Cathode materials and batteries

Abstract

A positive electrode material according to an aspect of the present disclosure includes a positive electrode active material and a first solid electrolyte that coats the surface of the positive electrode active material. The first solid electrolyte contains Li, M1, O, and X1. M1 is at least one element selected from the group consisting of Nb and Ta. X1 is at least one element selected from the group consisting of Cl, Br, and I.

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a battery using a halide as a solid electrolyte. Non-Patent Document 1 discloses a battery using a sulfide as a solid electrolyte. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 025582 [Non-patent literature]

[0004] [Non-Patent Document 1] Journal of Power Sources 159(2006), p193-199. Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides a positive electrode material that can improve the charge / discharge efficiency of a battery. [Means for solving the problem]

[0006] The positive electrode material according to one embodiment of the present disclosure comprises: a positive electrode active material, and a first solid electrolyte that coats the surface of the positive electrode active material; Includes. the first solid electrolyte comprises Li, M1, O, and X1; M1 is at least one element selected from the group consisting of Nb and Ta, The X1 is at least one element selected from the group consisting of Cl, Br, and I. [Effects of the Invention]

[0007] The present disclosure provides a positive electrode material that can improve the charge / discharge efficiency of a battery. [Brief explanation of the drawings]

[0008] [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 shows a schematic diagram of a pressure forming die used to evaluate the ionic conductivity of a solid electrolyte. [Figure 4] FIG. 4 is a graph showing a Cole-Cole plot obtained by measuring the impedance of the second solid electrolyte according to Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Findings that formed the basis of this disclosure) Patent Document 1 mentions that good charge / discharge characteristics can be obtained by using an all-solid-state secondary battery containing a solid electrolyte made of a halide containing Cl or Br.

[0010] On the other hand, as a result of extensive investigations, the present inventors have found that the ionic conductivity of the solid electrolyte in contact with the positive electrode active material contributes to the charge / discharge efficiency of the battery, and that better charge / discharge characteristics can be obtained by bringing a solid electrolyte having higher ionic conductivity into contact with the positive electrode active material.

[0011] Non-Patent Document 1 mentions that an all-solid-state secondary battery containing a sulfide solid electrolyte can provide good charge-discharge characteristics.

[0012] Meanwhile, the present inventors, through extensive research, have found that when a sulfide solid electrolyte is in contact with a positive electrode active material, the sulfide solid electrolyte undergoes oxidative decomposition during charging. Such oxidative decomposition of the solid electrolyte results in a decrease in the charge / discharge efficiency of the battery. According to the results of the inventors' research, by bringing a solid electrolyte having oxidation stability into contact with the positive electrode active material, it is possible to suppress oxidative decomposition of the sulfide solid electrolyte during charging.

[0013] The inventors of the present invention have proposed a method for coating the surface of a cathode active material with a solid electrolyte having oxidation stability, which may prevent the solid electrolyte from being oxidized.

[0014] Based on the above findings, the present inventors have arrived at the following positive electrode material of the present disclosure, which is capable of improving the charge / discharge efficiency of a battery.

[0015] (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, and a first solid electrolyte that coats the surface of the positive electrode active material; Includes. where: the first solid electrolyte comprises Li, M1, O, and X1; M1 is at least one element selected from the group consisting of Nb and Ta, The X1 is at least one element selected from the group consisting of Cl, Br, and I.

[0016] In the cathode material according to the first embodiment, the surface of the cathode active material is coated with a first solid electrolyte. Here, the first solid electrolyte may coat the entire surface of the cathode active material, or may coat only a portion of the surface of the cathode active material. That is, the first solid electrolyte only needs to coat at least a portion of the surface of the cathode active material. The first solid electrolyte has high ionic conductivity and high high-potential stability. Furthermore, since the first solid electrolyte has high oxidation resistance, it is not easily oxidized and decomposed by contact with the cathode active material. Thus, in the cathode material according to the first embodiment, the cathode active material is in contact with the first solid electrolyte, which has high ionic conductivity and high oxidation resistance. This allows the cathode material according to the first embodiment to improve the charge / discharge efficiency of the battery.

[0017] In the second embodiment of the present disclosure, for example, in the positive electrode material according to the first embodiment, X1 may include Cl.

[0018] The positive electrode material according to the second embodiment can further improve the charge / discharge efficiency of the battery.

[0019] In the third aspect of the present disclosure, for example, in the positive electrode material according to the first or second aspect, M1 may include Ta.

[0020] The positive electrode material according to the third aspect can further improve the charge / discharge efficiency of the battery.

[0021] In a fourth aspect of the present disclosure, for example, in the positive electrode material according to any one of the first to third aspects, a molar ratio Li / M1 of Li to M1 is 0.60 or more and 2.4 or less, The molar ratio O / X1 of O to X1 may be 0.16 or more and 0.35 or less.

[0022] The positive electrode material according to the fourth aspect can further improve the charge / discharge efficiency of the battery.

[0023] In a fifth aspect of the present disclosure, for example, in the positive electrode material according to the fourth aspect, the molar ratio Li / M1 of Li to M1 may be 0.96 or more and 1.20 or less.

[0024] The positive electrode material according to the fifth aspect can further improve the charge / discharge efficiency of the battery.

[0025] In a sixth aspect of the present disclosure, for example, in the positive electrode material according to any one of the first to fifth aspects, the positive electrode active material may contain Ni, Co, and Mn.

[0026] The positive electrode material according to the sixth embodiment can further improve the charge / discharge efficiency of the battery.

[0027] In a seventh aspect of the present disclosure, for example, the positive electrode material according to any one of the first to sixth aspects may further include a second solid electrolyte.

[0028] The positive electrode material according to the seventh embodiment can further improve the charge / discharge efficiency of the battery.

[0029] In an eighth aspect of the present disclosure, for example, in the positive electrode material according to the seventh aspect, the second solid electrolyte may be represented by the following composition formula (1): Li α M2 β X2 γ ...Equation (1) where: α, β, and γ are each independently greater than 0; M2 is at least one element selected from the group consisting of metalloid elements and metal elements other than Li, The X2 is at least one element selected from the group consisting of F, Cl, Br, and I.

