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

Abstract

The positive electrode active material according to the present disclosure contains a composite oxide represented by formula (1): LiNixMe1-xO2 as a main ingredient and has a water content of 2.9 to 44.7 ppm by mass, inclusive. In the formula, x satisfies the formula: 0.5 ≦ x ≦ 1, and Me represents at least one element selected from the group consisting of 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 producing a positive electrode active material. [Background technology]

[0002] Patent Document 1 discloses an all-solid-state battery using composite active material particles having a water content equal to or less than a predetermined level, and a sulfide solid electrolyte, each of which has active material particles and a coating layer that covers at least a portion of the surface of the active material particles. Patent Document 1 discloses that lithium ion conductive oxides such as lithium niobate, lithium titanate, lithium lanthanum zirconate, lithium tantalate, and lithium tungstate are used as the coating material, and that lithium niobate is particularly preferred. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-125214 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a battery with low internal resistance. [Means for solving the problem]

[0005] The positive electrode active material of the present disclosure is The composite oxide represented by the following formula (1) is the main component, and the amount of water generated when heated to 180°C, as measured by Karl Fischer titration, is 2.9 mass ppm or more and 44.7 mass ppm or less. LiNi x Me 1-x O2···(1) Here, x satisfies 0.5≦x≦1, and Me is at least one element selected from the group consisting of Mn, Co, and Al. [Effects of the Invention]

[0006] According to the present disclosure, a battery with low internal resistance can be obtained. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic configuration of a positive electrode material 1000 and a battery 2000 according to the first and second embodiments. [Figure 2] FIG. 2 is a Nyquist diagram showing an example of the evaluation results of reaction resistance by AC impedance measurement. DETAILED DESCRIPTION OF THE INVENTION

[0008] (Findings that formed the basis of this disclosure) The present inventors have conducted extensive research into factors that increase the battery resistance of all-solid-state lithium-ion batteries. As a result, the present inventors have discovered that trace amounts of water contained in active materials react with halide solid electrolytes, degrading the halide, and thereby increasing the resistance of all-solid-state lithium-ion batteries. Based on this discovery, the present inventors have concluded that measures must be taken to significantly reduce the amount of water contained in active materials when producing the active materials, and have therefore conducted further research. As a result, they have discovered that the amount of water contained in active materials can be significantly reduced by drying the active materials under specified conditions when producing them. When all-solid-state lithium-ion batteries were produced using the active materials produced in this manner, all-solid-state lithium-ion batteries with low battery resistance were obtained.

[0009] (Summary of one aspect of the present disclosure) The positive electrode active material according to the first embodiment of the present disclosure is The composite oxide represented by the following formula (1) is the main component, and the amount of water generated when heated to 180°C, as measured by Karl Fischer titration, is 2.9 mass ppm or more and 44.7 mass ppm or less. LiNi x Me 1-x O2···(1) Here, x satisfies 0.5≦x≦1, and Me is at least one element selected from the group consisting of Mn, Co, and Al.

[0010] The positive electrode active material according to the first embodiment has a low water content, which allows a reduction in the internal resistance of a battery using the positive electrode active material according to the first embodiment.

[0011] In a second aspect of the present disclosure, for example, the positive electrode active material according to the first aspect may further include a coating material that coats the surface of the positive electrode active material, and the coating material may include lithium element (Li) and at least one element selected from the group consisting of oxygen element (O), fluorine element (F), and chlorine element (Cl).

[0012] The positive electrode active material according to the second embodiment can reduce the internal resistance of the battery.

[0013] In a third aspect of the present disclosure, for example, in the positive electrode active material according to the second aspect, the coating material may include at least one selected from the group consisting of lithium niobate, lithium phosphate, lithium titanate, lithium tungstate, lithium fluorozirconate, lithium fluoroaluminate, lithium fluorotitanate, and lithium fluoromagnesium oxide.

[0014] The positive electrode active material according to the third embodiment can reduce the internal resistance of the battery.

[0015] A positive electrode material according to a fourth aspect of the present disclosure includes the positive electrode active material according to any one of the first to third aspects and a solid electrolyte.

[0016] The positive electrode material according to the fourth embodiment can reduce the internal resistance of the battery.

[0017] In a fifth aspect of the present disclosure, for example, in the positive electrode material according to the fourth aspect, the solid electrolyte is represented by the following formula (2): Li α M β X γ ···(2) where α, β, and γ are each independently greater than 0; M includes at least one selected from the group consisting of metal elements and metalloid elements other than Li, X comprises at least one selected from the group consisting of F, Cl, Br, and I.

[0018] The positive electrode material according to the fifth embodiment can reduce the internal resistance of the battery.

[0019] In a sixth aspect of the present disclosure, for example, in the positive electrode material according to the fifth aspect, the M may include yttrium.

