Lithium vanadium oxide, negative electrode active material, and battery

Abstract

This lithium vanadium oxide contains Li, V, M, and O, where M is at least one selected from the group consisting of tetravalent metal elements and tetravalent metalloids other than V, and the lithium vanadium oxide contains both a beta phase and a gamma phase as crystal phases.

Description

Technical Field

[0001] This disclosure relates to lithium vanadium oxide, negative electrode active materials, and batteries. Background Technology

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

[0003] Patent document 2 discloses a co-fired all-solid-state battery using a negative electrode active material obtained by doping element A and / or element B into Li3VO4. Element A is at least one element selected from Mg, Al, Ga, and Zn. Element B is at least one element selected from Zn, Al, Ga, Si, Ge, P, and Ti. The negative electrode active material has either a β phase or a γ phase.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2008-77847

[0007] Patent Document 2: International Publication No. 2019 / 044902 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] Doping lithium vanadium oxide with metal elements increases its expansion and contraction rate, thus decreasing its theoretical capacity. Increased expansion and contraction rate leads to decreased durability of batteries using lithium vanadium oxide. A decrease in theoretical capacity results in a decrease in battery capacity.

[0010] This disclosure provides a technique for balancing the capacity and durability of batteries using lithium vanadium oxide as the active material.

[0011] Problem-solving methods

[0012] This disclosure provides a lithium vanadium oxide containing Li, V, M, and O.

[0013] M is selected from at least one tetravalent metallic element and tetravalent metalloid element other than V.

[0014] The lithium vanadium oxide contains both β-phase and γ-phase as crystalline phases.

[0015] Invention Effects

[0016] According to this disclosure, it is possible to balance the capacity and durability of batteries using lithium vanadium oxide as the active material. Attached Figure Description

[0017] Figure 1 This is a schematic cross-sectional view showing the electrode material of the second embodiment.

[0018] Figure 2 This is a schematic cross-sectional view showing an example of the battery structure of the third embodiment.

[0019] Figure 3 This is a schematic cross-sectional view showing another example of the battery structure of the third embodiment.

[0020] Figure 4 This is a graph showing the X-ray diffraction patterns of Example 1, Comparative Example 1, and Comparative Example 2.

[0021] Figure 5 It is a graph showing the change in discharge capacity retention rate during charge-discharge cycles of Examples 1-3 and Comparative Example 1. Detailed Implementation

[0022] (The insights that form the basis of this disclosure)

[0023] In the case of lithium vanadium oxides having a β phase, a γ phase is sometimes also present. Batteries using lithium vanadium oxides with a β phase as the active material have a large capacity. However, this is disadvantageous from the viewpoint of battery durability due to the large expansion and contraction rate of the active material caused by the insertion and extraction of Li into the β phase. Conversely, active materials containing lithium vanadium oxides with a γ phase have a low expansion and contraction rate, which is advantageous from the viewpoint of battery durability. However, if the lithium vanadium oxide is doped with a metal element, the theoretical capacity will decrease. If the theoretical capacity decreases, it becomes difficult to obtain a high-capacity battery.

[0024] The inventors discovered that both the β phase and the γ phase can exist under specified conditions, which led to this disclosure.

[0025] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The present disclosure is not limited to these embodiments.

[0026] (First Embodiment)

[0027] The lithium vanadium oxide of the first embodiment contains Li, V, M, and O. M is selected from at least one tetravalent metal element and tetravalent metalloid element other than V. This lithium vanadium oxide contains both a β phase and a γ phase as crystalline phases.

[0028] The β phase is a crystalline phase with a crystal structure belonging to space group Pmn21. Specifically, the β phase has a crystal structure consisting of tetrahedra composed of LiO4 (hereinafter referred to as "LiO4 tetrahedra") and tetrahedra composed of VO4 (hereinafter referred to as "VO4 tetrahedra"). In the β phase crystal structure, the LiO4 tetrahedra and VO4 tetrahedra are oriented in the same direction (the c-axis direction, which is one side of the lattice) with adjacent tetrahedra sharing vertices. The β phase has a high theoretical capacity as an active material. On the other hand, the β phase exhibits a high expansion and contraction rate due to the insertion and extraction of Li into the crystalline phase.

[0029] The γ phase is a crystalline phase with a crystal structure belonging to the space group Pcmn. Specifically, the γ phase has the same crystal structure as the β phase, possessing LiO4 tetrahedra and VO4 tetrahedra. In the γ phase, LiO4 tetrahedra and VO4 tetrahedra exist in approximately equal proportions, with tetrahedra oriented roughly along one orientation (the +c axis, which is one side of the lattice) and tetrahedra oriented roughly along the opposite orientation (the -c axis, which is one side of the lattice). In the γ phase crystal structure, LiO4 tetrahedra share vertices and one side with adjacent LiO4 tetrahedra, and VO4 tetrahedra share vertices with adjacent LiO4 or VO4 tetrahedra. The γ phase can be stably obtained by replacing V (vanadium) sites in the lattice with tetravalent metals other than V. The γ phase is accompanied by the insertion and extraction of Li into the crystalline phase, and its expansion and contraction rate is very low. On the other hand, the γ phase reduces the theoretical capacity of lithium vanadium oxide, which is the active material.

[0030] In the lithium vanadium oxide based on the first embodiment, the ratio of the mass of V to the total mass of V and M (V / (M+V)) is, for example, greater than 0% and less than 10%. With this configuration, a mixed phase of β and γ phases is easily generated. Furthermore, if the firing temperature during the manufacture of the lithium vanadium oxide is high, the γ phase is more easily generated. Additionally, if a raw material with a low melting point is selected as the raw material for the lithium vanadium oxide, the γ phase is more easily generated at a lower firing temperature. Therefore, by appropriately selecting the ratio of the mass of V to the total mass of V and M, the firing temperature during the manufacture of the lithium vanadium oxide, and the type of raw material for the lithium vanadium oxide, the volume ratio of the β and γ phases can be controlled.

