Cathode Materials and Batteries

Abstract

A positive electrode material 1000 in one embodiment of the present disclosure comprises a positive electrode active material 110, a coating layer 111 that includes a first solid electrolyte and covers at least part of the surface of the positive electrode active material 110, and a second solid electrolyte 100. The first solid electrolyte contains Li, M1, and F. M1 is at least one selected from the group consisting of Ti, Al, and Zr. The second solid electrolyte 100 contains Li, M2, O, and X. M2 is at least one selected from the group consisting of Ta and Nb. X is at least one selected from the group consisting of F, Cl, Br, and I.

Description

[Technical Field]

[0001] The present disclosure relates to positive electrode materials for batteries and batteries. [Background technology]

[0002] Patent Document 1 discloses a battery using a solid electrolyte containing In as a cation and a halogen element such as Cl, Br, or I as an anion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-244734 Summary of the Invention [Problem to be solved by the invention]

[0004] In the prior art, it is desirable to suppress the increase in the internal resistance of the battery during charging. [Means for solving the problem]

[0005] In one embodiment of the present disclosure, the positive electrode material is a positive electrode active material; a coating layer including a first solid electrolyte and coating at least a portion of the surface of the positive electrode active material; a second solid electrolyte; Equipped with the first solid electrolyte comprises Li, M1, and F; M1 is at least one selected from the group consisting of Ti, Al, and Zr; the second solid electrolyte comprises Li, M, O, and X; M2 is at least one selected from the group consisting of Ta and Nb, X is at least one selected from the group consisting of F, Cl, Br and I. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to suppress an increase in the internal resistance of a battery during charging. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic configuration of a positive electrode material according to the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing a schematic configuration of a battery according to the second embodiment. [Figure 3] FIG. 3 is a graph showing the X-ray diffraction patterns of the second solid electrolytes according to Examples 1, 3 and 4. [Figure 4A] FIG. 4A is a diagram showing a Nyquist diagram at 4.3 V of the battery in Example 1. [Figure 4B] FIG. 4B is a diagram showing a Nyquist diagram at 4.3 V of the battery in Example 2. [Figure 4C] FIG. 4C is a diagram showing a Nyquist diagram at 4.3 V of the battery in Example 3. [Figure 4D] FIG. 4D is a diagram showing a Nyquist diagram at 4.3 V of the battery in Example 4. [Figure 4E] FIG. 4E is a diagram showing a Nyquist diagram at 4.3 V of the battery in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0008] (Findings that formed the basis of this disclosure) Patent Document 1 discloses an all-solid-state lithium secondary battery that uses a solid electrolyte made of a compound containing In as a cation and a halogen element such as Cl, Br, or I as an anion. It is stated that this battery exhibits good charge-discharge characteristics because the Li potential of the positive electrode active material is 3.9 V or less on average. It is also stated that the reason this battery exhibits good charge-discharge characteristics is that by setting the Li potential of the positive electrode active material to the above value, it is possible to suppress the formation of a film made of decomposition products due to oxidative decomposition. Patent Document 1 also lists LiCoO2, LiNi as positive electrode active materials that have an average Li potential of 3.9 V or less. 0.8 Co 0.15 Al 0.05 Common layered transition metal oxides such as O2 are disclosed.

[0009] Meanwhile, the present inventors have conducted extensive research into the resistance of halide solid electrolytes to oxidative decomposition. As a result, the present inventors have found that the resistance of solid electrolytes to oxidative decomposition varies depending on the type of element contained as anion. Here, a halide solid electrolyte is a solid electrolyte containing a halogen element such as F, Cl, Br, or I as an anion.

[0010] Specifically, the inventors discovered that when a halide solid electrolyte containing an element selected from the group consisting of Cl, Br, and I is used as a positive electrode material, the halide solid electrolyte undergoes oxidative decomposition during charging, even when the positive electrode active material has an average potential vs. Li of 3.9 V or less. Furthermore, the inventors discovered that when such a halide solid electrolyte undergoes oxidative decomposition, the product of oxidative decomposition functions as a resistive layer, resulting in an increase in the internal resistance of the battery during charging. The increase in the internal resistance of the battery during charging is presumably due to an oxidation reaction of the element selected from the group consisting of Cl, Br, and I contained in the halide solid electrolyte. Here, the oxidation reaction refers to a side reaction in which electrons are extracted from the halide solid electrolyte containing an element selected from the group consisting of Cl, Br, and I, which is in contact with the positive electrode active material, in addition to the normal charging reaction in which lithium ions and electrons are extracted from the positive electrode active material in the positive electrode material. The ionic radius of halogen elements is relatively large, resulting in a small interaction between the halogen elements and the cation components constituting the halide solid electrolyte. Therefore, it is thought that the oxidation reaction of the halide solid electrolyte is likely to occur. As a result of this oxidation reaction, an oxidative decomposition layer with poor lithium ion conductivity is formed between the positive electrode active material and the halide solid electrolyte. This oxidative decomposition layer acts as a large interfacial resistance in the electrode reaction of the positive electrode. This is thought to be the reason why the internal resistance of the battery increases during charging.

[0011] The inventors have also demonstrated that batteries using a fluorine-containing halide solid electrolyte as the positive electrode material exhibit excellent oxidation resistance and can suppress an increase in the battery's internal resistance during charging. While the details of this mechanism are unclear, it is presumed to be as follows: Fluorine has the highest electronegativity among halogen elements. When fluorine is contained in a halide solid electrolyte, it bonds strongly with cations. As a result, the oxidation reaction of fluorine, i.e., a side reaction in which electrons are extracted from fluorine, is less likely to proceed.

[0012] Based on the above findings, the present inventors arrived at the positive electrode material of the present disclosure, which is capable of suppressing an increase in the internal resistance of a battery during charging.

[0013] (Summary of one aspect of the present disclosure) The positive electrode material according to the first aspect of the present disclosure is a positive electrode active material; a coating layer including a first solid electrolyte and coating at least a portion of the surface of the positive electrode active material; a second solid electrolyte; Equipped with the first solid electrolyte comprises Li, M1, and F; M1 is at least one selected from the group consisting of Ti, Al, and Zr; the second solid electrolyte comprises Li, M, O, and X; M2 is at least one selected from the group consisting of Ta and Nb, X is at least one selected from the group consisting of F, Cl, Br and I.

[0014] According to the above configuration, it is possible to suppress an increase in the internal resistance of the battery during charging.

[0015] In a second aspect of the present disclosure, for example, in the positive electrode material according to the first aspect, the second solid electrolyte may include a crystalline phase having a peak in a diffraction angle 2θ range of 11.05° to 13.86° in an X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα radiation. A second solid electrolyte having such a configuration has high lithium ion conductivity because it is easy to form paths for lithium ion diffusion.

[0016] In a third aspect of the present disclosure, for example, in the positive electrode material according to the first or second aspect, the second solid electrolyte may have a molar ratio of Li to M2, Li / M2, of 0.60 or more and 2.4 or less, and a molar ratio of O to X, O / X, of 0.16 or more and 0.35 or less. In a second solid electrolyte having such a configuration, a crystalline phase with high lithium ion conductivity is likely to be formed. Therefore, the second solid electrolyte has higher lithium ion conductivity.

