Anode material, battery, method for manufacturing anode material, and method for manufacturing a battery

Abstract

To improve the performance of a negative electrode material.SOLUTION: Provided is a negative electrode material for batteries, which contains carbon, sodium tungstate that is provided on the surface of the carbon, and silicon that is provided on the surface of the carbon.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an anode material, a battery, a method for producing an anode material, and a method for producing a battery. [Background technology]

[0002] Carbon is sometimes used as the negative electrode material for lithium-ion secondary batteries. For example, Patent Document 1 describes a negative electrode in which tungsten trioxide is disposed on the surface of graphite. By disposing tungsten trioxide on the surface of graphite, it is possible to improve the diffusibility of lithium ions, thereby improving battery characteristics such as capacity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-45904 Summary of the Invention [Problem to be solved by the invention]

[0004] However, there is still room for improvement in the performance of such negative electrode materials.

[0005] The present invention has been made in view of the above, and an object of the present invention is to provide an anode material, a battery, a method for manufacturing an anode material, and a method for manufacturing a battery with improved performance. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the negative electrode material according to the present disclosure is a negative electrode material for a battery, and includes carbon, sodium tungstate provided on a surface of the carbon, and silicon provided on the surface of the carbon.

[0007] To solve the above problems and achieve the objectives, the battery according to the present disclosure includes the above-described negative electrode material and a positive electrode material.

[0008] In order to solve the above-mentioned problems and achieve the object, the method for producing a negative electrode material according to the present disclosure includes the steps of: adding silicon to a first solution containing sodium and a surfactant dissolved therein to produce a second solution in which the silicon is dispersed in the first solution; adding carbon to the second solution to produce a third solution in which the carbon is dispersed in the second solution; mixing the third solution with a tungsten solution containing tungsten to produce a fourth solution; and removing liquid components from the fourth solution to produce a negative electrode material.

[0009] In order to solve the above-mentioned problems and achieve the objectives, the method for manufacturing a battery according to the present disclosure includes the method for manufacturing the negative electrode material and a step of manufacturing a positive electrode material. [Effects of the Invention]

[0010] According to the present invention, the performance of the negative electrode material can be improved. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic partial cross-sectional view of a battery according to this embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view of an example of the negative electrode according to this embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view of another example of the negative electrode according to this embodiment. [Figure 4] FIG. 4 is a flowchart illustrating an example of a method for manufacturing a battery according to this embodiment. [Figure 5] FIG. 5 is a table showing the identification results of the negative electrode materials for each example. [Figure 6] FIG. 6 shows the results of XRD measurements of the negative electrode material of the example. [Figure 7] FIG. 7 is a photograph of the negative electrode material in the example. [Figure 8] FIG. 8 is a photograph of the negative electrode material in the example. [Figure 9] FIG. 9 is a photograph of the negative electrode material in the example. [Figure 10] FIG. 10 is a photograph of the negative electrode material in the example. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the following detailed description of the invention (hereinafter referred to as the embodiment). Furthermore, the components in the following embodiment include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiment can be combined as appropriate.

[0013] (battery) FIG. 1 is a schematic partial cross-sectional view of a battery according to this embodiment. The battery 1 according to this embodiment is a lithium-ion secondary battery. The battery 1 includes a casing 10, an electrode group 12, and an electrolyte (not shown). The casing 10 is a case that houses the electrode group 12 and the electrolyte. In addition to the electrode group 12, the casing 10 may also include wiring and terminals connected to the electrode group 12.

[0014] The electrode group 12 includes a negative electrode 14, a positive electrode 16, and a separator 18. The electrode group 12 is configured such that the separator 18 is disposed between the negative electrode 14 and the positive electrode 16. In the example of FIG. 1 , the electrode group 12 has a so-called stacked electrode group structure in which rectangular negative electrodes 14 and rectangular positive electrodes 16 are alternately stacked with a rectangular separator 18 sandwiched therebetween. However, the electrode group 12 is not limited to a stacked electrode group structure. For example, the electrode group 12 may have a wound electrode group structure in which strip-shaped negative electrodes 14 and strip-shaped positive electrodes 16 are stacked with a strip-shaped separator 18 sandwiched therebetween and then wound.

[0015] (Negative electrode) FIG. 2 is a schematic cross-sectional view of an example of a negative electrode according to this embodiment. As shown in FIG. 2, the negative electrode 14 includes a current collecting layer 20 and a negative electrode material layer 22. The current collecting layer 20 is a layer made of a conductive material. An example of the conductive material of the current collecting layer 20 is copper. The negative electrode material layer 22 is a layer containing the negative electrode material according to this embodiment. The negative electrode material layer 22 is provided on the surface of the current collecting layer 20. The thickness of the current collecting layer 20 may be, for example, approximately 15 μm to 40 μm, and the thickness of the negative electrode material layer 22 may be, for example, approximately 20 μm to 200 μm.

[0016] The negative electrode material layer 22 includes a negative electrode material. The negative electrode material includes carbon, sodium tungstate provided on the surface of the carbon, and silicon provided on the surface of the carbon. The sodium tungstate is Na x WO y where x and y are numbers greater than 0. x WO y Details will be given later.

