Battery

Abstract

This battery 1000 comprises a positive electrode 101, a negative electrode 103, and a solid electrolyte layer 102 disposed between the positive electrode 101 and the negative electrode 103. The negative electrode 103 includes a negative electrode active material including Li, V, M, and O, where M is at least one selected from among tetravalent metal elements excluding V. The ratio of the capacity of the negative electrode 103 to the capacity of the positive electrode 101 is greater than 0.64 and less than 1.3.

Description

battery

[0001] This disclosure relates to batteries.

[0002] Patent Document 1 discloses a non-aqueous secondary battery using Li3VO4 as the negative electrode active material.

[0003] Japanese Patent Publication No. 2008-77847

[0004] In batteries that use lithium vanadium oxide as the negative electrode active material, as disclosed in Patent Document 1, it is difficult to achieve both durability and energy density.

[0005] The purpose of this disclosure is to provide a battery suitable for achieving both durability and energy density.

[0006] This disclosure provides a battery comprising: a positive electrode; a negative electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode, wherein the negative electrode comprises a negative electrode active material containing Li, V, M, and O, where M is at least one selected from tetravalent metal elements other than V, the ratio of the amount of substance of Li atoms to the amount of substance of V atoms is greater than 3.0, and the ratio of the capacity of the negative electrode to the capacity of the positive electrode is greater than 0.64 and less than 1.3.

[0007] According to this disclosure, it is possible to provide a battery that is suitable for achieving both durability and energy density.

[0008] Figure 1 is a schematic cross-sectional view showing an example of the battery configuration according to an embodiment.

[0009] The embodiments of this disclosure will be described below with reference to the drawings. This disclosure is not limited to the embodiments described below.

[0010] [Embodiment] Figure 1 is a schematic cross-sectional view of a battery 1000 according to an embodiment of the present disclosure. The battery 1000 comprises a positive electrode 101, a negative electrode 103, and a solid electrolyte layer 102 disposed between the positive electrode 101 and the negative electrode 103. The negative electrode 103 comprises a negative electrode active material which is lithium vanadium oxide containing Li, V, M, and O. M is at least one selected from tetravalent metal elements other than V. The ratio of the capacity of the negative electrode 103 to the capacity of the positive electrode 101 is greater than 0.64 and less than 1.3.

[0011] With the above configuration, a battery 1000 suitable for achieving both durability and energy density can be obtained. Specifically, when the above ratio exceeds 0.64, the potential of the negative electrode 103 increases as the battery is charging, thereby suppressing the three-electron reaction of the lithium vanadium oxide. This three-electron reaction tends to be poorly reversible. Therefore, if this three-electron reaction is suppressed, the reversibility of charging and discharging of the battery is more easily maintained, thus improving the durability of the battery. Also, when the above ratio exceeds 0.64, the potential of the negative electrode 103 increases as the battery is charging, which suppresses, for example, the alloying of lithium and the current collector in the current collector of the negative electrode 103. Therefore, the durability of the battery 1000 can also be improved by suppressing the alloying in the negative electrode 103. When the above ratio is less than 1.3, the amount of negative electrode active material in the battery 1000 can be reduced, thus improving the energy density of the battery 1000.

[0012] The capacity of the positive electrode 101 is the capacity when the voltage of the positive electrode 101 reaches the upper limit charging voltage of the positive electrode 101, with the Li (lithium) potential as the reference. The capacity of the positive electrode 101 is, for example, the charging capacity when a half-cell of the positive electrode is charged at a constant current of 0.1C with the Li potential as the reference up to the upper limit charging voltage, and then charged at a constant voltage until the current decreases to 0.02C. The charging voltage of the positive electrode 101 may vary depending on the positive electrode active material used in the positive electrode 101.

[0013] If the positive electrode active material has a layered rock salt crystal structure such as lithium nickel cobalt manganese oxide (e.g., Li(Ni,Co,Mn)O2) or lithium nickel cobalt aluminum oxide (e.g., Li(Ni,Co,Al)O2), the upper limit charging voltage of the positive electrode 101 is 4.3V with respect to the Li potential. If the positive electrode active material has a spinel crystal structure such as lithium manganese oxide (e.g., LiMn2O4), the upper limit charging voltage of the positive electrode 101 is 4.3V with respect to the Li potential. If the positive electrode active material has an olivine crystal structure such as lithium iron phosphate (e.g., LiFePO4), the upper limit charging voltage of the positive electrode 101 is 3.7V with respect to the Li potential. 0.5 Mn 1.5 For lithium nickel manganese oxide having a spinel-type crystal structure such as O4, the upper limit charging voltage of the positive electrode 101 is 5.0V, with the Li potential as the reference.