[0017] In a fourth aspect of the present disclosure, for example, in the cathode material according to any one of the first to third aspects, the molar ratio of Li to M2 in the second solid electrolyte, Li / M2, may be 0.96 or more and 1.20 or less. In a second solid electrolyte having such a configuration, a crystalline phase with high lithium ion conductivity is more likely to be formed. Therefore, the second solid electrolyte has higher lithium ion conductivity.

[0018] In a fifth aspect of the present disclosure, for example, in the cathode material according to any one of the first to fourth aspects, M1 in the first solid electrolyte may be at least one selected from the group consisting of Ti and Al. The first solid electrolyte having such a configuration has high lithium ion conductivity and high oxidation resistance.

[0019] In a sixth aspect of the present disclosure, for example, in the positive electrode material according to the fifth aspect, the first solid electrolyte is Li 2.6 Ti 0.4 Al 0.6 The first solid electrolyte may contain F6. A first solid electrolyte having such a configuration has higher lithium ion conductivity, which can reduce the interfacial resistance between the first solid electrolyte and the positive electrode active material.

[0020] In a seventh aspect of the present disclosure, for example, in the cathode material according to any one of the first to fourth aspects, M1 in the first solid electrolyte may be Zr. A first solid electrolyte having such a configuration has high lithium ion conductivity. Therefore, the interfacial resistance between the first solid electrolyte and the cathode active material can be reduced.

[0021] In an eighth aspect of the present disclosure, for example, in the cathode material according to the seventh aspect, the first solid electrolyte may contain LiZrF. A first solid electrolyte having such a configuration has higher lithium ion conductivity. Therefore, the interfacial resistance between the first solid electrolyte and the cathode active material can be further reduced.

[0022] In a ninth aspect of the present disclosure, for example, in the positive electrode material according to any one of the first to eighth aspects, the positive electrode active material may include lithium nickel cobalt manganese oxide. A positive electrode active material having such a configuration can improve the energy density and charge / discharge efficiency of a battery.

[0023] A battery according to a tenth aspect of the present disclosure comprises: a positive electrode comprising the positive electrode material according to any one of the tenth to ninth aspects; a negative electrode; an electrolyte layer disposed between the positive electrode and the negative electrode; Equipped with.

[0024] According to the above configuration, it is possible to suppress an increase in the internal resistance of the battery during charging.

[0025] In an eleventh aspect of the present disclosure, for example, in the battery according to the tenth aspect, the electrolyte layer may include a third solid electrolyte, and the third solid electrolyte may be a solid electrolyte having the same composition as the first solid electrolyte, or a solid electrolyte having the same composition or containing the same crystalline phase as the second solid electrolyte. This configuration can improve the power density and charge / discharge characteristics of the battery.

[0026] In a twelfth aspect of the present disclosure, for example, in the battery according to the eleventh aspect, the third solid electrolyte may be a solid electrolyte having the same composition as the first solid electrolyte, which can further improve the power density and charge / discharge characteristics of the battery.

[0027] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0028] (Embodiment 1) FIG. 1 is a cross-sectional view showing a schematic configuration of a positive electrode material 1000 according to the first embodiment.

[0029] The positive electrode material 1000 in the first embodiment includes a coated active material 130 and a second solid electrolyte 100. The coated active material 130 includes a positive electrode active material 110 and a coating layer 111. The positive electrode active material 110 is, for example, in the form of particles. The coating layer 111 coats at least a portion of the surface of the positive electrode active material 110.

[0030] The coating layer 111 is a layer containing a first solid electrolyte. The coating layer 111 is provided on the surface of the positive electrode active material 110. The coating layer 111 may contain only the first solid electrolyte. "Containing only the first solid electrolyte" means that, with the exception of inevitable impurities, no materials other than the first solid electrolyte are intentionally added. For example, the raw materials of the first solid electrolyte and by-products generated when producing the first solid electrolyte are included in the inevitable impurities.

[0031] The second solid electrolyte 100 has, for example, a particulate shape. The second solid electrolyte 100 can ensure sufficient ionic conductivity in the positive electrode material 1000.

[0032] The positive electrode active material 110 is separated from the second solid electrolyte 100 by the coating layer 111. The positive electrode active material 110 does not need to be in direct contact with the second solid electrolyte 100. This is because the coating layer 111 has ion conductivity.

[0033] The coating layer 111 may uniformly coat the positive electrode active material 110. The coating layer 111 prevents direct contact between the positive electrode active material 110 and the second solid electrolyte 100, and suppresses side reactions in the second solid electrolyte 100. As a result, the charge / discharge efficiency of the battery can be improved, and an increase in the reaction overvoltage of the battery can be suppressed.

[0034] The coating layer 111 may cover only a portion of the surface of the positive electrode active material 110. The particles of the positive electrode active material 110 come into direct contact with each other through the portion not covered by the coating layer 111, thereby improving the electronic conductivity between the particles of the positive electrode active material 110. As a result, the battery can operate at high power output.

[0035] The thickness of the coating layer 111 may be, for example, not less than 1 nm and not more than 500 nm.

[0036] When the thickness of the coating layer 111 is 1 nm or more, contact between the positive electrode active material 110 and the second solid electrolyte 100 is suppressed, and side reactions of the second solid electrolyte 100 can be suppressed, thereby improving the charge / discharge efficiency of the battery.

[0037] Furthermore, by making the thickness of the coating layer 111 500 nm or less, it is possible to sufficiently reduce the internal resistance of the battery due to the thickness of the coating layer 111. As a result, it is possible to improve the energy density of the battery.

[0038] The method for measuring the thickness of the coating layer 111 is not particularly limited. For example, the thickness of the first solid electrolyte can be determined by direct observation using a transmission electron microscope or the like. Alternatively, the thickness of the coating layer 111 can be determined from changes in the spectrum derived from the active material by measuring XPS while scraping the coating layer 111 by Ar sputtering.

[0039] The positive electrode active material 110, the coating layer 111, and the second solid electrolyte 100 will now be described in more detail.

[0040] (Coating layer 111) The first solid electrolyte contained in the coating layer 111 contains Li, M1, and F. M1 is at least one selected from the group consisting of Ti, Al, and Zr. That is, the first solid electrolyte is a halide solid electrolyte containing F.

[0041] Batteries using halide solid electrolytes containing F as the positive electrode material exhibit excellent oxidation resistance and can suppress the increase in the battery's internal resistance during charging. Although the details of this mechanism are not clear, it is thought that when halide solid electrolytes contain F, which has a high electronegativity among halogen elements, as an anion, it bonds strongly with the cation, making it difficult for the oxidation reaction of F, i.e., a side reaction in which electrons are extracted from Cl, to proceed.

[0042] Thus, the first solid electrolyte containing Li, M1, and F, where M1 is at least one selected from the group consisting of Ti, Al, and Zr, exhibits high oxidation resistance, and therefore, when used as a positive electrode material, the increase in internal resistance during charging can be suppressed.