[0030] The positive electrode material according to the eighth embodiment can further improve the charge / discharge efficiency of the battery.

[0031] In a ninth embodiment of the present disclosure, for example, in the positive electrode material according to the eighth embodiment, M2 may include yttrium (ie, Y).

[0032] The positive electrode material according to the ninth embodiment can further improve the charge / discharge efficiency of the battery.

[0033] In a tenth aspect of the present disclosure, for example, in the positive electrode material according to the eighth or ninth aspect, in the composition formula (1), α, β, and γ are 2.5≦α≦3, 1≦β≦1.1, and γ=6; may be satisfied.

[0034] The positive electrode material according to the tenth aspect can further improve the charge / discharge efficiency of the battery.

[0035] In an eleventh aspect of the present disclosure, for example, in the positive electrode material according to any one of the eighth to tenth aspects, X2 may include at least one selected from the group consisting of Cl and Br.

[0036] The positive electrode material according to the eleventh aspect can further improve the charge / discharge efficiency of the battery.

[0037] In a twelfth embodiment of the present disclosure, for example, in the positive electrode material according to the eleventh embodiment, X2 may include Cl and Br.

[0038] The positive electrode material according to the twelfth embodiment can further improve the charge / discharge efficiency of the battery.

[0039] In a thirteenth aspect of the present disclosure, for example, in the positive electrode material according to any one of the eighth to twelfth aspects, the second solid electrolyte may contain Li3YBr2Cl4.

[0040] The positive electrode material according to the thirteenth aspect can further improve the charge / discharge efficiency of the battery.

[0041] In a fourteenth aspect of the present disclosure, for example, in the positive electrode material according to the seventh aspect, the second solid electrolyte may include a sulfide solid electrolyte.

[0042] The positive electrode material according to the fourteenth aspect can further improve the charge / discharge efficiency of the battery.

[0043] A battery according to a fifteenth aspect of the present disclosure comprises: a positive electrode comprising the positive electrode material according to any one of the first to fourteenth aspects; a negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode; Equipped with.

[0044] In the battery according to the fifteenth aspect, the charge / discharge efficiency can be improved.

[0045] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0046] (Embodiment 1) The cathode material in the first embodiment includes a cathode active material and a first solid electrolyte that coats the surface of the cathode active material. For example, the first solid electrolyte is located on the surface of the cathode active material to form a coating layer. The first solid electrolyte may coat the entire surface of the cathode active material, or may coat only a portion of the surface of the cathode active material.

[0047] The first solid electrolyte contains Li, M1, O, and X1. M1 is at least one element selected from the group consisting of Nb and Ta. X1 is at least one element selected from the group consisting of Cl, Br, and I.

[0048] In the cathode material of the first embodiment, the surface of the cathode active material is coated with a first solid electrolyte. The first solid electrolyte has high ionic conductivity and high potential stability. Furthermore, the first solid electrolyte has high oxidation resistance, and is therefore less susceptible to oxidative decomposition upon contact with the cathode active material. Thus, in the cathode material of the first embodiment, the cathode active material is in contact with the first solid electrolyte, which has high ionic conductivity and high oxidation stability. This allows the cathode material of the first embodiment to improve the charge / discharge efficiency of the battery. Furthermore, the cathode material of the first embodiment can suppress an increase in the reaction overvoltage of the battery.

[0049] In the positive electrode material according to the first embodiment, X1 contained in the first solid electrolyte may include Cl. That is, the first solid electrolyte may include Cl. By including Cl, the first solid electrolyte can have higher ionic conductivity and also higher oxidation stability. Therefore, according to this configuration, the positive electrode material can further improve the charge / discharge efficiency of the battery.

[0050] In the positive electrode material of the first embodiment, M1 contained in the first solid electrolyte may include Ta. That is, the first solid electrolyte may include Ta. By including Ta, the first solid electrolyte can have higher ionic conductivity and also higher oxidation stability. Therefore, according to this configuration, the positive electrode material can further improve the charge / discharge efficiency of the battery. Furthermore, the first solid electrolyte does not need to include sulfur.

[0051] In the positive electrode material of the first embodiment, the first solid electrolyte may have a molar ratio of Li to M1, Li / M1, of 0.60 or more and 2.4 or less, and a molar ratio of O to X1, O / X1, of 0.16 or more and 0.35 or less. The molar ratio of Li to M1 is calculated by the formula: (amount of substance of Li) / (total amount of substance of Ta and Nb). The molar ratio of O to X1 is calculated by the formula: (amount of substance of O) / (total amount of substance of Cl, Br, and I). When the molar ratio Li / M1 is 0.60 or more and 2.4 or less, and the molar ratio O / X1 is 0.16 or more and 0.35 or less, the first solid electrolyte can have higher ionic conductivity. Therefore, with this configuration, the positive electrode material can further improve the charge / discharge efficiency of the battery.

[0052] In the positive electrode material according to the first embodiment, the molar ratio Li / M1 of Li to M1 in the first solid electrolyte may be 0.96 or more and 1.20 or less. When the molar ratio Li / M1 satisfies 0.96 or more and 1.20 or less, the first solid electrolyte can have higher ionic conductivity. Therefore, according to this configuration, the positive electrode material can further improve the charge / discharge efficiency of the battery.

[0053] In the positive electrode material of the first embodiment, the positive electrode active material is, for example, a material having the property of absorbing and releasing metal ions (e.g., lithium ions). Examples of the positive electrode active material 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(Ni, Co, Al)O2, Li(Ni, Co, Mn)O2, and LiCoO2. When a lithium-containing transition metal oxide is used as the positive electrode active material, the manufacturing cost of the positive electrode can be reduced and the average discharge voltage can be increased.

[0054] In the first embodiment, the positive electrode active material may include Ni, Co, and Mn. For example, in the first embodiment, the positive electrode active material may be lithium nickel-cobalt-manganese oxide. For example, the positive electrode active material may be Li(Ni,Co,Mn)O.

[0055] According to the above configuration, the energy density and charge / discharge efficiency of the battery can be further increased.

