Vanadium oxide composite and battery using same

Abstract

A vanadium oxide composite according to the present disclosure comprises: particles that contain vanadium oxide; and a conductive material that covers at least a portion of the surface of each of the particles. The coverage ratio of the conductive material on the surface of each of the particles is 30% or more. The vanadium oxide composite has an average particle diameter of 0.5 μm-5.0 μm.

Description

Vanadium oxide composite and battery using the same

[0001] The present disclosure relates to a vanadium oxide composite and a battery using the same.

[0002] Li3VO4 has attracted attention as a next-generation negative electrode active material due to its low reaction potential and high capacity. Patent Document 1 discloses a nonaqueous secondary battery using Li3VO4 as a negative electrode active material.

[0003] Patent Document 2 discloses an electricity storage device that uses, as a negative electrode active material, a material that contains lithium vanadium oxide and carbon and has a dual structure consisting of an inner layer formed by a collection of multiple lithium vanadium oxide particles while maintaining grain boundaries, and an outer shell layer that encases the inner layer and is formed by at least some of the lithium vanadium oxide particles being connected without grain boundaries.

[0004] JP 2008-77847 A JP 2022-21220 A

[0005] The present disclosure provides novel vanadium oxide composites that can be used as battery materials.

[0006] The vanadium oxide composite of the present disclosure comprises particles containing vanadium oxide and a conductive material that coats at least a portion of the surface of the particles, wherein the coverage of the conductive material on the surface of the particles is 30% or more, and the average particle diameter is 0.5 μm or more and 5.0 μm or less.

[0007] The present disclosure provides novel vanadium oxide composites that can be used as battery materials.

[0008] Fig. 1 shows a cross-sectional view of a vanadium oxide composite 100 according to a first embodiment. Fig. 2 shows a cross-sectional view of a battery 1000 according to a second embodiment. Fig. 3 shows a cross-sectional view of an electrode material 200 according to a second embodiment. Fig. 4 is a graph showing the initial discharge characteristics and 10C discharge characteristics of the battery of Example 1.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0010] (First Embodiment) A vanadium oxide composite according to a first embodiment includes particles containing vanadium oxide and a conductive material that coats at least a portion of the surface of the particles. The coating rate of the conductive material on the surface of the particles is 30% or more. The average particle diameter of the vanadium oxide composite is 0.5 μm or more and 5.0 μm or less.

[0011] The vanadium oxide composite according to the first embodiment can be used as a battery material. The vanadium oxide composite according to the first embodiment can be used, for example, as a negative electrode active material. The vanadium oxide composite according to the first embodiment can be used, for example, to obtain a battery having excellent charge / discharge characteristics. The vanadium oxide composite according to the first embodiment is suitable, for example, for improving the capacity of a battery. An example of the battery is a solid-state battery. The solid-state battery may be a primary battery or a secondary battery.

[0012] FIG. 1 shows a cross-sectional view of a vanadium oxide composite 100 according to a first embodiment.

[0013] The vanadium oxide composite 100 comprises particles 101 containing vanadium oxide and a conductive material 102 .

[0014] The conductive material 102 has electronic conductivity. The conductive material 102 covers at least a portion of the surface of the vanadium oxide-containing particle 101. The coverage R of the conductive material 102 on the surface of the particle 101 is 30% or more. The coverage R may be 100% or less. With this configuration, many electron conduction paths are formed between the vanadium oxide-containing particle 101 and the conductive material 102. As a result, the electronic conductivity of the vanadium oxide composite 100 is improved.

[0015] The coverage rate R of the vanadium oxide composite 100 can be determined by the following method using a pellet, electrode, or battery (hereinafter referred to as a pellet, etc.) containing particles of the vanadium oxide composite 100. First, the pellet, etc. is processed using an ion milling device to form a smooth cross section. The cross section processing direction may be in any direction of the pellet, etc. The formed cross section is observed with a scanning electron microscope (SEM) to obtain an SEM image. For N1 vanadium oxide composite 100 particles included in the SEM image, the perimeter P and the length C of the portion covered by the conductive material 102 are measured. N1 is an integer of 2 or greater, for example, N1 = 50. The average of the values ​​calculated by 100 × C / P is regarded as the coverage rate R. Note that it is not necessary to observe all of the vanadium oxide composite 100 particles included in the formed cross section. Even if only a portion of the formed cross section is displayed in the SEM image, the coverage rate R can be calculated for the N1 vanadium oxide composite 100 particles included in that portion. The conductive material 102 that can be observed by SEM has a thickness of more than 3 nm. Therefore, the conductive material 102 that is the subject of calculation of the coverage ratio R is the conductive material 102 having a thickness of more than 3 nm.

[0016] The coverage R may be 40% or more. With this configuration, the vanadium oxide composite 100 can further improve the capacity of the battery.

[0017] The coverage R may be 55% or more. With this configuration, the vanadium oxide composite 100 can further improve the capacity of the battery.

[0018] The coverage R may be 70% or less. With this configuration, the insertion and desorption of Li into and from the vanadium oxide composite 100 can be promoted while ensuring electronic conductivity.

[0019] The shape of the vanadium oxide composite 100 is not limited. Examples of such shapes include needles, spheres, and ellipsoids. The vanadium oxide composite 100 may be in the form of particles. The vanadium oxide composite 100 may be formed into the shape of a pellet or a plate.

[0020] In this embodiment, the average particle size of the particles of the vanadium oxide composite 100 is 0.5 μm or more and 5.0 μm or less. With this configuration, the vanadium oxide composite 100 can be well dispersed with other materials, such as a solid electrolyte.

[0021] The average particle diameter of the vanadium oxide composite 100 particles can be determined by the following method using a pellet or the like containing the vanadium oxide composite 100 particles. First, a pellet or the like is processed using an ion milling device to form a smooth cross section. The cross section may be processed in any direction of the pellet or the like. The formed cross section is observed using a scanning electron microscope (SEM) to obtain an SEM image. The circle-equivalent diameters of N2 vanadium oxide composite 100 particles included in the SEM image are measured. N2 is an integer of 2 or more, for example, N2 = 50. The average of the circle-equivalent diameters is considered to be the average particle diameter. Note that it is not necessary to observe all of the vanadium oxide composite 100 particles included in the formed cross section. Even if only a portion of the formed cross section is shown in the SEM image, the average particle diameter can be calculated for the N2 vanadium oxide composite 100 particles included in that portion.

[0022] The average particle size of the particles of the vanadium oxide composite 100 may be 0.55 μm or more and 4.5 μm or less. With this configuration, the vanadium oxide composite 100 can further improve the capacity of the battery.

