Lithium vanadium oxide, composite, and battery

Abstract

A lithium vanadium oxide according to the present invention includes Li, V, and O or Li, V, M, and O. M is at least one element selected from among tetravalent metal elements that are not V and tetravalent metalloid elements. The lithium vanadium oxide includes a crystal phase that has a lattice volume VL (Å3) that satisfies expression (1). In expression (1), x is the ratio of the amount of M to the total of the amount of V and the amount of M.　(1) VL<12.5x+348.25

Description

Lithium vanadium oxide, composite, and battery

[0001] The present disclosure relates to lithium vanadium oxides, composites, and batteries.

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

[0003] Patent Document 2 discloses (Li[3-ax+(5-b)y]A x ) (V 1-y B y The document discloses a co-fired all-solid-state battery using a negative electrode active material represented by the formula (I)O4. Here, A is at least one element selected from the group consisting of Mg, Al, Ga, and Zn, and B is at least one element selected from the group consisting of Zn, Al, Ga, Si, Ge, P, and Ti. x and y satisfy the conditions 0≦x≦1.0 and 0≦y≦0.6, respectively. a is the average valence of A, and b is the average valence of B.

[0004] JP 2008-77847 A International Publication No. 2019 / 044902

[0005] When the lithium vanadium oxides disclosed in Patent Documents 1 and 2 are used as the negative electrode active material, it is difficult to obtain a battery having a sufficient discharge capacity.

[0006] An object of the present disclosure is to provide a lithium vanadium oxide suitable for improving the discharge capacity of a battery.

[0007] The present disclosure provides a lithium vanadium oxide containing Li, V, and O, or containing Li, V, M, and O, wherein M is at least one element selected from tetravalent metal elements and tetravalent metalloid elements excluding V, and the lithium vanadium oxide has a lattice volume V that satisfies the following formula (1): L [Å 3 Lithium vanadium oxide V, comprising a crystalline phase having the formula L <12.5x+348.25 (1) [wherein x is the ratio of the amount of substance of M to the sum of the amount of substance of V and the amount of substance of M] is provided.

[0008] According to the present disclosure, a lithium vanadium oxide suitable for improving the discharge capacity of a battery can be provided.

[0009] Fig. 1 is a schematic cross-sectional view showing a composite according to a second embodiment of the present disclosure. Fig. 2 is a schematic cross-sectional view showing a battery according to a third embodiment of the present disclosure. Fig. 3 is a schematic cross-sectional view showing an electrode material that can be used in the battery according to the third embodiment of the present disclosure. Fig. 4 is a graph showing the relationship between the ratio (x) of the amount of substance of Ti to the total amount of substance of V and the amount of substance of Ti and the lattice volume V in the lithium vanadium oxides of the examples and comparative examples. L 5 is a graph showing the relationship between the ratio (x) of the amount of substance of Ti to the total amount of substance of V and Ti in the lithium vanadium oxides of Examples and Comparative Examples, and the initial discharge capacity of the battery using the lithium vanadium oxide.

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0011] [First Embodiment] A lithium vanadium oxide according to a first embodiment contains Li, V, and O, or contains Li, V, M, and O. Here, M is at least one element selected from tetravalent metal elements and tetravalent metalloid elements excluding V. The "metal element" refers to all elements included in Groups 1 to 12 of the periodic table (excluding H) and all elements included in Groups 13 to 16 of the periodic table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se). The "metalloid element" refers to B, Si, Ge, As, Sb, and Te.

[0012] The lithium vanadium oxide according to the first embodiment has a lattice volume V that satisfies the following formula (1): L [Å 3 In formula (1), x is the ratio of the amount of substance of M to the sum of the amount of substance of V and the amount of substance of M.

[0013] V L <12.5x+348.25...(1)

[0014] The lithium vanadium oxide according to this embodiment can be used as a battery material. The lithium vanadium oxide can be used, for example, as a negative electrode active material. The lithium vanadium oxide is suitable for improving the discharge capacity of a battery. In the lithium vanadium oxide prepared by the inventors with the intention of introducing lattice defects by adjusting the valence of the raw materials, the lattice volume V L [Å 3 ] satisfied the formula (1). From this, the lattice volume V of the lithium vanadium oxide L When formula (1) is satisfied, it is believed that lattice defects are introduced into the crystal lattice of the crystalline phase. The improvement in the discharge capacity of the battery is presumed to be due to the introduction of the lattice defects. This is believed to be because the lattice defects increase the Li diffusion rate within the crystal structure. The lithium vanadium oxide is also suitable for improving the charge / discharge characteristics of the battery. An example of the battery is an all-solid-state battery. The all-solid-state battery may be a primary battery or a secondary battery.

[0015] The lattice volume V of the crystalline phase that satisfies formula (1) L [Å 3 ] may satisfy any one of the following formulas (2) to (4): According to this configuration, the discharge capacity of the battery can be further improved.

[0016] 343<V L <12.5x+348.25...(2)

[0017] 345<V L <12.5x+348.25...(3)

[0018] 347<V L <12.5x+348.25...(4)

[0019] The lithium vanadium oxide may be represented by the following composition formula (A): In composition formula (A), 0≦x<1.0 and 0<y≦1.5 may be satisfied. With this configuration, the discharge capacity of the battery can be further improved.

[0020] Li 3+x V 1-x M x O 4-y...(A)

[0021] The upper and lower limits of the range of x in composition formula (A) may be defined by any combination selected from the following: greater than 0 (i.e., 0<x), 0.01, 0.02, 0.03, 0.04, 0.05, 0.1, 0.15, 0.175, 0.2, and less than 1.0 (i.e., x<1.0). x may satisfy 0<x<0.2, 0<x≦0.175, or 0<x≦0.15. x may also satisfy 0.5≦x<0.2, 0.5≦x≦0.175, or 0.5≦x≦0.15.