[0014] In this disclosure, "(A, B, C)" means "at least one selected from the group consisting of A, B, and C."

[0015] The capacity of the negative electrode 103 is the capacity when the negative electrode 103 is charged to a voltage of 0.5V, with the Li potential as the reference. The capacity of the negative electrode 103 is, for example, the charging capacity when a half-cell of the negative electrode is charged at a constant current of 0.1C to 0.5V, and then charged at a constant voltage until the current decreases to 0.02C.

[0016] The ratio of the capacity of the negative electrode 103 to the capacity of the positive electrode 101 may be 1.1 or less. In this case, the energy density of the battery 1000 is further improved. The ratio of the capacity of the negative electrode 103 to the capacity of the positive electrode 101 may be 1.05 or less, 1.0 or less, 0.95 or less, or even 0.9 or less. In this case, the energy density of the battery 1000 is further improved.

[0017] The ratio of the capacity of the negative electrode 103 to the capacity of the positive electrode 101 may satisfy 0.7 or more. In this case, the three-electron reaction of the lithium vanadium oxide is more easily suppressed, whereby the durability of the battery is further improved. Further, durability of the battery 1000 can also be further improved by further easily suppressing alloying in the negative electrode 103.

[0018] The ratio of the molar amount of Li atoms to the molar amount of V atoms may be more than 3.0. The ratio of the molar amount of Li atoms to the molar amount of V atoms may be 3.5 or more. The ratio of the molar amount of Li atoms to the molar amount of V atoms may be 5.0 or less, and may further be 4.5 or less. The ratio of the molar amount of Li atoms to the molar amount of V atoms may be more than 3.0 and 5.0 or less, may be 3.5 or more and 5.0 or less, and may be 3.5 or more and 4.5 or less.

[0019] M may contain Ti. In this case, the capacity of the negative electrode 103 can be further improved. M may be Ti. According to such a configuration, the capacity of the negative electrode 103 can be further improved.

[0020] The negative electrode active material is represented by composition formula (1): Li 3+x V 1-x M x It may be a lithium vanadium oxide having a composition represented by O4, and may satisfy 0 < x < 1. According to such a configuration, the battery 1000 more suitable for achieving both durability and energy density can be provided.

[0021] In composition formula (1), x may satisfy 0 < x ≤ 0.2. In this case, insertion and desorption of Li ions into and from the lithium vanadium oxide becomes easier, so the capacity of the battery 1000 is further improved.

[0022] (Battery) As described above, the battery 1000 includes a positive electrode 101, a solid electrolyte layer 102, and a negative electrode 103. The solid electrolyte layer 102 is disposed between the positive electrode 101 and the negative electrode 103.

[0023] The positive electrode 101 contains, for example, positive electrode active material particles and solid electrolyte particles.

[0024] The solid electrolyte layer 102 contains, for example, a solid electrolyte material.

[0025] The negative electrode 103 contains, for example, negative electrode active material particles 110 and solid electrolyte particles 100.

[0026] (Negative electrode material) The negative electrode active material particles 110 are particles containing the above-mentioned lithium vanadium oxide. The negative electrode active material particles 110 may also be particles that contain the above-mentioned lithium vanadium oxide as the main component. Particles that contain lithium vanadium oxide as the main component mean particles in which the most abundant component by mass is lithium vanadium oxide. The negative electrode active material particles 110 may also be particles made of the above-mentioned lithium vanadium oxide.

[0027] The negative electrode active material particles 110 may have a median diameter of 0.1 μm or more and 100 μm or less. When the negative electrode active material particles 110 have a median diameter of 0.1 μm or more, the negative electrode active material particles 110 and the solid electrolyte particles 100 can form a good dispersion state in the negative electrode 103. This improves the charge and discharge characteristics of the battery 1000. When the negative electrode active material particles 110 have a median diameter of 100 μm or less, the lithium diffusion rate within the negative electrode active material particles 110 is improved. This allows the battery 1000 to operate at high power.

[0028] The negative electrode active material particles 110 may have a larger median diameter than the solid electrolyte particles 100. This allows the negative electrode active material particles 110 and the solid electrolyte particles 100 to form a good dispersion state. The median diameter of the particles refers to the particle size (d50) corresponding to 50% of the volume cumulative in the volume-based particle size distribution. The volume-based particle size distribution can be measured by a laser diffraction measuring device or an image analysis device.

[0029] To prevent the solid electrolyte particles 100 from reacting with the negative electrode active material particles 110, a coating layer may be formed on the surface of the negative electrode active material particles 110. This allows the battery 1000 to have high charge and discharge efficiency. Examples of coating materials included in the coating layer are sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, or halide solid electrolytes.