[0023] The average particle size of the particles of the vanadium oxide composite 100 may be 0.6 μm or more and 4.0 μm or less. With this configuration, the vanadium oxide composite 100 can further improve the capacity of the battery.

[0024] The average particle size of the particles of the vanadium oxide composite 100 may be 0.8 μm or more and 3.0 μm or less. With this configuration, the vanadium oxide composite 100 can further improve the capacity of the battery.

[0025] In this embodiment, the particles 101 contain vanadium oxide. The particles 101 may be particles containing vanadium oxide as a main component. The particles 101 containing vanadium oxide as a main component refer to particles in which vanadium oxide is the component contained in the largest amount by mass ratio. The particles 101 may be particles made of vanadium oxide. The shape of the particles 101 is, for example, spherical.

[0026] The vanadium oxide contained in the particles 101 may be represented by the following composition formula (1): Here, in composition formula (1), 0≦x<1 may be satisfied, and M may be at least one element selected from the group consisting of tetravalent metal elements and tetravalent metalloid elements. With this configuration, the vanadium oxide composite 100 can further improve the capacity of the battery.

[0027] Li 3+x V 1-x M x O4...(1)

[0028] In composition formula (1), 0 < x < 1 may be satisfied. Such a configuration further improves the capacity of a battery using the vanadium oxide composite 100. This is because the pentavalent V element is substituted with a tetravalent metal element and / or a tetravalent metalloid element, causing positively charged holes and / or Li ions to act as charge carriers, i.e., facilitating the insertion and desorption of Li into and from the vanadium oxide composite 100.

[0029] In composition formula (1), 0<x≦0.1 may be satisfied. Such a configuration further improves the capacity of a battery using the vanadium oxide composite 100. This is because, when composition formula (1) satisfies 0<x≦0.1, substitution of a tetravalent metal element and / or a tetravalent metalloid element occurs while the crystal structure of the vanadium oxide composite 100 is maintained, making it even easier to insert and extract Li into the vanadium oxide composite 100.

[0030] As described above, M may be at least one element selected from a tetravalent metal element and a tetravalent metalloid element. Examples of tetravalent metal elements and tetravalent metalloid elements include Ti, Zr, Si, Ge, and Sn. When the pentavalent V element is substituted with a tetravalent metal element and / or a tetravalent metalloid element, holes and / or Li ions become charge carriers. This further facilitates the insertion and desorption of Li into the vanadium oxide.

[0031] In composition formula (1), M may contain Ti. With this configuration, the vanadium oxide composite 100 can improve the capacity of the battery. Among tetravalent metal elements, the ionic radius of Ti is closest to the ionic radius of V, which is the substitution source. Therefore, when M contains Ti, substitution of Ti occurs while maintaining the crystal structure of the vanadium oxide composite 100. As a result, insertion and desorption of Li into the vanadium oxide composite 100 becomes even easier.

[0032] In composition formula (1), M may be Ti. With this configuration, the vanadium oxide composite 100 can further improve the capacity of the battery.

[0033] The vanadium oxide composite 100 may contain Li in an amount exceeding the stoichiometric composition. That is, the vanadium oxide contained in the vanadium oxide composite 100 may contain Li in an amount exceeding the amount represented by (3+x) in the above composition formula (1). In this case, insertion and desorption of Li into the vanadium oxide composite 100 becomes even easier. As a result, the vanadium oxide composite 100 can further improve the capacity of the battery.

[0034] For example, the vanadium oxide contained in the vanadium oxide composite 100 may be represented by the following composition formula (2).

[0035] Li 3+x+a V 1-x M x O 4+a / 2 ... (2)

[0036] Here, in composition formula (2), 0 < a < 1 may be satisfied. In other words, the vanadium oxide may contain Li and O in amounts exceeding those derived from the stoichiometric composition. According to this configuration, when 0 < a < 1 is satisfied in composition formula (2), the capacity of a battery using the vanadium oxide composite 100 is improved, for example. This is because the excess Li and O improve the electronic conductivity of the vanadium oxide, facilitating the insertion and desorption of Li into the vanadium oxide composite 100. A stoichiometric composition means a composition in which the molar ratio of the elements constituting the vanadium oxide is an integer multiple. For example, Li3VO4 has a stoichiometric composition.

[0037] The amount of Li and O represented by "a" in composition formula (2) may be incorporated inside the particle 101, or may exist outside the particle 101 as a second phase different from the first phase constituting the particle 101. It should be noted that the vanadium oxides disclosed in Patent Documents 1 and 2 do not contain Li and O equivalent to the amount represented by "a."

[0038] The particles containing vanadium oxide 101 may be primary particles, or may be secondary particles formed by aggregation of a plurality of primary particles.

[0039] When the vanadium oxide-containing particle 101 is a secondary particle, the conductive material 102 may be present inside the particle 101. That is, the conductive material 102 may be present at the interface of the primary particles that make up the particle 101. When the conductive material 102 is present inside the particle 101, electrons can be transported to the inside of the particle 101, and the electronic conductivity of the vanadium oxide composite 100 is further improved.

[0040] The presence of the conductive material 102 inside the particles 101 can be confirmed, for example, by observing a cross section of a pellet or the like containing particles of the vanadium oxide composite 100 with a transmission electron microscope (TEM).

[0041] The shape of the conductive material 102 itself is not particularly limited. For example, at least a portion of the surface of the vanadium oxide-containing particle 101 may be covered with a thin film formed by the accumulation of fine particles of the conductive material 102, such as plate-like, needle-like, spherical, or oval-spherical shapes.

[0042] The average thickness of the thin film of conductive material 102 may be 100 nm or less. Such a configuration makes it easier to insert and extract Li into and from the vanadium oxide composite 100. The average thickness of the thin film of conductive material 102 can be determined, for example, by observing the cross section of a pellet or the like containing particles of the vanadium oxide composite 100 with an SEM or TEM.

[0043] The conductive material 102 may contain a carbon material. With this configuration, the vanadium oxide composite 100 can be produced at low cost.

[0044] A carbon material may be used as the conductive material 102. With this configuration, the vanadium oxide composite 100 can be produced at lower cost.

[0045] Examples of carbon materials include graphite (graphene) having a six-membered ring network of carbon atoms, and amorphous carbon.

[0046] <Method for Producing Vanadium Oxide Composite> The vanadium oxide composite 100 according to the first embodiment can be produced by the following method. 3+x V 1-x M x A method for producing a vanadium oxide composite 100 having particles 101 containing vanadium oxide represented by O4 (x=0) will be described.