[0022] In composition formula (A), when x satisfies the above range, insertion and desorption of Li into and from the crystalline phase of the lithium vanadium oxide is facilitated, and therefore, a lithium vanadium oxide in which x satisfies the above range can further improve the discharge capacity of a battery.

[0023] The upper and lower limits of the range of y in composition formula (A) may be defined by any combination selected from values ​​greater than 0 (i.e., 0<y), 0.5, 1.0, and less than 1.5 (i.e., y<1.5). y may satisfy 0<y≦1 or 0<y≦0.5.

[0024] In composition formula (A), when y satisfies the above range, oxygen vacancies are appropriately introduced into the crystal lattice of the crystalline phase of the lithium vanadium oxide, and therefore, the lithium vanadium oxide in which y satisfies the above range can further improve the discharge capacity of the battery.

[0025] In composition formula (A), M may be at least one selected from the group consisting of Ti, Zr, Si, Ge, and Sn. With this configuration, when the lithium vanadium oxide is used in a battery, the discharge capacity of the battery is easily improved.

[0026] In composition formula (A), M may contain Ti. According to this configuration, when the lithium vanadium oxide is used in a battery, the discharge capacity of the battery is more likely to be improved. M may be Ti. According to this configuration, when the lithium vanadium oxide is used in a battery, the discharge capacity of the battery is more likely to be improved.

[0027] The crystalline phase satisfying formula (1) may be the main phase of lithium vanadium oxide. The "main phase" refers to the phase that is contained in the largest amount by mass in lithium vanadium oxide. The "main phase" may be contained in an amount of 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, or 90 mass% or more in lithium vanadium oxide. The lithium vanadium oxide may consist of only the main phase. The mass ratio of the crystalline phase can be calculated from the integrated value of peak intensities measured by XRD.

[0028] The main phase may be a γ phase. The expansion and contraction rate associated with the insertion and extraction of Li into and from the γ phase is low. Therefore, when a lithium vanadium oxide containing the γ phase as the main phase is used in a battery, the durability of the battery can be improved.

[0029] The γ phase is a crystalline phase having a crystalline structure belonging to the space group Pcmn. Specifically, the γ phase has tetrahedra composed of LiO4 (hereinafter simply referred to as "LiO4 tetrahedra") and tetrahedra composed of VO4 (hereinafter simply referred to as "VO4 tetrahedra"). In the γ phase, the LiO4 tetrahedra and VO4 tetrahedra exist as tetrahedra generally oriented in one direction (the +c-axis direction, which is one side of the crystal lattice) and tetrahedra generally oriented in one direction opposite to the one direction (the -c-axis direction, which is one side of the crystal lattice), with approximately half of each tetrahedron present. In the crystal structure of the γ phase, LiO4 tetrahedra share vertices and one side with adjacent LiO4 tetrahedra, and VO4 tetrahedra share vertices with adjacent LiO4 tetrahedra or VO4 tetrahedra. The γ phase can be stably obtained by partially substituting V (vanadium) sites in the crystal lattice with a tetravalent metal other than V.

[0030] The lithium vanadium oxide may contain a crystalline phase other than the main phase, such as a β phase.

[0031] The β-phase is a crystalline phase having a crystalline structure belonging to the space group Pmn21. Specifically, the crystalline structure of the β-phase has LiO4 tetrahedra and VO4 tetrahedra, similar to the crystalline structure of the γ-phase. In the crystalline structure of the β-phase, the LiO4 tetrahedra and the VO4 tetrahedra are oriented in the same direction (the c-axis direction, which is one side of the crystal lattice) with adjacent tetrahedra sharing vertices. The β-phase has a high theoretical capacity as an active material.

[0032] The shape of the lithium vanadium oxide is not limited. Examples of the shape include needles, spheres, and ellipsoids. The lithium vanadium oxide may be in the form of particles. The lithium vanadium oxide may be formed into a pellet or plate shape.

[0033] When the lithium vanadium oxide is particulate (e.g., spherical), the lithium vanadium oxide particles may have a median diameter of 0.1 μm or more and 100 μm or less, or may have a median diameter of 0.5 μm or more and 10 μm or less, which allows the lithium vanadium oxide and other materials, such as a solid electrolyte, to be dispersed well.

[0034] The median particle size means a particle size (d50) corresponding to a cumulative 50% volume in a volume-based particle size distribution. The volume-based particle size distribution can be measured using a laser diffraction measurement device or an image analysis device.

[0035] <Method for Producing Lithium Vanadium Oxide> The lithium vanadium oxide according to the first embodiment can be produced by the following method. 3+x V 1-x M x O 4-y A method for producing a lithium vanadium oxide in which M is Ti will be described.

[0036] Raw material powders are prepared to have a target composition. Specifically, Li raw material powder, V raw material powder, and Ti raw material powder are prepared. Examples of the raw material powders are oxides, hydroxides, carbonates, nitrates, or organic salts.

[0037] Assume that x is 0.05 and y is 0.475 when mixing raw materials. For example, Li2CO3, VO2, and TiO2 are prepared in a molar ratio of Li2CO3:VO2:TiO2 = (3.05 / 2):0.95:0.05.

[0038] As the Li raw material powder, lithium hydroxide or a hydrate thereof may be used instead of Li2CO3.