[0030] The coating material may be a sulfide solid electrolyte, an oxide solid electrolyte, or a polymer solid electrolyte. An example of a sulfide solid electrolyte is Li2S-P2S5. An example of an oxide solid electrolyte is trilithium phosphate. An example of a polymer solid electrolyte is a composite compound of polyethylene oxide and a lithium salt. An example of such a polymer solid electrolyte is lithium bis(trifluoromethanesulfonyl)imide.

[0031] From the viewpoint of the energy density and output of the battery 1000, the negative electrode 103 may have a thickness of 10 µm or more and 500 µm or less.

[0032] The solid electrolyte particles 100 contained in the negative electrode 103 may be a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, or an organic polymer solid electrolyte.

[0033] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li 3.25 Ge 0.25 P 0.75 S4, or Li 10 GeP2S 12 .

[0034] An example of a halide solid electrolyte is Li a Me b Y c X6, which is a compound represented by the formula. Here, the mathematical expressions: a + mb + 3c = 6 and c > 0 are satisfied. Me is at least one selected from the group consisting of metal elements other than Li and Y and metalloid elements. X is at least one element selected from the group consisting of F, Cl, Br, and I. The value of m represents the valence of Me.

[0035] The "metalloid elements" are B, Si, Ge, As, Sb, and Te. The "metal elements" are all elements contained in Groups 1 to 12 of the periodic table (excluding hydrogen), and all elements contained in Groups 13 to 16 of the periodic table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0036] To increase the ionic conductivity of the halide solid electrolyte, Me may be 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.

[0037] Another example of a halide solid electrolyte is Li α M β O γ X δ This is a compound represented by the following equation: Here, α, β, γ, and δ are all greater than 0, M is at least one element selected from the group consisting of metallic elements and metalloid elements other than Li, X is at least one element selected from the group consisting of Cl, Br, and I, and the following equations are satisfied: 0.9 ≤ α ≤ 1.2, β = 1.0, 1.0 ≤ γ ≤ 1.3, and 3.6 ≤ δ ≤ 4.0.

[0038] Examples of oxide solid electrolytes include: (i) NASICON-type solid electrolytes such as LiTi2(PO4)3 or its elemental substitutions; (ii) perovskite-type solid electrolytes such as (LaLi)TiO3; (iii) Li 14 ZnGe4O 16 , Li4SiO4, LiGeO4 or LISICON-type solid electrolytes such as elemental substitutions thereof, (iv)Li7La3Zr2O 12 Alternatively, it may be a garnet-type solid electrolyte such as an element-substituted derivative thereof, or (v) Li3PO4 or an N-substituted derivative thereof.

[0039] Examples of polymeric solid electrolytes include composite compounds of polyethylene oxide and lithium salts. An example of such a polymeric solid electrolyte is lithium bis(trifluoromethanesulfonyl)imide.

[0040] Examples of organic polymer solid electrolytes include polymer compounds and lithium salt compounds. Polymer compounds may have an ethylene oxide structure. Polymer compounds having an ethylene oxide structure can contain a large amount of lithium salt and therefore have higher ionic conductivity.

[0041] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. One lithium salt selected from these may be used alone, or a mixture of two or more lithium salts selected from these may be used.

[0042] In the negative electrode 103, the ratio of the volume of the conductive additive to the sum of the volume of the negative electrode active material particles 110 and the volume of the conductive additive may be 0.01 or more and 0.4 or less.

[0043] <Method for producing lithium vanadium oxide> The above lithium vanadium oxide can be produced by the following method.

[0044] The raw material powder is prepared to have the desired composition. Examples of raw material powders include oxides, hydroxides, carbonates, nitrates, or organic salts.

[0045] As an example, the chemical formula, Li 3+x V 1-x M x In O4, assume that M is Ti and x is 0.05 during raw material mixing. At this time, Li2CO3, V2O5, and TiO2 are mixed in a molar ratio of Li2CO3:V2O5:TiO2 = (3.05 / 2):(0.95 / 2):0.05.

[0046] Lithium hydroxide or its hydrate may be used instead of Li2CO3.

[0047] The reaction product is obtained by calcining a mixture of raw material powders. The atmosphere during calcination may be air or an inert gas atmosphere. An inert atmosphere is, for example, an argon atmosphere or a nitrogen atmosphere.

[0048] Alternatively, the mixture of raw material powders may be reacted mechanochemically (by mechanochemical milling) in a mixing device such as a planetary ball mill to obtain the reactant. By these methods, lithium vanadium oxide according to this embodiment can be obtained.