[0020] The positive electrode material according to the sixth embodiment can reduce the internal resistance of the battery.

[0021] In the seventh embodiment of the present disclosure, for example, in the positive electrode material according to the fifth or sixth embodiment, the formula (2) may satisfy 2.5≦α≦3, 1≦β≦1.1, and γ=6.

[0022] The positive electrode material according to the sixth embodiment can reduce the internal resistance of the battery.

[0023] In an eighth aspect of the present disclosure, for example, in the positive electrode material according to any one of the fifth to seventh aspects, the X may include at least one selected from the group consisting of Cl and Br.

[0024] The positive electrode material according to the eighth embodiment can reduce the internal resistance of the battery.

[0025] A battery according to a ninth aspect of the present disclosure includes: a positive electrode comprising the positive electrode material according to any one of the fourth to eighth aspects; a negative electrode; an electrolyte layer disposed between the positive electrode and the negative electrode; Equipped with.

[0026] In the battery according to the ninth embodiment, low internal resistance can be achieved.

[0027] In a tenth aspect of the present disclosure, for example, in the battery according to the ninth aspect, the electrolyte layer may include the solid electrolyte.

[0028] In the battery according to the tenth aspect, low internal resistance can be achieved.

[0029] In an eleventh aspect of the present disclosure, for example, in the battery according to the ninth or tenth aspect, the electrolyte layer may contain a halide solid electrolyte different from the solid electrolyte.

[0030] In the battery according to the eleventh embodiment, low internal resistance can be achieved.

[0031] In a twelfth aspect of the present disclosure, for example, in the battery according to any one of the ninth to eleventh aspects, the electrolyte layer may include a sulfide solid electrolyte.

[0032] In the battery according to the twelfth embodiment, low internal resistance can be achieved.

[0033] A method for producing a positive electrode active material according to a thirteenth aspect of the present disclosure includes: A method for producing a positive electrode active material according to any one of the first to third aspects, the manufacturing method includes a drying step of drying a material constituting the positive electrode active material, The drying step satisfies the following (A) or (B): (A) The drying step simply involves drying the material that constitutes the positive electrode active material at a temperature in the range of 70° C. or higher and lower than 120° C. for 12 hours or longer and 500 hours or shorter. (B) The drying step includes at least one step selected from the group consisting of drying the material constituting the positive electrode active material at a temperature in the range of 70°C or higher and lower than 120°C for 12 hours or higher and 500 hours or lower, 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 higher, and drying at a temperature of 600°C or higher and 850°C or lower for 0.5 hours or higher.

[0034] According to the production method of the thirteenth aspect, a positive electrode active material with a low water content can be produced, thereby realizing a reduction in the internal resistance of the battery.

[0035] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0036] (Embodiment 1) FIG. 1 is a cross-sectional view showing a schematic configuration of a positive electrode material 1000 according to the first embodiment.

[0037] The positive electrode material 1000 in the first embodiment 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, in the form of particles.

[0038] Here, the positive electrode active material 110 is mainly composed of a composite oxide represented by the following formula (1), and the amount of moisture generated when heated to 180°C by Karl Fischer titration is 2.9 mass ppm or more and 44.7 mass ppm or less. LiNi x Me 1-x O2···(1) x satisfies 0.5≦x≦1, and Me is at least one element selected from Mn, Co, and Al.

[0039] According to the above configuration, the resistance of the battery can be reduced.

[0040] Here, the "main component" refers to the component that is contained in the largest amount by mass.

[0041] The amount of water in the positive electrode active material 110 is determined by measuring the amount of water generated by Karl Fischer titration when heated to 180° C. The water generated at 180° C. is presumed to consist mainly of water physically adsorbed to the positive electrode active material 110 and hydrated water bound to surface impurities.

[0042] Positive electrode active material 110 may contain, in addition to the composite oxide represented by formula (1), a material that can be used as an active material in an all-solid-state lithium-ion battery.

[0043] Examples of materials that can be used as active materials in all-solid-state lithium-ion batteries are LiCoO2, LiNi x Co 1-x O2(0 <x<0.5)、LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMnO2, hetero-element substituted Li-Mn spinel (e.g. 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., Li4Ti5O 12 ), lithium metal phosphates (e.g., LiFePO4, LiMnPO4, LiCoPO4, or LiNiPO4), transition metal oxides (e.g., V2O5, MoO3).

[0044] Among the above materials, LiCoO2, LiNi x Co 1-x O2(0 <x<0.5)、LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 Lithium-containing composite oxides selected from O2, LiMnO2, heteroelement-substituted Li-Mn spinel, lithium metal phosphate, and the like are preferred.

