disposed between the positive electrode and the negative electrode. The positive electrode comprises the positive electrode material according to any one of claims 1 to 6.

8. The battery according to claim 7, The electrolyte layer contains the solid electrolyte.

9. The battery according to claim 7 or 8, The electrolyte layer contains a halide solid electrolyte, which is different from the solid electrolyte.

10. The battery according to claim 7 or 8, The electrolyte layer contains a sulfide solid electrolyte.

11. A method for manufacturing a cathode material, comprising the method for manufacturing the cathode material according to any one of claims 1 to 6. The manufacturing method includes step I of preparing the positive electrode active material and step II of mixing the positive electrode active material with the solid electrolyte. The process I includes a drying process of drying the materials constituting the positive electrode active material. The drying process satisfies either (A) or (B) below. (A) The drying process only includes the step of drying the material constituting the positive electrode active material at a temperature of 70°C or higher and below 120°C for 12 hours or more and 500 hours or less. (B) The drying process includes the step of drying the material constituting the positive electrode active material at a temperature of 70°C or higher and 120°C or lower for 12 hours or more and 500 hours or less, and at least one of the following steps: drying the material constituting the positive electrode active material at a temperature of 150°C or higher and 500°C or lower for 0.5 hours or more, and drying the material constituting the positive electrode active material at a temperature of 600°C or higher and 850°C or lower for 0.5 hours or more.

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