[0031] The lithium vanadium oxide of the first embodiment contains a β phase and a γ phase, for example, having Li 3+x V 1-x M xThe composition represented by the compositional formula (1) of O4 satisfies 0 < x < 1. With this composition, when using lithium vanadium oxide as the active material, the insertion and extraction of Li into and from the active material become easy, so the capacity of the battery using this lithium vanadium oxide as the active material is increased. The content x of M can satisfy 0 < x ≤ 0.2. With this composition, the capacity of the battery using this lithium vanadium oxide as the active material is further increased. The content x of M can be 0 < x < 0.1. With this composition, the capacity of the battery using this lithium vanadium oxide as the active material is further increased. The content x of M can be 0 < x < 0.08. With this composition, the capacity of the battery using this lithium vanadium oxide as the active material is further increased.

[0032] In addition, Li can also be contained in an excessive amount in a manner deviating from the composition ratio of the compositional formula (1). Specifically, based on the Li composition ratio of the compositional formula (1), Li can be contained in a range of 30% or less in excess. The excessive Li can enter the crystal phases of the β-phase and / or γ-phase of the lithium vanadium oxide, or can exist as a crystal phase other than the β-phase and / or γ-phase. With this composition, the capacity of the battery using this lithium vanadium oxide as the active material is further increased.

[0033] M can be selected from tetravalent metal elements and tetravalent metalloid elements other than V. M is, for example, at least one selected from Ti, Zr, Si, Ge, and Sn. With this composition, when using this lithium vanadium oxide as the active material, the active material easily maintains a high theoretical capacity. M can contain Ti. With this composition, when using this lithium vanadium oxide as the active material, the active material more easily maintains a high theoretical capacity. In addition, M can also be Ti. With this composition, when using this lithium vanadium oxide as the active material, it is easier to maintain a high theoretical capacity in the active material.

[0034] The volume ratio of the β-phase and γ-phase is not particularly limited. The volume ratio of the β-phase and γ-phase is related to the result of X-ray diffraction measurement of the lithium vanadium oxide, so the result of X-ray diffraction measurement can be a scale for the volume ratio of the β-phase and γ-phase. Among them, the intensity of the diffraction peak represents the height of the diffraction peak, and does not represent the area and volume of the β-phase and γ-phase. For example, in the X-ray diffraction pattern with Cu-Kα line as the radiation source, the ratio of the intensity of the diffraction peak of the (101) plane attributed to the β-phase to the intensity of the diffraction peak of the (011) plane attributed to the γ-phase is 0.1 or more and 10.0 or less. The ratio of the intensity of this diffraction peak can also be 0.1 or more and 7.0 or less. If the ratio of the intensity of the diffraction peak falls within such a range, when using this lithium vanadium oxide as the active material for a battery, a battery with good charge-discharge characteristics can be achieved.

[0035] The diffraction peak belonging to the (101) plane of the β phase appears at 22.7°±0.2°, taking into account the change in the lattice constant of the β phase caused by the doping of element M. Similarly, the diffraction peak belonging to the (011) plane of the γ phase appears at 22.4°±0.2°, taking into account the change in the lattice constant of the γ phase caused by the doping of element M. Therefore, in the X-ray diffraction pattern using Cu-Kα line as the X-ray source, under the condition of the ratio of the diffraction peak intensity at a diffraction angle 2θ of 22.7°±0.2° to that at a diffraction angle 2θ of 22.4°±0.2°, the ratio can be greater than 0.1 and less than 10.0. Furthermore, when two diffraction peaks exist within the overlap angle of "22.5° or higher and 22.6° or lower" at diffraction angles of "22.4°±0.2°" and "22.7°±0.2°", the correspondence between the diffraction peaks and crystal planes is determined by considering the intensity relationship of other comparable planes of the β and γ phases. Additionally, diffraction peaks belonging to the (011) plane of the γ phase tend to appear at 22.4°±0.1°, while diffraction peaks belonging to the (101) plane of the β phase tend to appear at 22.7°±0.1°. Therefore, in X-ray diffraction patterns using Cu-Kα lines as the X-ray source, the ratio of the intensity of the diffraction peak appearing at diffraction angle 2θ at 22.7°±0.1° to the intensity of the diffraction peak appearing at diffraction angle 2θ at 22.4°±0.1° can be 0.1 or higher and 10.0 or lower. The ratio of the intensity of the diffraction peak can also be above 0.1 and below 7.0.

[0036] The shape of the lithium vanadium oxide in the first embodiment is not limited. Examples of this shape include needle-like, spherical, or ellipsoidal. The lithium vanadium oxide in the first embodiment can be particles or formed into the shape of pellets or plates.

[0037] When the lithium vanadium oxide of the first embodiment is in the form of particles (e.g., spheres), it can have a median particle size of 0.1 μm or more and 100 μm or less, or a median particle size of 0.5 μm or more and 10 μm or less. In this way, the lithium vanadium oxide of the first embodiment and other materials can be well dispersed. The median particle size represents the particle size (d50) at 50% of the total volume in the volumetric particle size distribution. The volumetric particle size distribution can be measured using a laser diffraction apparatus or an image analysis apparatus.

[0038] The lithium vanadium oxide of the first embodiment can be included in the negative electrode active material.

[0039] <Method for manufacturing lithium vanadium oxide>

[0040] The lithium vanadium oxide of the first embodiment can be manufactured by the following method.

[0041] Prepare the raw material powder in a manner that has the desired composition. Examples of raw material powders include oxides, hydroxides, carbonates, nitrates, or organic salts of Li; oxides, hydroxides, carbonates, nitrates, or organic salts of V; and oxides, hydroxides, carbonates, nitrates, or organic salts of M.