[0043] To further enhance lithium ion conductivity, the first solid electrolyte may consist essentially of Li, M1, and F. Here, "the first solid electrolyte consists essentially of Li, M1, and F" means that the molar ratio of the total amount of substance of Li, M1, and F to the total amount of substance of all elements constituting the first solid electrolyte is 90% or more. As an example, the molar ratio may be 95% or more.

[0044] To achieve higher lithium ion conductivity, the first solid electrolyte may consist of only Li, M1, and F.

[0045] In the first solid electrolyte, M1 may be at least one selected from the group consisting of Ti and Al.

[0046] The first solid electrolyte having the above-described structure has high lithium ion conductivity and high oxidation resistance.

[0047] The first solid electrolyte is Li 2.6 Ti 0.4 Al 0.6 It may also contain F6.

[0048] The first solid electrolyte having the above-described configuration exhibits higher ionic conductivity, and therefore can achieve lower interfacial resistance with the positive electrode active material.

[0049] In the first solid electrolyte, M1 may be Zr.

[0050] The first solid electrolyte having the above-described configuration exhibits higher ionic conductivity, and therefore can achieve lower interfacial resistance with the positive electrode active material.

[0051] The first solid electrolyte may include Li2ZrF6.

[0052] The first solid electrolyte having the above-described configuration exhibits higher ionic conductivity, and therefore can achieve lower interfacial resistance with the positive electrode active material.

[0053] The first solid electrolyte may not contain Y (yttrium). The halide solid electrolyte may not contain sulfur. The first solid electrolyte may not contain sulfur.

[0054] (Second solid electrolyte) The second solid electrolyte 100 contains Li, M2, O, and X. M2 is at least one element selected from the group consisting of Ta and Nb. X is at least one element selected from the group consisting of F, Cl, Br, and I. That is, the second solid electrolyte is a halide solid electrolyte containing at least one element selected from the group consisting of Cl, Br, and I. The second solid electrolyte may be a halide solid electrolyte containing at least one element selected from the group consisting of Cl, Br, and I. The second solid electrolyte may also contain, for example, at least one element selected from the group consisting of Cl, Br, and I, and F.

[0055] The second solid electrolyte 100 has high lithium ion conductivity. Therefore, a good interface is formed between the second solid electrolyte 100 and the first solid electrolyte, and the charge transfer resistance between the second solid electrolyte 100 and the positive electrode active material can be reduced. Here, high lithium ion conductivity is, for example, 1×10 -3 That is, the second solid electrolyte 100 according to the first embodiment has a conductivity of, for example, 1×10 -3 It may have an ionic conductivity of mS / cm or more.

[0056] To further enhance lithium ion conductivity, the second solid electrolyte 100 may consist essentially of Li, M2, O, and X. Here, "the second solid electrolyte 100 consists essentially of Li, M2, O, and X" means that the molar ratio of the total amount of substance of Li, M2, O, and X to the total amount of substance of all elements constituting the second solid electrolyte 100 is 90% or more. As an example, the molar ratio may be 95% or more.

[0057] To further enhance lithium ion conductivity, the second solid electrolyte 100 may consist of only Li, M2, O, and X.

[0058] In the second solid electrolyte 100, X may be one selected from the group consisting of Cl, Br, and I.

[0059] The second solid electrolyte 100 may contain a crystalline phase having a peak in the diffraction angle 2θ range of 11.05° to 13.86° in an X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα radiation. Here, the "peak" refers to a diffraction peak in the X-ray diffraction pattern.

[0060] The second solid electrolyte 100 having the above configuration has high lithium ion conductivity because it is easy to form paths for lithium ions to diffuse.

[0061] The X-ray diffraction pattern of the solid electrolyte according to the first embodiment can be obtained by X-ray diffraction measurement by the θ-2θ method using Cu-Kα radiation (wavelengths of 1.5405 Å and 1.5444 Å, ie, wavelengths of 0.15405 nm and 0.15444 nm).

[0062] To further increase ionic conductivity, the second solid electrolyte 100 may further include another crystalline phase different from the crystalline phase having a peak in the above range of diffraction angles 2θ. That is, the second solid electrolyte 100 may further include another crystalline phase having a peak in the above range of diffraction angles 2θ in the X-ray diffraction pattern, the peak being different from the peak of the crystalline phase having a peak in the above range of diffraction angles 2θ. The other crystalline phase may be interposed between the crystalline phases having a peak in the above range of diffraction angles 2θ.

[0063] In the second solid electrolyte 100, the molar ratio of Li to M2, Li / M2, may be 0.60 or more and 2.4 or less, and the molar ratio of O to X, O / X, may be 0.16 or more and 0.35 or less.

[0064] The second solid electrolyte 100 having the above configuration can achieve higher lithium ion conductivity. Specifically, when the molar ratio Li / M2 is within the above range, the concentration of Li, which serves as a conductive carrier, can be optimized. When the molar ratio O / X is within the above range, a crystalline phase with high ion conductivity is easily achieved. This further improves lithium ion conductivity.

[0065] In the second solid electrolyte 100, the molar ratio of Li to M2, Li / M2, may be 0.96 or more and 1.20 or less.

[0066] The second solid electrolyte 100 having the above configuration has a higher lithium ion conductivity because a crystalline phase having high ion conductivity is more easily realized.

[0067] The second solid electrolyte 100 does not necessarily contain Y (yttrium). Also, the second solid electrolyte does not necessarily contain sulfur.

[0068] (Cathode active material) The positive electrode active material 110 includes a material capable of absorbing and releasing metal ions (e.g., lithium ions). Examples of the positive electrode active material 110 that can be used include lithium-containing transition metal oxides, transition metal fluorides, polyanion materials, fluorinated polyanion materials, transition metal sulfides, transition metal oxysulfides, and transition metal oxynitrides. Examples of lithium-containing transition metal oxides include Li(NiCoAl)O2, Li(NiCoMn)O2, and LiCoO2. In particular, using a lithium-containing transition metal oxide as the positive electrode active material 110 can reduce manufacturing costs and increase the average discharge voltage.

[0069] The positive electrode active material 110 may include Ni, Co, and Mn. The positive electrode active material 110 may include lithium nickel cobalt manganese oxide. For example, the positive electrode active material 110 may include Li(NiCoMn)O.

[0070] According to the above configuration, the energy density and charge / discharge efficiency of the battery can be further increased.

[0071] There are no particular limitations on the shape of the second solid electrolyte 100. When the second solid electrolyte 100 is a powder, its shape may be, for example, needle-like, spherical, oval-spherical, etc. For example, the second solid electrolyte 100 may be in the form of particles.

[0072] For example, when the second solid electrolyte 100 is particulate (e.g., spherical), the median diameter may be 100 μm or less. When the median diameter is 100 μm or less, the coated active material 130 and the second solid electrolyte 100 can be well dispersed in the positive electrode material 1000. This improves the charge / discharge characteristics of the battery. In the first embodiment, the median diameter of the second solid electrolyte 100 may be 10 μm or less.

[0073] According to the above configuration, in the positive electrode material 1000, the coated active material 130 and the second solid electrolyte 100 can be well dispersed.

[0074] In the first embodiment, the median diameter of the second solid electrolyte 100 may be smaller than the median diameter of the coated active material 130 .

