Vanadium oxide composite and battery using same

Abstract

This vanadium oxide composite is provided with particles containing a vanadium oxide, and a conductive material that covers at least a portion of the surface of the particles. The coverage of the conductive material on the surface of the particles is 30% or more. The vanadium oxide composite has an average particle diameter of 0.5 [mu] m or more and 5.0 [mu] m or less.

Description

Technical Field

[0001] This disclosure relates to vanadium oxide complexes and batteries using vanadium oxide complexes. Background Technology

[0002] Li3VO4 is attracting attention as a next-generation anode active material due to its low reaction potential and high capacity. Patent Document 1 discloses a non-aqueous secondary battery that uses Li3VO4 as the anode active material.

[0003] Patent document 2 discloses an energy storage device that uses a material containing lithium vanadium oxide and carbon as the negative electrode active material. The material has the following double-layer structure: the inner layer is formed by multiple particles of lithium vanadium oxide maintaining grain boundaries and aggregating together, and the outer shell wraps around the inner layer and at least a portion of the lithium vanadium oxide particles are connected by a grain boundary-free structure.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2008-77847 Patent Document 2: Japanese Patent Application Publication No. 2022-21220 Summary of the Invention

[0005] The problem that the invention aims to solve This disclosure provides a novel vanadium oxide composite that can be used as a battery material.

[0006] Methods for solving problems This disclosure relates to a vanadium oxide composite, wherein the vanadium oxide composite comprises: Particles containing vanadium oxide, and A conductive material covering at least a portion of the surface of the particles. The conductive material on the surface of the particle has a coverage rate of 30% or more. The average particle size is above 0.5 μm and below 5.0 μm.

[0007] Invention Effects This disclosure provides a novel vanadium oxide composite that can be used as a battery material. Attached Figure Description

[0008] Figure 1 A cross-sectional view showing the vanadium oxide composite 100 of the first embodiment.

[0009] Figure 2 A cross-sectional view showing the battery 1000 of the second embodiment.

[0010] Figure 3A cross-sectional view showing the electrode material 200 of the second embodiment.

[0011] Figure 4 This is a graph showing the initial discharge characteristics and 10C discharge characteristics of the battery in Example 1. Detailed Implementation

[0012] The embodiments of this disclosure will now be described with reference to the accompanying drawings. This disclosure is not limited to the following embodiments.

[0013] (First Embodiment) The vanadium oxide composite of the first embodiment comprises particles containing vanadium oxide and a conductive material covering at least a portion of the surface of the particles. The coverage of the conductive material on the surface of the particles is 30% or more. The average particle size of the vanadium oxide composite is 0.5 μm or more and 5.0 μm or less.

[0014] The vanadium oxide composite of the first embodiment can be used as a battery material. For example, the vanadium oxide composite of the first embodiment can be used as a negative electrode active material. For example, the vanadium oxide composite of the first embodiment can be used to obtain a battery with excellent charge-discharge characteristics. For example, the vanadium oxide composite of the first embodiment is suitable for improving battery capacity. An example of a battery is a solid-state battery. A solid-state battery can be a primary battery or a secondary battery.

[0015] Figure 1 A cross-sectional view showing the vanadium oxide composite 100 of the first embodiment.

[0016] The vanadium oxide composite 100 comprises vanadium oxide-containing particles 101 and a conductive material 102.

[0017] The conductive material 102 exhibits electronic conductivity. The conductive material 102 covers at least a portion of the surface of the vanadium oxide-containing particles 101. The coverage R of the conductive material 102 on the surface of the particles 101 is 30% or more. The coverage R can be 100% or less. With this configuration, numerous electronic conduction channels are formed between the vanadium oxide-containing particles 101 and the conductive material 102. As a result, the electronic conductivity of the vanadium oxide composite 100 is improved.

[0018] The coverage ratio R of the vanadium oxide complex 100 can be determined using granules, electrodes, or batteries (hereinafter referred to as granules, etc.) containing particles of the vanadium oxide complex 100, by the following method. First, the granules, etc., are processed using an ion milling device to form a smooth cross-section. The direction of the cross-section processing can be any direction of the granules, etc. The formed cross-section is observed using a scanning electron microscope (SEM) to obtain an SEM image. For N1 particles of vanadium oxide complex 100 contained 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 greater than or equal to 2, for example, N1 = 50. The average of the values ​​calculated by 100 × C / P is taken as the coverage ratio R. Furthermore, it is not necessary to observe all particles of vanadium oxide complex 100 contained in the formed cross-section. Even if only a portion of the formed cross-section is displayed in the SEM image, the coverage ratio R can be calculated from the N1 particles of vanadium oxide complex 100 contained in that portion. Furthermore, the conductive material 102, which can be observed using SEM, has a thickness exceeding 3 nm. Therefore, the conductive material 102 with a thickness exceeding 3 nm is considered when calculating the coverage R.

[0019] The coverage R can also be over 40%. Based on this composition, the vanadium oxide composite 100 can further improve the battery capacity.

[0020] The coverage R can also be above 55%. Based on this composition, the vanadium oxide composite 100 can further improve the battery capacity.

[0021] The coverage R can also be below 70%. With this configuration, electronic conductivity can be ensured while promoting the insertion / extraction of Li into the vanadium oxide complex 100.

[0022] The shape of the vanadium oxide complex 100 is not limited. Examples of this shape include needle-like, spherical, and ellipsoidal shapes. The vanadium oxide complex 100 can also be in particle form. The vanadium oxide complex 100 can also be formed into granular or plate-like shapes.

[0023] In this embodiment, the average particle size 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 and other materials can be well dispersed. These other materials are, for example, solid electrolytes.

[0024] The average particle size of the vanadium oxide complex 100 particles can be determined using granules containing vanadium oxide complex 100 particles by the following method. First, the granules are processed using an ion milling device to form a smooth cross-section. The direction of the cross-section processing can be any direction of the granules. The formed cross-section is observed using a scanning electron microscope (SEM) to obtain an SEM image. For N2 vanadium oxide complex 100 particles contained in the SEM image, their equivalent circle diameter is measured. N2 is an integer greater than or equal to 2, for example, N2 = 50. The average of the equivalent circle diameters is taken as the average particle size. Furthermore, it is not necessary to observe all vanadium oxide complex 100 particles contained in the formed cross-section. Even if only a portion of the formed cross-section is shown in the SEM image, the average particle size can be calculated from the N2 vanadium oxide complex 100 particles contained in that portion.

[0025] The average particle size of the vanadium oxide composite 100 can also be above 0.55 μm and below 4.5 μm. Based on this configuration, the vanadium oxide composite 100 can further improve the battery capacity.

[0026] The average particle size of the vanadium oxide composite 100 can also be above 0.6 μm and below 4.0 μm. Based on this configuration, the vanadium oxide composite 100 can further improve the battery capacity.