[0045] The cathode active material 110 has a water content of 2.9 ppm by mass or more and 44.7 ppm by mass or less. By keeping the water content in the cathode active material 110 at 44.7 ppm by mass or less, when the cathode active material 110 is applied to an all-solid-state lithium-ion battery, deterioration of the solid electrolyte 100 (described below) due to the water contained in the cathode active material 110 can be suppressed, and the solid electrolyte 100 maintains high conductivity. Therefore, by using the cathode active material 110, a battery with low battery resistance can be obtained. Furthermore, by keeping the water content in the cathode active material 110 at 2.9 ppm or more, oxidative decomposition of the solid electrolyte 100 due to contact with the cathode active material 110 during battery charging is suppressed, and a battery with low battery resistance can be obtained.

[0046] LiNi x Me 1-x In the case of O2, in a composition where 0.5≦x≦1, there is a concern that deterioration may occur due to a reaction between physically adsorbed water and the active material during high-temperature drying, so it is desirable to sufficiently remove physically adsorbed water at low temperatures.

[0047] The positive electrode active material 110 is dried, for example, by being heated in a temperature range of 70° C. or higher and lower than 120° C. for 12 hours or longer and 500 hours or shorter before forming the positive electrode material. Alternatively, the positive electrode active material 110 is dried, for example, by at least one method selected from the group consisting of heating in a temperature range of 70° C. or higher and lower than 120° C. for 12 hours or longer and 500 hours or shorter before forming the positive electrode material, heating at a temperature of 150° C. or higher and lower than 500° C. for 0.5 hours or longer, and heating at a temperature of 600° C. or higher and 850° C. for 0.5 hours or longer.

[0048] The drying atmosphere may be a vacuum or normal pressure atmosphere with a dew point of −60° C. or lower. If the dew point is −60° C. or lower, the atmosphere may be nitrogen gas or oxygen gas. The amount of moisture generated by heating the dried positive electrode active material 110 to 180° C. is measured using a Karl Fischer moisture analyzer.

[0049] The heating time at a temperature in the range of 70° C. or higher and lower than 120° C. may be 12 hours or longer and 350 hours or shorter, or even 24 hours or longer and 350 hours or shorter.

[0050] At least one period selected from the group consisting of heating at a temperature of 150°C or higher but lower than 500°C and heating at a temperature of 600°C or higher but lower than 850°C may be for 0.5 hours or longer but 24 hours or shorter, or even 1 hour or longer but 12 hours or shorter.

[0051] The amount of moisture generated by the positive electrode active material 110 when heated at 180° C., as measured by Karl Fischer titration, may be 30 ppm by mass or less, or may even be 20 ppm by mass or less. That is, the amount of moisture generated by the positive electrode active material 110 when heated at 180° C., as measured by Karl Fischer titration, may be 2.9 ppm by mass or more and 30 ppm by mass or less, or 2.9 ppm by mass or more and 20 ppm by mass or less.

[0052] The surface of the positive electrode active material 110 may be provided with a coating material 120. The coating material 120 may cover the entire surface of the positive electrode active material 110, or may cover only a portion of the surface.

[0053] The coating material 120 may include Li and at least one element selected from the group consisting of O, F, and Cl.

[0054] The coating material 120 may include at least one selected from the group consisting of lithium niobate, lithium phosphate, lithium titanate, lithium tungstate, lithium fluorozirconate, lithium fluoroaluminate, lithium fluorotitanate, and lithium fluoromagnesium oxide.

[0055] 1 shows a schematic configuration of a positive electrode material 1000. As shown in FIG. 1, the positive electrode material 1000 includes a positive electrode active material 110 and a solid electrolyte 100.

[0056] The solid electrolyte material contained in the solid electrolyte 100 may be a halide solid electrolyte.

[0057] The solid electrolyte 100 may be a compound represented by the following formula (2): Liα M β X γ ···(2) Here, α, β, and γ are values ​​greater than 0. M includes at least one element selected from the group consisting of metal elements and metalloid elements other than Li. X is at least one element selected from the group consisting of F, Cl, Br, and I.

[0058] Here, the metalloid elements are B, Si, Ge, As, Sb, or Te. The metal elements are all elements in Groups 1 to 12 of the periodic table except for hydrogen, and all elements in Groups 13 to 16 except for the metalloid elements C, N, P, O, S, and Se. In other words, the metal elements are a group of elements that can become cations when forming halide compounds and inorganic compounds.

[0059] Examples of the solid electrolyte 100 that can be used include Li3YX6, Li2MgX4, Li2FeX4, Li(Al,Ga,In)X4, and Li3(Al,Ga,In)X6, where X is at least one selected from the group consisting of F, Cl, Br, and I.

[0060] In the present disclosure, "(A,B,C)" means "at least one selected from the group consisting of A, B, and C."

[0061] According to the above configuration, the resistance of the battery can be reduced.