[0056] The positive electrode material in the first embodiment may further contain a second solid electrolyte.

[0057] The second solid electrolyte includes, for example, a material with high ionic conductivity. For example, a halide solid electrolyte or the like can be used for the second solid electrolyte. For example, a compound represented by the following composition formula (1) can be used. Here, α, β, and γ are each independently a value greater than 0.

[0058] Li α M2 β X2 γ ...Equation (1)

[0059] M2 is at least one element selected from the group consisting of metalloid elements and metal elements other than Li. "Metalloid elements" are B, Si, Ge, As, Sb, and Te. "Metal elements" are all elements in groups 1 to 12 of the periodic table except hydrogen, and all elements in groups 13 to 16 except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. In other words, this is a group of elements that can become cations when forming inorganic compounds with halogen compounds.

[0060] X2 is at least one element selected from the group consisting of F, Cl, Br, and I.

[0061] According to the above configuration, the ionic conductivity of the second solid electrolyte can be further improved, thereby further improving the charge / discharge efficiency of the battery.

[0062] In the composition formula (1), M2 may contain yttrium (that is, Y). That is, the second solid electrolyte may contain Y as a metal element.

[0063] According to the above configuration, the ionic conductivity of the second solid electrolyte can be further improved, thereby further improving the charge / discharge characteristics of the battery.

[0064] As the second solid electrolyte containing Y, for example, Li a Me b Y c The compound may be a compound represented by the composition formula X26, where a+mb+3c=6 and c>0 are satisfied. Me is at least one selected from the group consisting of metalloid elements and metal elements excluding Li and Y. Furthermore, m is the valence of Me.

[0065] As Me, at least one element 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.

[0066] According to the above configuration, the ionic conductivity of the second solid electrolyte can be further improved.

[0067] In the composition formula (1), the conditions 2.5≦α≦3, 1≦β≦1.1, and γ=6 may be satisfied.

[0068] According to the above configuration, the ionic conductivity of the second solid electrolyte can be further improved, thereby further improving the charge / discharge characteristics of the battery.

[0069] In the composition formula (1), X2 may contain at least one selected from the group consisting of Cl and Br, or may contain both Cl and Br.

[0070] According to the above configuration, the ionic conductivity of the second solid electrolyte can be further improved. Thereby, the charge and discharge characteristics of the battery can be further improved.

[0071] Note that the second solid electrolyte may be a material represented by the following compositional formula (B1). Li 6-3d Y d X26··· Formula (B1) Here, in the compositional formula (B1), X2 is at least one element selected from the group consisting of F, Cl, Br, and I. Also, in the compositional formula (B1), 0 < d < 2 is satisfied.

[0072] According to the above configuration, the ionic conductivity of the second solid electrolyte can be further improved. Thereby, the charge and discharge efficiency of the battery can be further improved.

[0073] Note that the second solid electrolyte may be a material represented by the following compositional formula (B2). Li3YX26··· Formula (B2) Here, in the compositional formula (B2), X2 is at least one element selected from the group consisting of F, Cl, Br, and I. [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​In the compositional formula (B3), -1 < δ < 2, 0 < a < 3, 0 < (3 - 3δ + a), 0 < (1 + δ - a), 0 ≤ x < 6, 0 < y ≤ 6, and (x + y) < 6 are satisfied.

[0077] According to the above configuration, the ionic conductivity of the second solid electrolyte can be further improved. Thereby, the charge-discharge efficiency of the battery can be further improved.

[0078] Note that the second solid electrolyte may be a material represented by the following compositional formula (B4). Li 3-3δ Y 1+δ-a Me a Cl 6-x-y Br x I y ··· Formula (B4) Here, in the compositional formula (B4), Me is one or more elements selected from the group consisting of Al, Sc, Ga, and Bi.

[0079] In the compositional formula (B4), -1 < δ < 1, 0 < a < 2, 0 < (1 + δ - a), 0 ≤ x < 6, 0 < y ≤ 6, and (x + y) < 6 are satisfied.

[0080] According to the above configuration, the ionic conductivity of the second solid electrolyte can be further improved. Thereby, the charge-discharge efficiency of the battery can be further improved.

[0081] Note that the second solid electrolyte may be a material represented by the following compositional formula (B5). Li 3-3δ-a Y 1+δ-a Me a Cl 6-x-y Br x I y ··· Formula (B5) Here, in the compositional formula (B5), Me is one or more elements selected from the group consisting of Zr, Hf, and Ti.

[0082] In the compositional formula (B5), -1 < δ < 1, 0 < a < 1.5, 0 < (3 - 3δ - a), 0 < (1 + δ - a), 0 ≤ x < 6, 0 < y ≤ 6, and (x + y) < 6 are satisfied.

[0083] According to the above configuration, the ionic conductivity of the second solid electrolyte can be further improved. Thereby, the charge-discharge efficiency of the battery can be further improved.

[0084] The second solid electrolyte may be a material represented by the following compositional formula (B6). Li 3-3δ-2a Y 1+δ-a Me a Cl 6-x-y Br x I y ··· Formula (B6) Here, in the compositional formula (B6), Me is one or more elements selected from the group consisting of Ta and Nb.

[0085] In the compositional formula (B6), -1 < δ < 1, 0 < a < 1.2, 0 < (3 - 3δ - 2a), 0 < (1 + δ - a), 0 ≤ x < 6, 0 < y ≤ 6, and (x + y) < 6 are satisfied.

[0086] According to the above configuration, the ionic conductivity of the second solid electrolyte can be further improved. Thereby, the charge-discharge efficiency of the battery can be further improved.

[0087] As the second solid electrolyte, for example, Li3YX6, Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, Li3(Al, Ga, In)X6, etc. can be used. Here, X may be at least one element selected from the group consisting of Cl and Br. The second solid electrolyte may contain, for example, Li3YBr2Cl4. Further, the halide solid electrolyte used as the second solid electrolyte may contain an oxygen atom as an anion other than the halogen element. Also, the second solid electrolyte may not contain sulfur.