[0042] As an example, in the presence of Li 3+x V 1-x M x In the lithium vanadium oxide composition represented by formula (1) of O4, M is assumed to be Ti, and x is 0.05 when the raw materials are mixed. Li2CO3, V2O5 and TiO2 are mixed in a molar ratio of Li2CO3:V2O5:TiO2 = (3.05 / 2):(0.95 / 2):0.05. Lithium hydroxide or its hydrate can also be used instead of Li2CO3.

[0043] The reactants are obtained by calcining a mixture of raw material powders. The calcination atmosphere can be atmospheric or an inert gas atmosphere. Inert atmospheres include, for example, argon or nitrogen. The raw material mixture can also be calcined in a reducing atmosphere. Reducing atmospheres include, for example, ammonia, methane, or hydrogen sulfide.

[0044] Lithium vanadium oxide can be obtained by mechanically and chemically reacting a mixture of raw material powders with each other in a mixing device such as a planetary ball mill (by a mechanical-chemical grinding method). The lithium vanadium oxide of the first embodiment can be obtained by these methods.

[0045] Here, the molar ratio of the raw materials during mixing may not be the same as the molar ratio of the reactants. This is because sometimes the raw materials may not be able to enter the reactants due to evaporation or other reasons during the reaction.

[0046] Therefore, the composition x of lithium vanadium oxide is determined by methods such as ICP emission spectroscopy, atomic absorption spectrometry, and EPMA (electron probe microanalysis).

[0047] (Second Implementation)

[0048] The second embodiment will be described below. Matters described in the first embodiment will be omitted as appropriate.

[0049] Figure 1The electrode material 100 of the second embodiment is shown. The electrode material 100 contains an active substance 111 and a solid electrolyte 112. To improve electronic conductivity, the electrode material 100 may contain a conductive additive 113. The active substance 111, the solid electrolyte 112, and the conductive additive 113 are, for example, in particulate form. The active substance 111 contains lithium vanadium oxide of the first embodiment. The lithium vanadium oxide of the first embodiment is suitable for reducing the expansion and contraction rate of the electrode material 100 and for facilitating the insertion and removal of Li in the electrode material 100.

[0050] The active material 111 may also contain lithium vanadium oxide of the first embodiment as a main component. "Contains lithium vanadium oxide of the first embodiment as a main component" means that the component with the highest content by mass percentage is lithium vanadium oxide of the first embodiment. The active material 111 may also be composed of lithium vanadium oxide of the first embodiment.

[0051] The conductive additive 113 can also be provided in a manner that coats at least a portion of the particles of the active material 111. In this way, the contact area between the particles of the conductive additive 113 and the particles of the active material 111 can be increased. As a result, when the electrode material 100 is used in the battery, the battery resistance is reduced, thereby improving the battery output.

[0052] The ratio of the particle volume of conductive additive 113 to the sum of the particle volume of active substance 111 and the particle volume of conductive additive 113 can be greater than 0.01 and less than 0.4.

[0053] Since the electrode material 100 of the second embodiment contains the lithium vanadium oxide of the first embodiment, if the electrode material 100 of the second embodiment is used, an electrode with high theoretical capacity and durability can be realized.

[0054] The electrode material 100 in the second embodiment can be included in the negative electrode.

[0055] (Third Implementation)

[0056] The third embodiment will be described below. Matters described in the first and second embodiments will be omitted as appropriate.

[0057] Figure 3 The battery 1000 is shown as an example of the third embodiment. The battery 1000 has a positive electrode 101, an electrolyte layer 102, and a negative electrode 103. The electrolyte layer 102 is disposed between the positive electrode 101 and the negative electrode 103.

[0058] The positive electrode 101 contains active materials and solid electrolytes.

[0059] Electrolyte layer 102 contains an electrolyte material. The electrolyte material is, for example, a solid electrolyte material.

[0060] The negative electrode 103 contains active material 111 and solid electrolyte 112.

[0061] The active material 111 of the negative electrode is a particle containing lithium vanadium oxide of the first embodiment. The active material 111 of the negative electrode may also be a particle containing lithium vanadium oxide of the first embodiment as a main component. "Particles containing lithium vanadium oxide of the first embodiment as a main component" means particles in which lithium vanadium oxide of the first embodiment is the most abundant component by mass ratio. The active material 111 of the negative electrode may also be a particle composed of lithium vanadium oxide of the first embodiment.

[0062] The negative electrode active material 111 can also have a median particle size of 0.1 μm or more and 100 μm or less. When the negative electrode active material 111 has a median particle size of 0.1 μm or more, the active material 111 and the solid electrolyte 112 can be well dispersed in the negative electrode 103. This improves the charge and discharge characteristics of the battery. When the negative electrode active material 111 has a median particle size of 100 μm or less, the lithium diffusion rate within the active material 111 is increased. This allows the battery 1000 to operate at high output.

[0063] The active material 111 of the negative electrode can also have a larger median particle size than the solid electrolyte 112. In this way, the active material 111 and the solid electrolyte 112 can be well dispersed.

[0064] In order to improve the energy density and output power of the battery 1000, in the negative electrode 103, the ratio of the volume of the active material 111 to the total volume of the active material 111 and the solid electrolyte 112 can be greater than 0.30 and less than 0.95.

[0065] To improve the energy density and output of the battery 1000, the negative electrode 103 can have a thickness of more than 10 μm and less than 500 μm.

[0066] The solid electrolyte 112 contained in the negative electrode 103 can be a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, or a polymer solid electrolyte.

[0067] 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 halogen elements but also oxygen.

[0068] 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 or Li 10 GeP2S 12 .

[0069] Examples of halide solid electrolytes include those made from Li a Me b Y c The compound represented by X6 satisfies a + mb + 3c = 6 and c > 0. Me is at least one metallic element and metalloid element selected from those 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.