[0027] The average particle size of the vanadium oxide composite 100 can also be above 0.8 μm and below 3.0 μm. Based on this configuration, the vanadium oxide composite 100 can further improve the battery capacity.

[0028] In this embodiment, particle 101 contains vanadium oxide. Particle 101 may also be a particle containing vanadium oxide as a main component. Particle 101 containing vanadium oxide as a main component refers to a particle whose majority component by mass is vanadium oxide. Particle 101 may also be a particle composed of vanadium oxide. The shape of particle 101 is, for example, spherical.

[0029] The vanadium oxide contained in particle 101 can also be represented by the following composition formula (1). Here, in composition formula (1), 0 ≤ x < 1 can also be satisfied, and M can also be at least one element selected from tetravalent metal elements and tetravalent half-metal elements. According to such a composition, the vanadium oxide complex 100 can further improve the battery capacity.

[0030] Li 3+x V 1-x M x O4 (1) In composition (1), 0 < x < 1 can also be satisfied. According to this composition, the capacity of the battery using vanadium oxide complex 100 can be further improved. This is because by replacing the 5-valent V element with a 4-valent metal element and / or a 4-valent half-metal element, positively charged holes and / or Li ions become charge carriers, that is, the insertion / deintercalation of Li into vanadium oxide complex 100 becomes easier.

[0031] In composition (1), 0 < x ≤ 0.1 can also be satisfied. According to this configuration, the capacity of the battery using vanadium oxide complex 100 can be further improved. This is because, when composition (1) satisfies 0 < x ≤ 0.1, the substitution of tetravalent metal elements and / or tetravalent half-metal elements occurs while the crystal structure of vanadium oxide complex 100 remains unchanged, thereby making it easier for Li to be inserted / deintercalated into vanadium oxide complex 100.

[0032] As mentioned above, M can also be at least one element selected from tetravalent metals and tetravalent half-metals. Examples of tetravalent metals and tetravalent half-metals include Ti, Zr, Si, Ge, Sn, etc. If a pentavalent V element is substituted with a tetravalent metal and / or a tetravalent half-metal, then holes and / or Li ions become charge carriers. This further facilitates the insertion / deintercalation of Li into vanadium oxides.

[0033] In composition (1), M may also contain Ti. With this configuration, the vanadium oxide complex 100 can improve the battery capacity. Among tetravalent metal elements, the ionic radius of Ti is closest to that of V, which serves as the substitution source. Therefore, when M contains Ti, Ti substitution occurs while the crystal structure of the vanadium oxide complex 100 remains unchanged. As a result, the insertion / deintercalation of Li into the vanadium oxide complex 100 becomes further facilitated.

[0034] In composition (1), M can also be Ti. Based on this composition, the vanadium oxide composite 100 can further improve the battery capacity.

[0035] The vanadium oxide complex 100 may also contain an amount of Li exceeding its stoichiometric composition. That is, the vanadium oxide contained in the vanadium oxide complex 100 may also have an amount of Li exceeding the amount represented by (3+x) in the above compositional formula (1). In this case, the insertion / extraction of Li into the vanadium oxide complex 100 becomes even easier. As a result, the vanadium oxide complex 100 can further improve the battery capacity.

[0036] For example, the vanadium oxide contained in the vanadium oxide complex 100 can also be represented by the following composition formula (2).

[0037] Li 3+x+a V 1-x M x O 4+a / 2 (1) Here, in composition (2), 0 < a < 1 can also be satisfied. That is, vanadium oxide can also contain more Li and O than those derived from the stoichiometric composition. According to this composition, by satisfying 0 < a < 1 in composition (2), the capacity of a battery using, for example, vanadium oxide complex 100 can be increased. This is because the electronic conductivity of vanadium oxide is increased by the excess Li and O, thereby facilitating the insertion / extraction of Li into vanadium oxide complex 100. Stoichiometric composition refers to a composition in which the molar ratio of the elements constituting vanadium oxide is an integer multiple. For example, Li3VO4 has a stoichiometric composition.

[0038] In composition (2), the amount of Li and O represented by "a" can be incorporated into the interior of particle 101 or exist as a second phase different from the first phase constituting particle 101 on the exterior of particle 101. It should be noted that the vanadium oxides disclosed in Patent Documents 1 and 2 do not contain an amount of Li and O equivalent to that represented by "a".

[0039] The particles containing vanadium oxide 101 can be either primary particles or secondary particles formed by the condensation of multiple primary particles.

[0040] When the vanadium oxide-containing particle 101 is a secondary particle, the conductive material 102 can also exist inside the particle 101. That is, the conductive material 102 can also exist at the interface of the primary particles constituting the particle 101. If the conductive material 102 exists inside the particle 101, electrons can be transported into the particle 101, thereby further improving the electronic conductivity of the vanadium oxide composite 100.

[0041] The conductive material 102 exists inside the particles 101, for example, by observing the cross-section of the granules containing the vanadium oxide composite 100 using a transmission electron microscope (TEM).

[0042] The shape of the conductive material 102 itself is not particularly limited. For example, a thin film formed by the aggregation of conductive material 102 particles such as plates, needles, spheres, and ellipsoids can also cover at least a portion of the surface of the particles 101 containing vanadium oxide.

[0043] The average thickness of the thin film of conductive material 102 can also be less than 100 nm. With this configuration, the insertion / deintercalation of Li into the vanadium oxide composite 100 becomes easier. The average thickness of the thin film of conductive material 102 can be determined, for example, by observing the cross-section of particles containing vanadium oxide composite 100 using SEM or TEM.

[0044] The conductive material 102 may also contain carbon materials. With this configuration, the vanadium oxide composite 100 can be manufactured at low cost.

[0045] The conductive material 102 can also be a carbon material. Based on this configuration, the vanadium oxide composite 100 can be manufactured at a lower cost.

[0046] Examples of carbon materials include graphite (graphene), which has a six-membered ring network of carbon atoms, and amorphous carbon.

[0047] <Method for manufacturing vanadium oxide complexes> The vanadium oxide composite 100 of the first embodiment can be manufactured by the following method. As an example, the vanadium oxide composite having the following compositional formula (1): Li 3+x V 1-x M x The method for manufacturing vanadium oxide complex 100, which is represented by vanadium oxide particles 101 of O4 (x = 0), is described.

[0048] First, prepare a raw material powder of vanadium oxide to have the target composition. Examples of raw material powders of vanadium oxide 101 include oxides, hydroxides, carbonates, nitrates, organic salts, etc. At this time, it is also possible to prepare a raw material powder such that the amount of Li in the composition formula (1) is excessive. It is also possible to prepare a Li raw material powder such that it is an excess of the V raw material powder in a molar ratio of 3:1 relative to the stoichiometric ratio. For example, it is also possible to prepare a Li raw material powder in excess in a molar ratio range of 6:1 to 30:1 relative to the V raw material powder. As a Li raw material powder, lithium hydroxide monohydrate can be used, for example. As a V raw material powder, ammonium vanadate can be used, for example.