[0088] The second solid electrolyte may be a sulfide solid electrolyte. Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, and Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 , etc. can be used. In addition to these, LiX, Li2O, MO q , Li p MO q etc. may be added. Here, X is one or more elements selected from the group consisting of F, Cl, Br, and I. Furthermore, M is one or more elements selected from the group consisting of P, Si, Ge, B, Al, Ga, In, Fe, and Zn. Furthermore, p and q are each independently a natural number.

[0089] In the first embodiment, the second solid electrolyte may be a sulfide solid electrolyte. For example, the sulfide solid electrolyte may contain lithium sulfide and phosphorus sulfide. For example, the sulfide solid electrolyte may be Li2S-P2S5.

[0090] Li2S-P2S5 has high ionic conductivity and is stable against oxidation and reduction, so the use of Li2S-P2S5 can further improve the charge-discharge efficiency of batteries.

[0091] FIG. 1 is a cross-sectional view showing a schematic configuration of a cathode material 1000 according to the first embodiment. The cathode material 1000 according to the first embodiment includes a second solid electrolyte 100, a cathode active material 110, and a first solid electrolyte 111 that coats the surface of the cathode active material 110. For example, the first solid electrolyte 111 is located on the surface of the cathode active material 110 to form a coating layer. As shown in FIG. 1, the second solid electrolyte 100 and the cathode active material 110 may be in a particulate form.

[0092] The thickness of first solid electrolyte 111 may be not less than 1 nm and not more than 500 nm.

[0093] By making the thickness of the first solid electrolyte 111 1 nm or more, contact between the positive electrode active material 110 and the second solid electrolyte 100 can be suppressed, and side reactions of the first solid electrolyte can be suppressed, thereby improving charge / discharge efficiency.

[0094] Furthermore, by setting the thickness of first solid electrolyte 111 to 500 nm or less, the thickness of first solid electrolyte 111 does not become too thick, which allows the internal resistance of the battery to be sufficiently small, and as a result, the energy density of the battery can be increased.

[0095] Alternatively, the first solid electrolyte 111 may uniformly cover the entire surface of the positive electrode active material 110. This prevents direct contact between the positive electrode active material 110 and the second solid electrolyte 100, and more reliably suppresses side reactions in the second solid electrolyte 100. This further improves the charge / discharge characteristics of the battery and also suppresses an increase in the reaction overvoltage of the battery.

[0096] Alternatively, the first solid electrolyte 111 may cover a portion of the surface of the positive electrode active material 110. Particles of the positive electrode active material 110 come into direct contact with each other through the portion not covered by the first solid electrolyte 111, thereby improving electronic conductivity between the particles of the positive electrode active material 110. This enables the battery to operate at high power output.

[0097] The method for measuring the thickness of the first solid electrolyte 111 is not particularly limited, and for example, the thickness can be determined by directly observing the thickness of the first solid electrolyte 111 using a transmission electron microscope or the like. Alternatively, the thickness of the first solid electrolyte 111 can be determined from changes in the spectrum derived from the active material by measuring XPS while scraping the first solid electrolyte 111 by Ar sputtering.

[0098] The shape of second solid electrolyte 100 in embodiment 1 is not particularly limited and may be, for example, needle-like, spherical, oval-spherical, etc. For example, second solid electrolyte 100 may be in the form of particles.

[0099] For example, when the second solid electrolyte 100 in the first embodiment is particulate (e.g., spherical), the median diameter may be 100 μm or less. When the median diameter is 100 μm or less, the positive electrode active material 110 and the second solid electrolyte 100 are well dispersed in the positive electrode material 1000, thereby improving the charge / discharge characteristics. In the first embodiment, the median diameter may be 10 μm or less.

[0100] According to the above configuration, in the positive electrode material 1000, the positive electrode active material 110 and the second solid electrolyte 100 can be well dispersed.

[0101] In the first embodiment, the second solid electrolyte 100 may have a smaller median diameter than the positive electrode active material 110 .

[0102] According to the above configuration, the second solid electrolyte 100 and the positive electrode active material 110 can be dispersed in a better state in the electrode.

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

[0104] 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 second solid electrolyte 100 are well dispersed in the positive electrode material 1000, thereby improving the charge / discharge characteristics of the battery. Furthermore, when the median diameter of the positive electrode active material 110 is 100 μm or less, lithium diffuses quickly within the positive electrode active material 110, making it easier for the battery to operate at high power.

[0105] The median diameter of the positive electrode active material 110 may be larger than the median diameter of the second solid electrolyte 100. This allows the positive electrode active material 110 and the second solid electrolyte 100 to form a good dispersed state.

[0106] 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.

[0107] On the surface of the positive electrode active material 110, a Li-Nb-O compound such as LiNbO3, a Li-BO compound such as LiBO2 or Li3BO3, a Li-Al-O compound such as LiAlO2, a Li-Si-O compound such as Li4SiO4, Li2SO4, Li4Ti5O 12 Li-Ti-O compounds such as LiZrO, Li-Zr-O compounds such as LiZrO, Li-Mo-O compounds such as LiMoO, Li-VO compounds such as LiVO, Li-WO compounds such as LiWO, or Li-PO compounds such as LiPO.

[0108] According to the above configuration, oxidation of the second solid electrolyte 100 in the positive electrode can be suppressed.

[0109] In the positive electrode material 1000 according to the first embodiment, the second solid electrolyte 100 and the first solid electrolyte 111 may be in contact with each other as shown in FIG.

[0110] The positive electrode material 1000 in the first embodiment may include a plurality of particles of the second solid electrolyte 100 and a plurality of particles of the positive electrode active material 110.

[0111] Furthermore, in the positive electrode material 1000 of the first embodiment, the content of the second solid electrolyte 100 and the content of the positive electrode active material 110 may be the same as or different from each other.

[0112] <Method for producing the first solid electrolyte and the second solid electrolyte> The first solid electrolyte and the second solid electrolyte in the first embodiment can be produced, for example, by the following method.

[0113] Raw material powders are prepared and mixed to achieve the desired composition. Examples of raw material powders include oxides, hydroxides, halides, and oxyhalides. For example, to produce Li3YCl6, LiCl and YCl3 are prepared in a molar ratio of 3:1.