[0039] As the V raw material powder, depending on the value of y, either V2O2 or V2O3 may be used instead of VO2, or a combination of V, V2O2, V2O3, VO2, and V2O5 may be used.

[0040] The mixture of raw material powders is fired to obtain a reaction product. The firing atmosphere may be air or an inert gas atmosphere. The inert atmosphere is, for example, an argon atmosphere or a nitrogen atmosphere.

[0041] Alternatively, a mixture of raw material powders may be reacted with each other mechanochemically (by mechanochemical milling) in a mixing device such as a planetary ball mill to obtain a reactant.

[0042] In this way, the lithium vanadium oxide according to the first embodiment is obtained.

[0043] Here, the molar ratio of the raw materials when mixed does not necessarily match the molar ratio of the reactants, because the raw materials may not be incorporated into the reactants due to evaporation or the like during the reaction.

[0044] The composition of lithium vanadium oxide, for example, the values ​​of x and y in composition formula (A), can be determined by high-frequency inductively coupled plasma (ICP) atomic emission spectroscopy, atomic absorption spectroscopy, or EPMA (Electron Probe Micro Analyzer). The value of x in composition formula (A) can be determined from the amount of substance of element M in the lithium vanadium oxide. The value of y in composition formula (A) can be determined from the amount of substance of element O in the lithium vanadium oxide.

[0045] Lattice volume V of the crystalline phase of lithium vanadium oxide L The value of can be determined by Rietveld analysis of an X-ray diffraction pattern using Cu-Kα as a radiation source.

[0046] Second Embodiment A second embodiment will be described below, and the matters described in the first embodiment will be omitted as appropriate.

[0047] The composite 100 according to the second embodiment includes the lithium vanadium oxide according to the first embodiment and a carbon material 105. Specifically, the composite 100 includes particles 101 containing the lithium vanadium oxide according to the first embodiment and a carbon material 105. The particles 101 may be particles containing the lithium vanadium oxide according to the first embodiment as a main component. Particles containing the lithium vanadium oxide according to the first embodiment as a main component refer to particles in which the lithium vanadium oxide according to the first embodiment is the component contained in the largest amount by mass. The particles 101 may be particles made of the lithium vanadium oxide according to the first embodiment.

[0048] The composite 100 according to the present embodiment can be used as a battery material. For example, the composite 100 can be used as a negative electrode material. The composite 100 is suitable for improving the discharge capacity of a battery.

[0049] The carbon material 105 may coat the particles 101. With this configuration, when the composite 100 is used as an electrode material, the discharge capacity of the battery can be further improved.

[0050] The coverage R of the carbon material 105 on the surface of the particle 101 may be 30% or more. The coverage R may be 100% or less. With such a configuration, the composite 100 can further improve the discharge capacity of the battery.

[0051] The coverage R may be 40% or more. With this configuration, the composite 100 can further improve the discharge capacity of the battery.

[0052] The coverage R may be 55% or more. With this configuration, the composite 100 can further improve the discharge capacity of the battery.

[0053] The coverage R may be 70% or less. With this configuration, the insertion and desorption of Li into and from the composite 100 can be promoted while ensuring the electronic conductivity of the composite 100.

[0054] The particles 101 may be primary particles or secondary particles formed by aggregation of a plurality of primary particles.

[0055] When the particle 101 is a secondary particle, the carbon material 105 may be present inside the particle 101. That is, the carbon material 105 may be present at the interface of the primary particles that constitute the particle 101. When the carbon material 105 is present inside the particle 101, electrons can be transported to the inside of the particle 101, and the electronic conductivity of the composite 100 is further improved.

[0056] The presence of the carbon material 105 inside the particles 101 can be confirmed, for example, by observing a cross section of a pellet or the like containing the particles of the composite 100 with a transmission electron microscope (TEM).

[0057] The shape of the carbon material 105 itself is not particularly limited. For example, a thin film formed by the accumulation of fine particles of the carbon material 105 in a plate-like, needle-like, spherical, oval-spherical, or other shape may cover at least a portion of the surface of the particle 101 containing lithium vanadium oxide.

[0058] The average thickness of the thin film of the carbon material 105 may be 100 nm or less. Such a configuration facilitates the insertion and desorption of Li into and from the composite 100. The average thickness of the thin film of the carbon material 105 can be determined, for example, by observing a cross section of a pellet or the like containing particles of the composite 100 with an SEM or a TEM.

[0059] Examples of the carbon material 105 include graphite (graphene) having a six-membered ring network of carbon atoms, and amorphous carbon.

[0060] The shape of the composite 100 is not limited. Examples of such shapes include a needle shape, a sphere shape, or an oval sphere shape. The composite 100 may be in the form of particles. The composite 100 may be formed to have a pellet or plate shape.

[0061] When the composite 100 is particulate (e.g., spherical), the particles of the composite 100 may have a median diameter of 0.1 μm or more and 100 μm or less, or may have a median diameter of 5 μm or more and 10 μm or less. This configuration allows the composite 100 to be well dispersed with other materials. The other materials are, for example, solid electrolytes.

[0062] <Method for Producing Composite> The composite 100 according to the second embodiment can be produced by the following method. In the following, as in the method for producing lithium vanadium oxide according to the first embodiment, the lithium vanadium oxide contained in the composite 100 is a lithium vanadium oxide having a composition formula (A): Li 3+x V 1-x M x O 4-y A method for producing the composite 100 in which M is Ti will be described.

[0063] First, Li raw material powder, V raw material powder, and Ti raw material powder are prepared in the same raw material powders and molar ratios as those in the method for producing lithium vanadium oxide according to the first embodiment.