[0049] Here, the molar ratio of the raw materials during mixing does not necessarily match the molar ratio of the reactants. This is because some of the raw materials may not be incorporated into the reactants due to evaporation or other factors during the reaction.

[0050] Therefore, the composition x of the lithium vanadium oxide is determined by methods such as ICP emission spectrometry, atomic absorption spectrometry, and EPMA (Electron Probe Micro Analyzer).

[0051] (Positive electrode material) The positive electrode 101 contains a material capable of intercalating and releasing metal ions such as lithium ions. The positive electrode 101 contains, for example, a positive electrode active material (e.g., positive electrode active material particles).

[0052] An example of a positive electrode active material is a lithium-containing transition metal oxide. The positive electrode active material may have at least one crystal structure selected from the group consisting of layered rock salt crystal structure, spinel crystal structure, and olivine crystal structure.

[0053] Examples of positive electrode active materials having a layered rock salt crystal structure are lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide. The positive electrode active material may include at least one selected from the group consisting of lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide. An example of lithium nickel cobalt manganese oxide is Li(Ni,Co,Mn)O2. An example of lithium nickel cobalt aluminum oxide is Li(Ni,Co,Al)O2.

[0054] An example of a cathode active material having a spinel-type crystal structure is lithium manganese oxide. An example of lithium manganese oxide is LiMn₂O₄.

[0055] Another example of a cathode active material having a spinel-type crystal structure is LiNi 0.5 Mn 1.5 It is O4.

[0056] An example of a cathode active material having an olivine-type crystal structure is lithium iron phosphate. An example of lithium iron phosphate is LiFePO4.

[0057] The positive electrode active material particles may have a median diameter of 0.1 μm or more and 100 μm or less. When the positive electrode active material particles have a median diameter of 0.1 μm or more, the positive electrode active material particles and solid electrolyte particles can form a good dispersion state in the positive electrode 101. This improves the charge and discharge characteristics of the battery 1000. When the positive electrode active material particles have a median diameter of 100 μm or less, the lithium diffusion rate within the positive electrode active material particles improves. This allows the battery 1000 to operate at high power.

[0058] The positive electrode active material particles may have a larger median diameter than the solid electrolyte particles. This allows the positive electrode active material particles and the solid electrolyte particles to form a good dispersion state.

[0059] From the viewpoint of the energy density and output of the battery 1000, the ratio of the volume of positive electrode active material particles to the sum of the volume of positive electrode active material particles and the volume of solid electrolyte particles in the positive electrode 101 may be 0.30 or more and 0.95 or less.

[0060] To prevent the electrode active material particles from reacting with the solid electrolyte particles, a coating layer may be formed on the surface of the electrode active material particles. This can suppress the rise in the reaction overpotential of the battery 1000. Examples of coating materials included in the coating layer are sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, or halide solid electrolytes.

[0061] 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, or Li 10 GeP2S 12 That is the case.

[0062] Examples of oxide solid electrolytes include: (i) NASICON-type solid electrolytes such as LiTi2(PO4)3 or its elemental substitutions; (ii) perovskite-type solid electrolytes such as (LaLi)TiO3; (iii) Li 14 ZnGe4O 16 , Li4SiO4, LiGeO4 or LISICON-type solid electrolytes such as elemental substitutions thereof, (iv)Li7La3Zr2O 12Alternatively, it may be a garnet-type solid electrolyte such as an element-substituted derivative thereof, or (v) Li3PO4 or an N-substituted derivative thereof.

[0063] An example of a solid halogen electrolyte is Li a Me b Y c This is a compound represented by X6. Here, the equation a + mb + 3c = 6 and c > 0 are satisfied. Me is at least one element selected from the group consisting of metallic elements other than Li and Y and metalloid elements. X is at least one element selected from the group consisting of F, Cl, Br, and I. The value of m represents the valence of Me'.

[0064] "Metallic elements" are B, Si, Ge, As, Sb, and Te. "Metallic elements" are all elements in groups 1 through 12 of the periodic table (except hydrogen), and all elements in groups 13 through 16 of the periodic table (except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0065] To increase the ionic conductivity of the halide solid electrolyte, Me may be 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.

[0066] Another example of a halide solid electrolyte is Li α M β O γ X δ This is a compound represented by the following equation: Here, α, β, γ, and δ are all greater than 0, M is at least one element selected from the group consisting of metallic elements and metalloid elements other than Li, X is at least one element selected from the group consisting of Cl, Br, and I, and the following equations are satisfied: 0.9 ≤ α ≤ 1.2, β = 1.0, 1.0 ≤ γ ≤ 1.3, and 3.6 ≤ δ ≤ 4.0.