[0062] Equation (2) may satisfy 2.5≦α≦3, 1≦β≦1.1, and γ=6.

[0063] In formula (2), X may include at least one selected from the group consisting of Cl and Br.

[0064] In formula (2), M may include yttrium (Y).

[0065] As a solid electrolyte containing Y, for example, Lia M' b Y c The compound may be a compound represented by the composition formula X6, where a+mb+3c=6 and c>0. M' is at least one selected from the group consisting of metal elements and metalloid elements other than Li and Y. m represents the valence of M'. X is at least one selected from the group consisting of F, Cl, Br, and I.

[0066] As M', at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb may be used.

[0067] Specific examples of Y-containing solid electrolytes include 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, etc. can be used.

[0068] According to the above configuration, the resistance of the battery can be further reduced.

[0069] The halide solid electrolyte does not necessarily contain sulfur. The shapes of the solid electrolyte 100 and the positive electrode active material 110 in the first embodiment are not particularly limited, and may be, for example, needle-like, spherical, or oval-spherical. For example, the solid electrolyte 100 and the positive electrode active material 110 may be particulate.

[0070] For example, when solid electrolyte 100 in the first embodiment is in the form of particles (for example, spheres), the median diameter may be 100 μm or less.

[0071] When 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 be well dispersed in the positive electrode material 1000. This improves the charge / discharge characteristics of the battery.

[0072] In the first embodiment, the median diameter of solid electrolyte 100 may be 10 μm or less.

[0073] According to the above configuration, in the positive electrode material 1000, the positive electrode active material 110 and the solid electrolyte 100 can be well dispersed.

[0074] In the first embodiment, the median diameter of the solid electrolyte 100 may be smaller than the median diameter of the positive electrode active material 110 .

[0075] According to the above configuration, the solid electrolyte 100 and the positive electrode active material 110 in the positive electrode material 1000 can be dispersed in a better state.

[0076] The median diameter of the positive electrode active material 110 may be 0.1 μm or more and 100 μm or less.

[0077] When 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 be well dispersed in the positive electrode material 1000. As a result, the charge / discharge characteristics of the battery are improved.

[0078] Furthermore, when the median diameter of the positive electrode active material 110 is 100 μm or less, a sufficient diffusion rate of lithium is ensured within the positive electrode active material 110. This enables the battery to operate at high power output.

[0079] In the present disclosure, the term "median diameter" refers to the particle size when the cumulative volume in the volume-based particle size distribution is equal to 50%. The volume-based particle size distribution is measured, for example, by a laser diffraction measurement device or an image analysis device.

[0080] In the positive electrode material 1000 according to the first embodiment, the particles of the solid electrolyte 100 and the particles of the positive electrode active material 110 may be in contact with each other, as shown in Fig. 1. In this case, the coating material 120 and the positive electrode active material 110 are in contact with each other.

[0081] Moreover, the positive electrode material 1000 in the first embodiment may include a plurality of particles of the solid electrolyte 100 and a plurality of particles of the positive electrode active material 110 .

[0082] Furthermore, in the positive electrode material 1000 according to the first embodiment, the content of the solid electrolyte 100 and the content of the positive electrode active material 110 may be the same as or different from each other.

[0083] (Embodiment 2) The following describes the second embodiment. Explanations that overlap with the first embodiment will be omitted where appropriate.

[0084] FIG. 1 is a cross-sectional view showing a schematic configuration of a battery 2000 according to the second embodiment.

[0085] The battery 2000 in the second embodiment includes a positive electrode 201 , an electrolyte layer 202 , and a negative electrode 203 .

[0086] The positive electrode 201 includes a positive electrode material 1000 .

[0087] The electrolyte layer 202 is disposed between the positive electrode 201 and the negative electrode 203 .

[0088] According to the above configuration, the discharge voltage of the battery can be improved.

[0089] The volume ratio "v1:100-v1" of the positive electrode active material 110 and the solid electrolyte 100 contained in the positive electrode 201 may satisfy 30≦v1≦95. When 30≦v1 is satisfied, the energy density of the battery 2000 is sufficiently ensured. Furthermore, when v1≦95 is satisfied, high-power operation is possible.

[0090] The thickness of the positive electrode 201 may be 10 μm or more and 500 μm or less. When the thickness of the positive electrode 201 is 10 μm or more, the energy density of the battery 2000 is sufficiently ensured. When the thickness of the positive electrode 201 is 500 μm or less, high-power operation is possible.

[0091] 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 may be a solid electrolyte layer. As the solid electrolyte, any of the materials exemplified as the material of the solid electrolyte 100 in the first embodiment may be used. That is, the electrolyte layer 202 may contain a solid electrolyte having the same composition as the composition of the solid electrolyte 100 contained in the positive electrode material 1000.