[0114] At this time, by selecting the type of raw material powder, it is possible to determine "M1," "M2," "Me," "X1," and "X2" in the above composition formula. In addition, by adjusting the raw materials, compounding ratio, and synthesis process, it is possible to adjust the above values ​​"α," "β," "γ," "d," "δ," "a," "x," and "y."

[0115] After the raw material powders are thoroughly mixed, they are mixed, pulverized, and reacted with each other using a mechanochemical milling method, or alternatively, the raw material powders may be thoroughly mixed and then sintered in a vacuum.

[0116] As a result, the first solid electrolyte and the second solid electrolyte are obtained.

[0117] The constitution of the crystalline phase in the solid electrolyte (ie, the crystalline structure) can be determined by adjusting the reaction method and reaction conditions for the raw material powders.

[0118] <Method for producing a positive electrode active material coated with a first solid electrolyte> The positive electrode active material 110 coated with the first solid electrolyte 111 can be produced by the following method.

[0119] A powder of the positive electrode active material 110 and a powder of the first solid electrolyte 111 are mixed in an appropriate ratio to obtain a mixture. The mixture is then milled to impart mechanical energy to the mixture. A mixing device such as a ball mill can be used for the milling process. To prevent oxidation of the materials, the milling process may be performed in a dry and inert atmosphere.

[0120] The positive electrode active material 110 coated with the first solid electrolyte 111 may be manufactured by a dry particle compositing method. The treatment by the dry particle compositing 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 111. The positive electrode active material 110 and the first solid electrolyte 111 are mixed in an appropriate ratio.

[0121] (Embodiment 2) The following describes the second embodiment. Explanations that overlap with the first embodiment will be omitted where appropriate.

[0122] FIG. 2 is a cross-sectional view showing a schematic configuration of a battery 2000 according to the second embodiment.

[0123] The battery 2000 in the second embodiment includes a positive electrode 201 , an electrolyte layer 202 , and a negative electrode 203 .

[0124] The positive electrode 201 includes the positive electrode material 1000 in the first embodiment.

[0125] The electrolyte layer 202 is disposed between the positive electrode 201 and the negative electrode 203 .

[0126] According to the above configuration, the charge / discharge efficiency of the battery 2000 can be improved.

[0127] The volume ratio "v1:100-v1" of the positive electrode active material 110 to the second solid electrolyte 100 contained in the positive electrode 201 may satisfy 30≦v1≦95. Here, v1 represents the volume ratio of the positive electrode active material 110 when the total volume of the positive electrode active material 110 and the second solid electrolyte 100 contained in the positive electrode 201 is taken as 100. When 30≦v1 is satisfied, it is easy to ensure a sufficient energy density of the battery 2000. When v1≦95 is satisfied, it is easier for the battery 2000 to operate at high output.

[0128] 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, it is easy to ensure a sufficient energy density of the battery 2000. When the thickness of the positive electrode 201 is 500 μm or less, it is easier for the battery 2000 to operate at high output.

[0129] The electrolyte layer 202 is disposed between the positive electrode 201 and the negative electrode 203 .

[0130] The electrolyte layer 202 is a layer including an electrolyte material. The electrolyte material is, for example, a solid electrolyte (i.e., a third solid electrolyte). That is, the electrolyte layer 202 may be a solid electrolyte layer.

[0131] The third solid electrolyte contained in electrolyte layer 202 may be a halide solid electrolyte having the same composition as the first solid electrolyte and / or the second solid electrolyte described in the above-mentioned embodiment 1. That is, electrolyte layer 202 may include a halide solid electrolyte having the same composition as the first solid electrolyte and / or the second solid electrolyte in the above-mentioned embodiment 1.

[0132] According to the above configuration, the charge / discharge efficiency of the battery 2000 can be further improved.

[0133] The third solid electrolyte included in the electrolyte layer 202 may be a halide solid electrolyte having a composition different from that of the first solid electrolyte and the second solid electrolyte described in the above-mentioned embodiment 1. That is, the electrolyte layer 202 may include a halide solid electrolyte having a composition different from that of the first solid electrolyte and the second solid electrolyte described in the above-mentioned embodiment 1.

[0134] According to the above configuration, the output density and charge / discharge efficiency of the battery 2000 can be improved.

[0135] The halide solid electrolyte contained in the electrolyte layer 202 may contain Y as a metal element.

[0136] According to the above configuration, the output density and charge / discharge efficiency of the battery 2000 can be further improved.

[0137] A sulfide solid electrolyte may be used as the third solid electrolyte contained in the electrolyte layer 202. That is, the electrolyte layer 202 may include a sulfide solid electrolyte.

[0138] According to the above configuration, since the sulfide solid electrolyte having excellent reduction stability is included, 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.

[0139] The sulfide solid electrolyte of the third solid electrolyte is Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 , etc. can be used. In addition to these, LiX, Li2O, MO q , Li p MO q etc. may be added. Here, X is one or more elements selected from the group consisting of F, Cl, Br, and I. Furthermore, M is one or more elements selected from the group consisting of P, Si, Ge, B, Al, Ga, In, Fe, and Zn. Furthermore, p and q are each independently a natural number.

[0140] The sulfide solid electrolyte of the third solid electrolyte may be a sulfide solid electrolyte having the same composition as the second solid electrolyte described in the above-mentioned embodiment 1. That is, the electrolyte layer 202 may include a sulfide solid electrolyte having the same composition as the second solid electrolyte in the above-mentioned embodiment 1.

[0141] According to the above configuration, since the electrolyte layer 202 contains a sulfide solid electrolyte having excellent reduction stability, it is possible to use low-potential negative electrode materials such as graphite and metallic lithium, thereby improving the energy density of the battery. Furthermore, if the electrolyte layer 202 contains the same sulfide solid electrolyte as the second solid electrolyte in the first embodiment, the charge / discharge characteristics of the battery can be improved.

[0142] The third solid electrolyte included in the electrolyte layer 202 may be an oxide solid electrolyte, a polymer solid electrolyte, or a complex hydride solid electrolyte.