[0064] Furthermore, raw material powder of the carbon material 105 is prepared. The raw material powder of the carbon material 105 may be prepared in a range of 0.5 mass % to 25 mass % or in a range of 1 mass % to 12 mass % with respect to the total mass of the V raw material powder and the Ti raw material powder. As the raw material powder of the carbon material 105, for example, graphene oxide may be used.

[0065] Next, the mixture of Li raw material powder, V raw material powder, Ti raw material powder, and raw material powder of the carbon material is dissolved in a solvent to obtain a raw material solution. The solvent may be, for example, water or an organic solvent. The organic solvent may be, for example, an alcohol such as ethanol or ethylene glycol.

[0066] Next, in order to prevent aggregation of the synthesized product in the subsequent thermal synthesis, the raw material solution is subjected to a dispersion treatment to obtain a dispersion solution. For the dispersion treatment, for example, an ultrasonic disperser, a pressure disperser, or the like can be used.

[0067] Finally, the dispersion solution is heated to perform thermal synthesis in the liquid phase. This causes the powdery composite 100 to precipitate as a reactant in the liquid phase. The precipitated composite 100 is separated from the liquid. In this manner, the composite 100 is obtained. The composite 100 may then be calcined.

[0068] Here, the molar ratio of the raw material powders when mixed does not necessarily match the molar ratio of the reactants, because the raw material powders may not be incorporated into the reactants due to evaporation or other reasons during thermal synthesis.

[0069] In the composite 100 produced by the above method, at least a portion of the surface of the lithium vanadium oxide-containing particle 101, which is a secondary particle, is coated with the carbon material 105. The carbon material 105 is also present at the interface between the primary particles constituting the particle 101.

[0070] Third Embodiment A third embodiment will be described below. Matters described in the first and second embodiments will be omitted as appropriate.

[0071] The battery according to the third embodiment includes a positive electrode, an electrolyte, and a negative electrode. The electrolyte is located between the positive electrode and the negative electrode. The negative electrode includes the lithium vanadium oxide according to the first embodiment. Alternatively, the negative electrode includes the composite 100 according to the second embodiment (see FIG. 1 ) instead of or in addition to the lithium vanadium oxide according to the first embodiment.

[0072] The battery according to the third embodiment is excellent in discharge capacity.

[0073] FIG. 2 shows a cross-sectional view of a battery 1000 according to a third embodiment.

[0074] The battery 1000 includes a positive electrode 200, an electrolyte 300, and a negative electrode 400. The electrolyte 300 is disposed between the positive electrode 200 and the negative electrode 400.

[0075] The positive electrode 200 contains a positive electrode active material 201 and a solid electrolyte 202 .

[0076] The electrolyte 300 contains an electrolyte material, such as a solid electrolyte material.

[0077] The negative electrode 400 contains a negative electrode active material 401 and a solid electrolyte 402 .

[0078] The negative electrode active material 401 is a particle containing the lithium vanadium oxide according to the first embodiment. The negative electrode active material 401 may be a particle containing the lithium vanadium oxide according to the first embodiment as a main component. The particle containing the lithium vanadium oxide according to the first embodiment as a main component means a particle in which the lithium vanadium oxide according to the first embodiment is the component contained in the largest amount by mass. The negative electrode active material 401 may be a particle made of the lithium vanadium oxide according to the first embodiment.

[0079] The negative electrode active material 401 may have a median diameter of 0.1 μm or more and 100 μm or less. When the negative electrode active material 401 has a median diameter of 0.1 μm or more, the negative electrode active material 401 and the solid electrolyte 402 can be well dispersed in the negative electrode 400. This improves the charge / discharge characteristics of the battery 1000. When the negative electrode active material 401 has a median diameter of 100 μm or less, the diffusion rate of lithium in the negative electrode active material 401 improves. This allows the battery 1000 to operate at high power.

[0080] The negative electrode active material 401 may have a larger median diameter than the solid electrolyte 402. This allows the negative electrode active material 401 and the solid electrolyte 402 to be dispersed well.

[0081] In order to improve the energy density and output of the battery 1000, in the negative electrode 400, the ratio of the volume of the negative electrode active material 401 to the sum of the volume of the negative electrode active material 401 and the volume of the solid electrolyte 402 may be 0.30 or more and 0.95 or less.

[0082] To improve the energy density and output of the battery 1000, the negative electrode 400 may have a thickness of 10 μm or more and 500 μm or less.

[0083] The solid electrolyte 402 included in the negative electrode 400 may be a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, or a polymer solid electrolyte.

[0084] In the present disclosure, a "sulfide solid electrolyte" refers to a solid electrolyte containing sulfur. An "oxide solid electrolyte" refers to a solid electrolyte containing oxygen. The oxide solid electrolyte may contain anions other than oxygen (excluding sulfur anions and halogen anions). A "halide solid electrolyte" refers to a solid electrolyte that contains a halogen element but does not contain sulfur. The halide solid electrolyte may contain not only a halogen element but also oxygen.

[0085] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, and Li 3.25 Ge 0.25 P 0.75S4 or Li 10 GeP2S 12 is.

[0086] Examples of halide solid electrolytes include Li a Me b Y c X6, where the formula: a + mb + 3c = 6 and c > 0 is satisfied. Me is at least one element 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.

[0087] In order 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.

[0088] Another example of a halide solid electrolyte is Li α Me' β O γ X δ where α, β, γ, and δ are all greater than 0, Me′ is at least one element selected from the group consisting of metal elements and metalloid elements other than Li, X is at least one element selected from the group consisting of Cl, Br, and I, and the following mathematical formulas are satisfied: 0.9≦α≦1.2, β=1.0, 1.0≦γ≦1.3, and 3.6≦δ≦4.0.