[0075] According to the above configuration, the second solid electrolyte 100 and the coated active material 130 can be dispersed in the positive electrode material 1000 in a more favorable manner.

[0076] The median diameter of the coated active material 130 may be 0.1 μm or more and 100 μm or less.

[0077] When the median diameter of the coated active material 130 is 0.1 μm or more, the coated active material 130 and the second 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] When the median diameter of the coated active material 130 is 100 μm or less, a sufficient diffusion rate of lithium is ensured within the coated active material 130. This allows the battery to operate at high power output.

[0079] The median diameter of the coated active material 130 may be larger than the median diameter of the second solid electrolyte 100. This allows the coated active material 130 and the second solid electrolyte 100 to form a well-dispersed state.

[0080] Here, the median diameter means 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 measuring device or an image analyzer.

[0081] At least a portion of the surface of the covering layer 111 may be covered with a different coating material.

[0082] Different coating materials include Li-Nb-O compounds such as LiNbO3, Li-BO compounds such as LiBO2 and Li3BO3, Li-Al-O compounds such as LiAlO2, Li-Si-O compounds such as Li4SiO4, Li2SO4, Li4Ti5O 12 Li-Ti-O compounds such as Li2ZrO3, Li-Zr-O compounds such as Li2MoO3, Li-VO compounds such as LiV2O5, Li-WO compounds such as Li2WO4, or Li-PO compounds such as Li3PO4.

[0083] According to the above configuration, oxidation of the first solid electrolyte contained in coating layer 111 can be suppressed in the positive electrode.

[0084] The second solid electrolyte 100 and the coated active material 130 may be in contact with each other, as shown in Fig. 1. In this case, the coating layer 111 and the positive electrode active material 110 are in contact with each other.

[0085] It may include a plurality of second solid electrolyte 100 particles and a plurality of coated active material 130 particles.

[0086] The content of the second solid electrolyte 100 and the content of the coated active material 130 may be the same or different from each other.

[0087] According to the above configuration, it is possible to suppress an increase in the internal resistance of the battery during charging.

[0088] <Method for producing the first solid electrolyte and the second solid electrolyte> The first solid electrolyte contained in the coating layer 111 and the second solid electrolyte 100 can be produced, for example, by the following method.

[0089] The raw material powders of binary halides are prepared and mixed to obtain the desired composition. For example, Li 2.6 Ti 0.4 Al 0.6When producing F6, LiF, TiF4, and AlF3 are prepared in a molar ratio of approximately 2.6:0.4:0.6. Taking into account changes in composition during the synthesis process, the compounding ratio may be adjusted in advance to offset the changes.

[0090] After the raw material powders are thoroughly mixed, they are mixed, pulverized, and reacted with each other using a mechanochemical milling method.

[0091] After thoroughly mixing the raw material powders, the raw material powders may be fired in a vacuum or in an inert atmosphere. The firing conditions are preferably, for example, within a range of 100°C to 300°C for 1 hour or longer. Furthermore, to prevent changes in composition during the firing process, it is preferable to sinter the raw material powders in a sealed container such as a quartz tube.

[0092] As a result, the first solid electrolyte and the second solid electrolyte 100 are obtained.

[0093] The composition of the solid electrolyte can be determined, for example, by ICP emission spectroscopy or ion chromatography.

[0094] The position of the X-ray diffraction peak in the solid electrolyte, i.e., the structure of the crystalline phase, can be adjusted to the desired one by selecting the raw material powders, setting the mixing ratio of the raw material powders, and adjusting the reaction method and reaction conditions for the raw material powders.

[0095] <Method of manufacturing coated active material> The coated active material 130 can be produced, for example, by the following method.

[0096] A powder of the positive electrode active material 110 and a powder of the first solid electrolyte are prepared in a predetermined mass ratio. For example, a powder of Li(NiCoMn)O2 is used as the positive electrode active material 110, and a powder of Li(NiCoMn)O2 is used as the first solid electrolyte. 2.7 Ti 0.3 Al 0.7First, powder of F6 is prepared. These two materials are placed in the same reaction vessel, and a rotating blade is used to apply shear force to the two materials. Alternatively, the two materials may be collided with each other using a jet stream. By applying mechanical energy, the first solid electrolyte can be coated on at least a portion of the surface of the positive electrode active material.

[0097] Before applying mechanical energy to the mixture of the positive electrode active material 110 powder and the first solid electrolyte powder, the mixture may be milled. A mixing device such as a ball mill may be used for the milling. To prevent oxidation of the materials, the milling may be performed in a dry and inert atmosphere.

[0098] The coated active material 130 may be manufactured by a dry particle compounding method. The treatment by the dry particle compounding method includes applying at least one mechanical energy selected from the group consisting of impact, compression, and shear to the positive electrode active material 110 and the first solid electrolyte. The positive electrode active material 110 and the first solid electrolyte are mixed in an appropriate ratio.

[0099] The apparatus used in the method for producing the coated active material 130 is not particularly limited, and may be an apparatus capable of applying mechanical energy such as impact, compression, and shear to a mixture of the positive electrode active material 110 and the first solid electrolyte. Examples of apparatus capable of applying mechanical energy include a ball mill, a jet mill, compression shear processing apparatuses (particle composite apparatuses) such as "Mechanofusion" (manufactured by Hosokawa Micron Corporation) and "Nobilta" (manufactured by Hosokawa Micron Corporation), and a "Hybridization System (high-velocity airflow impact apparatus)" (manufactured by Nara Machinery Works, Ltd.).

[0100] "Mechanofusion" is a particle compounding device that uses dry mechanical compounding technology by applying strong mechanical energy to particles of multiple different materials. In mechanofusion, powder raw materials are fed between a rotating container and a press head, and mechanical energy such as compression, shear, and friction is applied to them, causing the particles to compound.

[0101] "Nobilta" is a particle compounding device that uses dry mechanical compounding technology, an advanced form of particle compounding technology, to compound nanoparticles as raw materials. Nobilta produces composite particles by applying mechanical energy of impact, compression, and shear to multiple raw material powders.

[0102] In the Nobilta, a rotor positioned at a predetermined gap between itself and the inner wall of a horizontal cylindrical mixing vessel rotates at high speed, forcing the raw material powder through the gap, a process that is repeated multiple times. This applies impact, compression, and shear forces to the mixture, producing composite particles of the positive electrode active material 110 and the first solid electrolyte. Conditions such as the rotor rotation speed, processing time, and feed amount can be adjusted as needed.

[0103] In the "hybridization system," raw material powder is dispersed in a high-speed airflow while a force, primarily an impact, is applied, thereby producing composite particles of the positive electrode active material 110 and the first solid electrolyte.

[0104] <Method of manufacturing positive electrode material> The positive electrode material 1000 is obtained by mixing the coated active material 130 and the second solid electrolyte 100. The method for mixing the coated active material 130 and the second solid electrolyte 100 is not particularly limited. For example, the coated active material 130 and the second solid electrolyte 100 may be mixed using a tool such as a mortar, or may be mixed using a mixing device such as a ball mill. The mixing ratio of the coated active material 130 and the second solid electrolyte 100 is not particularly limited.