[0143] Examples of oxide solid electrolytes include NASICON-type solid electrolytes, such as LiTi2(PO4)3 and its elemental substitution products, (LaLi)TiO3-based perovskite-type solid electrolytes, and 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 and glass ceramics based on Li-BO compounds such as LiBO2 and LiBO3 to which LiSO4, LiCO3, etc. are added, can be used.

[0144] As the polymer solid electrolyte, for example, a compound of a polymer compound and a lithium salt can be used. The polymer compound may have an ethylene oxide structure. By having an ethylene oxide structure, a large amount of lithium salt can be contained, and ionic conductivity can be further increased. 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 can be used alone. Alternatively, as the lithium salt, a mixture of two or more types of lithium salts selected from these can be used.

[0145] Examples of the complex hydride solid electrolyte that can be used include LiBH4-LiI and LiBH4-P2S5.

[0146] The electrolyte layer 202 may contain the third solid electrolyte as a main component, i.e., the electrolyte layer 202 may contain the third solid electrolyte in a mass ratio of 50% or more relative to the entire electrolyte layer 202.

[0147] According to the above configuration, the charge / discharge characteristics of the battery 2000 can be further improved.

[0148] Furthermore, the electrolyte layer 202 may contain the third solid electrolyte in a mass ratio of 70% or more relative to the entire electrolyte layer 202, for example.

[0149] According to the above configuration, the charge / discharge characteristics of the battery 2000 can be further improved.

[0150] The electrolyte layer 202 contains the third solid electrolyte as a main component, and may further contain unavoidable impurities, or starting materials, by-products, and decomposition products used in synthesizing the second solid electrolyte.

[0151] Furthermore, the electrolyte layer 202 may contain the third solid electrolyte in a mass ratio of 100% relative to the entire electrolyte layer 202, excluding unavoidable impurities, for example.

[0152] According to the above configuration, the charge / discharge characteristics of the battery 2000 can be further improved.

[0153] As described above, the electrolyte layer 202 may be composed of only the third solid electrolyte.

[0154] The electrolyte layer 202 may contain two or more of the materials listed as the third solid electrolyte. For example, the solid electrolyte layer may contain a halide solid electrolyte and a sulfide solid electrolyte.

[0155] 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 possibility of short-circuiting between the positive electrode 201 and the negative electrode 203 is reduced. Furthermore, when the thickness of the electrolyte layer 202 is 300 μm or less, high-power operation is facilitated. In other words, if the thickness of the electrolyte layer 202 is appropriately adjusted, sufficient safety of the battery 2000 can be ensured, and the battery 2000 can be operated at high power.

[0156] 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.

[0157] The negative electrode active material may be a metal material, a carbon material, an oxide, a nitride, a tin compound, or a silicon compound. The metal material may be a single metal. Alternatively, the metal material may be an alloy. Examples of metal materials include lithium metal or lithium alloys. Examples of carbon materials 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), a silicon compound, or a tin compound may be used.

[0158] The negative electrode 203 may contain a fourth solid electrolyte. This configuration improves the lithium ion conductivity inside the negative electrode, enabling high-power operation. The fourth solid electrolyte contained in the negative electrode 203 can be any of the materials listed as examples of the third solid electrolyte of the electrolyte layer 202.

[0159] The median diameter of the negative electrode active material particles may be 0.1 μm or more and 100 μm or less. When the median diameter of the negative electrode active material particles is 0.1 μm or more, the negative electrode active material particles and the third solid electrolyte are well dispersed in the negative electrode 203, thereby improving the charge / discharge characteristics of the battery 2000. When the median diameter of the negative electrode active material particles is 100 μm or less, lithium diffuses quickly within the negative electrode active material particles, making it easier for the battery to operate at high power.

[0160] The median diameter of the negative electrode active material particles may be larger than the median diameter of the fourth solid electrolyte, thereby achieving a good dispersion state between the negative electrode active material particles and the solid electrolyte.

[0161] The volume ratio "v2:100-v2" of the negative electrode active material particles to the fourth solid electrolyte contained in the negative electrode 203 may satisfy 30≦v2≦95. When 30≦v2 is satisfied, it is easy to ensure a sufficient energy density of the battery 2000. When v2≦95 is satisfied, it is easier for the battery 2000 to operate at high output.

[0162] 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, it is easy to ensure a sufficient energy density of the battery 2000. When the thickness of the negative electrode 203 is 500 μm or less, it is easier for the battery 2000 to operate at high power.

[0163] 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 and the electrolyte layer. 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.

[0164] 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 or artificial graphite, carbon blacks such as acetylene black or ketjen black, conductive fibers such as carbon fiber or metal fiber, metal powders such as carbon fluoride or 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, or polythiophene. Using a carbon conductive additive can reduce costs.

[0165] The battery 2000 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, or a laminated type.

[0166] The battery 2000 in the second embodiment may be manufactured, for example, by preparing the positive electrode material 1000 in the first embodiment, a material for forming the electrolyte layer, and a material for forming the negative electrode, and by using a known method to fabricate a laminate in which the positive electrode, the electrolyte layer, and the negative electrode are arranged in this order. [Example]

[0167] Hereinafter, the present disclosure will be described in more detail with reference to examples and comparative examples.

[0168] <<Example 1>> [Preparation of second solid electrolyte] In an argon glove box with a dew point of -60°C or less, raw material powders LiCl, LiBr, and YCl3 were weighed out so that the molar ratio of LiCl:LiBr:YCl3 = 1:2:1. Then, using a planetary ball mill (Fritsch, P-5 model), the mixture was milled at 600 rpm for 25 hours to obtain a powder of the second solid electrolyte Li3YBr2Cl4.

[0169] (Evaluation of ionic conductivity) FIG. 3 shows a schematic diagram of a pressing die 300 used to evaluate the ionic conductivity of the solid electrolyte.

[0170] The pressure molding die 300 had an upper punch 301, a frame 302, and a lower punch 303. The frame 302 was made of insulating polycarbonate. The upper punch 301 and the lower punch 303 were made of electronically conductive stainless steel.