[0092] The electrolyte layer 202 may include a halide solid electrolyte having a composition different from the composition of the solid electrolyte included in the cathode material 1000 .

[0093] The electrolyte layer 202 may include a sulfide solid electrolyte.

[0094] The electrolyte layer 202 may contain only one solid electrolyte selected from the above-mentioned group of solid electrolytes, or may contain two or more solid electrolytes selected from the above-mentioned group of solid electrolytes. The multiple solid electrolytes have different compositions. For example, the electrolyte layer 202 may contain a halide solid electrolyte and a sulfide solid electrolyte.

[0095] The thickness of the electrolyte layer 202 may be 1 μm or more and 300 μm or less. When 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 short-circuit. When the thickness of the electrolyte layer 202 is 300 μm or less, high-output operation is possible.

[0096] The negative electrode 203 includes a material having the property of absorbing and releasing metal ions (for example, lithium ions). The negative electrode 203 includes, for example, a negative electrode active material.

[0097] The negative electrode active material may be a metal material, a carbon material, an oxide, a nitride, a tin compound, a silicon compound, or the like. The metal material may be a simple metal. Alternatively, the metal material may be an alloy. Examples of the metal material include lithium metal and a lithium alloy. Examples of the carbon material include natural graphite, coke, partially graphitized carbon, carbon fiber, spherical carbon, artificial graphite, amorphous carbon, or the like. From the viewpoint of capacity density, silicon (Si), tin (Sn), a silicon compound, or a tin compound can be preferably used.

[0098] The negative electrode 203 may contain a solid electrolyte material. According to the above configuration, the lithium ion conductivity inside the negative electrode 203 is increased, enabling high-power operation. The material exemplified in the first embodiment may be used as the solid electrolyte. In other words, the negative electrode 203 may contain a solid electrolyte having the same composition as the solid electrolyte contained in the positive electrode material 1000.

[0099] The median diameter of the negative electrode active material may be 0.1 μm or more and 100 μm or less.

[0100] When 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 be well dispersed, which improves the charge / discharge characteristics of the battery.

[0101] Furthermore, when the median diameter of the negative electrode active material is 100 μm or less, the diffusion rate of lithium within the negative electrode active material is sufficiently ensured, which enables the battery to operate at high power output.

[0102] The median diameter of the negative electrode active material may be larger than the median diameter of the solid electrolyte material, thereby enabling the negative electrode active material and the solid electrolyte material to be well dispersed.

[0103] The volume ratio "v2:100-v2" of the negative electrode active material and the solid electrolyte material contained in the negative electrode 203 may satisfy 30≦v2≦95. When 30≦v2 is satisfied, the energy density of the battery 2000 is sufficiently ensured. Furthermore, when v2≦95 is satisfied, high-power operation is possible.

[0104] The thickness of the negative electrode 203 may be 10 μm or more and 500 μm or less. When the thickness of the negative electrode 203 is 10 μm or more, the energy density of the battery 2000 is sufficiently ensured. When the thickness of the negative electrode 203 is 500 μm or less, high-power operation is possible.

[0105] At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a binder to improve adhesion between particles. The binder is used to improve the binding of the materials constituting the electrode. Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl ester of acrylic acid, polyethyl ester of acrylic acid, polyhexyl ester of acrylic acid, polymethacrylic acid, polymethyl ester of methacrylic acid, polyethyl ester of methacrylic acid, polyhexyl ester of methacrylic acid, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, and carboxymethyl cellulose. The binder may be a copolymer of two or more materials selected from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene. Alternatively, a mixture of two or more materials selected from these may be used as the binder.

[0106] At least one selected from the group consisting of the positive electrode 201 and the negative electrode 203 may contain a conductive additive to enhance electronic conductivity. Examples of conductive additives that can be used 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, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide or potassium titanate, conductive metal oxides such as titanium oxide, and conductive polymer compounds such as polyaniline, polypyrrole, and polythiophene. Using a carbon conductive additive can reduce costs.

[0107] The battery in the second embodiment can be configured as batteries of various shapes, such as coin type, cylindrical type, square type, sheet type, button type, flat type, and laminated type. [Example]

[0108] Hereinafter, the present disclosure will be described in more detail with reference to examples.

[0109] Example 1 [Preparation of positive electrode active material] Cathode active material LiNi 0.8 (Co,Mn) 0.2 After vacuum drying at 100°C for two weeks, the LiNi 0.8 (Co,Mn) 0.2 O2 is referred to as NCM. In this manner, the positive electrode active material of Example 1 was obtained.

[0110] In this example, it was confirmed that physically adsorbed water could be sufficiently removed from the positive electrode active material by vacuum drying for two weeks at 100° C. Specifically, it was confirmed that the amount of water in the positive electrode active material according to this example was 1 ppm or less when measured by Karl Fischer titration at 120° C.