[0067] In the halogen solid electrolyte material, if X is F, the stability of the halogen solid electrolyte material at high potential is improved. Therefore, the battery 1000 has high charge and discharge efficiency.

[0068] The oxide solid electrolyte may be a lithium niobium oxide or polyanionic material that has excellent stability even at high potentials. This allows the battery 1000 to have high charge and discharge efficiency.

[0069] Examples of polymeric solid electrolytes include composite compounds of polyethylene oxide and lithium salts. An example of such a polymeric solid electrolyte is lithium bis(trifluoromethanesulfonyl)imide.

[0070] From the viewpoint of the energy density and output of the battery 1000, the positive electrode 101 may have a thickness of 10 μm or more and 500 μm or less.

[0071] The solid electrolyte particles contained in the positive electrode 101 may be a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, or an organic polymer solid electrolyte.

[0072] The positive electrode 101 may contain a conductive additive for the purpose of enhancing its electronic conductivity.

[0073] (Solid Electrolyte Layer) The solid electrolyte layer 102 contains a solid electrolyte material. The solid electrolyte material contained in the solid electrolyte layer 102 may be a sulfide solid electrolyte, a halide solid electrolyte, or a polymer solid electrolyte.

[0074] The solid electrolyte layer 102 may have a thickness of 1 μm or more and 100 μm or less. If the solid electrolyte layer 102 has a thickness of 1 μm or more, the positive electrode 101 and the negative electrode 103 are less likely to short-circuit. If the solid electrolyte layer 102 has a thickness of 100 μm or less, the battery 1000 can operate at high output.

[0075] In this disclosure, "sulfide solid electrolyte" means a solid electrolyte containing sulfur. "Oxide solid electrolyte" means a solid electrolyte containing oxygen. Oxide solid electrolytes may contain anions other than oxygen (except sulfur anions and halogen anions). "Halide solid electrolyte" means a solid electrolyte containing a halogen element but not sulfur. Halide solid electrolytes may contain oxygen in addition to halogen elements.

[0076] At least one selected from the group consisting of the positive electrode 101, the solid electrolyte layer 102, and the negative electrode 103 may contain a non-aqueous electrolyte, a gel electrolyte, or an ionic liquid for the purpose of facilitating the transfer of lithium ions and improving the output characteristics of the battery 1000.

[0077] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents include cyclic carbonate solvents, linear carbonate solvents, cyclic ether solvents, linear ether solvents, cyclic ester solvents, linear ester solvents, or fluorine solvents. Examples of cyclic carbonate solvents include ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of linear carbonate solvents include dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of cyclic ether solvents include tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Examples of linear ether solvents include 1,2-dimethoxyethane or 1,2-diethoxyethane. An example of a cyclic ester solvent is γ-butyrolactone. An example of a linear ester solvent is methyl acetate. Examples of fluorinated solvents include fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, or fluorodimethylene carbonate. One non-aqueous solvent selected from these may be used alone, or a mixture of two or more non-aqueous solvents selected from these may be used.

[0078] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. One lithium salt selected from these may be used alone, or a mixture of two or more lithium salts selected from these may be used. The concentration of the lithium salt is, for example, in the range of 0.5 mol / liter to 2 mol / liter.

[0079] As the gel electrolyte, polymer materials impregnated with a non-aqueous electrolyte can be used. Examples of polymer materials include polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or polymers having ethylene oxide bonds.

[0080] Examples of cations contained in ionic liquids include (i) aliphatic quaternary salts such as tetraalkylammonium or tetraalkylphosphonium, (ii) aliphatic cyclic ammonium compounds such as pyrrolidinium, morpholinium, imidazolinium, tetrahydropyrimidinium, piperadinium, or piperidinium, or (iii) nitrogen-containing heterocyclic aromatic cations such as pyridinium or imidazolium.

[0081] An example of anion contained in an ionic liquid is PF6. - BF4 - SbF6 - AsF6 - SO3CF3 - , N(SO2CF3)2 - , N(SO2C2F5)2 - , N(SO2CF3)(SO2C4F9) - , or C(SO2CF3)3 - That is the case.

[0082] The ionic liquid may contain a lithium salt.

[0083] At least one selected from the group consisting of the positive electrode 101, the solid electrolyte layer 102, and the negative electrode 103 may contain a binder for the purpose of improving the adhesion between particles.

[0084] 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, or carboxymethylcellulose. Copolymers may also be used as binders. Examples of such binders include copolymers 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. Mixtures of two or more materials selected from the above materials may also be used.

[0085] At least one of the positive electrode 101 and the negative electrode 103 may contain a conductive additive for the purpose of enhancing electronic conductivity.