[0089] Examples of oxide solid electrolytes include: (i) NASICON-type solid electrolytes such as LiTi2(PO4)3 or its elemental substitution products; (ii) perovskite-type solid electrolytes such as (LaLi)TiO3; (iii) Li 14 ZnGeO 16 LISICON-type solid electrolytes such as LiSiO, LiGeO, or elemental substitutions thereof; (iv) LiLaZrO 12 or an element-substituted product thereof, or (v) Li3PO4 or an N-substituted product thereof.

[0090] An example of a polymer solid electrolyte is a compound of a polymer compound and a lithium salt. The polymer compound may have an ethylene oxide structure. A polymer compound having an ethylene oxide structure can contain a large amount of lithium salt, and therefore has higher ionic conductivity. The polymer solid electrolyte may be, for example, a composite compound of polyethylene oxide and a lithium salt. An example of such a polymer solid electrolyte is lithium bis(trifluoromethanesulfonyl)imide.

[0091] Examples of lithium salts include LiPF, LiBF, LiSbF, LiAsF, LiSOCF, LiN(SOCF), LiN(SOCF), LiN(SOCF)(SOCF), or LiC(SOCF). One lithium salt selected from these may be used alone. Alternatively, a mixture of two or more lithium salts selected from these may be used.

[0092] The positive electrode 200 contains a material capable of absorbing and releasing metal ions such as lithium ions. The positive electrode 200 contains, for example, a positive electrode active material 201.

[0093] Examples of the positive electrode active material 201 include a lithium-containing transition metal oxide, a transition metal fluoride, a polyanion material, a fluorinated polyanion material, a transition metal sulfide, a transition metal oxysulfide, and a transition metal oxynitride. Examples of the lithium-containing transition metal oxide include Li(Ni, Co, Al)O, Li(Ni, Co, Mn)O, and LiCoO.

[0094] In the present disclosure, "(A, B, C)" means "at least one selected from the group consisting of A, B, and C."

[0095] From the viewpoint of the cost and safety of the battery 1000, lithium phosphate may be used as the positive electrode active material 201.

[0096] The positive electrode active material 201 may have a median diameter of 0.1 μm or more and 100 μm or less. When the positive electrode active material 201 has a median diameter of 0.1 μm or more, the positive electrode active material 201 and the solid electrolyte 202 can be well dispersed in the positive electrode 200. This improves the charge / discharge characteristics of the battery 1000. When the positive electrode active material 201 has a median diameter of 100 μm or less, the lithium diffusion rate within the positive electrode active material 201 improves. This allows the battery 1000 to operate at high power.

[0097] The positive electrode active material 201 may have a larger median diameter than the solid electrolyte 202. This allows the positive electrode active material 201 and the solid electrolyte 202 to be dispersed well.

[0098] In order to improve the energy density and output of the battery 1000, in the positive electrode 200, the ratio of the volume of the positive electrode active material 201 to the sum of the volume of the positive electrode active material 201 and the volume of the solid electrolyte 202 may be 0.30 or more and 0.95 or less.

[0099] To improve the energy density and output of the battery 1000, the positive electrode 200 may have a thickness of 10 μm or more and 500 μm or less.

[0100] The solid electrolyte 202 included in the positive electrode 200 may be a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, or an organic polymer solid electrolyte.

[0101] The electrolyte 300 contains an electrolyte material. The electrolyte material is, for example, a solid electrolyte material. The electrolyte 300 may contain a solid electrolyte material. The solid electrolyte material contained in the electrolyte 300 may be a sulfide solid electrolyte, a halide solid electrolyte, or a polymer solid electrolyte.

[0102] The electrolyte 300 may be layered. That is, the electrolyte 300 may be an electrolyte layer. The electrolyte 300 may have a thickness of 1 μm or more and 100 μm or less. When the electrolyte 300 has a thickness of 1 μm or more, the positive electrode 200 and the negative electrode 400 are less likely to short-circuit. When the electrolyte 300 has a thickness of 100 μm or less, the battery 1000 can operate at high power.

[0103] At least one selected from the group consisting of the positive electrode 200, the electrolyte 300, and the negative electrode 400 may contain a non-aqueous electrolyte, a gel electrolyte, or an ionic liquid for the purpose of facilitating the exchange of lithium ions and improving the output characteristics of the battery 1000.

[0104] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent are cyclic carbonate ester solvents, chain carbonate ester solvents, cyclic ether solvents, chain ether solvents, cyclic ester solvents, chain ester solvents, and fluorine solvents. Examples of the cyclic carbonate ester solvent are ethylene carbonate, propylene carbonate, and butylene carbonate. Examples of the chain carbonate ester solvent are dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. Examples of the cyclic ether solvent are tetrahydrofuran, 1,4-dioxane, and 1,3-dioxolane. Examples of the chain ether solvent are 1,2-dimethoxyethane and 1,2-diethoxyethane. An example of the cyclic ester solvent is γ-butyrolactone. An example of the chain ester solvent is methyl acetate. Examples of fluorine-containing solvents include fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, and fluorodimethylene carbonate. One non-aqueous solvent selected from these may be used alone. Alternatively, a mixture of two or more non-aqueous solvents selected from these may be used.

[0105] Examples of lithium salts include LiPF, LiBF, LiSbF, LiAsF, LiSOCF, LiN(SOCF), LiN(SOCF), LiN(SOCF)(SOCF), or LiC(SOCF). One lithium salt selected from these may be used alone. Alternatively, 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 / L to 2 mol / L.