[0070] "Metalloid 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).

[0071] To improve the ionic conductivity of halide solid electrolytes, Me can be at least one element selected from Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0072] Another example of a halide solid electrolyte is that made of Li α’ M β O γ X δ The compound is represented by the following formula. α, β, γ, and δ are all values ​​greater than 0. M is at least one element selected from metallic and metalloid elements other than Li. X is at least one element selected from Cl, Br, and I. In this compound composition, 0.9 ≤ α ≤ 1.2, β = 1.0, 1.0 ≤ γ ≤ 1.3, and 3.6 ≤ δ ≤ 4.0.

[0073] Examples of oxide solid electrolytes include:

[0074] (i) NASICON-type solid electrolytes such as LiTi2(PO4)3 or its elemental substitutes.

[0075] (ii) Perovskite-type solid electrolytes such as (LaLi)TiO3.

[0076] (iii)Li 14 ZnGe4O 16LISICON-type solid electrolytes such as Li4SiO4, LiGeO4, or their elemental substitutions.

[0077] (iv)Li7La3Zr2O 12 Garnet-type solid electrolytes, or their elemental substitutions, or

[0078] (v)Li3PO4 or its N-substituted derivatives.

[0079] Examples of polymeric solid electrolytes include compounds of polymers and lithium salts. The polymers can have an oxyethylene structure. Polymers with an oxyethylene structure can contain more lithium salts, thus exhibiting higher ionic conductivity. Polymeric solid electrolytes can be, for example, composite compounds of polyoxyethylene and lithium salts. An example of such polymeric solid electrolytes is lithium bis(trifluoromethanesulfonyl)imide.

[0080] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or 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.

[0081] The positive electrode 101 contains a material capable of absorbing and releasing metal ions (e.g., lithium ions). The positive electrode 101 may contain, for example, an active material (e.g., particles of the active material).

[0082] 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 oxysulfides, or transition metal oxynitrides. Examples of lithium-containing transition metal oxides include Li(Ni,Co,Al)O2, Li(Ni,Co,Mn)O2, or LiCoO2.

[0083] In this disclosure, “(A, B, C)” means “at least one selected from A, B and C”.

[0084] From the perspective of cost and safety of Battery 1000, lithium phosphate can also be used as the active material for the positive electrode.

[0085] The positive electrode active material can also have a median particle size of 0.1 μm or more and 100 μm or less. When the positive electrode active material has a median particle size of 0.1 μm or more, the active material and solid electrolyte can be well dispersed in the positive electrode 101. This improves the charge-discharge characteristics of the battery 1000. When the positive electrode active material has a median particle size of 100 μm or less, the lithium diffusion rate within the positive electrode active material is increased. This allows the battery 1000 to operate at high output.

[0086] The active material of the positive electrode can also have a larger median particle size than the solid electrolyte. In this way, the active material of the positive electrode and the solid electrolyte can be well dispersed.

[0087] In order to improve the energy density and output power of the battery 1000, in the positive electrode 101, the ratio of the volume of the active material to the total volume of the active material and the solid electrolyte can be greater than 0.30 and less than 0.95.

[0088] A coating layer can also be formed on the surface of the electrode active material. This helps suppress the rise of the battery's reactive overvoltage. Examples of coating materials include sulfide solid electrolytes, oxide solid electrolytes, polymeric solid electrolytes, or halide solid electrolytes.

[0089] The coating material can be a halide solid electrolyte material or an oxide solid electrolyte material. The halide solid electrolyte material may contain fluorine (F). This improves the stability of the coating material at high potentials. Therefore, the battery 1000 has high charge / discharge efficiency. The oxide solid electrolyte can be lithium niobate or a polyanionic material, which also exhibits stability at high potentials. This also results in high charge / discharge efficiency for the battery 1000.

[0090] To improve the energy density and output of the battery 1000, the cathode 101 can have a thickness of more than 10 μm and less than 500 μm.

[0091] The solid electrolyte contained in the positive electrode 101 can be a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, or an organic polymer solid electrolyte.

[0092] Electrolyte layer 102 contains an electrolyte material. This electrolyte material is, for example, a solid electrolyte material. Electrolyte layer 102 can also be a solid electrolyte layer. The solid electrolyte material contained in electrolyte layer 102 can be a sulfide solid electrolyte, a halide solid electrolyte, or a polymer solid electrolyte.

[0093] The electrolyte layer 102 can have a thickness of 1 μm or more but less than 100 μm. When the electrolyte layer 102 has a thickness of 1 μm or more, the positive electrode 101 and the negative electrode 103 are less prone to short circuits. When the electrolyte layer 102 has a thickness of less than 100 μm, the battery 1000 can operate at high output.

[0094] Figure 3 A battery 2000 is shown as another example of the third embodiment. Figure 3 In this example, the battery 2000 has a positive electrode 201, an electrolyte layer 202, and a negative electrode 203. In this example, the electrolyte layer 202 includes an electrolyte layer 212 (hereinafter referred to as the "first electrolyte layer") with the same configuration as the electrolyte layer 102 described above, and an electrolyte layer 222 (hereinafter referred to as the "second electrolyte layer") separately configured with the electrolyte layer 212. The second electrolyte layer 222 is disposed between the first electrolyte layer 212 and the negative electrode 203. Furthermore, the positive electrode 201 and the negative electrode 203 are respectively connected to… Figure 2 The positive electrode 101 and the negative electrode 103 shown are constructed in the same way.

[0095] When the electrolyte layer 202 is composed of a first electrolyte layer 212 and a second electrolyte layer 222, the second electrolyte layer 222 can also be composed of other solid electrolyte materials that are electrochemically more stable than the first electrolyte layer 212. Specifically, the reduction potential of the solid electrolyte material constituting the second electrolyte layer 222 can be lower than the reduction potential of the solid electrolyte material constituting the first electrolyte layer 212. In this way, it can be used without reducing the solid electrolyte material contained in the first electrolyte layer 212. As a result, the charge and discharge efficiency of the battery can be improved.