[0086] Examples of conductive additives include: (i) graphites such as natural or artificial graphite; (ii) carbon blacks such as acetylene black or Ketjen black; (iii) conductive fibers such as carbon fibers or metal fibers; (iv) carbon fluoride; (v) metal powders such as aluminum; (vi) conductive whiskers such as zinc oxide or potassium titanate; (vii) conductive metal oxides such as titanium oxide; or (viiii) conductive polymer compounds such as polyaniline, polypyrrole, or polythiophene. To reduce costs, conductive additives of (i) or (ii) above may be used.

[0087] The conductive additive may be provided so as to cover at least a portion of the positive electrode active material particles and / or negative electrode active material particles 110. In this case, the contact area between the conductive additive and the positive electrode active material particles and / or negative electrode active material particles 110 can be increased. As a result, the resistance in the battery 1000 is reduced, and the output of the battery 1000 can be increased.

[0088] Examples of the shape of the battery 1000 according to this embodiment include coin-shaped, cylindrical, rectangular, sheet-shaped, button-shaped, flat, or stacked types.

[0089] [Other Embodiments] (Note) The above description of embodiments discloses the following technologies.

[0090] (Technical 1) A battery comprising a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode, wherein the negative electrode comprises a negative electrode active material containing Li, V, M, and O, where M is at least one selected from tetravalent metal elements other than V, and the ratio of the capacity of the negative electrode to the capacity of the positive electrode is greater than 0.64 and less than 1.3.

[0091] According to this disclosure, it is possible to provide a battery that is suitable for achieving both durability and energy density.

[0092] (Technology 2) The battery described in Technology 1, wherein M contains Ti. With this configuration, the energy density of the battery is further improved.

[0093] (Technology 3) A battery according to Technology 1 or 2, wherein the ratio of the amount of substance of Li atoms to the amount of substance of V atoms is greater than 3.0.

[0094] (Technical 4) The negative electrode active material is Li 3+x V 1-x M x A battery according to Technology 3, having a composition represented by O4 and satisfying 0 < x < 1. With such a configuration, a suitable battery can be provided by achieving both durability and energy density.

[0095] (Technology 5) A battery as described in Technology 4, satisfying 0 < x ≤ 0.2. With this configuration, the battery's durability is further improved.

[0096] (Technology 6) A battery according to any one of Technologies 1 to 5, wherein the ratio is 1.1 or less. With such a configuration, the energy density of the battery is further improved.

[0097] (Technology 7) A battery according to any one of Technologies 1 to 6, wherein the ratio is 0.7 or higher. With such a configuration, the durability of the battery is further improved.

[0098] (Technical 8) The battery according to any one of Technical 1 to 7, wherein the positive electrode comprises a positive electrode active material, and the positive electrode active material comprises at least one selected from the group consisting of lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide. With such a configuration, the durability and energy density of the battery are further improved.

[0099] The details of this disclosure will be explained below using examples. However, the batteries of this disclosure are not limited to the following examples.

[0100] <Sample 1> [Fabrication of positive and negative electrodes and measurement of capacity] The capacity of the positive electrode active material and the negative electrode active material was measured by the following method.

[0101] (Fabrication of positive electrode and measurement of capacity) [Preparation of positive electrode active material] As the positive electrode active material, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 powder was prepared.

[0102] [Preparation of the positive electrode] The positive electrode active material and sulfide solid electrolyte were weighed so that their volume ratio was 60:40. The conductive additive was weighed so that their weight ratio was 100:3.42. Furthermore, the binder was weighed so that its weight ratio was 100:4.31. Tetralin was added as a solvent and mixed using an ultrasonic disperser to obtain a slurry containing the positive electrode active material, sulfide solid electrolyte, conductive additive, binder, and solvent. The positive electrode was obtained by coating this slurry onto an aluminum current collector and drying it.

[0103] [Fabrication of a battery for measuring positive electrode capacity] The fabricated positive electrode was subjected to pressure molding with a solid electrolyte layer containing a sulfide solid electrolyte and metallic lithium inserted. Subsequently, a current collector was placed and sealed by lamination to obtain a half-cell for measuring positive electrode capacity.

[0104] [Capacity Measurement of Positive Electrode Active Material] A battery for measuring the positive electrode capacity was placed in a constant temperature bath maintained at 25°C. Next, it was charged at a current value that was 0.1C rate (10-hour rate) relative to the theoretical capacity of the positive electrode until the voltage relative to the Li potential of the positive electrode reached 4.3V. After that, it was charged at a constant voltage of 4.3V until the current value was 0.02C rate (50-hour rate). The capacity of the positive electrode active material was calculated by dividing the obtained capacity by the weight of the positive electrode active material. At this time, the capacity of the positive electrode active material was 175 mAH / g.