[0105] (Embodiment 2) The following describes the second embodiment. Explanations that overlap with the first embodiment will be omitted where appropriate.

[0106] FIG. 2 is a cross-sectional view showing a schematic configuration of a battery 2000 according to the second embodiment.

[0107] The battery 2000 in the second embodiment includes a positive electrode 201 , an electrolyte layer 202 , and a negative electrode 203 .

[0108] The positive electrode 201 includes the positive electrode material 1000 in the first embodiment.

[0109] The electrolyte layer 202 is disposed between the positive electrode 201 and the negative electrode 203 .

[0110] According to the above configuration, it is possible to suppress an increase in the internal resistance of the battery 2000 during charging.

[0111] The volume ratio "v1:100-v1" of the positive electrode material 1000 to the second solid electrolyte 100 contained in the positive electrode 201 may satisfy 30≦v1≦98. Here, v1 represents the volume ratio of the positive electrode material 1000 when the total volume of the positive electrode material 1000 and the second solid electrolyte 100 contained in the positive electrode 201 is taken as 100. When 30≦v1 is satisfied, a sufficient energy density of the battery can be ensured. When v1≦98 is satisfied, high-power operation of the battery 2000 becomes easier.

[0112] 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.

[0113] The electrolyte layer 202 is a layer containing an electrolyte. The electrolyte is, for example, a solid electrolyte. The solid electrolyte contained in the electrolyte layer 202 is called a third solid electrolyte. That is, the electrolyte layer 202 may contain the third solid electrolyte.

[0114] The third solid electrolyte may be a halide solid electrolyte. As the third solid electrolyte, a solid electrolyte having the same composition as the first solid electrolyte in the first embodiment, or a solid electrolyte having the same composition as or including the same crystalline phase as the second solid electrolyte may be used. That is, the electrolyte layer 202 may include a solid electrolyte having the same composition as the first solid electrolyte in the first embodiment, or a solid electrolyte having the same composition as or including the same crystalline phase as the second solid electrolyte.

[0115] The third solid electrolyte may be a solid electrolyte having the same composition as the first solid electrolyte in embodiment 1. That is, electrolyte layer 202 may include a solid electrolyte having the same composition as the first solid electrolyte in embodiment 1.

[0116] According to the above configuration, the output density and charge / discharge characteristics of the battery can be further improved.

[0117] The third solid electrolyte may be a halide solid electrolyte having a different composition from the first solid electrolyte, or may be a halide solid electrolyte having a different composition from the second solid electrolyte or including a different crystalline phase. That is, the electrolyte layer 202 may include a halide solid electrolyte having a different composition from the first solid electrolyte, or may include a halide solid electrolyte having a different composition from the second solid electrolyte or including a different crystalline phase.

[0118] The third solid electrolyte may be a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, or a complex hydride solid electrolyte.

[0119] When the third solid electrolyte is a sulfide solid electrolyte, examples of the sulfide solid electrolyte include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, and Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 These can be used in addition to LiX, Li2O, MOq , Li p MO q The element X in "LiX" is at least one element selected from the group consisting of F, Cl, Br, and I. q " and "Li p MO q "The element M is at least one element selected from the group consisting of P, Si, Ge, B, Al, Ga, In, Fe, and Zn. q " and "Li p MO q " p and q in this expression are independent natural numbers.

[0120] According to the above configuration, since the electrolyte layer 202 contains a sulfide solid electrolyte having excellent reduction stability, a low potential negative electrode material such as graphite or metallic lithium can be used, and the energy density of the battery 2000 can be improved.

[0121] When the third solid electrolyte is an oxide solid electrolyte, examples of the oxide solid electrolyte include NASICON-type solid electrolytes represented by LiTi2(PO4)3 and its element substitution products, (LaLi)TiO3-based perovskite-type solid electrolytes, Li 14 ZnGeO 16 , Li4SiO4, LiGeO4 and their element-substituted LISICON-type solid electrolytes, Li7La3Zr2O 12 Garnet-type solid electrolytes, such as those typified by LiN and its element substitution products, LiN and its H-substituted products, LiPO4 and its N-substituted products, and glasses or glass ceramics based on Li-BO compounds such as LiBO2 and LiBO3, to which materials such as LiSO4 and LiCO3 have been added, can be used.

[0122] When the third solid electrolyte is a polymer solid electrolyte, for example, a compound of a polymer compound and a lithium salt can be used as the polymer solid electrolyte. The polymer compound may have an ethylene oxide structure. By having an ethylene oxide structure, the polymer compound can contain a large amount of lithium salt. This can further increase ionic conductivity. As the lithium salt, LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), LiC(SO2CF3)3, etc. can be used. As the lithium salt, one type of lithium salt selected from these may be used alone, or a mixture of two or more types of lithium salts selected from these may be used.

[0123] When the third solid electrolyte is a complex hydride solid electrolyte, for example, LiBH4-LiI, LiBH4-P2S5, or the like can be used as the complex hydride solid electrolyte.

[0124] The electrolyte layer 202 may contain the third solid electrolyte as a main component, i.e., the electrolyte layer 202 may contain, for example, 50% or more of the third solid electrolyte in terms of mass ratio to the entire electrolyte layer 202 (i.e., 50 mass% or more).

[0125] According to the above configuration, the charge and discharge characteristics of the battery 2000 can be further improved.

[0126] The electrolyte layer 202 may contain the third solid electrolyte in a mass ratio relative to the entire electrolyte layer 202 of 70% or more (ie, 70 mass % or more).

[0127] According to the above configuration, the charge / discharge characteristics of the battery 2000 can be further improved.

[0128] The electrolyte layer 202 contains the third solid electrolyte as a main component, and may further contain unavoidable impurities, or starting materials, by-products, decomposition products, etc. used in synthesizing the third solid electrolyte.

[0129] The electrolyte layer 202 may contain, for example, 100% (ie, 100 mass %) of the third solid electrolyte in terms of mass ratio to the entire electrolyte layer 202, excluding unavoidable impurities.

[0130] According to the above configuration, the charge / discharge characteristics of the battery 2000 can be further improved.

[0131] As described above, the electrolyte layer 202 may be composed of only the third solid electrolyte.

[0132] The electrolyte layer 202 may contain two or more of the materials listed as the third solid electrolyte. For example, the electrolyte layer 202 may contain a halide solid electrolyte and a sulfide solid electrolyte.

[0133] 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 cathode 201 and the anode 203 are less likely to short-circuit. When the thickness of the electrolyte layer 202 is 300 μm or less, the battery 2000 can operate at high power.

[0134] 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.

[0135] 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 single metal. Alternatively, the metal material may be an alloy. Examples of the metal material include lithium metal and lithium alloys. Examples of the carbon material include natural graphite, coke, partially graphitized carbon, carbon fiber, spherical carbon, artificial graphite, and amorphous carbon. From the viewpoint of capacity density, silicon (Si), tin (Sn), silicon compounds, and tin compounds may be used.

[0136] The negative electrode 203 may contain a solid electrolyte. As the solid electrolyte, any of the solid electrolytes exemplified as materials constituting the electrolyte layer 202 may be used. With the above configuration, the lithium ion conductivity inside the negative electrode 203 is increased, and the battery 2000 can operate at a high output.