[0106] The gel electrolyte may be a polymer material impregnated with a non-aqueous electrolyte, such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or a polymer having an ethylene oxide bond.

[0107] Examples of cations contained in the ionic liquid are: (i) aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium; (ii) aliphatic cyclic ammoniums such as pyrrolidiniums, morpholiniums, imidazoliniums, tetrahydropyrimidiniums, piperaziniums, or piperidiniums; or (iii) nitrogen-containing heterocyclic aromatic cations such as pyridiniums or imidazoliums.

[0108] An example of an 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 - is.

[0109] The ionic liquid may contain a lithium salt.

[0110] At least one selected from the group consisting of the positive electrode 200, the electrolyte 300, and the negative electrode 400 may contain a binder for the purpose of improving adhesion between particles.

[0111] 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. 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. A mixture of two or more materials selected from the above materials may also be used as the binder.

[0112] At least one selected from the positive electrode 200 and the negative electrode 400 may contain a conductive additive for the purpose of increasing electronic conductivity.

[0113] Examples of the conductive additive include: (i) graphites such as natural graphite or artificial graphite, (ii) carbon blacks such as acetylene black or ketjen black, (iii) conductive fibers such as carbon fiber or metal fiber, (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 (viii) conductive polymer compounds such as polyaniline, polypyrrole, or polythiophene. To reduce costs, the conductive additives (i) or (ii) may be used.

[0114] The negative electrode 400 may contain not only the negative electrode active material 401 but also a conductive additive 403. Examples of materials for the conductive additive 403 are as described above.

[0115] The conductive additive 403 may cover at least a part of the surface of the negative electrode active material 401. This increases the contact area between the conductive additive 403 and the negative electrode active material 401. As a result, the resistance of the battery 1000 decreases, and the output can be increased.

[0116] In the negative electrode 400, the ratio of the volume of the conductive additive 403 to the total volume of the negative electrode active material 401 and the conductive additive 403 may be 0.01 or more and 0.4 or less.

[0117] FIG. 3 shows a cross-sectional view of an electrode material 500 that can be used in the battery 1000 (see FIG. 2) according to the third embodiment. The electrode material 500 shown in FIG. 3 may be contained in the negative electrode 400 (see FIG. 2). In order to prevent the solid electrolyte 502 from reacting with the negative electrode active material (i.e., the electrode active material 501), a coating layer 505 may be formed on the surface of the electrode active material 501. This allows the battery 1000 to have high charge / discharge efficiency.

[0118] Examples of the coating material included in the coating layer 505 include a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, or a halide solid electrolyte.

[0119] 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.

[0120] Examples of the shape of the battery 1000 according to the third embodiment include a coin type, a cylindrical type, a square type, a sheet type, a button type, a flat type, and a laminate type.

[0121] The battery 1000 according to the third embodiment may be manufactured, for example, by preparing a material for forming a positive electrode, a material for forming an electrolyte layer, and a material for forming a negative electrode, and by using a known method to fabricate a laminate in which the positive electrode, the electrolyte, and the negative electrode are arranged in this order.

[0122] [Other Embodiments] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0123] (Technology 1) A lithium vanadium oxide containing Li, V, and O, or containing Li, V, M, and O, wherein M is at least one element selected from tetravalent metal elements other than V and tetravalent metalloid elements, and the lithium vanadium oxide has a lattice volume V that satisfies the following formula (1): L [Å 3 In formula (1), x is the ratio of the amount of substance of M to the sum of the amount of substance of V and the amount of substance of M. L <12.5x+348.25...(1)

[0124] According to the present disclosure, a lithium vanadium oxide suitable for improving the discharge capacity of a battery can be provided.

[0125] (Technology 2) Li 3+x V 1-x M x O 4-y and satisfying 0≦x<1 and 0<y≦1.5. With this configuration, when the lithium vanadium oxide is used in a battery, the discharge capacity of the battery can be further improved.

[0126] (Technology 3) The lithium vanadium oxide according to Technology 1 or 2, which satisfies 0<x<0.2. With this configuration, when the lithium vanadium oxide is used in a battery, the discharge capacity of the battery can be further improved.

[0127] (Technology 4) The lattice volume V L [Å 3 3. The lithium vanadium oxide according to any one of the first to third aspects, wherein V satisfies the following formula (2): 343<V L <12.5x+348.25...(2)

[0128] (Technology 5) The lithium vanadium oxide according to any one of Technologies 1 to 4, wherein M contains Ti. According to this configuration, when the lithium vanadium oxide is used in a battery, the discharge capacity of the battery can be more easily improved.

[0129] (Technology 6) The lithium vanadium oxide according to any one of Technologies 1 to 5, wherein the crystalline phase is a main phase. With this configuration, when the lithium vanadium oxide is used in a battery, the discharge capacity of the battery can be more easily improved.

[0130] (Technology 7) The lithium vanadium oxide according to Technology 6, wherein the main phase is a γ phase. With this configuration, when the lithium vanadium oxide is used in a battery, the durability of the battery can be improved.

[0131] (Technology 8) A composite comprising the lithium vanadium oxide according to any one of Technologies 1 to 7 and a carbon material. According to the present disclosure, a composite suitable for improving the discharge capacity of a battery can be provided.

[0132] (Technology 9) A battery comprising a positive electrode, a negative electrode, and an electrolyte located between the positive electrode and the negative electrode, wherein the negative electrode contains the lithium vanadium oxide according to any one of Technologies 1 to 7. According to the present disclosure, a battery suitable for improving discharge capacity can be provided.