[0047] First, vanadium oxide raw material powder is prepared to have a target composition. Examples of vanadium oxide 101 raw material powder include oxide, hydroxide, carbonate, nitrate, and organic salt. The raw material powder may be prepared so that the amount of Li in composition formula (1) is in excess. The Li raw material powder may be prepared in an amount that exceeds the stoichiometric molar ratio of 3:1 relative to the V raw material powder. For example, the Li raw material powder may be prepared in excess of the V raw material powder in a molar ratio range of 6:1 to 30:1. For example, lithium hydroxide monohydrate may be used as the Li raw material powder. For example, ammonium vanadate may be used as the V raw material powder.

[0048] Furthermore, raw material powder of the conductive material 102 is prepared. The raw material powder of the conductive material 102 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 amount of the raw material powder of V. As the raw material powder of the conductive material 102, for example, graphene oxide may be used.

[0049] Next, the mixture of Li raw material powder, V raw material powder, and raw material powder of the conductive material 102 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 is, for example, an alcohol such as ethanol or ethylene glycol.

[0050] 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.

[0051] Finally, the dispersion solution is heated to perform thermal synthesis in the liquid phase. As a result, a powdered vanadium oxide composite 100 is precipitated as a reactant in the liquid. The precipitated vanadium oxide composite 100 is separated from the liquid. In this manner, the vanadium oxide composite 100 is obtained. The vanadium oxide composite 100 may then be calcined.

[0052] 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.

[0053] The composition of the vanadium oxide 101 in the vanadium oxide composite 100 is determined by quantitative analysis. For example, the value of "x" in composition formula (1) is quantified by high-frequency inductively coupled plasma (ICP) atomic emission spectrometry. The value of "x" in composition formula (1) can be determined from the amount of M in the vanadium oxide 101.

[0054] In the vanadium oxide composite 100 produced by the above method, at least a portion of the surface of the vanadium oxide-containing particle 101, which is a secondary particle, is coated with the conductive material 102. The conductive material 102 is also present at the interface between the primary particles that make up the particle 101.

[0055] Second Embodiment A second embodiment will be described below, and the matters described in the first embodiment will be omitted as appropriate.

[0056] The battery according to the second embodiment includes a positive electrode, an electrolyte layer, and a negative electrode. The electrolyte layer is disposed between the positive electrode and the negative electrode. The negative electrode includes the vanadium oxide composite according to the first embodiment.

[0057] The battery according to the second embodiment has excellent charge / discharge characteristics.

[0058] FIG. 2 shows a cross-sectional view of a battery 1000 according to a second embodiment.

[0059] The battery 1000 includes a positive electrode 201, an electrolyte layer 202, and a negative electrode 203. The electrolyte layer 202 is disposed between the positive electrode 201 and the negative electrode 203.

[0060] The positive electrode 201 contains positive electrode active material particles 204 and solid electrolyte particles 206 .

[0061] The electrolyte layer 202 contains an electrolyte material, such as a solid electrolyte material.

[0062] The negative electrode 203 contains negative electrode active material particles 205 and solid electrolyte particles 206 .

[0063] The negative electrode active material particles 205 are particles containing the vanadium oxide composite 100 according to the first embodiment. The negative electrode active material particles 205 may be particles containing the vanadium oxide composite 100 as a main component. Particles containing the vanadium oxide composite 100 as a main component refer to particles in which the vanadium oxide composite 100 is the component contained in the largest amount by mass ratio. The negative electrode active material particles 205 may be particles made of the vanadium oxide composite 100. The shape of the negative electrode active material particles 205 is, for example, spherical.

[0064] The negative electrode active material particles 205 may have a median diameter of 0.1 μm or more and 100 μm or less. When the negative electrode active material particles 205 have a median diameter of 0.1 μm or more, the negative electrode active material particles 205 and the solid electrolyte particles 206 can be well dispersed in the negative electrode 203. This improves the charge / discharge characteristics of the battery 1000. When the negative electrode active material particles 205 have a median diameter of 100 μm or less, the Li diffusion rate within the negative electrode active material particles 205 improves. This allows the battery 1000 to operate at a high output.

[0065] In the present disclosure, the median particle size refers to the particle size (d50) corresponding to 50% cumulative volume in the 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.

[0066] The negative electrode active material particles 205 may have a larger median diameter than the solid electrolyte particles 206. This allows the negative electrode active material particles 205 and the solid electrolyte particles 206 to be dispersed well.

[0067] In order to improve the energy density and output of the battery 1000, in the negative electrode 203, the ratio of the volume of the negative electrode active material particles 205 to the sum of the volume of the negative electrode active material particles 205 and the volume of the solid electrolyte particles 206 may be 0.30 or more and 0.95 or less.

[0068] To improve the energy density and output of the battery 1000, the negative electrode 203 may have a thickness of 10 μm or more and 500 μm or less.

[0069] The solid electrolyte particles 206 contained in the negative electrode 203 may be a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, or a polymer solid electrolyte.

[0070] 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.

[0071] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, and Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 And so on.

[0072] Examples of halide solid electrolytes include Li b Me c Y d X6, where the mathematical formula: b + mc + 3d = 6, and d > 0 is satisfied. Me is at least one element selected from the group consisting of metal elements and metalloid elements other than Li and Y. 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.

[0073] "Metalloid elements" are B, Si, Ge, As, Sb, and Te. "Metal elements" are all elements in groups 1 to 12 of the periodic table (except H) and all elements in groups 13 to 16 of the periodic table (except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0074] In order to increase the ionic conductivity of the halide solid electrolyte, Me may be at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0075] Examples of halide solid electrolytes include 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. 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.

[0076] Examples of oxide solid electrolytes include: (i) NASICON-type solid electrolytes such as LiTi2(PO4)3 and elemental substitution products thereof; (ii) perovskite-type solid electrolytes such as (LaLi)TiO3; (iii) Li 14 ZnGeO 16 LISICON-type solid electrolytes such as LiSiO, LiGeO, and elemental substitution products thereof; (iv) LiLaZrO 12 (v) Li3PO4 or an N-substituted LiPO4, or a garnet-type solid electrolyte such as LiPO4, LiPO4, or an element-substituted LiPO4.

[0077] 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.

[0078] Examples of lithium salts include LiPF, LiBF, LiSbF, LiAsF, LiSOCF, LiN(SOCF), LiN(SOCF), LiN(SOCF)(SOCF), LiC(SOCF), etc. 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.

[0079] The positive electrode 201 contains a material capable of absorbing and releasing metal ions such as lithium ions, and also contains, for example, a positive electrode active material (for example, positive electrode active material particles 204).

[0080] Examples of the positive electrode active material include lithium-containing transition metal oxides, transition metal fluorides, polyanion materials, fluorinated polyanion materials, transition metal sulfides, transition metal oxysulfides, transition metal oxynitrides, etc. Examples of lithium-containing transition metal oxides include Li(Ni,Co,Al)O, Li(Ni,Co,Mn)O, LiCoO, etc.