[0111] [Moisture content measurement] The moisture content of the prepared positive electrode active material of Example 1 was measured using a Karl Fischer moisture analyzer (CA-310 manufactured by Mitsubishi Chemical Analytech). The heating temperature of the measurement sample was set to 180° C. The moisture content of the positive electrode active material of Example 1 was 44.7 ppm by mass.

[0112] [Preparation of halide solid electrolytes] In an argon glove box with a dew point below -60°C, raw material powders LiCl, LiBr, and YCl3 were weighed out in a molar ratio of LiCl:LiBr:YCl3 = 1:2:1. These were ground and mixed in a mortar. Then, they were milled in a planetary ball mill at 600 rpm for 12 hours.

[0113] As a result of the above, a halide solid electrolyte powder represented by the composition formula Li3YBr2Cl4 was obtained.

[0114] [Preparation of cathode material] In an argon glove box with a dew point of −60° C. or less, Li3YBr2Cl4 and the positive electrode active material of Example 1 were weighed out in a mass ratio of 20:80. These were mixed in an agate mortar to produce the positive electrode material of Example 1.

[0115] [Preparation of sulfide solid electrolyte] In an argon glove box with a dew point of -60°C or less, Li2S and P2S5 were weighed out so that the molar ratio of Li2S:P2S5 was 75:25. These were then crushed and mixed in a mortar. A planetary ball mill (Fritsch P-7) was then used to mill the mixture at 510 rpm for 10 hours, yielding a glassy solid electrolyte. The glassy solid electrolyte was then heat-treated at 270°C for 2 hours in an inert atmosphere. This resulted in a glass-ceramic sulfide solid electrolyte.

[0116] [Battery construction] The following steps were carried out using Li3YBr2Cl4, the positive electrode material of Example 1, and the sulfide solid electrolyte.

[0117] First, 80 mg of sulfide solid electrolyte, 40 mg of Li3YBr2Cl4, and 12 mg of the positive electrode material of Example 1 were layered in this order in an insulating outer cylinder. This was then pressure molded at a pressure of 720 MPa to obtain a positive electrode and a solid electrolyte layer.

[0118] Next, metallic Li (thickness: 200 μm) was laminated on the side of the solid electrolyte layer opposite to the side in contact with the positive electrode, and this was press-molded at a pressure of 80 MPa to produce a laminate consisting of a positive electrode, a solid electrolyte layer, and a negative electrode.

[0119] Next, stainless steel current collectors were placed on the top and bottom of the laminate, and current collecting leads were attached to the current collectors.

[0120] Finally, the insulating outer cylinder was sealed using an insulating ferrule to isolate the inside of the insulating outer cylinder from the outside atmosphere, thereby producing the battery of Example 1.

[0121] [Electrochemical Testing] Using the battery of Example 1, a charge / discharge test was carried out under the following conditions.

[0122] The battery was placed in a thermostatic chamber at 25°C and connected to a potentiostat (Solartron) equipped with a frequency response analyzer.

[0123] The battery was charged at a constant current of 96 μA, which corresponds to a 0.05C rate (20-hour rate) relative to the theoretical capacity of the battery, and charging was completed at a voltage of 4.3 V.

[0124] Next, the reaction resistance of the battery was measured at room temperature by electrochemical AC impedance measurement.

[0125] FIG. 2 is a Nyquist diagram showing an example of the evaluation results of reaction resistance by AC impedance measurement.

[0126] In Figure 2, the semicircular waveform appearing in the obtained Nyquist diagram was attributed to the positive electrode resistance and the resistance of the negative electrode, In, and the positive electrode resistance value was calculated by performing fitting analysis. In Example 1, the reaction resistance of the positive electrode of the battery was 49 Ω.

[0127] Examples 2 to 4 [Preparation of positive electrode active material] The NCM was vacuum dried at 100°C for 2 weeks, and then calcined at 300°C for 1 hour in a nitrogen gas atmosphere. It was then removed from the dry atmosphere with a dew point of -20°C or lower. In this way, the positive electrode active material of Example 2 was obtained.

[0128] The NCM was vacuum dried at 100°C for 2 weeks, and then calcined at 400°C for 1 hour in a nitrogen gas atmosphere. Thereafter, it was taken out into a dry atmosphere with a dew point of -20°C or lower. In this way, the positive electrode active material of Example 3 was obtained.

[0129] The NCM was vacuum dried at 100°C for 2 weeks, and then calcined in a nitrogen gas atmosphere at 800°C for 1 hour. Thereafter, it was taken out into a dry atmosphere with a dew point of -20°C or lower. In this way, the positive electrode active material of Example 4 was obtained.