[0133] (Technology 10) The battery according to Technology 9, wherein the negative electrode further contains a conductive additive. With this configuration, the electronic conductivity of the negative electrode can be increased.

[0134] The present disclosure will be described in detail below using examples and comparative examples, but the lithium vanadium oxide, composite, and battery of the present disclosure are not limited to the following examples.

[0135] Composition formula (A): Li 3+x V 1-x Ti x O 4-y Lithium vanadium oxides according to the examples and comparative examples were prepared as follows so as to have a composition represented by the following formula:

[0136] Example 1 (Preparation of Lithium Vanadium Oxide) Li2CO3 (manufactured by Kojundo Chemical Laboratory, purity 99.9%), VO2 (manufactured by Kojundo Chemical Laboratory, purity 99.9%), and TiO2 (manufactured by Kojundo Chemical Laboratory, purity 99.9%) were prepared in a molar ratio of Li2CO3:VO2:TiO2 = 1.5:0.95:0.05. Li2CO3 was added in an amount of 1 mass% excess relative to the mass of Li2CO3 in the above molar ratio. These raw material powders were mixed in a mortar to obtain a mixed powder. The obtained mixed powder was pre-fired at 600°C for 3 hours in the air. The obtained pre-fired powder was then fired at 920°C for 15 hours in the air. In both the pre-fired and post-fired processes, the heating rate was 10°C per minute, and the cooling rate was 5°C per minute. In this manner, the lithium vanadium oxide of Example 1 was obtained.

[0137] Example 2 V2O3 (manufactured by Kojundo Chemical Laboratory, purity 99.9%) was used as the V raw material. Li2CO3, V2O3, and TiO2 were prepared in a molar ratio of Li2CO3:V2O3:TiO2 = 1.525:0.475:0.05. Except for the above points, lithium vanadium oxide according to Example 2 was produced in the same manner as in Example 1.

[0138] [Example 3] Li2CO3, VO2, and TiO2 were prepared in a molar ratio of Li2CO3:VO2:TiO2 = 1.55:0.9:0.1, and lithium vanadium oxide according to Example 3 was produced in the same manner as in Example 1, except for the above points.

[0139] Example 4 V2O3 was used as the V raw material. Li2CO3, V2O3, and TiO2 were prepared in a molar ratio of Li2CO3:VO2:TiO2 = 1.55:0.45:0.1. Except for the above points, lithium vanadium oxide according to Example 4 was produced in the same manner as in Example 1.

[0140] [Example 5] Li2CO3, VO2, and TiO2 were prepared in a molar ratio of Li2CO3:VO2:TiO2 = 1.575:0.85:0.15, and lithium vanadium oxide according to Example 5 was produced in the same manner as in Example 1, except for the above points.

[0141] Comparative Example 1: V2O5 was used as the V raw material. Li2CO3, V2O5, and TiO2 were prepared in a molar ratio of Li2CO3:V2O5:TiO2 = 1.525:0.475:0.05. Except for the above points, lithium vanadium oxide according to Comparative Example 1 was produced in the same manner as in Example 1.

[0142] Comparative Example 2: V2O5 was used as the V raw material. Li2CO3, V2O5, and TiO2 were prepared in a molar ratio of Li2CO3:V2O5:TiO2 = 1.55:0.45:0.1. Except for the above points, lithium vanadium oxide according to Comparative Example 2 was produced in the same manner as in Example 1.

[0143] Comparative Example 3: V2O5 was used as the V raw material. Li2CO3, V2O5, and TiO2 were prepared in a molar ratio of Li2CO3:V2O5:TiO2 = 1.575:0.425:0.15. Except for the above points, lithium vanadium oxide according to Comparative Example 3 was produced in the same manner as in Example 1.

[0144] (Composition Analysis) In the lithium vanadium oxides of Examples 1 to 5 and Comparative Examples 1 to 3, "x" in composition formula (A) was determined by analysis using an ICP optical emission spectrometer (PS3520VDDII, manufactured by Hitachi High-Tech Science).

[0145] The calculation results of "x" in composition formula (A) by composition analysis are shown in Table 1. Note that "y" in composition formula (A) shown in Table 1 was calculated from the shortage of oxygen in the raw material powder of lithium vanadium oxide.

[0146] (Crystal Structure Analysis) In the lithium vanadium oxides of Examples 1 to 5 and Comparative Examples 1 to 3, the crystal structure of the lithium vanadium oxide was identified by analyzing the diffraction pattern using an X-ray diffractometer (MiniFlex600, manufactured by RIGAKU Corporation). Cu-Kα was used as the radiation source in the X-ray diffraction. In the lithium vanadium oxides of Examples 1 to 5 and Comparative Examples 1 to 3, the lattice volume V L The value of was calculated by Rietveld analysis of the diffraction pattern. For the Rietveld analysis, analysis software (RIETAN-FP VENUS, default settings) was used.

[0147] The results of identifying the crystal structure of the lithium vanadium oxide by crystal structure analysis and the calculation results of the lattice volume are shown in Table 1. In addition, the value of "x" (amount of substance of Ti / (amount of substance of V+amount of substance of Ti)) in formula (1) and the lattice volume V L The relationship between and is shown in Figure 4. The dashed line in Figure 4 represents V, which is obtained by replacing the inequality in equation (1) with an equality. L = 12.5x + 348.25.