[0081] In the present disclosure, "(A, B, C)" means "at least one selected from the group consisting of A, B, and C."

[0082] From the viewpoint of cost and safety of the battery 1000, lithium phosphate or lithium-containing transition metal phosphate may be used as the positive electrode active material.

[0083] The positive electrode active material particles 204 may have a median diameter of 0.1 μm or more and 100 μm or less. When the positive electrode active material particles 204 have a median diameter of 0.1 μm or more, the positive electrode active material particles 204 and the solid electrolyte particles 206 can be well dispersed in the positive electrode 201. This improves the charge / discharge characteristics of the battery 1000. When the positive electrode active material particles 204 have a median diameter of 100 μm or less, the Li diffusion rate within the positive electrode active material particles 204 improves. This allows the battery 1000 to operate at high output.

[0084] The positive electrode active material particles 204 may have a larger median diameter than the solid electrolyte particles 206. This allows the positive electrode active material particles 204 and the solid electrolyte particles 206 to be dispersed well.

[0085] In order to improve the energy density and output of the battery 1000, in the positive electrode 201, the ratio of the volume of the positive electrode active material particles 204 to the sum of the volume of the positive electrode active material particles 204 and the volume of the solid electrolyte particles 206 may be 0.30 or more and 0.95 or less.

[0086] To improve the energy density and output of the battery 1000, the positive electrode 201 may have a thickness of 10 μm or more and 500 μm or less.

[0087] The solid electrolyte particles 206 contained in the positive electrode 201 may be a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, an organic polymer solid electrolyte, or the like.

[0088] 3 shows a cross-sectional view of an electrode material 200 according to a second embodiment. The electrode material 200 may be contained in at least one selected from the group consisting of a positive electrode 201 and a negative electrode 203. The electrode material 200 includes electrode active material particles 208 and solid electrolyte particles 206.

[0089] The electrode material 200 is contained in, for example, the positive electrode 201. In order to prevent the solid electrolyte particles 206 from reacting with the positive electrode active material (i.e., the electrode active material particles 208), at least a portion of the surface of the electrode active material particles 208 may be coated with a coating material 209. With this configuration, an increase in the reaction overvoltage of the battery 1000 can be suppressed.

[0090] The electrode material 200 may be contained in the negative electrode 203. In order to prevent the solid electrolyte particles 206 from reacting with the negative electrode active material (i.e., the electrode active material particles 208), at least a portion of the surface of the electrode active material particles 208 may be coated with a coating material 209. With this configuration, an increase in the reaction overvoltage of the battery 1000 can be suppressed.

[0091] The vanadium oxide composite 100 according to the first embodiment contained in the negative electrode 203 may be further coated with a coating material 209. With such a configuration, an increase in the reaction overvoltage of the battery 1000 can be suppressed.

[0092] Examples of the coating material 209 include a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, and a halide solid electrolyte.

[0093] The coating material 209 may be a halide solid electrolyte material or an oxide solid electrolyte material. The halide solid electrolyte material may contain F. This configuration improves the stability of the coating material 209 at high potentials. This allows the battery 1000 to have high charge / discharge efficiency. The oxide solid electrolyte may be lithium niobate or a polyanion material, which has excellent stability even at high potentials. This configuration allows the battery 1000 to have high charge / discharge efficiency.

[0094] 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.

[0095] The electrolyte layer 202 contains an electrolyte material. The electrolyte material is, for example, a solid electrolyte material. The electrolyte layer 202 may be a solid electrolyte layer. The solid electrolyte material contained in the electrolyte layer 202 may be a sulfide solid electrolyte, a halide solid electrolyte, or a polymer solid electrolyte.

[0096] The electrolyte layer 202 may have a thickness of 1 μm or more and 100 μm or less. When the electrolyte layer 202 has a thickness of 1 μm or more, the cathode 201 and the anode 203 are less likely to short-circuit. When the electrolyte layer 202 has a thickness of 100 μm or less, the battery 1000 can operate at high power.

[0097] At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a non-aqueous electrolyte, a gel electrolyte, or an ionic liquid in order to facilitate the exchange of lithium ions and improve the output characteristics of the battery 1000.

[0098] The nonaqueous electrolyte contains a nonaqueous solvent and a lithium salt dissolved in the nonaqueous solvent. Examples of the nonaqueous solvent include 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 solvents include ethylene carbonate, propylene carbonate, and butylene carbonate. Examples of the chain carbonate ester solvents include dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. Examples of the cyclic ether solvents include tetrahydrofuran, 1,4-dioxane, and 1,3-dioxolane. Examples of the chain ether solvents include 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.

[0099] Examples of lithium salts include LiPF, LiBF, LiSbF, LiAsF, LiSOCF, LiN(SOCF), LiN(SOCF), LiN(SOCF)(SOCF), 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.

[0100] The gel electrolyte may be a polymer material impregnated with a non-aqueous electrolyte solution, such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or a polymer having an ethylene oxide bond.

[0101] Examples of cations contained in the ionic liquid include: (i) aliphatic chain quaternary salts such as tetraalkylammonium and tetraalkylphosphonium; (ii) aliphatic cyclic ammoniums such as pyrrolidiniums, morpholiniums, imidazoliniums, tetrahydropyrimidiniums, piperaziniums, and piperidiniums; and (iii) nitrogen-containing heterocyclic aromatic cations such as pyridiniums and imidazoliums.

[0102] 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) - , C(SO2CF3)3 - And so on.

[0103] The ionic liquid may contain a lithium salt.

[0104] At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a binder for the purpose of improving adhesion between particles.

[0105] 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. Mixtures of two or more of the above materials may also be used.

[0106] At least one selected from the positive electrode 201 and the negative electrode 203 may further contain a conductive additive for the purpose of increasing electronic conductivity.

[0107] Examples of the conductive additive include: (i) graphites such as natural graphite and artificial graphite, (ii) carbon blacks such as acetylene black and ketjen black, (iii) conductive fibers such as carbon fiber and metal fiber, (iv) carbon fluoride, (v) metal powders such as aluminum, (vi) conductive whiskers such as zinc oxide and potassium titanate, (vii) conductive metal oxides such as titanium oxide, or (viii) conductive polymer compounds such as polyaniline, polypyrrole, and polythiophene. To reduce costs, the conductive additives (i) or (ii) above may be used.

[0108] 2, the negative electrode 203 may further contain a conductive additive 207 in addition to the negative electrode active material particles 205. With such a configuration, the electronic conductivity of the negative electrode 203 can be further improved.

[0109] Examples of the material of the conductive additive 207 are as described above.