[0105] (Preparation of the negative electrode and measurement of its capacity) [Preparation of the negative electrode active material] As raw material powders, Li2CO3, V2O5, and TiO2 were prepared in a molar ratio of Li2CO3:V2O5:TiO2 = 1.6:0.4:0.2. These raw material powders were mixed in a mortar to obtain a mixed powder. The obtained mixed powder was calcined in air at 600°C for 3 hours. The obtained calcined powder was then fully calcined in air at 920°C for 15 hours. In this way, a negative electrode active material consisting of lithium vanadium oxide was obtained. The value of x (M = Ti) in composition formula (1) was 0.2. The value of x was determined by ICP emission spectrometry.

[0106] [Preparation of the negative electrode] The negative electrode active material and sulfide solid electrolyte were weighed in a volume ratio of 65:35. The binder was weighed in a weight ratio of 100:1.7 to the negative electrode active material. Tetralin was added as a solvent and mixed using an ultrasonic disperser to obtain a slurry containing the negative electrode active material, sulfide solid electrolyte, binder, and solvent. The negative electrode was obtained by coating this slurry onto an aluminum current collector and drying it.

[0107] In preparing the negative electrode, the amount of slurry applied to the aluminum current collector was adjusted so that the ratio of the negative electrode capacity to the positive electrode capacity was 1.10. The ratio of the negative electrode capacity to the positive electrode capacity was calculated using the following formula, based on the measured values ​​of the positive electrode active material capacity (175 mAh / g) and the negative electrode active material capacity (280 mAh / g). Here, M1 is the weight of the positive electrode active material contained in the positive electrode, and M2 is the weight of the negative electrode active material contained in the negative electrode.

[0108] (Ratio of negative electrode capacity to positive electrode capacity) = (280 × M²) ÷ (175 × M¹)

[0109] [Fabrication of a battery for negative electrode capacity measurement] The fabricated negative electrode was subjected to pressure molding with a solid electrolyte layer containing a sulfide solid electrolyte and an In-Li alloy inserted. Subsequently, a current collector was placed and sealed by lamination to obtain a half-cell for negative electrode capacity measurement.

[0110] [Capacity Measurement of Negative Electrode Active Material] A battery for negative electrode capacity measurement was placed in a constant temperature bath maintained at 25°C. Next, it was charged at a current value that was 0.05 C rate (20-hour rate) relative to the theoretical capacity of the negative electrode until the voltage relative to the Li potential of the negative electrode reached 0.5 V. The capacity of the negative electrode active material was calculated by dividing the obtained capacity by the weight of the negative electrode active material. At this time, the capacity of the negative electrode active material was 280 mAH / g.

[0111] [Battery Fabrication] A solid electrolyte layer containing a sulfide solid electrolyte was inserted between the fabricated positive and negative electrodes, and pressure molding was performed. Subsequently, current collector plates were placed on the positive and negative sides of the resulting laminate, and the laminate was sealed by lamination to obtain a laminate-type secondary battery according to Sample 1.

[0112] <Sample 2> A laminate-type secondary battery was obtained using the same method as in Sample 1, except that the thickness of the negative electrode was changed so that the ratio of the negative electrode capacity to the positive electrode capacity was 1.00.

[0113] <Sample 3> A laminate-type secondary battery was obtained using the same method as in Sample 1, except that the thickness of the negative electrode was changed so that the ratio of the negative electrode capacity to the positive electrode capacity was 0.90.

[0114] <Sample 4> A laminate-type secondary battery was obtained using the same method as in Sample 1, except that the thickness of the negative electrode was changed so that the ratio of the negative electrode capacity to the positive electrode capacity was 0.80.

[0115] <Sample 5> A laminate-type secondary battery was obtained using the same method as in Sample 1, except that the thickness of the negative electrode was changed so that the ratio of the negative electrode capacity to the positive electrode capacity was 1.30.

[0116] <Sample 6> A laminate-type secondary battery was obtained using the same method as in Sample 1, except that the thickness of the negative electrode was changed so that the ratio of the negative electrode capacity to the positive electrode capacity was 0.64.

[0117] In Sample 6, the ratio of the negative electrode capacity to the positive electrode capacity was small, causing the negative electrode potential to drop to 0.14V relative to the Li potential as the battery charged. At such a negative electrode potential, it was suspected that an irreversible reaction at the negative electrode or an alloying reaction of the negative electrode current collector would occur, resulting in insufficient durability. Therefore, the following tests were not performed.