[0148] (Fabrication of Batteries) Batteries were fabricated using the lithium vanadium oxides of the Examples and Comparative Examples, respectively, as follows. In an argon atmosphere with a dew point of -60°C or lower, lithium vanadium oxides of the Examples and Comparative Examples and solid electrolyte Li3PS4 were prepared in a volume ratio of 60:40. These materials were mixed in an agate mortar. In this way, negative electrode mixtures of the Examples and Comparative Examples were obtained.

[0149] The negative electrode mixture (6.5 mg) and the solid electrolyte Li3PS4 (80 mg) were stacked in an insulating cylinder having an inner diameter of 9.5 mm to obtain a laminate according to the example and comparative example. A pressure of 360 MPa was applied to the laminate to form a solid electrolyte layer and a negative electrode. The solid electrolyte layer had a thickness of 500 μm.

[0150] Next, Li (thickness: 300 μm) was laminated on the solid electrolyte layer, and a pressure of 80 MPa was applied to this laminate to form a positive electrode.

[0151] Next, current collectors made of stainless steel were attached to the positive and negative electrodes, and current collecting leads were attached to the current collectors.

[0152] Finally, the inside of the insulating tube was isolated from the outside atmosphere using an insulating ferrule, and the inside of the tube was sealed.

[0153] As a result, batteries according to the examples and comparative examples were obtained. The batteries according to the examples and comparative examples were fabricated as single-electrode test cells, with the negative electrode as the working electrode and the positive electrode as the counter electrode, in order to test the performance of the negative electrode. The working electrode was the negative electrode to be tested, and a sufficient amount of metallic Li was used as the counter electrode active material to cover the reaction of the working electrode. The negative electrode whose performance was tested using such a single-electrode test cell can be used as a secondary battery, for example, by combining it with a positive electrode containing a positive electrode active material such as that described in the above-mentioned embodiment, such as a transition metal oxide containing Li.

[0154] (Charge / Discharge Test) A charge / discharge test was performed using the batteries according to the Examples and Comparative Examples as follows. As described above, the batteries according to the Examples and Comparative Examples are single-electrode test cells, corresponding to half cells of the negative electrode. Therefore, in the batteries according to the Examples and Comparative Examples, the direction in which Li ions are inserted into the negative electrode and the potential of the half cell decreases is called charging, and the direction in which the potential increases is called discharging. That is, in the batteries according to the Examples and Comparative Examples, charging is essentially discharging (i.e., in the case of a bipolar test cell (full cell)), and discharging is essentially charging.

[0155] The battery according to Example 1 was placed in a thermostatic chamber maintained at 25° C. The batteries according to the Example and Comparative Examples were charged at a current value corresponding to a 0.1 C rate (10-hour rate) relative to the theoretical capacity of the battery until the voltage reached 0.3 V. Next, the batteries according to the Example and Comparative Examples were discharged at a current value corresponding to a 0.05 C rate until the voltage reached 2.5 V.

[0156] The initial discharge capacities of the batteries of the Examples and Comparative Examples, measured by charge-discharge tests, are shown in Table 1. The relationship between the value of "x" (amount of substance of Ti / (amount of substance of V+amount of substance of Ti)) in formula (1) for the lithium vanadium oxides of the Examples and Comparative Examples and the initial discharge capacity of the batteries using the lithium vanadium oxides is shown in Figure 5.

[0157]

[0158] (Discussion) As shown in Table 1 and FIG. 4, the lattice volume V of the lithium vanadium oxide according to the example L [Å 3 ] is represented by the above formula (1): V L <12.5x + 348.25. The batteries according to the examples using such lithium vanadium oxide as the active material had high discharge capacities. Specifically, as shown in Table 1 and FIG. 5, the batteries according to the examples had discharge capacities of 375 mAh / g or more (see the dashed line in FIG. 5).

[0159] Note that the same effect can be expected when at least one selected from tetravalent metal elements and tetravalent metalloid elements other than V is used as M instead of Ti, because metal elements and metalloid elements that are tetravalent like Ti have properties similar to those of Ti.

[0160] As described above, the lithium vanadium oxide according to the present disclosure is suitable for improving the discharge capacity of a battery.

[0161] The lithium vanadium oxide according to the present disclosure can be used as a battery material, for example, as a material for all-solid-state lithium-ion secondary batteries.

Claims

1. A lithium vanadium oxide containing Li, V, and O, or containing Li, V, M, and O, wherein M is at least one element selected from tetravalent metal elements other than V and tetravalent metalloid elements, and the lithium vanadium oxide has a lattice volume V that satisfies the following formula (1): L [Å 3 Lithium vanadium oxide, comprising a crystalline phase having the formula: L <12.5x+348.25 (1) [In formula (1), x is the ratio of the amount of substance M to the sum of the amount of substance V and the amount of substance M.] 2. Li 3+x V 1-x M x O 4-y The lithium vanadium oxide according to claim 1 , having a composition represented by the following formula:

3. The lithium vanadium oxide according to claim 1, wherein 0<x<0.2 is satisfied.

4. The lattice volume V L [Å 3 2. The lithium vanadium oxide according to claim 1, wherein 343<V L <12.5x+348.25...(2) 5. The lithium vanadium oxide according to claim 1, wherein M includes Ti.

6. The lithium vanadium oxide of claim 1, wherein the crystalline phase is the predominant phase.

7. The lithium vanadium oxide according to claim 6, wherein the main phase is the γ phase.

8. A composite comprising the lithium vanadium oxide according to claim 1 and a carbon material.

9. A battery comprising: a positive electrode; a negative electrode; and an electrolyte located between said positive electrode and said negative electrode, wherein said negative electrode comprises the lithium vanadium oxide of claim 1.

10. The battery according to claim 9, wherein the negative electrode further contains a conductive additive.

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