[0096] Selected from composition Figure 2 At least one of the positive electrode 101, electrolyte layer 102, and negative electrode 103 of the battery 1000 shown may contain a non-aqueous electrolyte, a gel electrolyte, or an ionic liquid to promote lithium-ion donation and acceptance and improve the battery's output characteristics. (Selected from the components...) Figure 3 At least one of the positive electrode 201, electrolyte layer 202 and negative electrode 203 of the battery 2000 shown may contain a non-aqueous electrolyte, a gel electrolyte or an ionic liquid.

[0097] Non-aqueous electrolytes contain 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, or fluorinated solvents. Examples of cyclic carbonate solvents include ethylene carbonate, propylene carbonate, or butyl carbonate. Examples of chain carbonate solvents include dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of cyclic ether solvents include tetrahydrofuran, 1,4-dihydrofuran, etc. Alkane or 1,3-dioxolane. Examples of chain ether solvents include 1,2-dimethoxyethane or 1,2-diethoxyethane. Examples of cyclic ester solvents include γ-butyrolactone. Examples of chain ester solvents include methyl acetate.

[0098] Examples of fluorinated solvents include fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, (fluoroethyl) (methyl) carbonate, or dimethyl fluorocarbonate. A single non-aqueous solvent selected from these can be used. Alternatively, a mixture of two or more non-aqueous solvents selected from these can be used.

[0099] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or 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.

[0100] As a gel electrolyte, polymeric materials impregnated with a non-aqueous electrolyte can be used. Examples of polymeric materials include polyoxyethylene, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or polymers containing oxyethylene bonds.

[0101] Examples of cations contained in ionic liquids include:

[0102] (i) Tetraalkylammonium or tetraalkyl Aliphatic chain quaternary salts,

[0103] (ii) Pyrrolidine morpholine Imidazolium Tetrahydropyrimidine Piperazine or piperidine Aliphatic cyclic ammonium compounds, and

[0104] (iii) Pyridine or imidazole Nitrogen-containing heterocyclic aromatic cations, such as...

[0105] Examples of anions contained in ionic liquids include PF6. - BF4 - SbF6 - AsF6 - SO3CF3 - N(SO2CF3)2 - N(SO2C2F5)2 - N(SO2CF3)(SO2C4F9) -Or C(SO2CF3)3 - .

[0106] Ionic liquids can contain lithium salts.

[0107] Selected from composition Figure 2 At least one of the positive electrode 101, electrolyte layer 102, and negative electrode 103 of the battery 1000 shown may contain a binder to improve the adhesion between particles. (Selected from the components) Figure 3 At least one of the positive electrode 201, electrolyte layer 202 and negative electrode 203 of the battery 2000 shown may also contain a binder.

[0108] 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, hexafluoropolypropylene, styrene-butadiene rubber, and carboxymethyl cellulose. Copolymers can also be used as adhesives. Examples of such adhesives include 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.

[0109] To improve electronic conductivity, construct Figure 2 The negative electrode 103 of the battery 1000 shown may also contain a conductive additive 113. (Construction) Figure 3 The negative electrode 203 of the battery 2000 shown may also contain conductive additives.

[0110] Examples of conductive additives include:

[0111] (i) Graphite, such as natural or artificial graphite.

[0112] (ii) Carbon blacks such as acetylene black or Ketjen black.

[0113] (iii) Conductive fibers such as carbon fiber or metal fiber.

[0114] (iv) Fluorocarbon,

[0115] (v) Metal powders such as aluminum

[0116] (vi) Conductive whiskers such as zinc oxide or potassium titanate.

[0117] (vii) Conductive metal oxides such as titanium dioxide, and

[0118] (viii) Conductive polymers such as polyaniline, polypyrrole or polythiophene.

[0119] To reduce costs, the conductive additives described in (i) or (ii) above can be used.

[0120] constitute Figure 2 The positive electrode 101 of the battery 1000 shown may contain not only active material but also conductive additives. Examples of conductive additive materials are described above. (Composition) Figure 3 The positive electrode 201 of the battery 2000 shown may contain not only active material, but also conductive additives.

[0121] exist Figure 2 In the negative electrode 103 of the battery 1000 shown, the conductive additive 113 may also coat at least a portion of the surface of the active material 111. This increases the contact area between the conductive additive 113 and the active material 111. As a result, the battery resistance decreases, thereby improving output. Figure 3 The negative electrode 203 of the battery 2000 shown can also be constructed in the same manner as described above. Figure 2 In the positive electrode 101 shown, the conductive additive may also coat at least a portion of the surface of the active material. Figure 3 The positive electrode 201 of the battery 2000 shown can also be configured in the same way as described above.

[0122] exist Figure 2 In the negative electrode 103 of the battery 1000 shown, the ratio of the volume of the conductive additive 113 to the total volume of the active material 111 and the conductive additive 113 can be 0.01 or more and 0.4 or less. Figure 3 The negative electrode 203 of the battery 2000 shown can also be constructed in the same manner as described above. Figure 2 In the positive electrode 101 of the battery 1000 shown, the ratio of the volume of the conductive additive to the total volume of the active material and the conductive additive can be 0.01 or more and 0.4 or less. Figure 3 The positive electrode 201 of the battery 2000 shown can also be configured in the same way as described above.

[0123] Figure 1 The electrode material 100 shown may also be included Figure 2 In the negative electrode 103 shown, when the electrode material 100 is included in the negative electrode 103, a coating layer can be formed on the surface of the active material 111 to prevent the solid electrolyte 112 from reacting with the active material 111. In this way, the battery has high charge / discharge efficiency. Similarly, Figure 1 The electrode material 100 shown may also be included Figure 3 In the negative electrode 203 of the battery 2000 shown. Figure 3 In the battery 2000 shown, a coating layer can also be formed on the surface of the active material of the negative electrode.