[0049] Furthermore, a raw material powder for conductive material 102 is prepared. The amount of the raw material powder for conductive material 102 relative to the amount of raw material powder V can be prepared in the range of 0.5% to 25% by mass, or in the range of 1% to 12% by mass. Graphene oxide can be used as a raw material powder for conductive material 102, for example.

[0050] Next, a mixture of Li raw material powder, V raw material powder, and conductive material 102 raw material powder is dissolved in a solvent to obtain a raw material solution. For example, water or an organic solvent can be used as the solvent. Examples of organic solvents include alcohols such as ethanol or ethylene glycol.

[0051] Next, in order to suppress the aggregation of products during subsequent thermal synthesis, the raw material solution is dispersed to obtain a dispersed solution. Dispersion treatment can be performed using, for example, an ultrasonic disperser or a pressure disperser.

[0052] Finally, the dispersion solution is heated to carry out thermal synthesis in the liquid phase. As a result, the powdered vanadium oxide complex 100 precipitates as a reactant in the liquid. The precipitated vanadium oxide complex 100 is then separated from the liquid. Thus, vanadium oxide complex 100 is obtained. The vanadium oxide complex 100 can also be subsequently calcined.

[0053] Here, the molar ratio of the raw material powder during mixing may not be the same as the molar ratio of the reactants. This is because in thermal synthesis, the raw material powder may sometimes not be incorporated into the reactants due to evaporation or other reasons.

[0054] The composition of vanadium oxide 101 in vanadium oxide complex 100 is determined by quantitative analysis. For example, the value of “x” in composition formula (1) can be quantified by high-frequency inductively coupled plasma (ICP) emission spectroscopy. The value of “x” in composition formula (1) can be determined by the amount of M in vanadium oxide 101.

[0055] In the vanadium oxide composite 100 manufactured by the above method, at least a portion of the surface of the vanadium oxide-containing particles 101, which are secondary particles, is covered by a conductive material 102. Furthermore, the conductive material 102 is also present at the interfaces of the primary particles constituting the particles 101.

[0056] (Second Implementation) The second embodiment will now be described. Matters described in the first embodiment may be omitted as appropriate.

[0057] The battery of 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 contains the vanadium oxide composite of the first embodiment.

[0058] The battery of the second embodiment has excellent charge and discharge characteristics.

[0059] Figure 2 A cross-sectional view showing the battery 1000 of the second embodiment.

[0060] The battery 1000 has 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.

[0061] The positive electrode 201 contains positive electrode active material particles 204 and solid electrolyte particles 206.

[0062] Electrolyte layer 202 contains an electrolyte material. The electrolyte material may be, for example, a solid electrolyte material.

[0063] The negative electrode 203 contains negative electrode active material particles 205 and solid electrolyte particles 206.

[0064] The negative electrode active material particle 205 is a particle containing the vanadium oxide complex 100 of the first embodiment. The negative electrode active material particle 205 may also be a particle containing the vanadium oxide complex 100 as a main component. A particle containing the vanadium oxide complex 100 as a main component means a particle whose most abundant component by mass ratio is the vanadium oxide complex 100. The negative electrode active material particle 205 may also be a particle composed of the vanadium oxide complex 100. The shape of the negative electrode active material particle 205 is, for example, spherical.

[0065] The negative electrode active material particles 205 can also have a median particle size of 0.1 μm or more and 100 μm or less. When the negative electrode active material particles 205 have a median particle size 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 particle size of 100 μm or less, the Li diffusion rate within the negative electrode active material particles 205 is increased. This allows the battery 1000 to operate at high output power.

[0066] In this disclosure, the median particle size refers to the particle size (d50) at which the volumetric accumulation in the particle size distribution of the volume reference is equivalent to 50%. The particle size distribution of the volume reference can be determined using a laser diffraction apparatus or an image analysis apparatus.

[0067] The negative electrode active material particles 205 can also have a larger median particle size than the solid electrolyte particles 206. Therefore, the negative electrode active material particles 205 and the solid electrolyte particles 206 can be well dispersed.

[0068] In order to improve the energy density and output power of the battery 1000, in the negative electrode 203, the ratio of the volume of the negative electrode active material particles 205 to the total volume of the negative electrode active material particles 205 and the solid electrolyte particles 206 can also be 0.30 or more and 0.95 or less.

[0069] To improve the energy density and output power of the battery 1000, the negative electrode 203 can also have a thickness of more than 10 μm and less than 500 μm.

[0070] The solid electrolyte particles 206 contained in the negative electrode 203 can also be sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes or polymer solid electrolytes.

[0071] In this disclosure, "sulfide solid electrolyte" refers to a solid electrolyte containing sulfur. "Oxide solid electrolyte" refers to a solid electrolyte containing oxygen. Oxide solid electrolytes may also contain anions other than oxygen (except for sulfide anions and halide anions). "Halide solid electrolyte" refers to a solid electrolyte containing halogens but not sulfur. Halide solid electrolytes may contain not only halogens but also oxygen.

[0072] Examples of sulfide solid electrolytes include Li₂S-P₂S₅, Li₂S-SiS₂, Li₂S-B₂S₃, Li₂S-GeS₂, and Li₂S-P₂S₅. 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 wait.

[0073] An example of a halide solid electrolyte is the use of Li b Me c Y d The compound represented by X6 satisfies the mathematical formula: b + mc + 3d = 6 and d > 0. Me is at least one element selected from metallic and half-metallic elements other than Li and Y. X is at least one element selected from F, Cl, Br, and I. The value of m represents the valence number of Me.

[0074] "Half-metallic elements" are B, Si, Ge, As, Sb, and Te. "Metallic elements" are all elements contained in Groups 1 to 12 of the periodic table (except H) and all elements contained in Groups 13 to 16 of the periodic table (except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0075] To improve the ionic conductivity of halide solid electrolytes, Me can also be at least one selected from Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0076] An example of a halide solid electrolyte is the use of Li α Me' β Oγ X' δ The compound is represented by α, β, γ, and δ, all of which are greater than 0. Me' is at least one element selected from metallic and half-metallic elements other than Li. X' is at least one element selected from Cl, Br, and I. It satisfies the mathematical formulas: 0.9 ≤ α ≤ 1.2, β = 1.0, 1.0 ≤ γ ≤ 1.3, and 3.6 ≤ δ ≤ 4.0.