[0118] (Charge-Discharge Test) Batteries from samples 1 to 5 were placed in a constant temperature bath maintained at 25°C. Next, each battery from samples 1 to 5 was charged at a current value that was 0.05C rate (20-hour rate) relative to the theoretical capacity of the positive electrode, until the voltage relative to the Li potential of the positive electrode reached 4.3V (the voltage when the capacity of the positive electrode active material was 175mAh / g in the measurement of the capacity of the negative electrode active material described above). The voltage between the positive and negative electrodes when this charging was completed was used as the charging voltage for the charge-discharge test. The charging voltages were 3.65V for sample 1, 3.77V for sample 2, 3.89V for sample 3, 4.00V for sample 4, and 3.42V for sample 5. Next, the batteries from samples 1 to 5 were discharged at a current value that was 0.05C rate until the voltage reached 1V. The charge-discharge cycle was performed twice at the above rates.

[0119] Subsequently, the battery was transferred to a constant temperature bath maintained at 50°C. Discharge was then performed under a constant power value. The charging and discharging processes were then repeated. Discharge was performed at several different power values ​​between 0mW and 150mW, and the discharge time (the time from when the battery began to discharge until the voltage between the positive and negative electrodes reached 1V) was measured for each power value. For each power value, the relationship between power value and discharge time was plotted as a power value versus discharge time graph, and an approximation curve was obtained from the plot. The power value corresponding to a discharge time of 90 seconds was calculated based on this regression line. The calculated value was used as the output before the durability test.

[0120] (Energy Density) After two charge-discharge cycles of the above charge-discharge test, the energy density (Wh / L) of the batteries from samples 1 to 5 was measured.

[0121] Table 1 shows the energy densities of batteries from samples 1 to 5 as ratios to the energy density of battery from sample 2.

[0122] In Sample 5, the battery's energy density was low at 0.90, making it impossible to achieve a battery with a high energy density. Therefore, the following durability tests were not conducted.

[0123] (Durability Test) Batteries from samples 1 to 4 were placed in a constant temperature chamber maintained at 60°C and then charged under constant current and constant voltage conditions to the charging voltage used in the charge-discharge test. Next, a durability test was performed on the charged batteries, maintaining the charging voltage for 168 hours. After that, the batteries were moved to a constant temperature chamber maintained at 50°C, the same as in the charge-discharge test. Then, as in the charge-discharge test above, charging and discharging were repeatedly performed at multiple power values ​​with different values, and the power value corresponding to a discharge time of 90 seconds was calculated. The calculated value was taken as the output after the durability test.

[0124] The output after the durability test was calculated as the output before the durability test versus the output before the durability test. The results of the output maintenance rate calculation are shown in Table 1.

[0125]

[0126] As shown in Table 1, the relative energy density increased as the ratio of the negative electrode capacity to the positive electrode capacity decreased. As the results for Sample 5 show, the relative energy density was 90% when the ratio of the negative electrode capacity to the positive electrode capacity was 1.3.

[0127] In Sample 6, the ratio of the negative electrode capacity to the positive electrode capacity was 0.64. In this case, the relative energy density of the battery was thought to increase compared to Samples 1 through 4. However, as mentioned above, in Sample 6, as the battery charging progressed, the decrease in the negative electrode potential caused irreversible reactions at the negative electrode and alloying reactions of the negative electrode's current collector, which were thought to prevent a sufficient power retention rate from being obtained.

[0128] In contrast, as the results for samples 1 to 4 show, if the ratio of the negative electrode capacity to the positive electrode capacity was greater than 0.64 and less than 1.3, then both battery durability and energy density were achieved.

[0129] The technology described herein can be used, for example, in lithium-ion all-solid-state secondary batteries.

Claims

1. A battery comprising: a positive electrode; a negative electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode, wherein the negative electrode comprises a negative electrode active material containing Li, V, M, and O, where M is at least one selected from tetravalent metal elements other than V, and the ratio of the capacity of the negative electrode to the capacity of the positive electrode is greater than 0.64 and less than 1.

3.

2. The battery according to claim 1, wherein M includes Ti.

3. The battery according to claim 1, wherein the ratio of the amount of substance of Li atoms to the amount of substance of V atoms is greater than 3.

0.

4. The negative electrode active material is Li 3+x V 1-x M x The battery according to claim 3, having a composition represented by O4 and satisfying 0 < x < 1.

5. The battery according to claim 4, satisfying 0 < x ≤ 0.

2.

6. The battery according to claim 1, wherein the ratio is 1.1 or less.

7. The battery according to claim 1, wherein the ratio is 0.7 or more.

8. The battery according to claim 1, wherein the positive electrode comprises a positive electrode active material, and the positive electrode active material comprises at least one selected from the group consisting of lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide.

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