[0124] Examples of coating materials included in the coating layer include sulfide solid electrolytes, oxide solid electrolytes, polymeric solid electrolytes, or halide solid electrolytes.

[0125] Examples of sulfide solid electrolytes include Li₂S-P₂S₅. Examples of oxide solid electrolytes include trilithium phosphate. Examples of polymeric solid electrolytes include composites of polyethylene oxide and lithium salts. Another example of such polymeric solid electrolytes is lithium bis(trifluoromethanesulfonyl)imide.

[0126] Examples of the battery shape in the third embodiment include coin type, cylindrical type, square type, sheet type, button type, flat type, or stacked type.

[0127] The battery of the third embodiment can be manufactured by, for example, preparing materials for forming a positive electrode, materials for forming an electrolyte layer, and materials for forming a negative electrode, and using known methods to create a laminate in which a positive electrode, an electrolyte layer, and a negative electrode are sequentially arranged.

[0128] (Other implementation methods)

[0129] (Postscript)

[0130] Based on the description of the above embodiments, the following technology is disclosed.

[0131] (Technology 1)

[0132] A lithium vanadium oxide, which is a lithium vanadium oxide containing Li, V, M and O.

[0133] M is selected from at least one tetravalent metallic element and tetravalent metalloid element other than V.

[0134] The lithium vanadium oxide contains both β-phase and γ-phase as crystalline phases.

[0135] According to this disclosure, lithium vanadium oxide, by containing both β-phase and γ-phase as crystalline phases, can balance the capacity and durability of batteries using lithium vanadium oxide as active material.

[0136] (Technology 2)

[0137] The lithium vanadium oxide according to technology 1 has Li 3+x V 1-x M x The composition is represented by O4, and satisfies 0 < x < 1. With this configuration, the capacity of the battery using lithium vanadium oxide as the active material is increased.

[0138] (Technology 3)

[0139] According to the lithium vanadium oxide described in Technology 2, it satisfies 0 < x ≤ 0.2. With this configuration, using this lithium vanadium oxide as the active material, the battery capacity is further improved.

[0140] (Technology 4)

[0141] According to any one of techniques 1-3, the lithium vanadium oxide contains Ti in M. With this configuration, when the lithium vanadium oxide is used as an active material, the active material easily maintains a high theoretical capacity.

[0142] (Technology 5)

[0143] According to any one of techniques 1 to 4, in the X-ray diffraction pattern using Cu-Kα rays as the radiation source, the ratio of the intensity of the diffraction peak belonging to the (101) plane of the β phase to the intensity of the diffraction peak belonging to the (011) plane of the γ phase is 0.1 or more and 10.0 or less. With this configuration, when the lithium vanadium oxide is used as an active material in a battery, a battery with good charge-discharge characteristics can be realized.

[0144] (Technology 6)

[0145] According to any one of techniques 1 to 4, in an X-ray diffraction pattern using Cu-Kα rays as the radiation source, the intensity of the diffraction peak appearing at a diffraction angle 2θ of 22.7° ± 0.2° is 0.1 or more and 10.0 or less relative to the intensity of the diffraction peak appearing within the range of a diffraction angle 2θ of 22.4° ± 0.2°. With this configuration, when this lithium vanadium oxide is used as an active material in a battery, a battery with excellent charge-discharge characteristics can be achieved.

[0146] (Technology 7)

[0147] A negative electrode active material comprising lithium vanadium oxide as described in any one of techniques 1 to 6. With this configuration, the negative electrode active material includes both β-phase and γ-phase as crystalline phases, resulting in a battery that balances capacity and durability.

[0148] (Technology 8)

[0149] A battery comprising: a positive electrode, a negative electrode containing the negative electrode active material described in Technique 7, and an electrolyte disposed between the positive electrode and the negative electrode. With this configuration, the negative electrode active material contains both β-phase and γ-phase as crystalline phases, resulting in a battery that balances capacity and durability.

[0150] (Technology 9)

[0151] According to the battery of technology 8, the negative electrode contains a conductive additive. With this configuration, the negative electrode contains a conductive additive, thereby improving the conductivity of the negative electrode.

[0152] Example

[0153] The following examples and comparative examples will be used to describe the details of this disclosure. Furthermore, lithium vanadium oxide, negative electrode active material, and battery are not limited to the examples described below.

[0154] <Example 1>

[0155] [Production of Lithium Vanadium Oxide]

[0156] The lithium vanadium oxide of Example 1 was prepared as follows. As raw material powders, Li2CO3 (manufactured by High Purity Chemical Research Institute Co., Ltd., purity 99.9%), V2O5 (manufactured by High Purity Chemical Research Institute Co., Ltd., purity 99.9%), and TiO2 (manufactured by High Purity Chemical Research Institute Co., Ltd., purity 99.9%) were prepared in a molar ratio of Li2CO3:V2O5:TiO2 = 1.525:0.475:0.05. A 10% by mass excess of Li2CO3 was prepared relative to the aforementioned composition. That is, Li2CO3 was prepared in a 10% by mass excess relative to the molar ratio described above. These raw material powders were mixed in a mortar to obtain a mixed powder. The obtained mixed powder was pre-calcined at 600°C in air for 3 hours. The resulting pre-calcined powder was then formally calcined at 965°C in air for 15 hours. Here, the heating was carried out at an average rate of 5°C / minute, and the cooling was carried out at an average rate of 3°C / minute. In this way, the lithium vanadium oxide of Example 1 was obtained.

[0157] <Example 2>

[0158] Except that the formal firing temperature was changed to 900°C, the lithium vanadium oxide of Example 2 was prepared using the same method as in Example 1.