[0077] Examples of oxide solid electrolytes are: (i) LiTi2(PO4)3, and its elemental substitutes, are NASICON-type solid electrolytes. (ii) Perovskite-type solid electrolytes such as (LaLi)TiO3, (iii) Li 14 ZnGe4O 16 LISICON-type solid electrolytes, such as Li4SiO4, LiGeO4, and their elemental substitutes. (iv)Li7La3Zr2O 12 Garnet-type solid electrolytes, such as their elemental substitution bodies, or (v) Li3PO4 or its N-substituted derivatives, etc.

[0078] Examples of polymeric solid electrolytes are compounds of polymers and lithium salts. The polymers can also have an ethylene oxide structure. Polymers with an ethylene oxide structure can contain a larger amount of lithium salt, thus exhibiting higher ionic conductivity. Polymeric solid electrolytes can also be, for example, composite compounds of polyethylene oxide and lithium salts. An example of such a polymeric solid electrolyte is lithium bis(trifluoromethanesulfonyl)imide.

[0079] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), and LiC(SO2CF3)3. A single lithium salt selected from these can be used alone. Alternatively, a mixture of two or more lithium salts selected from these can be used.

[0080] The positive electrode 201 contains a material capable of inserting and deintercalating metal ions such as lithium ions. The positive electrode 201 may contain, for example, a positive electrode active material (e.g., positive electrode active material particles 204).

[0081] Examples of positive electrode active materials include lithium-containing transition metal oxides, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal sulfides, and transition metal nitrides. Examples of lithium-containing transition metal oxides include Li(Ni,Co,Al)O2, Li(Ni,Co,Mn)O2, and LiCoO2.

[0082] In this disclosure, “(A,B,C)” means “at least one selected from A, B and C”.

[0083] From the perspective of cost and safety of Battery 1000, lithium phosphate or lithium-containing transition metal phosphates can also be used as positive electrode active materials.

[0084] The positive electrode active material particles 204 can also have a median particle size of 0.1 μm or more and 100 μm or less. When the positive electrode active material particles 204 have a median particle size 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 particle size of 100 μm or less, the Li diffusion rate within the positive electrode active material particles 204 is increased. This allows the battery 1000 to operate at high output power.

[0085] The positive electrode active material particles 204 can also have a larger median particle size than the solid electrolyte particles 206. Therefore, the positive electrode active material particles 204 and the solid electrolyte particles 206 can be well dispersed.

[0086] In order to improve the energy density and output power of the battery 1000, in the positive electrode 201, the ratio of the volume of the positive electrode active material particles 204 to the total volume of the positive electrode active material particles 204 and the solid electrolyte particles 206 can also be 0.30 or more and 0.95 or less.

[0087] To improve the energy density and output power of the battery 1000, the positive electrode 201 can also have a thickness of more than 10 μm and less than 500 μm.

[0088] The solid electrolyte particles 206 contained in the positive electrode 201 can also be sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, organic polymer solid electrolytes, etc.

[0089] Figure 3This is a cross-sectional view showing the electrode material 200 according to the second embodiment. The electrode material 200 may also include at least one selected from the positive electrode 201 and the negative electrode 203. The electrode material 200 contains electrode active material particles 208 and solid electrolyte particles 206.

[0090] Electrode material 200 is contained, for example, in positive electrode 201. To prevent solid electrolyte particles 206 from reacting with the positive electrode active material (i.e., electrode active material particles 208), at least a portion of the surface of the electrode active material particles 208 may also be covered by a covering material 209. With this configuration, the rise of the reaction overpotential of the battery 1000 can be suppressed.

[0091] Electrode material 200 may also be contained in negative electrode 203. To prevent solid electrolyte particles 206 from reacting with negative electrode active material (i.e., electrode active material particles 208), at least a portion of the surface of electrode active material particles 208 may also be covered by covering material 209. With this configuration, the rise of reaction overpotential in battery 1000 can be suppressed.

[0092] The vanadium oxide composite 100 of the first embodiment contained in the negative electrode 203 can also be further covered by the covering material 209. With this configuration, the rise of the reaction overpotential of the battery 1000 can be suppressed.

[0093] Examples of covering materials 209 include sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, and halide solid electrolytes.

[0094] The covering material 209 can also be a halide solid electrolyte material or an oxide solid electrolyte material. The halide solid electrolyte material may also contain F. With this configuration, the stability of the covering material 209 at high potentials is improved. Therefore, the battery 1000 has high charge-discharge efficiency. The oxide solid electrolyte can also be lithium niobate or a polyanionic material, which exhibits excellent stability even at high potentials. With this configuration, the battery 1000 has high charge-discharge efficiency.

[0095] Examples of sulfide solid electrolytes include Li₂S-P₂S₅. Examples of oxide solid electrolytes include lithium triphosphate. Examples of polymeric solid electrolytes include composites of polyethylene oxide and lithium salts. An example of such a polymeric solid electrolyte is lithium bis(trifluoromethanesulfonyl)imide.

[0096] Electrolyte layer 202 contains an electrolyte material. This electrolyte material may be, for example, a solid electrolyte material. Electrolyte layer 202 may also be a solid electrolyte layer. The solid electrolyte material contained in electrolyte layer 202 may also be a sulfide solid electrolyte, a halide solid electrolyte, or a polymer solid electrolyte.

[0097] The electrolyte layer 202 can also have a thickness of 1 μm or more but less than 100 μm. When the electrolyte layer 202 has a thickness of 1 μm or more, short circuits are less likely to occur between the positive electrode 201 and the negative electrode 203. When the electrolyte layer 202 has a thickness of less than 100 μm, the battery 1000 can operate at high output power.

[0098] At least one of the positive electrode 201, electrolyte layer 202 and negative electrode 203 may contain a non-aqueous electrolyte, gel electrolyte or ionic liquid for the purpose of facilitating the acceptance of lithium ions and improving the output characteristics of the battery 1000.

[0099] The non-aqueous electrolyte comprises a non-aqueous solvent and a lithium salt dissolved in that non-aqueous solvent. Examples of non-aqueous solvents include cyclic carbonate solvents, chain carbonate solvents, cyclic ether solvents, chain ether solvents, cyclic ester solvents, chain ester solvents, and fluorinated solvents. Examples of cyclic carbonate solvents include ethylene carbonate, propylene carbonate, and butyl carbonate. Examples of chain carbonate solvents include dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate. Examples of cyclic ether solvents include tetrahydrofuran, 1,4-dioxane, and 1,3-dioxapentane. Examples of chain ether solvents include 1,2-dimethoxyethane and 1,2-diethoxyethane. Examples of cyclic ester solvents include γ-butyrolactone. Examples of chain ester solvents include methyl acetate. Examples of fluorinated solvents include fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, methyl ethyl fluorocarbonate, and dimethyl fluorocarbonate. Alternatively, one of these non-aqueous solvents may be used alone. Alternatively, a mixture of two or more non-aqueous solvents selected from them can be used.