[0110] In the negative electrode 203, the ratio of the volume of the conductive additive 207 to the total volume of the negative electrode active material particles 205 and the conductive additive 207 may be 0.01 or more and 0.4 or less. With such a configuration, the electronic conductivity of the negative electrode 203 can be further improved.

[0111] When the negative electrode 203 further contains a conductive additive 207, in the vanadium oxide composite 100 according to the first embodiment as the negative electrode active material particles 205, the coverage R of the conductive material 102 on the surface of the particles 101 containing the vanadium oxide represented by the composition formula (1) above may be 30% or more and 60% or less. With this configuration, the effect of improving the electronic conductivity of the conductive additive 207 in the negative electrode 203 can be easily obtained. As a result, the capacity of the battery 1000 is further improved.

[0112] When the coverage R of the vanadium oxide composite 100 as the negative electrode active material particles 205 is 30% or more and 60% or less, the content of the conductive additive 207 may be 2.0% or more and 5.0% or less by weight. With this configuration, the effect of improving the electronic conductivity of the conductive additive 207 in the negative electrode 203 can be more easily obtained.

[0113] In the present disclosure, the content of the conductive additive 207 refers to the weight percentage relative to the NH 4 VO 3 used in producing the vanadium oxide contained in the vanadium oxide composite 100 .

[0114] Examples of the shape of the battery according to the second embodiment include coin type, cylindrical type, square type, sheet type, button type, flat type, and laminate type.

[0115] The battery according to the second 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 a known method, fabricating a laminate in which the positive electrode, the electrolyte layer, and the negative electrode are arranged in this order.

[0116] (Other Embodiments) (Additional Notes) The above description of the embodiments discloses the following techniques.

[0117] (Technology 1) A vanadium oxide composite comprising: particles containing vanadium oxide; and a conductive material covering at least a portion of the surface of the particles, wherein a coverage of the conductive material on the surface of the particles is 30% or more; and the average particle diameter is 0.5 μm or more and 5.0 μm or less.

[0118] The vanadium oxide composite according to Technology 1 is a novel substance that can be used as a battery material. The vanadium oxide composite according to Technology 1 can be used, for example, as a negative electrode active material. The vanadium oxide composite according to Technology 1 is suitable for improving, for example, the charge / discharge characteristics of a battery, and is suitable for improving, for example, the capacity of a battery.

[0119] (Technology 2) The vanadium oxide composite according to Technology 1, wherein the conductive material is a carbon material. With this configuration, the vanadium oxide composite can be produced at lower cost.

[0120] (Technology 3) The vanadium oxide composite according to Technology 1 or 2, wherein the average particle size is 0.55 μm or more and 4.5 μm or less. With this configuration, the vanadium oxide composite can further improve the capacity of a battery.

[0121] (Technology 4) The vanadium oxide composite according to any one of Technologies 1 to 3, wherein the average particle size is 0.6 μm or more and 4.0 μm or less. With this configuration, the vanadium oxide composite can further improve the capacity of a battery.

[0122] (Technology 5) The vanadium oxide composite according to any one of Technologies 1 to 4, wherein the average particle size is 0.8 μm or more and 3.0 μm or less. With this configuration, it is possible to promote insertion and desorption of Li into and from the vanadium oxide composite while ensuring electronic conductivity.

[0123] (Technology 6) The vanadium oxide composite according to any one of Technologies 1 to 5, wherein the coverage is 40% or more. With this configuration, the vanadium oxide composite can further improve the capacity of the battery.

[0124] (Technology 7) The vanadium oxide composite according to any one of Technologies 1 to 6, wherein the coverage is 55% or more. With this configuration, the vanadium oxide composite can further improve the capacity of the battery.

[0125] (Technology 8) The vanadium oxide composite according to any one of Technologies 1 to 7, wherein the coverage is 70% or less. With this configuration, it is possible to promote insertion and desorption of Li into the vanadium oxide composite while ensuring electronic conductivity.

[0126] (Technology 9) The vanadium oxide has the composition formula (1): Li 3+x V 1-x M x O4, wherein in composition formula (1), 0≦x<1 is satisfied, and M is at least one element selected from the group consisting of tetravalent metal elements and tetravalent metalloid elements. With this configuration, the vanadium oxide composite can further improve the capacity of a battery.

[0127] (Technology 10) The vanadium oxide composite according to Technology 9, wherein in the composition formula (1), 0<x<1 is satisfied. With this configuration, the capacity of a battery using the vanadium oxide composite is further improved.

[0128] (Technology 11) The vanadium oxide composite according to Technology 9 or 10, wherein in the composition formula (1), M contains Ti. With this configuration, the vanadium oxide composite can improve the capacity of a battery.

[0129] (Technology 12) A battery comprising: a positive electrode; a negative electrode; and an electrolyte layer disposed between the positive electrode and the negative electrode, wherein the negative electrode contains the vanadium oxide composite according to any one of Technologies 1 to 11.

[0130] The battery of Technology 12 has excellent charge and discharge characteristics.

[0131] (Technology 13) The battery according to Technology 12, wherein the negative electrode further contains a conductive additive. With this configuration, the electronic conductivity of the negative electrode can be further improved.

[0132] (Technology 14) The battery according to Technology 12, wherein the negative electrode further contains a conductive additive, and the coverage of the vanadium oxide composite is 30% or more and 60% or less. With this configuration, the conductive additive is likely to improve the electronic conductivity of the negative electrode, and as a result, the battery capacity is further improved.

[0133] (Technology 15) The battery according to Technology 14, wherein the content of the conductive additive is 2.0 wt % or more and 5.0 wt % or less. With this configuration, the effect of improving the electronic conductivity of the conductive additive in the negative electrode can be more easily obtained.

[0134] The present disclosure will be described in more detail below using examples and comparative examples. The vanadium oxide contained in the vanadium oxide composite of the examples has the composition formula (1): Li 3+x V 1-x M x It can be expressed as O4 (x=0).