[0130] [Moisture content measurement] The moisture content of the prepared positive electrode active materials of Examples 2 to 4 was measured in the same manner as in Example 1. The moisture content of the positive electrode active materials of Examples 2 to 4 is shown in Table 1.

[0131] [Preparation of cathode material] The positive electrode active materials of Examples 2 to 4 were prepared in the same manner as in Example 1, except that the positive electrode active materials of Examples 2 to 4 were used as the positive electrode active materials.

[0132] [Battery construction] The batteries of Examples 2 to 4 were fabricated in the same manner as in Example 1, except that the positive electrode materials of Examples 2 to 4 were used as the positive electrode materials.

[0133] [Electrochemical Testing] Using the batteries of Examples 2 to 4, charge / discharge tests were carried out in the same manner as in Example 1. The reaction resistance of the positive electrodes of the batteries of Examples 2 to 4 is shown in Table 1 below.

[0134] Examples 5 to 8 [Preparation of positive electrode active material] In the same manner as in Example 2, a positive electrode active material of Example 5 was obtained.

[0135] In the same manner as in Example 3, a positive electrode active material of Example 6 was obtained.

[0136] The NCM was vacuum dried at 100°C for 2 weeks, and then calcined at 450°C for 1 hour in a nitrogen gas atmosphere. Thereafter, it was taken out into a dry atmosphere with a dew point of -20°C or lower. In this way, the positive electrode active material of Example 7 was obtained.

[0137] In the same manner as in Example 4, a positive electrode active material of Example 8 was obtained.

[0138] [Moisture content measurement] The moisture content of the prepared positive electrode active materials of Examples 5 to 8 was measured in the same manner as in Example 1. The moisture content of the positive electrode active materials of Examples 5 to 8 is shown in Table 1.

[0139] [Preparation of halide solid electrolytes] In an argon glove box with a dew point of -60°C or less, raw material powders LiCl and YCl3 were weighed out so that the molar ratio was LiCl:YCl3 = 3:1. These were then ground and mixed in a mortar. Then, they were milled at 600 rpm for 12 hours using a planetary ball mill.

[0140] As a result of the above, a halide solid electrolyte powder represented by the composition formula Li3YCl6 was obtained.

[0141] [Preparation of cathode material] In an argon glove box with a dew point of −60° C. or less, Li3YCl6 and the positive electrode active material of Example 5 were weighed out in a weight ratio of 20:80. These were mixed in an agate mortar to produce the positive electrode material of Example 5.

[0142] The positive electrode active materials of Examples 6 to 8 were prepared in the same manner as in Example 5, except that the positive electrode active materials of Examples 6 to 8 were used as the positive electrode active materials.

[0143] [Battery construction] A battery of Example 5 was fabricated in the same manner as in Example 1 using Li3YCl6, the positive electrode material of Example 5, and a sulfide solid electrolyte.

[0144] The batteries of Examples 6 to 8 were fabricated in the same manner as in Example 5, except that the positive electrode materials of Examples 6 to 8 were used as the positive electrode materials.

[0145] [Electrochemical Testing] Using the batteries of Examples 5 to 8, charge / discharge tests were carried out in the same manner as in Example 1. The reaction resistance of the positive electrodes of the batteries of Examples 5 to 8 is shown in Table 1 below.

[0146] Comparative Example 1 [Preparation of positive electrode active material] The NCM kept in a dry atmosphere with a dew point of −20° C. or less was used as the positive electrode active material of Comparative Example 1.

[0147] [Moisture content measurement] The moisture content of the positive electrode active material of Comparative Example 1 was measured in the same manner as in Example 1. The moisture content of the positive electrode active material of Comparative Example 1 was 274.8 ppm by mass.

[0148] [Preparation of cathode material] In an argon glove box with a dew point of −60° C. or less, Li3YBr2Cl4 and the positive electrode active material of Comparative Example 1 were weighed out in a weight ratio of 20:80. These were mixed in an agate mortar to produce the positive electrode material of Comparative Example 1.

[0149] [Battery construction] A battery of Comparative Example 1 was fabricated in the same manner as in Example 1 using Li3YBr2Cl4, the positive electrode material of Comparative Example 1, and a sulfide solid electrolyte.

[0150] [Electrochemical Testing] A charge-discharge test was carried out using the battery of Comparative Example 1 in the same manner as in Example 1. The reaction resistance of the positive electrode of the battery of Comparative Example 1 is shown in Table 1 below.

[0151] Comparative Example 2 [Preparation of positive electrode active material] The NCM was vacuum dried at 100°C for two weeks, and then calcined in a nitrogen gas atmosphere at 500°C for one hour. Thereafter, it was taken out into a dry atmosphere with a dew point of -20°C or lower. In this way, a positive electrode active material of Comparative Example 2 was obtained.