[0100] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), and LiC(SO2CF3)3. A single lithium salt selected from these can be used. Alternatively, a mixture of two or more lithium salts selected from these can be used. The concentration of the lithium salt is, for example, in the range of 0.5 mol / L or more and 2 mol / L or less.

[0101] As a gel electrolyte, polymeric materials impregnated with a non-aqueous electrolyte can be used. Examples of polymeric materials include polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, and polymers containing ethylene oxide bonds.

[0102] Examples of cations contained in ionic liquids are: (i) Aliphatic chain quaternary salts such as tetraalkylammonium and tetraalkylphosphonium, (ii) Aliphatic cyclic ammonium compounds such as pyrrolidinemonium, morpholinium, imidazolinemonium, tetrahydropyrimidinemonium, piperazinemonium, and piperidinemonium, or (iii) Nitrogen-containing heterocyclic aromatic cations such as pyridinium and imidazoline.

[0103] An example of anion contained in ionic liquids is PF6. - BF4 - SbF6 - AsF6 - SO3CF3 - N(SO2CF3)2 - N(SO2C2F5)2 - N(SO2CF3)(SO2C4F9) - C(SO2CF3)3 - wait.

[0104] Ionic liquids can also contain lithium salts.

[0105] The material is selected from at least one of the positive electrode 201, electrolyte layer 202 and negative electrode 203 for the purpose of improving the adhesion between particles, and may also contain a binder.

[0106] Examples of adhesives include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aromatic polyamide resins, polyamides, polyimides, polyamide-imides, polyacrylonitrile, polyacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, polyhexafluoropropylene, styrene-butadiene rubber, carboxymethyl cellulose, etc. Copolymers can also be used as adhesives. Examples of such adhesives are copolymers selected from two or more materials chosen from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ethers, vinylidene fluoride, trifluorochloroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene. Mixtures of two or more materials selected from the above materials can also be used.

[0107] The electrode is selected from at least one of the positive electrode 201 and the negative electrode 203 for the purpose of improving electronic conductivity, and may further contain a conductive additive.

[0108] Examples of conductive additives are: (i) Graphite types 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) Fluorocarbon, (v) Metal powders such as aluminum, (vi) Conductive whiskers such as zinc oxide and potassium titanate, (vii) Conductive metal oxides such as titanium dioxide, or (viii) Conductive polymers such as polyaniline, polypyrrole, and polythiophene. To reduce costs, conductive additives described in (i) or (ii) above may also be used.

[0109] like Figure 2 As shown, the negative electrode 203 not only contains negative electrode active material particles 205, but may also further contain conductive additives 207. Based on this configuration, the electronic conductivity of the negative electrode 203 can be further improved.

[0110] Examples of materials for conductive additive 207 are as described above.

[0111] 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 can be 0.01 or more and 0.4 or less. With this configuration, the electronic conductivity of the negative electrode 203 can be further improved.

[0112] When the negative electrode 203 further contains a conductive additive 207, the coverage R of the conductive material 102 on the surface of the vanadium oxide composite 100 containing the vanadium oxide particles 101 represented by the above compositional formula (1) in the first embodiment, which serves as the negative electrode active material particles 205, can also be 30% or more and 60% or less. With this configuration, an improvement in electronic conductivity based on the conductive additive 207 can be easily obtained in the negative electrode 203. As a result, the capacity of the battery 1000 is further increased.

[0113] When the coverage R of the vanadium oxide composite 100, which serves as the negative electrode active material particle 205, is 30% or more and 60% or less, the content of the conductive additive 207 can also be 2.0% by weight or more and 5.0% by weight or less. With this configuration, the improved electronic conductivity based on the conductive additive 207 can be more easily obtained in the negative electrode 203.

[0114] In this disclosure, the content of conductive additive 207 refers to the weight of NH4VO3 used in the production of vanadium oxide in vanadium oxide composite 100.

[0115] Examples of the battery shape in the second embodiment include coin type, cylindrical type, square type, sheet type, button type, flat type, and stacked type.

[0116] The battery of the second embodiment can also be manufactured in the following manner: a positive electrode forming material, an electrolyte layer forming material and a negative electrode forming material are prepared, and a laminate in which a positive electrode, an electrolyte layer and a negative electrode are sequentially arranged is made using a known method.

[0117] (Other implementation methods) (Postscript) Based on the description of the above embodiments, the following technology is disclosed.

[0118] (Technology 1) A vanadium oxide composite, wherein the vanadium oxide composite comprises: Particles containing vanadium oxide, and A conductive material covering at least a portion of the surface of the particles. The conductive material on the surface of the particle has a coverage rate of 30% or more. The average particle size is above 0.5 μm and below 5.0 μm.

[0119] The vanadium oxide composite of Technology 1 is a novel material that can be used as a battery material. For example, the vanadium oxide composite of Technology 1 can be used as a negative electrode active material. For example, the vanadium oxide composite of Technology 1 is suitable for improving the charge-discharge characteristics of a battery, such as increasing the battery capacity.

[0120] (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 manufactured at a lower cost.

[0121] (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 battery capacity.

[0122] (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 battery capacity.

[0123] (Technology 5) The vanadium oxide complex 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, electronic conductivity can be ensured while promoting the insertion / deintercalation of Li into the vanadium oxide complex.

[0124] (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 battery capacity.

[0125] (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 battery capacity.

[0126] (Technology 8) The vanadium oxide complex according to any one of Technologies 1 to 7, wherein the coverage is 70% or less. With this configuration, electronic conductivity can be ensured while promoting the insertion / deintercalation of Li into the vanadium oxide complex.

[0127] (Technology 9) A vanadium oxide composite according to any one of Technologies 1 to 8, wherein the vanadium oxide is composed of the formula (1): Li 3+x V 1-x M x O4 represents the composition, where in the composition (1), 0 ≤ x < 1 is satisfied, and M is at least one element selected from tetravalent metals and tetravalent half-metals. Based on this composition, the vanadium oxide complex can further improve the battery capacity.

[0128] (Technology 10) According to Technology 9, the vanadium oxide composite material satisfies 0 < x < 1 in the composition formula (1). With this configuration, the capacity of the battery using the vanadium oxide composite material is further improved.

[0129] (Technology 11) The vanadium oxide composite according to Technology 9 or 10, wherein M in the composition (1) comprises Ti. According to such a configuration, the vanadium oxide composite can improve the capacity of the battery.

[0130] (Technology 12) A battery, wherein the battery comprises: positive electrode, Negative electrode, and An electrolyte layer disposed between the positive electrode and the negative electrode; The negative electrode contains a vanadium oxide composite as described in any one of techniques 1 to 11.