[0135] Example 1 Preparation of Vanadium Oxide Composite: As vanadium oxide raw material powders, 1.47 g of lithium hydroxide monohydrate (LiOH·H2O: Fujifilm Wako Pure Chemical Industries, Ltd., Wako Special Grade) and 0.176 g of ammonium vanadate (NH4VO3: Fujifilm Wako Pure Chemical Industries, Ltd., Wako Special Grade) were prepared, respectively, so that the molar ratio of LiOH·H2O:NH4VO3 was 23.3:1. As a conductive material, 2.5 mL of graphene oxide dispersion (Sigma-Aldrich, graphene oxide concentration: 0.004 g / mL) was prepared so that the weight of graphene oxide in the dispersion was 5.7 wt% relative to the weight of NH4VO3. These raw materials were dissolved in 37.5 mL of purified water to obtain a raw material solution. The raw material solution was subjected to a dispersion treatment by ultrasonic irradiation using an ultrasonic disperser (UH-50, manufactured by SMT Corporation) for 90 minutes to obtain a dispersion solution. The dispersion solution was placed in an aluminum dish and heated in the atmosphere for 50 minutes in an aluminum bead bath set at 150°C to obtain a heated solution. The heated solution was centrifuged to separate a supernatant liquid and a precipitate. The precipitate was washed with purified water and then dried in a vacuum at 70°C for 1 hour to obtain a dry powder. The dry powder was crushed in a mortar and then fired in a nitrogen atmosphere at 600°C for 2 hours. The heating rate during firing was 10°C per minute and the cooling rate was 5°C per minute. After firing, the weight of the powder obtained was 0.2 g. In this manner, the vanadium oxide composite of Example 1 was produced. In the vanadium oxide composite of Example 1, the vanadium oxide had a composition in which Li was in excess in composition formula (1).

[0136] In the vanadium oxide composite of Example 1, the conductive material covered at least a portion of the surface of the vanadium oxide-containing particle. The coverage R of the conductive material on the surface of the vanadium oxide-containing particle of Example 1 was 35%.

[0137] The coverage ratio R was determined by the method described above. Specifically, vanadium oxide composite particles and zinc powder were first mixed in a mortar to obtain a mixed powder. The mixed powder was pressure-molded to form a pellet. Next, the pellet was processed using an ion milling device (ArBlade 5000, manufactured by Hitachi High-Technologies Corporation) to form a smooth cross section. The formed cross section was observed with a field emission scanning electron microscope (FE-SEM: Regulus 8230, manufactured by Hitachi High-Technologies Corporation) to obtain an FE-SEM image. For 50 vanadium oxide composite particles included in the FE-SEM image, the perimeter P and the length C of the portion covered with the conductive material were measured. The average of the values ​​calculated by 100 × C / P was considered to be the coverage ratio R.

[0138] It should be noted that some of the conductive materials contained in the vanadium oxide composite had thicknesses that made it difficult to confirm using FE-SEM. For example, when the cross section of a pellet was observed using a transmission electron microscope (TEM), it was confirmed that conductive materials with a thickness of 3 nm or less were present not only on the surfaces of the particles containing vanadium oxide but also inside the particles containing vanadium oxide, i.e., at the interfaces of the primary particles. Therefore, for example, when calculating the coverage rate R, the target is a conductive material with a thickness exceeding 3 nm.

[0139] The average particle size of the particles of the vanadium oxide composite of Example 1 was 1.1 μm.

[0140] The average particle size of the vanadium oxide composite particles was determined by the method described above. Specifically, first, the vanadium oxide composite particles and zinc powder were mixed in a mortar to obtain a mixed powder. The mixed powder was pressure-molded to form a pellet. Next, the pellet was processed using an ion milling device (ArBlade 5000, manufactured by Hitachi High-Technologies Corporation) to form a smooth cross section. The formed cross section was observed with a field emission scanning electron microscope (FE-SEM: Regulus 8230, manufactured by Hitachi High-Technologies Corporation) to obtain an FE-SEM image. The circle-equivalent diameter of 50 vanadium oxide composite particles included in the FE-SEM image was measured. The average of the circle-equivalent diameters was considered to be the average particle size.

[0141] [Battery Fabrication] The vanadium oxide composite of Example 1 and the solid electrolyte Li3PS4 were prepared in a volume ratio of 60:40 in an argon atmosphere with a dew point of -60°C or less. These materials were mixed in an agate mortar. In this way, a negative electrode mixture was obtained.

[0142] A stack of 80 mg of Li3PS4 solid electrolyte and 6.5 mg of the negative electrode mixture was placed in an insulating tube with an inner diameter of 9.5 mm. A pressure of 360 MPa was applied to the stack to form an electrolyte layer and a negative electrode. The electrolyte layer had a thickness of 500 μm.

[0143] Next, Li (thickness: 300 μm) was laminated on the electrolyte layer, and a pressure of 80 MPa was applied to form a positive electrode.

[0144] Next, current collectors made of stainless steel were attached to the positive and negative electrodes, respectively, and current collecting leads were attached to each current collector.

[0145] Finally, an insulating ferrule was used to isolate the inside of the insulating cylinder from the outside atmosphere, and the inside of the cylinder was sealed.

[0146] As described above, a battery of Example 1 was fabricated. The battery of Example 1 is a single-electrode test cell having a negative electrode as a working electrode and a positive electrode as a counter electrode, and is used to test the performance of the negative electrode. Specifically, the negative electrode to be tested is used as the working electrode, and an appropriate active material in an amount sufficient to cover the reaction of the working electrode is used as the counter electrode. Since this test cell is intended to test the performance of the negative electrode, metallic Li was used as the counter electrode. The negative electrode whose performance has been tested using such a 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 embodiment, such as a transition metal oxide containing Li.

[0147] [Charge / Discharge Test] A charge / discharge test was carried out using the battery of Example 1 as follows. As described above, the battery of Example 1 is a single-electrode test cell, corresponding to a half cell of the negative electrode. Therefore, in the battery of Example 1, the direction in which Li ions are inserted into the negative electrode and the potential of the half cell decreases is referred to as charging, and the direction in which the potential increases is referred to as discharging. That is, in the battery of Example 1, charging is essentially discharging (i.e., in the case of a full cell), and discharging in the battery of Example 1 is essentially charging. Hereinafter, unless otherwise specified, charging refers to charging in a half cell, and discharging refers to discharging in a half cell.

[0148] The battery was placed in a thermostatic chamber maintained at 25°C.

[0149] The battery was discharged at a constant current value corresponding to a 0.1 C rate (10-hour rate) relative to the theoretical capacity of the battery, and the discharge was terminated when the voltage reached 0.3 V. Next, the battery was charged at a constant current value corresponding to a 0.05 C rate, and the charge was terminated when the voltage reached 2.5 V. This charge / discharge cycle is called the "initial charge / discharge."

[0150] After the initial charge / discharge, the battery was discharged at a constant current value corresponding to a 0.1 C rate relative to the theoretical capacity of the battery, and the discharge was terminated when the voltage reached 0.3 V. Next, the battery was charged at a constant current value corresponding to a 0.05 C rate, and the charge was terminated when the voltage reached 2.5 V. This charge / discharge cycle is called the "secondary charge / discharge."