[0137] The median diameter of the particles of the negative electrode active material may be 0.1 μm or more and 100 μm or less. When the median diameter of the particles of the negative electrode active material is 0.1 μm or more, the negative electrode active material and the solid electrolyte can be well dispersed in the negative electrode. This improves the charge / discharge characteristics of the battery 2000. When the median diameter of the particles of the negative electrode active material is 100 μm or less, lithium diffusion within the negative electrode active material is accelerated. This allows the battery 2000 to operate at high power.

[0138] The median diameter of the particles of the negative electrode active material may be larger than the median diameter of the particles of the solid electrolyte contained in the negative electrode 203. This allows the particles of the negative electrode active material and the particles of the solid electrolyte to be well dispersed.

[0139] The volume ratio "v2:100-v2" of the negative electrode active material to the solid electrolyte contained in the negative electrode 203 may satisfy 30≦v2≦95. Here, v2 represents the volume ratio of the negative electrode active material particles when the total volume of the negative electrode active material particles and the solid electrolyte contained in the negative electrode 203 is taken as 100. When 30≦v2, a sufficient energy density of the battery 2000 can be ensured. When v2≦95, the battery 2000 can operate at high output.

[0140] 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, a sufficient energy density of the battery 2000 can be ensured. When the thickness of the negative electrode 203 is 500 μm or less, the battery 2000 can operate at high power.

[0141] At least one 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 properties of the materials constituting the electrodes. Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, 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 the group consisting of tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene, or a mixture of two or more materials selected from these.

[0142] At least one 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 and artificial graphite, carbon blacks such as acetylene black and ketjen black, conductive fibers such as carbon fiber and metal fiber, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and conductive polymer compounds such as polyaniline, polypyrrole, and polythiophene. Using a carbon conductive additive as the conductive additive can reduce costs.

[0143] The battery in the second embodiment 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, and a laminated type. [Example]

[0144] Hereinafter, the present disclosure will be described in detail using examples and comparative examples.

[0145] Example 1 [Preparation of the first solid electrolyte] In an argon atmosphere with a dew point of -60°C or less, the raw material powders LiF, TiF4, and AlF3 were weighed out so that the molar ratio of LiF:TiF4:AlF3 = 2.6:0.4:0.6. The resulting mixture was then milled for 12 hours at 500 rpm using a planetary ball mill (Fritsch, P-7 model). 2.6 Ti 0.4 Al 0.6 A powder of the first solid electrolyte according to Example 1 was obtained, which was represented by the composition formula F6. The composition of the first solid electrolyte according to Example 1 is shown in Table 1.

[0146] [Preparation of second solid electrolyte] In an argon atmosphere with a dew point of -60°C or lower, raw material powders of Li2O2 and TaCl5 were weighed out so that the molar ratio of Li2O2:TaCl5 was 1:2. The resulting mixture was then milled for 12 hours at 600 rpm using a planetary ball mill (Fritsch, Model P-7). The mixture was further milled for 3 hours at 200°C to obtain a powder of the second solid electrolyte according to Example 1, which was composed of Li, Ta, O, and Cl. The constituent elements of the second solid electrolyte according to Example 1 are shown in Table 1.

[0147] The X-ray diffraction pattern of the second solid electrolyte according to Example 1 was measured by the θ-2θ method using an X-ray diffractometer (MiniFlex600, manufactured by Rigaku Co., Ltd.) in a dry environment with a dew point of −50° C. or less. Cu-Kα radiation (wavelengths 1.5405 Å and 1.5444 Å) was used as the X-ray source.

[0148] Fig. 3 is a graph showing the X-ray diffraction pattern of the second solid electrolyte according to Example 1. As shown in Fig. 3, the crystalline phase contained in the second solid electrolyte according to Example 1 had a peak in the diffraction angle 2θ range of 11.05° or more and 13.86° or less in the X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα radiation.

[0149] In the second solid electrolyte of Example 1, the molar ratio of Li to Ta, Li / Ta, was 1.0 (feed ratio), and the molar ratio of O to Cl, O / Cl, was 0.2 (feed ratio).

[0150] [Preparation of coated active material] In an argon atmosphere with a dew point of -60°C or less, the positive electrode active material Li(NiCoMn)O2 (hereinafter referred to as NCM) and the first solid electrolyte according to Example 1 were weighed out so that the mass ratio was 100:3. These materials were placed in a dry particle compositing device, Nobilta (manufactured by Hosokawa Micron Co., Ltd.), and a compositing process was carried out at 6000 rpm for 30 minutes, thereby forming a coating layer made of the first solid electrolyte on the surface of the particles of the positive electrode active material. This resulted in the production of the coated active material according to Example 1.

[0151] [Preparation of cathode material] In an argon atmosphere with a dew point of −60° C. or less, the coated active material according to Example 1 and the second solid electrolyte were weighed out so that the mass ratio was 77.09:22.91. These materials were mixed in a mortar to produce the positive electrode material according to Example 1.

[0152] Example 2 [Preparation of the first solid electrolyte] In an argon atmosphere with a dew point of -60°C or less, raw material powders of LiF and ZrF4 were weighed out so that the molar ratio of LiF:ZrF4 was 2:1. The resulting mixture was then milled for 12 hours at 500 rpm using a planetary ball mill (Fritsch, Model P-7). This yielded a powder of the first solid electrolyte according to Example 2, represented by the formula Li2ZrF6. The composition of the first solid electrolyte according to Example 2 is shown in Table 1.

[0153] [Preparation of second solid electrolyte] In an argon atmosphere with a dew point of -60°C or lower, raw material powders of Li2O2 and TaCl5 were weighed out so that the molar ratio of Li2O2:TaCl5 was 1:2. The resulting mixture was then milled for 12 hours at 600 rpm using a planetary ball mill (Fritsch, Model P-7). The mixture was further milled for 3 hours at 200°C to obtain powders of Li, Ta, O, and Cl, the second solid electrolyte of Example 2. The constituent elements of the second solid electrolyte of Example 2 are shown in Table 1.

[0154] The X-ray diffraction pattern of the second solid electrolyte of Example 2 was measured in the same manner as in Example 1. The crystalline phase contained in the second solid electrolyte of Example 2 had a peak in the diffraction angle 2θ range of 11.05° or more and 13.86° or less in the X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα radiation.

[0155] In the second solid electrolyte of Example 2, the molar ratio of Li to Ta, Li / Ta, was 1.0 (feed ratio), and the molar ratio of O to Cl, O / Cl, was 0.2 (feed ratio).

[0156] [Preparation of coated active material] In an argon atmosphere with a dew point of -60°C or less, the positive electrode active material NCM and the first solid electrolyte according to Example 2 were weighed out so that the mass ratio was 100:3. These materials were placed in a dry particle compositing device, Nobilta (manufactured by Hosokawa Micron Co., Ltd.), and composite processing was carried out at 6000 rpm for 30 minutes, thereby forming a coating layer made of the first solid electrolyte on the surface of the positive electrode active material particles. This resulted in the production of the coated active material according to Example 2.