[0131] The battery of Technology 12 has excellent charge and discharge characteristics.

[0132] (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.

[0133] (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, an improvement in electronic conductivity based on the conductive additive can be easily obtained in the negative electrode. As a result, the battery capacity is further increased.

[0134] (Technology 15) In the battery according to Technology 14, the content of the conductive additive is 2.0% by weight or more and 5.0% by weight or less. With this configuration, it is easier to obtain an improvement in electronic conductivity based on the conductive additive in the negative electrode.

[0135] Example The present disclosure will be described in more detail below using examples and comparative examples. The vanadium oxide complex of the examples contains vanadium oxides that can be composed of formula (1): Li 3+x V 1-x M x O4 (x = 0) represents this.

[0136] (Example 1) [Preparation of Vanadium Oxide Complex] As raw material powders for vanadium oxide, 1.47 g and 0.176 g of lithium hydroxide monohydrate (LiOH·H2O: manufactured by Fujifilm and Wako Pure Chemical Industries, Ltd., Wako Special Grade) and ammonium vanadate (NH4VO3: manufactured by Fujifilm and Wako Pure Chemical Industries, Ltd., Wako Special Grade) were prepared, respectively, resulting in a molar ratio of LiOH·H2O:NH4VO3 of 23.3:1. As a conductive material, 2.5 mL of graphene oxide dispersion in water (manufactured by Sigma-Ardrich, graphene oxide concentration: 0.004 g / mL) was prepared, resulting in a graphene oxide weight relative to NH4VO3 weight of 5.7%. These raw materials were dissolved in 37.5 mL of purified water to obtain a raw material solution. The raw material solution was dispersed for 90 minutes using an ultrasonic disperser (manufactured by SMT, UH-50) by ultrasonic irradiation to obtain a dispersion solution. The dispersion solution was placed in an aluminum dish and heated in an aluminum bead bath at 150°C for 50 minutes in the atmosphere to obtain a heated solution. The heated solution was centrifuged to separate the supernatant and precipitate. The precipitate was washed with purified water and dried in a vacuum at 70°C for 1 hour to obtain a dry powder. The dry powder was ground in a mortar and calcined at 600°C for 2 hours in a nitrogen atmosphere. The heating rate during calcination was 10°C per minute and the cooling rate was 5°C per minute. After calcination, the weight of the obtained powder was 0.2 g. In this way, the vanadium oxide composite of Example 1 was prepared. In the vanadium oxide composite of Example 1, the vanadium oxide has a composition with Li excess in the compositional formula (1).

[0137] In the vanadium oxide composite of Example 1, a conductive material covers at least a portion of the surface of the vanadium oxide-containing particles. The coverage R of the conductive material on the surface of the vanadium oxide-containing particles in Example 1 is 35%.

[0138] The coverage ratio R was determined using the method described above. Specifically, firstly, vanadium oxide composite particles and zinc powder were mixed in a mortar to obtain a mixed powder. The mixed powder was then pressurized to form granules. Next, the granules were processed using an ion milling apparatus (Hitachi High-Technologies, ArBlade 5000) to create a smooth cross-section. The formed cross-section was observed using a field emission scanning electron microscope (FE-SEM: Hitachi High-Technologies, Regulus 8230) to obtain an FE-SEM image. For each 50 vanadium oxide composite particles contained in the FE-SEM image, the perimeter P and the length C of the portion covered by the conductive material were measured. The average of the values ​​calculated from 100 × C / P was taken as the coverage ratio R.

[0139] Furthermore, within the conductive material contained in vanadium oxide composites, there exist thicknesses that are difficult to detect using FE-SEM. For example, observation of the cross-section of the granules using transmission electron microscopy (TEM) confirmed that conductive material with a thickness of less than 3 nm exists not only on the surface of the vanadium oxide-containing particles but also within the particles themselves, i.e., at the interfaces of the primary particles. Therefore, conductive material with a thickness exceeding 3 nm becomes the target when calculating coverage R, for example.

[0140] The average particle size of the vanadium oxide composite in Example 1 is 1.1 μm.

[0141] The average particle size of the vanadium oxide complex particles was determined using the method described above. Specifically, firstly, the vanadium oxide complex particles and zinc powder were mixed in a mortar to obtain a mixed powder. The mixed powder was then pressurized to form granules. Next, the granules were processed using an ion milling apparatus (Hitachi High-Technologies, ArBlade 5000) to create a smooth cross-section. The resulting cross-section was observed using a field emission scanning electron microscope (FE-SEM: Hitachi High-Technologies, Regulus 8230) to obtain an FE-SEM image. For each 50 vanadium oxide complex particles contained in the FE-SEM image, their equivalent circle diameter was measured. The average of these equivalent circle diameters was taken as the average particle size.

[0142] [Battery Manufacturing] The vanadium oxide composite of Example 1 and the solid electrolyte Li3PS4 were prepared in an argon atmosphere with a dew point below -60°C at a volume ratio of 60:40. These materials were mixed in an agate mortar. This yielded the negative electrode mixture.

[0143] In an insulating cylinder with an inner diameter of 9.5 mm, a solid electrolyte Li3PS4 (80 mg) and a negative electrode mixture (6.5 mg) are stacked to obtain a laminate. A pressure of 360 MPa is applied to the laminate to form the electrolyte layer and the negative electrode. The electrolyte layer has a thickness of 500 μm.

[0144] Next, Li (thickness: 300 μm) is stacked on the electrolyte layer, and a pressure of 80 MPa is applied to form the positive electrode.

[0145] Next, stainless steel current collectors are installed on the positive and negative terminals respectively, and current collector leads are installed on each current collector.

[0146] Finally, an insulating hoop is used to isolate the inside of the insulating cylinder from the external atmosphere, thereby sealing the inside of the cylinder.

[0147] As described above, the battery of Example 1 was thus fabricated. Furthermore, the battery of Example 1 is a single-electrode test cell with a negative electrode as the working electrode and a positive electrode as the counter electrode, used to test the performance of the negative electrode. Specifically, the working electrode is the negative electrode of the test object, and the counter electrode is a suitable active material sufficient to maintain the reaction of the working electrode. Since this test cell is a cell for testing the performance of the negative electrode, metallic Li is used as the counter electrode. The negative electrode used to test the performance of such a test cell can be used as a secondary battery, for example, by combining it with a positive electrode containing the positive electrode active material described in the above embodiments, such as a transition metal oxide containing Li.