[0159] <Example 3>

[0160] As raw material powders, Li₂CO₃, V₂O₅, and TiO₂ were prepared in a molar ratio of Li₂CO₃:V₂O₅:TiO₂ = 1.525:0.475:0.05. Li₂CO₃ was prepared in a 3% mass excess relative to the aforementioned molar ratio. The resulting mixed powder was pre-calcined using the same method as in Example 1, and then formally calcined at 800°C in atmospheric atmosphere for 15 hours. This produced the lithium vanadium oxide of Example 3.

[0161] <Comparative Example 1>

[0162] As raw material powders, Li₂CO₃ and V₂O₅ were prepared in a molar ratio of Li₂CO₃:V₂O₅ = 1.5:0.5. Li₂CO₃ was prepared in a 3% mass excess relative to the molar ratio described above. The resulting mixed powder was pre-calcined using the same method as in Example 1, and then formally calcined at 800°C in atmospheric atmosphere for 15 hours. This produced the lithium vanadium oxide of Comparative Example 1.

[0163] <Comparative Example 2>

[0164] Except for changing the molar ratio of the raw material powders to Li2CO3:V2O5:TiO2 = 1.55:0.45:0.10, the lithium vanadium oxide of Comparative Example 2 was prepared using the same method as in Example 1.

[0165] X-ray diffraction measurement

[0166] In a dry atmosphere with a dew point below -45°C, X-ray diffraction measurements were performed on the lithium vanadium oxides of Example 1, Comparative Example 1, and Comparative Example 2 using an X-ray diffraction apparatus (RIGAKU, MiniFlex 600). Cu-Kα lines (wavelengths 1.5405 Å and 1.5444 Å) were used as the X-ray source.

[0167] Figure 4 This is a graph showing the X-ray diffraction patterns of Example 1, Comparative Example 1, and Comparative Example 2. (See diagram below.) Figure 4 As shown, the diffraction pattern of the lithium vanadium oxide in Example 1 has both diffraction peaks belonging to the crystal plane of the β phase and diffraction peaks belonging to the crystal plane of the γ phase. Although Figure 4 Although not shown in the diagram, the diffraction patterns of the lithium vanadium oxides in Examples 2 and 3 are similar to those in Example 1, exhibiting both diffraction peaks belonging to the crystal plane of the β phase and diffraction peaks belonging to the crystal plane of the γ phase. That is, the lithium vanadium oxides of Examples 1-3 respectively contain both the β phase and the γ phase as crystalline phases.

[0168] In the diffraction peaks obtained from the lithium vanadium oxide of Example 1, the ratio of the intensity of the diffraction peak belonging to the γ phase (011) plane at 2θ = 22.7° to the intensity of the diffraction peak belonging to the γ phase (101) plane at 2θ = 22.4°, i.e., I(β phase) / I(γ phase), is 0.41. In the diffraction peaks obtained from the lithium vanadium oxide of Example 2, the I(β phase) / I(γ phase) value is 0.83. In the diffraction peaks obtained from the lithium vanadium oxide of Example 3, the I(β phase) / I(γ phase) value is 2.28.

[0169] like Figure 4 As shown, the diffraction pattern of the lithium vanadium oxide in Comparative Example 1 only contains diffraction peaks belonging to the crystal plane of the β phase. That is, the lithium vanadium oxide in Comparative Example 1 only contains the β phase. Furthermore, the diffraction pattern of the lithium vanadium oxide in Comparative Example 2 only contains diffraction peaks belonging to the crystal plane of the γ phase. That is, the lithium vanadium oxide in Comparative Example 2 only contains the γ phase.

[0170] [ICP emission spectroscopy analysis]

[0171] The Ti composition ratio of the lithium vanadium oxide in Example 1 was analyzed using ICP emission spectroscopy. An ICP emission spectroscopy apparatus (Hitachi High-Tech Science, PS3520VDDII) was used in the analysis. In the lithium vanadium oxide of Example 1, x in composition formula (1) was 0.05. The Ti composition ratio of the lithium vanadium oxides in Examples 2, 3, and Comparative Example 2 was analyzed using the same method as in Example 1. In the lithium vanadium oxides of Examples 2 and 3, x in composition formula (1) was 0.05. In the lithium vanadium oxide of Comparative Example 2, x in composition formula (1) was 0.1. When the lithium vanadium oxides calculated based on the compositions of Examples 1-3 and Comparative Examples 1-2 are used as active materials, the theoretical capacity of the active material is shown in Table 1.

[0172] [Making the negative electrode]

[0173] Li3PS4 (hereinafter referred to as "LPS") was prepared as a solid electrolyte. Lithium vanadium oxide from Example 1 was prepared as the negative electrode active material. LPS, the negative electrode active material, a conductive additive, a solvent containing a binder, and an organic solvent were added to a polypropylene container, and the materials were stirred using an ultrasonic homogenizer. The negative electrode slurry was coated onto a current collector foil to form a coating film. The current collector foil with the coating film was placed on a hot plate, and the organic solvent was removed from the coating film under an argon atmosphere. In this way, a negative electrode was obtained. The negative electrode was pre-dried at 70°C for 20 minutes, and then formally dried at 110°C for 30 minutes.

[0174] [The production of the positive electrode]

[0175] LPS was prepared as a solid electrolyte. Lithium nickel cobalt aluminum oxide (hereinafter referred to as "NCA") was prepared as the positive electrode active material. LPS, NCA, a conductive additive, a binder-containing solvent, and an organic solvent were added to a polypropylene container, and the materials were stirred using an ultrasonic homogenizer. The positive electrode slurry was coated onto a current collector foil to form a coating film. The current collector foil with the coating film was placed on a hot plate, and the organic solvent was removed from the coating film under an argon atmosphere. The positive electrode was thus obtained. The positive electrode was pre-dried at 70°C for 20 minutes and then formally dried at 120°C for 30 minutes.