[0151] After the secondary charge / discharge, the battery was discharged at a constant current value corresponding to a 10 C rate relative to the theoretical capacity of the battery, and discharge was terminated when the voltage reached 0.3 V. Next, the battery was charged at a constant current value corresponding to a 0.05 C rate, and charging was terminated when the voltage reached 2.5 V. This charge / discharge cycle is referred to as "10 C charge / discharge." The discharge capacity when discharged at a constant current of 10 C rate during the 10 C charge / discharge is referred to as "10 C discharge capacity."

[0152] 4 is a graph showing the initial discharge characteristics and 10 C discharge characteristics of the battery of Example 1. In FIG. 4, the horizontal axis represents discharge capacity (mAh / g) and the vertical axis represents voltage (V). As a result of carrying out a series of charge / discharge tests including initial charge / discharge, secondary charge / discharge, and 10 C charge / discharge, the battery of Example 1 had a 10 C discharge capacity of 91.2 mAh / g.

[0153] (Examples 2 to 4, Comparative Examples 1 to 3) [Preparation of Vanadium Oxide Composite] In Example 2, 3.75 mL of graphene oxide dispersion was prepared so that the weight of graphene oxide present in the dispersion was 8.5 wt % relative to the weight of NH4VO3. Furthermore, all raw materials were dissolved in 36.25 mL of purified water to obtain a raw material solution. Except for these, the vanadium oxide composite of Example 2 was obtained in the same manner as in Example 1. The coverage R of Example 2 was 61%. The average particle size of the particles of the vanadium oxide composite of Example 2 was 1.1 μm.

[0154] In Example 3, 5 mL of graphene oxide dispersion was prepared so that the weight of graphene oxide present in the dispersion was 11.4 wt % relative to the weight of NH4VO3. Furthermore, all raw materials were dissolved in 35 mL of purified water to obtain a raw material solution. Except for these, the vanadium oxide composite of Example 3 was obtained in the same manner as in Example 1. The coverage R of Example 3 was 81%. The average particle size of the vanadium oxide composite particles of Example 3 was 1.2 μm.

[0155] In Example 4, 3.75 mL of graphene oxide dispersion was prepared so that the weight of graphene oxide present in the dispersion was 8.5 wt % relative to the weight of NH4VO3. Furthermore, all raw materials were dissolved in 76.25 mL of purified water to obtain a raw material solution. Except for these, the vanadium oxide composite of Example 4 was obtained in the same manner as in Example 1. The coverage ratio R of Example 4 was 53%. The average particle size of the vanadium oxide composite particles of Example 2 was 3.4 μm.

[0156] In Comparative Example 1, no graphene oxide dispersion water was used. Furthermore, all raw materials were dissolved in 40 mL of purified water to obtain a raw material solution. Except for these, the vanadium oxide composite of Comparative Example 1 was obtained in the same manner as in Example 1. That is, the surface of the vanadium oxide composite of Comparative Example 1 did not have a portion coated with a conductive material. The average particle size of the particles of the vanadium oxide composite of Comparative Example 1 was 1.7 μm.

[0157] In Comparative Example 2, 3.75 mL of graphene oxide dispersion was prepared so that the weight of graphene oxide present in the dispersion was 8.5 wt % relative to the weight of NH4VO3. Furthermore, all raw materials were dissolved in 16.25 mL of purified water to obtain a raw material solution. Except for these, the vanadium oxide composite of Comparative Example 1 was obtained in the same manner as in Example 1. The coverage ratio R of Comparative Example 2 was 46%. The average particle size of the vanadium oxide composite particles of Comparative Example 2 was 0.4 μm.

[0158] In Comparative Example 3, the raw material solution was not subjected to dispersion treatment by ultrasonic irradiation, and with the exception of this, a vanadium oxide composite of Comparative Example 3 was obtained in the same manner as in Example 1. The coverage R of Comparative Example 3 was 44%. The average particle size of the particles of the vanadium oxide composite of Comparative Example 3 was 6.0 μm.

[0159] [Fabrication of Battery] Using the vanadium oxide composites of Examples 2 to 4 and Comparative Examples 2 to 3, batteries of Examples 2 to 4 and Comparative Examples 2 to 3 were fabricated in the same manner as in Example 1.

[0160] In the preparation of the battery of Comparative Example 1, the vanadium oxide composite of Comparative Example 1 and the solid electrolyte Li3PS4 were prepared in a volume ratio of 60:40 in an argon atmosphere having a dew point of -60°C or lower. Additionally, acetylene black was prepared as a conductive additive. The acetylene black was prepared so that its concentration was 5.7 wt % relative to the NH4VO3 used in preparing the vanadium oxide. These materials were mixed in an agate mortar to obtain the negative electrode mixture of Comparative Example 1. The battery of Comparative Example 1 was prepared in the same manner as in Example 1, except that the negative electrode mixture of Comparative Example 1 was used as the negative electrode mixture.

[0161] [Charge / Discharge Test] The batteries of Examples 2 to 4 and Comparative Examples 1 to 3 were subjected to a charge / discharge test in the same manner as in Example 1, and the 10 C discharge capacity was measured. The measurement results are shown in Table 1.

[0162]

[0163] (Discussion) As can be seen from a comparison of the 10 C discharge capacities of Examples 1 to 4 and Comparative Examples 1 to 3, the batteries of Examples 1 to 4 using vanadium oxide composites with a coverage R of 30% or more and an average particle size of 0.5 μm or more and 5.0 μm or less had high discharge capacities even at a high rate of 10 C.

[0164] The weight of graphene oxide used in the vanadium oxide composite of Example 1 (5.7 wt%) was the same as the weight of acetylene black (5.7 wt%) used in the negative electrode mixture of Comparative Example 1. However, the battery of Example 1 had a higher 10 C discharge capacity than the battery of Comparative Example 1. This result shows that a higher 10 C discharge capacity can be obtained in a battery when the conductive material is present in a form that coats the surfaces of particles containing vanadium oxide, rather than being dispersed in the negative electrode mixture as a conductive additive.

[0165] It is presumed that when the average particle size is smaller than 0.5 μm, as in the vanadium oxide composite of Comparative Example 2, aggregation of the vanadium oxide composite occurs during preparation of the negative electrode mixture, reducing the dispersibility of the negative electrode mixture. Therefore, it is presumed that the 10 C discharge capacity was low in the battery of Comparative Example 2 due to an increase in the electronic resistance of the negative electrode mixture and a decrease in Li ion conductivity.

[0166] It is presumed that the contact area between the vanadium oxide composite and the solid electrolyte in the negative electrode mixture was reduced when the average particle size was greater than 5.0 μm, as in the vanadium oxide composite of Comparative Example 3. Therefore, it is presumed that the 10 C discharge capacity was low in the battery of Comparative Example 3 due to the reduced Li ion conductivity of the negative electrode mixture.