[0148] [Charge / Discharge Test] Using the battery of Example 1, charge-discharge tests were performed as follows. Furthermore, as mentioned above, the battery of Example 1 is a unipolar test cell, equivalent to a half-cell with the negative electrode. Therefore, in the battery of Example 1, the direction in which the potential of the half-cell decreases due to the insertion of Li ions into the negative electrode is called charging, while the direction in which the potential increases is called discharging. That is, in the battery of Example 1, charging is essentially discharging (i.e., in the case of a full cell), and discharging is essentially charging. Hereinafter, unless otherwise specified, charging refers to charging within a half-cell, and discharging refers to discharging within a half-cell.

[0149] The battery is placed in a constant temperature bath maintained at 25°C.

[0150] The battery is discharged at a constant current rate of 0.1C (10-hour rate) relative to its theoretical capacity, and the discharge ends when the voltage reaches 0.3V. Then, it is charged at a constant current rate of 0.05C, and the charging ends when the voltage reaches 2.5V. This charge-discharge cycle is called the "initial charge-discharge".

[0151] After the initial charge and discharge, a constant current discharge is performed at a rate of 0.1C relative to the battery's theoretical capacity, ending the discharge when the voltage reaches 0.3V. Next, a constant current charge is performed at a rate of 0.05C, ending the charge when the voltage reaches 2.5V. This charge-discharge cycle is called a "two-cycle charge-discharge".

[0152] After two charge-discharge cycles, the battery is discharged at a constant current rate of 10C relative to its theoretical capacity, ending when the voltage reaches 0.3V. Then, it is charged at a constant current rate of 0.05C, ending when the voltage reaches 2.5V. This charge-discharge cycle is called a "10C charge-discharge". The discharge capacity during a 10C charge-discharge cycle at a constant current rate is called the "10C discharge capacity".

[0153] Figure 4 This is a graph showing the initial discharge characteristics and 10C discharge characteristics of the battery in Example 1. Figure 4 In the diagram, the horizontal axis represents the discharge capacity (mAh / g), and the vertical axis represents the voltage (V). A series of charge-discharge tests were conducted, including initial charge-discharge, two charge-discharge cycles, and 10C charge-discharge. The results showed that the battery in Example 1 had a 10C discharge capacity of 91.2 mAh / g.

[0154] (Examples 2-4, Comparative Examples 1-3) [Preparation of Vanadium Oxide Complex] In Example 2, 3.75 mL of graphene oxide was dispersed in water, such that the weight of graphene oxide present in the dispersion was 8.5% by weight relative to the weight of NH4VO3. Additionally, all raw materials were dissolved in 36.25 mL of purified water to obtain a raw material solution. Otherwise, the vanadium oxide composite of Example 2 was obtained using the same method as in Example 1. The coverage R of Example 2 was 61%. The average particle size of the vanadium oxide composite of Example 2 was 1.1 μm.

[0155] In Example 3, 5 mL of graphene oxide was dispersed in water, such that the weight of graphene oxide present in the dispersion was 11.4% by weight relative to the weight of NH4VO3. Additionally, all raw materials were dissolved in 35 mL of purified water to obtain a raw material solution. Otherwise, the vanadium oxide composite of Example 3 was obtained using the same method as in Example 1. The coverage R of Example 3 was 81%. The average particle size of the vanadium oxide composite of Example 3 was 1.2 μm.

[0156] In Example 4, 3.75 mL of graphene oxide was dispersed in water, such that the weight of graphene oxide present in the dispersion was 8.5% by weight relative to the weight of NH4VO3. Additionally, all raw materials were dissolved in 76.25 mL of purified water to obtain a raw material solution. Otherwise, the vanadium oxide composite of Example 4 was obtained using the same method as in Example 1. The coverage R of Example 4 was 53%. The average particle size of the vanadium oxide composite of Example 2 was 3.4 μm.

[0157] In Comparative Example 1, graphene oxide was not used to disperse in water. Instead, all raw materials were dissolved in 40 mL of purified water to obtain a raw material solution. Otherwise, the vanadium oxide composite of Comparative Example 1 was obtained using the same method as in Example 1. That is, the surface of the vanadium oxide composite of Comparative Example 1 was not covered by a conductive material. The average particle size of the vanadium oxide composite of Comparative Example 1 was 1.7 μm.

[0158] In Comparative Example 2, 3.75 mL of graphene oxide was dispersed in water, such that the weight of graphene oxide present in the dispersion water was 8.5% by weight relative to the weight of NH4VO3. Additionally, all raw materials were dissolved in 16.25 mL of purified water to obtain a raw material solution. Otherwise, the vanadium oxide composite of Comparative Example 1 was obtained using the same method as in Example 1. The coverage R of Comparative Example 2 was 46%. The average particle size of the vanadium oxide composite of Comparative Example 2 was 0.4 μm.

[0159] In Comparative Example 3, the raw material solution was not subjected to ultrasonic irradiation-based dispersion treatment; otherwise, the vanadium oxide composite of Comparative Example 3 was obtained using the same method as in Example 1. The coverage R of Comparative Example 3 was 44%. The average particle size of the vanadium oxide composite of Comparative Example 3 was 6.0 μm.

[0160] [Battery Manufacturing] Using the vanadium oxide composites of Examples 2-4 and Comparative Examples 2-3, the batteries of Examples 2-4 and Comparative Examples 2-3 were prepared using the same method as in Example 1.

[0161] Regarding the fabrication of the battery of Comparative Example 1, the vanadium oxide composite of Comparative Example 1 and the solid electrolyte Li3PS4 were prepared in an argon atmosphere with a dew point below -60°C at a volume ratio of 60:40. Furthermore, acetylene black was prepared as a conductive additive. The acetylene black was prepared at a weight of 5.7% relative to the NH4VO3 used in the fabrication of the vanadium oxide. These materials were mixed in an agate mortar to obtain the negative electrode mixture of Comparative Example 1. Using the negative electrode mixture of Comparative Example 1 as the negative electrode mixture, the battery of Comparative Example 1 was fabricated using the same method as in Example 1.

[0162] [Charge / Discharge Test] For the batteries of Examples 2-4 and Comparative Examples 1-3, charge-discharge tests were conducted using the same method as in Example 1, and the 10C discharge capacity was measured. The results are shown in Table 1.

[0163] (Inspection) As can be understood from the comparison of the 10C discharge capacity of Examples 1-4 with that of Comparative Examples 1-3, the batteries of Examples 1-4, which use 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, have a high discharge capacity even at a high rate of 10C.

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

[0165] As with the vanadium oxide complex in Comparative Example 2, when the average particle size is less than 0.5 μm, agglomeration of the vanadium oxide complex occurs during the preparation of the negative electrode mixture, suggesting a decrease in the dispersibility of the negative electrode mixture. Therefore, in the battery of Comparative Example 2, the resistance of the negative electrode mixture increases and the Li ion conductivity decreases, thus suggesting a lower 10C discharge capacity.