[0171] The impedance of the second solid electrolyte of Example 1 was measured by the following method using the pressure molding die 300 shown in FIG.

[0172] In a dry atmosphere having a dew point of −30° C. or less, the second solid electrolyte of Example 1 was filled into a pressure molding die 300. Inside the pressure molding die 300, a pressure of 300 MPa was applied to the second solid electrolyte of Example 1 (i.e., solid electrolyte powder 304 in FIG. 3 ) using an upper punch 301 and a lower punch 303.

[0173] While pressure was still applied, the upper punch 301 and the lower punch 303 were connected to a potentiostat (Princeton Applied Research, VersaSTAT4) equipped with a frequency response analyzer. The upper punch 301 was connected to a working electrode and a potential measurement terminal. The lower punch 303 was connected to a counter electrode and a reference electrode. The impedance of the solid electrolyte was measured at room temperature by electrochemical impedance measurement.

[0174] FIG. 4 is a graph showing a Cole-Cole plot obtained by measuring the impedance of the second solid electrolyte according to Example 1.

[0175] 4, the real value of the impedance at the measurement point where the absolute value of the phase of the complex impedance is smallest was considered to be the resistance value to ion conduction of the second solid electrolyte of Example 1. The real value is indicated by the arrow R SE Using the resistance value, the ionic conductivity was calculated based on the following formula (1). σ=(R SE ×S / t) -1 ···(1) Here, σ represents ionic conductivity, S represents the contact area between the solid electrolyte and the upper punch portion 201 (equal to the area of ​​the hollow portion of the frame mold 302 in FIG. 3), and R SE represents the resistance value of the solid electrolyte, and t represents the thickness of the solid electrolyte (the thickness of the layer formed from the solid electrolyte powder 304 in FIG. 3).

[0176] The ionic conductivity of the second solid electrolyte, Li3YBr2Cl4, measured at 22°C is 1.41 × 10 -3 S / cm.

[0177] [Preparation of a positive electrode active material coated with a first solid electrolyte] (Preparation of first solid electrolyte) In a dry atmosphere with a dew point of -30°C or less (hereinafter referred to as "dry atmosphere"), Li2O2 and NbCl5 were weighed as raw material powders in a molar ratio of Li2O2:NbCl5 = 1:2. These were pulverized and mixed in a mortar to obtain a mixed powder. The obtained mixed powder was milled at 600 rpm for 24 hours using a planetary ball mill. The mixed powder was then fired at 200°C for 6 hours.

[0178] As a result, a powder of the first solid electrolyte of Example 1 was obtained, which consisted of Li, Nb, O, and Cl. The composition of the obtained first solid electrolyte of Example 1 was measured by ICP atomic emission spectroscopy for Li and Nb, ion chromatography for Cl, and inert gas fusion-infrared absorption spectroscopy for O. The devices used to measure the composition were an ICP atomic emission spectroscopy analyzer ("iCAP 7400" manufactured by Thermo Fisher Scientific), an ion chromatograph ("ICS-2000" manufactured by Dionex), and an oxygen analyzer ("EMGA-930" manufactured by Horiba, Ltd.). In the first solid electrolyte of Example 1, the molar ratio Li / Nb was 1.20, and the molar ratio O / Cl was 0.35.

[0179] (Evaluation of ionic conductivity) The ionic conductivity of the first solid electrolyte was measured using the same method as that of the second solid electrolyte. The ionic conductivity of the first solid electrolyte of Example 1 measured at 22°C was 9.2 × 10 -3 S / cm.

[0180] (Preparation of a positive electrode active material coated with a first solid electrolyte) Li(Ni, Co, Mn)O2 (hereinafter referred to as NCM) was used as the positive electrode active material. To form a coating layer made of the first solid electrolyte LiNbOCl on the NCM, a compressive shear treatment was performed using a particle composite device (NOB-MINI, manufactured by Hosokawa Micron Corporation). Specifically, the positive electrode active material and the first solid electrolyte were weighed out to a mass ratio of 93.72:6.28, and the blade clearance was set to 2 mm and the treatment time to 45 min, thereby forming a coating layer made of the first solid electrolyte on the surface of the NCM particles. In this manner, the coated positive electrode active material of Example 1 was produced.

[0181] [Preparation of cathode material] In an argon glove box, the positive electrode active material of the coated positive electrode active material of Example 1, the first solid electrolyte of Example 1, and the second solid electrolyte of Example 1 were weighed out so that the volume ratio of the positive electrode active material:(first solid electrolyte+second solid electrolyte)=73:27 was obtained. These were mixed in an agate mortar to produce the positive electrode material of Example 1.

[0182] <<Example 2>> The first solid electrolyte was prepared as raw material powder by weighing out Li2O2, TaCl5, and NbCl5 in a molar ratio of Li2O2:TaCl5:NbCl5 = 1:1.8:0.2, and used as a coating layer for the positive electrode active material. The positive electrode material of Example 2 was obtained in the same manner as in Example 1 above. The ionic conductivity of the first solid electrolyte was 9.9 × 10 -3 S / cm.

[0183] <<Example 3>> The first solid electrolyte was prepared by weighing out Li2O2 and TaCl5 as raw material powders in a molar ratio of Li2O2:TaCl5 = 1:2, and used as a coating layer for the positive electrode active material. The other steps were carried out in the same manner as in Example 1, to obtain the positive electrode material of Example 3. The ionic conductivity of the first solid electrolyte was 8.2 × 10 -3 S / cm.

[0184] <<Example 4>> [Preparation of second solid electrolyte] In an argon glove box with a dew point of -60°C or less, Li2S and P2S5 were weighed out to a molar ratio of Li2S:P2S5 = 75:25. These were ground and mixed in a mortar. Then, a planetary ball mill (Fritsch, P-7) was used to mill the mixture at 510 rpm for 10 hours to obtain 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 solid electrolyte, Li2S-P2S5.

[0185] (Evaluation of ionic conductivity) The ionic conductivity of the second solid electrolyte of Example 4 was measured by the same method as that of the second solid electrolyte of Example 1. The ionic conductivity of the second solid electrolyte of Example 4 measured at 22°C was 0.60 × 10 -3 S / cm.