[0167] As can be seen from a comparison of the 10 C discharge capacities of Examples 1 to 4 and Comparative Examples 1 to 3, when the composition of composition formula (1) has an excess amount of Li, the vanadium oxide composite contains a large amount of Li, which is responsible for charging and discharging in the battery. It is therefore presumed that the 10 C discharge capacities were particularly high in the batteries of Examples 1 to 4. However, if Li is too excessive, it is presumed that Li is too densely packed and cannot diffuse satisfactorily during charging and discharging in the battery, resulting in a decrease in Li ion conductivity.

[0168] As in Examples 1 to 3, a negative electrode mixture with excellent electronic conductivity and Li ion conductivity was obtained by using a vanadium oxide composite in which the surface of the vanadium oxide was coated with a conductive material at a suitable ratio and which had a suitable average particle size. By using such a negative electrode mixture, a battery with a high discharge capacity even at a high rate of 10C was fabricated.

[0169] [Fabrication of Batteries] Using the vanadium oxide composites of Examples 1 to 3, batteries of Examples 1-1, 1-2, 1-3, Example 2-1, and Example 3-1 were fabricated by the following method.

[0170] In fabricating the battery of Example 1-1, the vanadium oxide composite of Example 1 and the solid electrolyte Li3PS4 were prepared in a volume ratio of 60:40 in an argon atmosphere having a dew point of -60°C or lower. Additionally, acetylene black was prepared as a conductive additive. The acetylene black was prepared so that its concentration was 2.3 wt % relative to the NH4VO3 used in preparing the vanadium oxide. These materials were mixed in an agate mortar to obtain the negative electrode mixture of Example 1-1. The battery of Example 1-1 was fabricated in the same manner as Example 1, except that the negative electrode mixture of Example 1-1 was used as the negative electrode mixture.

[0171] In the preparation of the battery of Example 1-2, acetylene black was prepared so that its content was 3.5 wt % relative to the NH4VO3 used in preparing the vanadium oxide. Except for this, the battery of Example 1-2 was obtained in the same manner as in Example 1-1.

[0172] In the preparation of the battery of Example 1-3, acetylene black was prepared so that its content was 4.6 wt % relative to the NH4VO3 used in preparing the vanadium oxide. Except for this, the battery of Example 1-3 was obtained in the same manner as in Example 1-1.

[0173] In the production of the battery of Example 2-1, the vanadium oxide composite of Example 2 was used as the vanadium oxide composite. In addition, acetylene black was prepared so that its content was 2.3 wt % relative to the NH4VO3 used in producing the vanadium oxide. With these exceptions, the battery of Example 2-1 was obtained in the same manner as in Example 1-1.

[0174] In the production of the battery of Example 3-1, the vanadium oxide composite of Example 3 was used as the vanadium oxide composite. Also, acetylene black was prepared so that its content was 2.3 wt % relative to the NH4VO3 used in producing the vanadium oxide. With these exceptions, the battery of Example 3-1 was obtained in the same manner as in Example 1-1.

[0175] [Charge / Discharge Test] The batteries of Examples 1-1, 1-2, 1-3, 2-1, and 3-1 were subjected to a charge / discharge test in the same manner as in Example 1, and the 10 C discharge capacity was measured. The measurement results are shown in Table 2.

[0176]

[0177] (Discussion) As can be seen from a comparison of the 10 C discharge capacity of Example 1 with that of Examples 1-1 to 1-3, when the negative electrode contained a conductive additive, the 10 C discharge capacity of the battery was further improved by ensuring that the coverage rate R of the vanadium oxide composite was 30% or more and 60% or less. On the other hand, as is clear from a comparison of the 10 C discharge capacity of Example 2 with that of Example 2-1, and a comparison of the 10 C discharge capacity of Example 3 with that of Example 3-1, when the negative electrode contained a conductive additive, the 10 C discharge capacity of the battery tended to decrease when the coverage rate R of the vanadium oxide composite exceeded 60%. These results demonstrate that when the negative electrode contained a conductive additive, the effect of improving the electronic conductivity of the conductive additive in the negative electrode was easily achieved by ensuring that the coverage rate R of the vanadium oxide composite was 30% or more and 60% or less.

[0178] As described above, the vanadium oxide composite according to the present disclosure is suitable for providing a battery having excellent charge / discharge characteristics even at high rates.

[0179] The vanadium oxide composite of the present disclosure is used as a battery material, for example, as a material for all-solid-state lithium-ion secondary batteries.

Claims

1. particles containing vanadium oxide; a conductive material that coats at least a portion of the surface of the particle; Equipped with a coverage of the conductive material on the surface of the particle is 30% or more; The average particle size is 0.5 μm or more and 5.0 μm or less, the particles containing vanadium oxide are secondary particles formed by aggregation of a plurality of primary particles, the conductive material is present on the surface of the vanadium oxide-containing particle and on the interface between the plurality of primary particles constituting the vanadium oxide-containing particle; Vanadium oxide complex.

2. The conductive material is a carbon material. The vanadium oxide composite of claim 1 .

3. The average particle size is 0.55 μm or more and 4.5 μm or less. The vanadium oxide composite of claim 1 .

4. The average particle size is 0.6 μm or more and 4.0 μm or less. The vanadium oxide composite of claim 1 .

5. The average particle size is 0.8 μm or more and 3.0 μm or less. The vanadium oxide composite of claim 1 .

6. The coverage is 40% or more. The vanadium oxide composite of claim 1 .

7. The coverage is 55% or more. The vanadium oxide composite of claim 1 .

8. The coverage is 70% or less. The vanadium oxide composite of claim 1 .

9. The vanadium oxide has the composition formula (1): Li 3+x V 1-x M x O 4 is expressed as Here, in the composition formula (1), 0≦x<1 is satisfied, and M is at least one element selected from the group consisting of tetravalent metal elements and tetravalent metalloid elements; The vanadium oxide composite of claim 1 .

10. In the composition formula (1), 0<x<1 is satisfied. The vanadium oxide composite of claim 9.

11. In the composition formula (1), M contains Ti. The vanadium oxide composite of claim 9.

12. A positive electrode and a negative electrode; an electrolyte layer disposed between the positive electrode and the negative electrode; Equipped with The negative electrode comprises the vanadium oxide composite according to any one of claims 1 to 11. battery.

13. The negative electrode further contains a conductive additive. The battery of claim 12.

14. The negative electrode further contains a conductive additive, The coverage of the vanadium oxide composite is 30% or more and 60% or less. The battery of claim 12.

15. The content of the conductive additive is 2.0% by weight or more and 5.0% by weight or less.

15. The battery of claim 14.