[0157] [Preparation of cathode material] The coated active material according to Example 2 and the second solid electrolyte were weighed out in an argon atmosphere with a dew point of −60° C. or less so that the mass ratio was 72.81:27.19. These materials were mixed in a mortar to produce the positive electrode material according to Example 2.

[0158] Example 3 [Preparation of the first solid electrolyte] In an argon atmosphere with a dew point of -60°C or less, the raw material powders LiF, TiF4, and AlF3 were weighed out so that the molar ratio of LiF:TiF4:AlF3 = 2.6:0.4:0.6. The resulting mixture was then milled for 12 hours at 500 rpm using a planetary ball mill (Fritsch, P-7 model). 2.6 Ti 0.4 Al 0.6 A powder of the first solid electrolyte according to Example 3 was obtained, which was represented by the composition formula F6. The composition of the first solid electrolyte according to Example 3 is shown in Table 1.

[0159] [Preparation of second solid electrolyte] In an argon atmosphere with a dew point of -60°C or lower, raw material powders of Li2O2 and NbCl5 were weighed out so that the molar ratio of Li2O2:NbCl5 was 1:2. The resulting mixture was then milled for 12 hours at 600 rpm using a planetary ball mill (Fritsch, Model P-7). Further processing was carried out at 80°C for 3 hours to obtain a powder of the second solid electrolyte according to Example 3, which was composed of Li, Nb, O, and Cl. The constituent elements of the second solid electrolyte according to Example 3 are shown in Table 1.

[0160] The X-ray diffraction pattern of the second solid electrolyte according to Example 3 was measured in the same manner as in Example 1. As shown in Fig. 3, the crystalline phase contained in the second solid electrolyte according to Example 3 had a peak in the diffraction angle 2θ range of 11.05° or more and 13.86° or less in the X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα radiation.

[0161] In the second solid electrolyte of Example 3, the molar ratio of Li to Nb, Li / Nb, was 1.0 (feed ratio), and the molar ratio of O to Cl, O / Cl, was 0.2 (feed ratio).

[0162] [Preparation of coated active material] In an argon atmosphere with a dew point of -60°C or less, the positive electrode active material NCM and the first solid electrolyte according to Example 3 were weighed out so that the mass ratio was 100:3. These materials were placed in a dry particle compositing device, Nobilta (manufactured by Hosokawa Micron Co., Ltd.), and composite processing was carried out at 6000 rpm for 30 minutes, thereby forming a coating layer made of the first solid electrolyte on the surface of the positive electrode active material particles. This resulted in the production of the coated active material according to Example 3.

[0163] [Preparation of cathode material] In an argon atmosphere with a dew point of −60° C. or less, the coated active material according to Example 3 and the second solid electrolyte were weighed out so that the mass ratio was 82.04:17.96. These materials were mixed in a mortar to produce the positive electrode material according to Example 3.

[0164] Example 4 [Preparation of the first solid electrolyte] In an argon atmosphere with a dew point of -60°C or less, the raw material powders LiF, TiF4, and AlF3 were weighed out so that the molar ratio of LiF:TiF4:AlF3 = 2.6:0.4:0.6. The resulting mixture was then milled for 12 hours at 500 rpm using a planetary ball mill (Fritsch, P-7 model). 2.6 Ti 0.4 Al 0.6 A powder of the first solid electrolyte according to Example 4 was obtained, which was represented by the composition formula F6. The composition of the first solid electrolyte according to Example 4 is shown in Table 1.

[0165] [Preparation of second solid electrolyte] In an argon atmosphere with a dew point of -60°C or lower, raw material powders of Li2O2, TaCl5, and NbCl5 were weighed out so that the molar ratio of Li2O2:TaCl5:NbCl5 was 1:1:1. The resulting mixture was then milled for 12 hours at 600 rpm using a planetary ball mill (Fritsch, Model P-7). The mixture was further milled for 3 hours at 200°C to obtain a powder of the second solid electrolyte according to Example 4, which consisted of Li, Ta, Nb, O, and Cl. The constituent elements of the second solid electrolyte according to Example 4 are shown in Table 1.

[0166] The X-ray diffraction pattern of the second solid electrolyte of Example 4 was measured in the same manner as in Example 1. As shown in Fig. 3, the crystalline phase contained in the second solid electrolyte of Example 4 had a peak in the diffraction angle 2θ range of 11.05° or more and 13.86° or less in the X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα radiation.

[0167] In the second solid electrolyte of Example 4, the molar ratio of Li to the total of Ta and Nb, Li / (Ta+Nb), was 1.0 (feed ratio), and the molar ratio of O to Cl, O / Cl, was 0.2 (feed ratio).

[0168] [Preparation of coated active material] In an argon atmosphere with a dew point of -60°C or less, the positive electrode active material NCM and the first solid electrolyte according to Example 4 were weighed out so that the mass ratio was 100:3. These materials were placed in a dry particle compositing device, Nobilta (manufactured by Hosokawa Micron Co., Ltd.), and composite processing was carried out at 6000 rpm for 30 minutes, thereby forming a coating layer made of the first solid electrolyte on the surface of the positive electrode active material particles. This resulted in the production of the coated active material according to Example 4.

[0169] [Preparation of cathode material] In an argon atmosphere with a dew point of −60° C. or less, the coated active material according to Example 4 and the second solid electrolyte were weighed out so that the mass ratio was 79.49:20.51. These materials were mixed in a mortar to produce the positive electrode material according to Example 4.

[0170] Comparative Example 1 [Preparation of cathode material] NCM, which is a positive electrode active material, and the second solid electrolyte of Example 1 were weighed out to have a mass ratio of 77.09:22.91. These materials were mixed in a mortar to produce a positive electrode material of Comparative Example 1.

[0171] [Battery construction] The following steps were carried out using the positive electrode materials of Examples 1 to 4 and Comparative Example 1 described above, a glass-ceramic Li2S-P2S5 (hereinafter referred to as LPS) as a sulfide solid electrolyte, and Li3Y1Br2Cl4 (hereinafter referred to as LYBC) as a halide solid electrolyte.

[0172] First, in an insulating outer cylinder, LPS in an amount equivalent to a thickness of 550 μm (equivalent to 80 mg), LYBC in an amount equivalent to a thickness of 50 μm (equivalent to 20 mg), and the positive electrode material were laminated in this order. The mass of the positive electrode material was adjusted so that the mass of the positive electrode active material contained therein was 8.2 mg. The mass of the positive electrode material in Example 1 was 10.47 mg. The mass of the positive electrode material in Example 2 was 10.91 mg. The mass of the positive electrode material in Example 3 was 10.08 mg. The mass of the positive electrode material in Example 4 was 10.21 mg. The mass of the positive electrode material in Comparative Example 1 was 10.32 mg. Each laminate was pressure-molded at a pressure of 360 MPa to obtain a positive electrode and a solid electrolyte layer.

[0173] Next, a 200 μm thick layer of metallic Li was laminated on the side of the solid electrolyte layer opposite to the side in contact with the positive electrode, and the resulting laminate was press-molded at a pressure of 80 MPa to produce a laminate consisting of the positive electrode, the solid electrolyte layer, and the negative electrode.