[0186] [Preparation of cathode material] In an argon glove box, the sum of the positive electrode active material of the coated positive electrode active material of Example 2, the first solid electrolyte of the coated positive electrode active material of Example 2, and the second solid electrolyte of Example 4 was weighed out so as to give a volume ratio of positive electrode active material:(first solid electrolyte+second solid electrolyte)=50:50. These were mixed in an agate mortar to produce the positive electrode material of Example 4.

[0187] <<Comparative Example 1>> A positive electrode material of Comparative Example 1 was obtained in the same manner as in Example 1, except that no positive electrode active material coating layer was formed and an NCM without a coating layer was used.

[0188] <<Comparative Example 2>> A positive electrode material of Comparative Example 2 was obtained in the same manner as in Example 4, except that no positive electrode active material coating layer was formed and an NCM without a coating layer was used.

[0189] [Battery construction] The following steps were carried out using the positive electrode materials of Examples 1 to 4, Comparative Examples 1 and 2, Li3YBr2Cl4, and glass ceramic Li2S-P2S5.

[0190] First, 60 mg of Li2S-P2S5, 20 mg of Li3YBr2Cl4, and the positive electrode material were layered in this order in an insulating outer cylinder. The mass of the positive electrode material was weighed so that the mass of the positive electrode active material was 14 mg. This was then press-molded at a pressure of 720 MPa to obtain a positive electrode and solid electrolyte layer.

[0191] 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.

[0192] 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.

[0193] Finally, an insulating ferrule was used to seal and isolate the inside of the insulating outer cylinder from the outside atmosphere, thereby completing the battery.

[0194] In this manner, the batteries of Examples 1 to 4, Comparative Example 1, and Comparative Example 2 were fabricated.

[0195] [Charging test] Using the batteries of Examples 1 to 4, Comparative Example 1, and Comparative Example 2 described above, charging tests were carried out under the following conditions.

[0196] The battery was placed in a thermostatic chamber at 25°C.

[0197] The battery was charged at a constant current of 140 μA, which corresponds to a 0.05 C rate (20-hour rate) relative to the theoretical capacity of the battery, up to a voltage of 4.3 V, and then rested for 20 minutes.Then, the battery was discharged at a constant current of 140 μA, which corresponds to a 0.05 C rate (20-hour rate), down to a voltage of 2.5 V, and then rested for 20 minutes.

[0198] The ratio of the charge capacity to the discharge capacity obtained above was defined as the charge-discharge efficiency. The results are shown in Table 1 below. In Table 1, "LYBC" represents Li3YBr2Cl4, and "LPS" represents Li2S-P2S5.

[0199] [Table 1]

[0200] <<Considerations>> The results of Examples 1 to 3 and Comparative Example 1 shown in Table 1 confirm that when a halide solid electrolyte is used as the second solid electrolyte, providing the first solid electrolyte on the surface of the positive electrode active material improves the charge / discharge efficiency of the battery. Furthermore, the results of Example 4 and Comparative Example 2 shown in Table 1 also confirm that when a sulfide solid electrolyte is used as the second solid electrolyte, using a positive electrode material in which the first solid electrolyte is coated on the surface of the positive electrode active material improves the charge / discharge efficiency of the battery. This is believed to be because the first solid electrolyte, which has high ionic conductivity and high oxidation resistance, coats the surface of the positive electrode active material. The insertion / desorption of Li between the active material and the electrolyte is rate-determined by the ionic conductivity of the electrolyte. In Examples 1 to 4, the resistance to insertion / desorption of Li is believed to be reduced by improving the conductivity of the electrolyte in contact with the active material. Furthermore, the first solid electrolyte, which has high oxidation resistance, coats the surface of the positive electrode active material, thereby suppressing oxidation of the second solid electrolyte. These results suggest that the batteries of Examples 1 to 4 have improved charge / discharge efficiency. [Industrial Applicability]

[0201] The battery of the present disclosure can be used, for example, as an all-solid-state lithium secondary battery. [Explanation of symbols]

[0202] 1000 cathode materials 100 Second solid electrolyte 110 Cathode active material 111 1st solid electrolyte 2000 batteries 201 Positive electrode 202 Electrolyte layer 203 Negative electrode 300 pressure forming die 301 Punch top 302 Frame type 303 Punch bottom 304 Solid electrolyte powder

Claims

1. positive electrode active material, a first solid electrolyte that coats the surface of the positive electrode active material; and Second solid electrolyte Including, the first solid electrolyte is composed of Li, M1, O, and X1; M1 is at least one element selected from the group consisting of Nb and Ta, X1 is at least one element selected from the group consisting of Cl, Br, and I, a molar ratio Li / M1 of Li to M1 is 0.96 or more and 1.20 or less; a molar ratio O / X1 of O to X1 is 0.16 or more and 0.35 or less; The second solid electrolyte is a sulfide solid electrolyte or is represented by the following composition formula: Li α M2 β X2 γ where: α, β, and γ are each independently greater than 0; M2 is at least one element selected from the group consisting of metalloid elements and metal elements other than Li, X2 is at least one element selected from the group consisting of F, Cl, Br, and I; Positive electrode material.

2. The X1 includes Cl. The positive electrode material according to claim 1 .

3. The M1 includes Ta. The positive electrode material according to claim 1 or 2.

4. The positive electrode active material contains Ni, Co, and Mn. The positive electrode material according to claim 1 .

5. The M2 includes yttrium. The positive electrode material according to claim 1 .

6. In the composition formula, α, β, and γ are 2.5≦α≦3, 1≦β≦1.1, and γ=6; fulfill, The positive electrode material according to any one of claims 1 to 5.

7. X2 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 6.

8. X2 includes Cl and Br; The positive electrode material according to claim 7.

9. The second solid electrolyte is Li 3 YBr 2 Cl 4 Including, The positive electrode material according to any one of claims 1 to 8.

10. A positive electrode comprising the positive electrode material according to any one of claims 1 to 9. a negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode; Equipped with battery.

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