[0176] [Making a Second-hand Battery]

[0177] In an insulating outer cylinder, a sulfide solid electrolyte Li₂S-P₂S₅ layer (equivalent to 550 μm thick, 80 mg) and a positive electrode are sequentially stacked. The positive electrode, after being fabricated as described above, is stamped to a size of φ9.2 mm and stacked on the sulfide solid electrolyte material. Next, a negative electrode is stacked on the side opposite to the positive electrode contacting the solid electrolyte layer. The negative electrode, after being fabricated as described above, is stamped to a size of φ9.2 mm and stacked on the solid electrolyte layer. The positive and negative electrodes are combined such that the theoretical capacity of the negative electrode is 1.2 times that of the theoretical capacity of the positive electrode. By pressing the film stacked in the above order under a pressure of 80 MPa, a laminate consisting of a positive electrode, a solid electrolyte layer, and a negative electrode is produced.

[0178] Next, stainless steel current collectors are installed on the positive and negative terminals respectively, and current collector leads are installed on each current collector.

[0179] Finally, an insulating sleeve is used to isolate the interior of the insulating outer cylinder from the external atmosphere, thus sealing the interior of the cylinder. The battery of Example 1 is manufactured as described above. Batteries of Example 2, Example 3, Comparative Example 1, and Comparative Example 2 are manufactured using the same method as in Example 1.

[0180] [Charge / Discharge Test]

[0181] The batteries of Examples 1-3 and Comparative Examples 1-2 were respectively placed in a thermostatic bath maintained at 25°C. They were charged with a constant current at a rate of 0.05C (20-hour rate) relative to the theoretical capacity of the batteries. The charging termination voltage was 3.6V. The batteries were then discharged at a current value at a rate of 0.05C until a voltage of 1.0V was reached. After two cycles of charge-discharge at a rate of 0.05C, a durability test was performed. Under the durability test conditions, at a C rate, 100 charge-discharge cycles were performed with a current value at a rate of 1C (1-hour rate).

[0182] Figure 5 The discharge capacity retention rates of the batteries of Examples 1-3 and Comparative Example 1 after 100 cycles are shown. Table 1 shows the discharge capacity retention rates of the batteries of Examples 1-3 and Comparative Example 1 after 100 cycles. Here, "discharge capacity retention rate after 100 cycles" refers to the ratio of the discharge capacity of the 100th charge-discharge cycle to the discharge capacity of the first cycle.

[0183] [Table 1]

[0184]

[0185] (Inspection)

[0186] As shown in Examples 1-3, by doping with Ti, a negative electrode active material composed of lithium vanadium oxide containing both β and γ phases was obtained while maintaining a high theoretical capacity. The negative electrode active material composed of lithium vanadium oxide in Example 3 has a high β / γ ratio, exhibiting a mixed-phase state dominated by the β phase. Nevertheless, the battery of Example 3 exhibits a high discharge capacity retention rate.

[0187] The negative electrode active material composed of lithium vanadium oxide in Comparative Example 1 only contains the β phase. Therefore, the discharge capacity retention rate of the battery in Comparative Example 1 is low. As shown in the results of Comparative Example 2, a single γ phase can be prepared by increasing the ratio of the mass of V to the total mass of V and M to 10%. However, if the mass of Ti is increased, the theoretical capacity will decrease significantly, and therefore the advantages of lithium vanadium oxide cannot always be fully utilized.

[0188] As described above, the lithium vanadium oxide of this disclosure is suitable for providing batteries that can balance capacity and durability.

[0189] Industry availability

[0190] The lithium vanadium oxide disclosed herein can, for example, be used as an active material in lithium-ion secondary batteries.

[0191] Explanation of reference numerals in the attached figures

[0192] 100 electrode material

[0193] 111 active substances

[0194] 112 solid electrolyte

[0195] 113 conductive additive

[0196] 101, 201 positive electrode

[0197] 102202 Electrolyte Layer

[0198] 103, 203 negative electrode

[0199] 212 First Electrolyte Layer

[0200] 222 Second Electrolyte Layer

[0201] 1000 and 2000 batteries

Claims

1. A lithium vanadium oxide, which is a lithium vanadium oxide containing Li, V, M and O, M is selected from at least one tetravalent metallic element and tetravalent metalloid element other than V. The lithium vanadium oxide contains both β-phase and γ-phase as crystalline phases.

2. The lithium vanadium oxide as described in claim 1, wherein it has Li 3+x V 1-x M x O4 represents the composition, and satisfies 0 < x < 1.

3. The lithium vanadium oxide as described in claim 2, wherein 0 < x ≤ 0.

2.

4. The lithium vanadium oxide as claimed in claim 1, wherein M comprises Ti.

5. The lithium vanadium oxide as described in claim 1, wherein in the X-ray diffraction pattern using Cu-Kα rays as the radiation source, the ratio of the intensity of the diffraction peak belonging to the (101) plane of the β phase to the intensity of the diffraction peak belonging to the (011) plane of the γ phase is 0.1 or more and 10.0 or less.

6. The lithium vanadium oxide as claimed in claim 1, wherein in the X-ray diffraction pattern using Cu-Kα rays as the radiation source, the ratio of the intensity of the diffraction peak appearing at a diffraction angle 2θ of 22.7°±0.2° to the intensity of the diffraction peak appearing in the range of diffraction angle 2θ of 22.4°±0.2° is 0.1 or more and 10.0 or less.

7. A negative electrode active material comprising lithium vanadium oxide as described in any one of claims 1 to 6.

8. A battery having: positive electrode, A negative electrode comprising the negative electrode active material as described in claim 7, and An electrolyte disposed between the positive electrode and the negative electrode.

9. The battery of claim 8, wherein the negative electrode contains a conductive additive.

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