[0174] Next, stainless steel current collectors were placed on the top and bottom of the laminate, and current collecting leads were attached to each current collector.

[0175] Finally, the insulating outer cylinder was sealed with an insulating ferrule to isolate the inside of the outer cylinder from the outside atmosphere.

[0176] In this manner, the batteries of Examples 1 to 4 and Comparative Example 1 were fabricated.

[0177] [Charging test] Using each of the batteries of Examples 1 to 4 and Comparative Example 1 described above, a charging test was carried out under the following conditions.

[0178] The battery was placed in a thermostatic chamber at 25°C.

[0179] The battery was charged at a constant current of 0.05C (20-hour rate) to the theoretical capacity, with the end-of-charge voltage set to 4.3V (vs. Li).

[0180] Next, the battery was measured using the AC impedance method. The voltage amplitude was ±10 mV and the frequency was 10 7 -10 -2 The frequency was measured at 1000 kJ / s, and the frequency was measured at 1000 kJ / s. The measurement was performed using an electrochemical measurement system manufactured by Solartron. Figures 4A to 4E are diagrams showing Nyquist diagrams at 4.3 V for the batteries in Examples 1 to 4 and Comparative Example 1, respectively. The horizontal and vertical axes in Figures 4A to 4E represent the real and imaginary parts of the impedance, respectively. The semicircular arc waveforms shown in the Nyquist diagrams were assigned to the resistance component with the positive electrode and the resistance component with metallic Li, which is the negative electrode, and curve fitting analysis was performed to calculate the interface resistance with the positive electrode for each of Examples 1 to 4 and Comparative Example 1.

[0181] Next, the battery was discharged at a current value similarly resulting in a rate of 0.05 C. The discharge end voltage was set to 2.5 V (vs. Li).

[0182] The above charge / discharge cycle at a rate of 0.05C was repeated twice, and the increase ratio of the interface resistance with the positive electrode after charging was calculated.

[0183] Table 1 shows the increase ratio of the interface resistance value with the positive electrode in each of Examples 1 to 4 and Comparative Example 1.

[0184] [Table 1]

[0185] ≪Consideration≫ The results of Examples 1 to 4 and Comparative Example 1 shown in Table 1 indicate that when the surface of the positive electrode active material is not covered with a coating layer made of a halide solid electrolyte containing F as the first solid electrolyte, the interfacial resistance with the positive electrode increases with each cycle. This is thought to be because the halide solid electrolyte containing Cl as the second solid electrolyte contained in the positive electrode material oxidizes and decomposes as the battery is charged, causing an increase in the interfacial resistance with the positive electrode. On the other hand, when the surface of the positive electrode active material is covered with a coating layer made of a halide solid electrolyte containing F as the first solid electrolyte, the increase in the internal resistance of the battery during charging is suppressed.

[0186] As shown by the above examples, according to the present disclosure, it is possible to suppress an increase in the internal resistance of a battery during charging. [Industrial Applicability]

[0187] The battery of the present disclosure can be used, for example, as an all-solid-state lithium-ion secondary battery. [Explanation of symbols]

[0188] 1000 cathode materials 100 Second solid electrolyte 110 Cathode active material 111 Covering layer 130 Coated active material 2000 batteries 201 Positive electrode 202 Electrolyte layer 203 Negative electrode

Claims

1. a positive electrode active material; a coating layer including a first solid electrolyte and coating at least a portion of a surface of the positive electrode active material; a second solid electrolyte; Equipped with the first solid electrolyte comprises Li, M1, and F; M1 is at least one selected from the group consisting of Ti, Al, and Zr; the second solid electrolyte comprises Li, M, O, and X; M2 is at least one selected from the group consisting of Ta and Nb, X is at least one selected from the group consisting of F, Cl, Br, and I; The second solid electrolyte contains a crystalline phase having a peak in a diffraction angle 2θ range of 11.05° or more and 13.86° or less in an X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu—Kα radiation. Positive electrode material.

2. In the second solid electrolyte, the molar ratio of Li to M2, Li / M2, is 0.60 or more and 2.4 or less; the molar ratio O / X of O to X is 0.16 or more and 0.35 or less; The positive electrode material according to claim 1 .

3. In the second solid electrolyte, The molar ratio of Li to M2, Li / M2, is 0.96 or more and 1.20 or less; The positive electrode material according to claim 1 or 2.

4. In the first solid electrolyte, M1 is at least one selected from the group consisting of Ti and Al; The positive electrode material according to claim 1 .

5. The first solid electrolyte is Li 2.6 Ti 0.4 Al 0.6 F 6 Including, The positive electrode material according to claim 4.

6. In the first solid electrolyte, M1 is Zr; The positive electrode material according to claim 1 .

7. The first solid electrolyte is Li 2 ZrF 6 Including, The positive electrode material according to claim 6.

8. The positive electrode active material includes lithium nickel cobalt manganese oxide. The positive electrode material according to any one of claims 1 to 7.

9. A positive electrode active material; a coating layer including a first solid electrolyte and coating at least a portion of a surface of the positive electrode active material; a second solid electrolyte; Equipped with the first solid electrolyte comprises Li, M1, and F; M1 is at least one selected from the group consisting of Ti, Al, and Zr; the second solid electrolyte comprises Li, M, O, and X; M2 is at least one selected from the group consisting of Ta and Nb, X is at least one selected from the group consisting of F, Cl, Br, and I; In the second solid electrolyte, the molar ratio of Li to M2, Li / M2, is 0.60 or more and 2.4 or less; the molar ratio O / X of O to X is 0.16 or more and 0.35 or less; Positive electrode material.

10. A positive electrode active material; a coating layer including a first solid electrolyte and coating at least a portion of a surface of the positive electrode active material; a second solid electrolyte; Equipped with the first solid electrolyte comprises Li, M1, and F; M1 is at least one selected from the group consisting of Ti, Al, and Zr; the second solid electrolyte comprises Li, M, O, and X; M2 is at least one selected from the group consisting of Ta and Nb, X is at least one selected from the group consisting of F, Cl, Br, and I; In the second solid electrolyte, The molar ratio of Li to M2, Li / M2, is 0.96 or more and 1.20 or less; Positive electrode material.

11. A positive electrode active material; a coating layer including a first solid electrolyte and coating at least a portion of a surface of the positive electrode active material; a second solid electrolyte; Equipped with the first solid electrolyte contains Li2.6Ti0.4Al0.6F6; the second solid electrolyte comprises Li, M, O, and X; M2 is at least one selected from the group consisting of Ta and Nb, X is at least one selected from the group consisting of F, Cl, Br and I; Positive electrode material.

12. A positive electrode comprising the positive electrode material according to any one of claims 1 to 11; a negative electrode; an electrolyte layer disposed between the positive electrode and the negative electrode; A battery.

13. the electrolyte layer includes a third solid electrolyte; the third solid electrolyte is a solid electrolyte having the same composition as the first solid electrolyte, or a solid electrolyte having the same composition as the second solid electrolyte or containing the same crystalline phase as the second solid electrolyte; The battery of claim 12.

14. The third solid electrolyte is a solid electrolyte having the same composition as the first solid electrolyte.

14. The battery of claim 13.

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