[0166] As with the vanadium oxide complex in Comparative Example 3, when the average particle size is greater than 5.0 μm, it can be inferred that the contact area between the vanadium oxide complex and the solid electrolyte in the negative electrode mixture is reduced. Therefore, in the battery of Comparative Example 3, the Li-ion conductivity of the negative electrode mixture is reduced, and thus a lower 10C discharge capacity can be inferred.

[0167] As can be understood from the comparison of the 10C discharge capacity of Examples 1-4 with that of Comparative Examples 1-3, when the composition (1) has an excess of Li, the vanadium oxide complex contains more Li in the battery to carry out charge and discharge. Therefore, it can be inferred that the 10C discharge capacity is particularly high in the batteries of Examples 1-4. However, if Li is too excessive, Li will be too dense and unable to diffuse sufficiently during the charge and discharge of the battery, which can be inferred to lead to a decrease in Li ion conductivity.

[0168] As in Examples 1-3, by using a vanadium oxide composite with a preferred average particle size and a surface covered by a conductive material in a preferred proportion, a negative electrode mixture with excellent electronic conductivity and Li-ion conductivity can be obtained. Using such a negative electrode mixture, a battery with high discharge capacity can be fabricated even at a high discharge rate of 10C.

[0169] [Battery Manufacturing] Using the vanadium oxide composites of Examples 1-3, the batteries of Examples 1-1, 1-2, 1-3, 2-1 and 3-1 were prepared by the following method.

[0170] Regarding the fabrication of the battery in Example 1-1, the vanadium oxide composite of Example 1 and the solid electrolyte Li3PS4 were prepared in an argon atmosphere with a dew point below -60°C at a volume ratio of 60:40. Furthermore, acetylene black was prepared as a conductive additive. The acetylene black was prepared at a weight of 2.3% relative to the NH4VO3 used in the fabrication of the vanadium oxide. These materials were mixed in an agate mortar to obtain the negative electrode mixture of Example 1-1. Using the negative electrode mixture of Example 1-1 as the negative electrode mixture, the battery of Example 1-1 was fabricated using the same method as in Example 1.

[0171] In the fabrication of the batteries in Examples 1-2, acetylene black was prepared at a weight of 3.5% relative to the NH4VO3 used in the fabrication of vanadium oxide. Otherwise, the batteries of Examples 1-2 were obtained using the same method as in Examples 1-1.

[0172] In the fabrication of the batteries in Examples 1-3, acetylene black was prepared at a weight of 4.6% relative to the NH4VO3 used in the fabrication of vanadium oxide. Otherwise, the batteries of Examples 1-3 were obtained using the same method as in Examples 1-1.

[0173] In the fabrication of the battery in Example 2-1, the vanadium oxide composite of Example 2 was used as the vanadium oxide composite. Additionally, acetylene black was prepared at a concentration of 2.3% by weight relative to the NH4VO3 used in the fabrication of the vanadium oxide. Otherwise, the battery of Example 2-1 was obtained using the same method as in Example 1-1.

[0174] In the fabrication of the battery in Example 3-1, the vanadium oxide composite of Example 3 was used as the vanadium oxide composite. Additionally, acetylene black was prepared at a concentration of 2.3% by weight relative to the NH4VO3 used in the fabrication of the vanadium oxide. Otherwise, the battery of Example 3-1 was obtained using the same method as in Example 1-1.

[0175] [Charge / Discharge Test] For the batteries of Examples 1-1, 1-2, 1-3, 2-1, and 3-1, charge-discharge tests were conducted using the same method as in Example 1, and the 10C discharge capacity was measured. The results are shown in Table 2.

[0176] (Inspection) As can be understood from the comparison of the 10C discharge capacity based on Example 1 with that of Examples 1-1 to 1-3, when the negative electrode contains a conductive additive, the 10C discharge capacity of the battery can be further improved by satisfying that the coverage R of the vanadium oxide complex is 30% or more and 60% or less. On the other hand, as shown by the comparison of the 10C discharge capacity of Example 2 with that of Example 2-1 and the comparison of the 10C discharge capacity of Example 3 with that of Example 3-1, when the negative electrode contains a conductive additive, if the coverage R of the vanadium oxide complex exceeds 60%, there is a tendency for the 10C discharge capacity of the battery to decrease. From this result, it can be seen that when the negative electrode contains a conductive additive, by satisfying that the coverage R of the vanadium oxide complex is 30% or more and 60% or less, the effect of improving electronic conductivity based on the conductive additive can be easily obtained in the negative electrode.

[0177] As stated above, the vanadium oxide composite of this disclosure is suitable for providing batteries with excellent charge-discharge characteristics even at high rates.

[0178] Industrial availability The vanadium oxide composite disclosed herein can be used as a battery material, for example, as a material for all-solid-state lithium-ion secondary batteries.

Claims

1. A vanadium oxide composite, wherein, The vanadium oxide composite comprises: Particles containing vanadium oxide, and A conductive material covering at least a portion of the surface of the particles; The conductive material on the surface of the particle has a coverage rate of 30% or more. The average particle size is above 0.5 μm and below 5.0 μm.

2. The vanadium oxide composite according to claim 1, wherein, The conductive material is a carbon material.

3. The vanadium oxide composite according to claim 1, wherein, The average particle size is above 0.55 μm and below 4.5 μm.

4. The vanadium oxide composite according to claim 1, wherein, The average particle size is greater than 0.6 μm and less than 4.0 μm.

5. The vanadium oxide composite according to claim 1, wherein, The average particle size is greater than 0.8 μm and less than 3.0 μm.

6. The vanadium oxide composite according to claim 1, wherein, The coverage rate is over 40%.

7. The vanadium oxide composite according to claim 1, wherein, The coverage rate is over 55%.

8. The vanadium oxide composite according to claim 1, wherein, The coverage rate is below 70%.

9. The vanadium oxide composite according to claim 1, wherein, The vanadium oxide is composed of formula (1): Li 3+x V 1-x M x O4 is used to represent it. Here, in the composition (1), Satisfying 0≤x<1, and M is at least one element selected from tetravalent metals and tetravalent half-metals.

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

11. The vanadium oxide composite according to claim 9, wherein, In the composition (1), M contains Ti.

12. A battery, wherein, The battery has the following features: positive electrode, Negative electrode, and An electrolyte layer disposed between the positive electrode and the negative electrode; The negative electrode contains the vanadium oxide composite as described in any one of claims 1 to 11.

13. The battery according to claim 12, wherein, The negative electrode further contains a conductive additive.

14. The battery according to claim 12, wherein, The negative electrode further contains a conductive additive. The coverage of the vanadium oxide composite is above 30% and below 60%.

15. The battery according to claim 14, wherein, The conductive additive has a content of 2.0% by weight or more and 5.0% by weight or less.

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