[0152] [Moisture content measurement] The moisture content of the prepared 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 moisture content of the positive electrode active material of Comparative Example 2 was 2.5 ppm by mass.

[0153] [Preparation of cathode material] In an argon glove box with a dew point of −60° C. or less, Li3YBr2Cl4 and the positive electrode active material of Comparative Example 2 were weighed out in a weight ratio of 20:80. These were mixed in an agate mortar to produce the positive electrode material of Comparative Example 2.

[0154] [Battery construction] A battery of Comparative Example 2 was fabricated in the same manner as in Example 1 using Li3YBr2Cl4, the positive electrode material of Comparative Example 2, and a sulfide solid electrolyte.

[0155] [Electrochemical Testing] A charge-discharge test was carried out 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.

[0156] [Table 1]

[0157] ≪Consideration≫ As shown by the results of Example 1, when the amount of water generated by the positive electrode active material by Karl Fischer titration is 2.9 mass ppm or more and 44.7 mass ppm or less when heated at 180°C, the reaction resistance of the battery is low. This is because reducing the amount of water in the positive electrode active material suppresses the hydration and hydrolysis of the halide solid electrolyte Li3YBr2Cl4.

[0158] On the other hand, as shown in the results of Comparative Example 1, when the water content of the positive electrode active material is high, the reaction resistance of the battery is high. This is because the halide solid electrolyte Li3YBr2Cl4 comes into contact with the water on the surface of the positive electrode active material, causing hydration and hydrolysis.

[0159] As shown by the results of Comparative Example 2, when the amount of water generated by the positive electrode active material by Karl Fischer titration when heated to 180°C is less than 2.9 ppm by mass, the reaction resistance of the battery is large. This is because the hydration and hydrolysis of the halide solid electrolyte Li3YBr2Cl4 are suppressed too much, causing contact between the positive electrode active material powder and the halide solid electrolyte Li3YBr2Cl4, which then undergoes oxidative decomposition as the battery is charged.

[0160] Furthermore, the results of Comparative Example 2 show that when the temperature during drying of the positive electrode active material is 500°C, the reaction resistance of the battery is large. This is because temperature affects the state of the surface of the active material. For example, when the drying temperature reaches 500°C, it is thought that the surface of the active material enters a state in which the reaction resistance increases. Furthermore, when the drying temperature reaches a higher temperature of 600°C or higher, it is thought that the surface of the active material enters a state in which the reaction resistance decreases.

[0161] As shown by the above examples, according to the present disclosure, the internal resistance of a battery during charging can be reduced. [Industrial Applicability]

[0162] The battery of the present disclosure can be used, for example, as an all-solid-state battery. [Explanation of symbols]

[0163] 1000 cathode materials 100 solid electrolyte 110 Cathode active material 120 Covering materials 2000 batteries 201 Positive electrode 202 Electrolyte layer 203 Negative electrode

Claims

1. A positive electrode material comprising a positive electrode active material and a solid electrolyte, The positive electrode active material contains, as a main component, a composite oxide represented by the following formula (1), and the amount of water generated when heated at 180°C, as measured by Karl Fischer titration, is 2.9 ppm by mass or more and 44.7 ppm by mass or less, LiNi x Me 1-x Oh 2 ・・・(1) wherein x satisfies 0.5≦x≦1, and Me is at least one element selected from the group consisting of 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 independently a value greater than 0; M includes at least one selected from the group consisting of metal elements and metalloid elements other than Li, X comprises at least one selected from the group consisting of F, Cl, Br, and I; Positive electrode material.

2. Further provided is a coating material that coats the surface of the positive electrode active material, The coating material contains lithium (Li) and at least one element selected from the group consisting of oxygen (O), fluorine (F), and chlorine (Cl). The positive electrode material according to claim 1 .

3. the coating material includes at least one selected from the group consisting of lithium niobate, lithium phosphate, lithium titanate, lithium tungstate, lithium fluorozirconate, lithium fluoroaluminate, lithium fluorotitanate, and lithium fluoromagnesium oxide; The positive electrode material according to claim 2 .

4. The M includes yttrium. The positive electrode material according to any one of claims 1 to 3.

5. The formula (2) satisfies 2.5≦α≦3, 1≦β≦1.1, and γ=6. The positive electrode material according to any one of claims 1 to 4.

6. X includes at least one selected from the group consisting of Cl and Br. The positive electrode material according to any one of claims 1 to 5.

7. A positive electrode comprising the positive electrode material according to any one of claims 1 to 6; a negative electrode; an electrolyte layer disposed between the positive electrode and the negative electrode; battery.

8. The battery of claim 7 , wherein the electrolyte layer comprises the solid electrolyte.

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

10. The electrolyte layer includes a sulfide solid electrolyte. The battery of any one of claims 7 to 9.

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

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