[0017] In addition, sodium tungstate has a crystal structure of Na x WO y Not only in the form of Na2WO4 and Na5W 14 O 44 In addition, Na2WO4 has a valence of 2 for Na, 1 for W, and 4 for O, so Na x WO y It can be said that it is expressed by the chemical formula Na5W 14 O 44 When the valence of W is converted to 1, Na 5 / 14 WO 44 / 14 (That is, the valence of Na is 5 / 14, the valence of W is 1, and the valence of O is 44 / 14), so Na x WO y It can be said that it is expressed by the chemical formula: Na x WO ySodium tungstate represented by the chemical formula above can be said to refer to sodium tungstate in which the ratio of the valence of Na, the valence of W, and the valence of O is X:1:Y.

[0018] More specifically, the negative electrode material of the negative electrode material layer 22 is a mixture of carbon particles 30, which are particles of carbon, and sodium tungstate particles, Na x WO y The negative electrode material of this embodiment includes (sodium tungstate) particles 32 and silicon particles 33, which are silicon particles. The particles here are not limited to being spherical in shape, but may be any shape, such as linear or sheet-like. Furthermore, the particle surface may be smooth or uneven. The negative electrode material of this embodiment may also contain unavoidable impurities as the remainder.

[0019] The sodium tungstate provided on the surface of carbon includes at least one of the following: sodium tungstate directly adhered to carbon; sodium tungstate indirectly adhered to carbon via silicon adhered to carbon; silicon indirectly adhered to carbon via sodium tungstate adhered to carbon; and composite particles of sodium tungstate and silicon directly adhered to carbon, directly or indirectly adhered to carbon. Note that the negative electrode material in this embodiment preferably contains at least silicon and carbon to which sodium tungstate is adhered.

[0020] The negative electrode material of the negative electrode layer 22 includes a plurality of carbon particles 30. The carbon particles 30 include amorphous carbon or graphite.

[0021] Amorphous carbon is non-crystalline carbon that does not have a crystalline structure. Amorphous carbon is also called amorphous carbon or diamond-like carbon, and can be said to be carbon with a mixture of sp2 bonds and sp3 bonds. Amorphous carbon particles are composed entirely of amorphous carbon, and preferably contain no components other than amorphous carbon, except for unavoidable impurities. Specifically, amorphous carbon particles preferably do not contain graphite.

[0022] Graphite is carbon with a planar crystalline structure.

[0023] The carbon particles 30 preferably have an average particle size of 1 μm or more and 50 μm or less, and more preferably 1 μm or more and 20 μm or less. When the average particle size is in this range, the strength of the electrode film can be maintained.

[0024] The negative electrode material of the negative electrode material layer 22 further contains a plurality of Na x WO y The carbon particles 30 include a plurality of Na particles 32 and a plurality of silicon particles 33. x WO y The silicon particles 32 and the silicon particles 33 are provided. x WO y One of the particles 32 is Na x WO y The particles 32 are provided on the surface of the carbon particles 30. x WO y The other Na of particle 32 x WO y The particles 32 are provided on the surfaces of the silicon particles 33. More specifically, the silicon particles 33 are in close contact with the surfaces of the carbon particles 30, and Na x WO y The carbon particles 30 and Na x WO yThe particles 32 and the silicon particles 33 may be composited. Alternatively, the carbon particles 30 and the silicon particles 33 may be composited, and the carbon particles 30 and the Na x WO y The negative electrode material of the negative electrode material layer 22 may be a composite of the carbon particles 30 and the Na x WO y The carbon particles 30 and the silicon particles 33 are composited together, and the carbon particles 30 and the Na x WO y The particle 32 may be composited with the particle 32. Furthermore, sodium tungstate has a crystal structure containing Na x WO y Not only in the form of Na2WO4 and Na5W 14 O 44 In addition, Na2WO4 has a valence of 2 for Na, 1 for W, and 4 for O, so Na x WO y It can be said that it is expressed by the chemical formula Na5W 14 O 44 When the valence of W is converted to 1, Na 5 / 14 WO 44 / 14 (That is, the valence of Na is 5 / 14, the valence of W is 1, and the valence of O is 44 / 14), so Na x WO y It can be said that it is expressed by the chemical formula: Na x WO y Sodium tungstate represented by the chemical formula above can be said to refer to sodium tungstate in which the ratio of the valence of Na, the valence of W, and the valence of O is X:1:Y.

[0025] The term "composite" used here means, at least when no external force is applied, separating the silicon particles 33 from the carbon particles 30 and separating the silicon particles 33 from the Na x WO y Separating from particle 32, and Na x WO yThis refers to a state in which it is impossible to separate the particles 32 from the carbon particles 30. For example, the external force refers to the force that occurs when a battery using the negative electrode material is operated and an SEI (Solid Electrolyte Interphase) coating is formed to cover the entire surface and expands and contracts.

[0026] For example, the composite is formed by disposing silicon particles 33 on the surface of carbon particles 30 and disposing Na on the surface of the silicon particles 33. x WO y forming a composite in which the carbon particles 32 are arranged; x WO y Particle 32 is arranged in Na x WO y forming a composite in which silicon particles 33 are arranged on the surface of the particle 32; forming a composite in which silicon particles 33 are arranged on the surface of the carbon particle 30; x WO y The silicon particles 33 are arranged on the surface of the silicon particles 33 to form a complex. x WO y The carbon particles 30 are formed on the surface thereof. x WO y Particles 32 and Si particles 33 are arranged, and Na x WO y The particles 32 and the Si particles 33 are also in close contact with each other.

[0027] Na contained in the negative electrode material of the negative electrode material layer 22 x WO y The particles 32 preferably have y (valence of O) of 3, in other words, Na x The negative electrode material of the negative electrode material layer 22 is preferably WO3. x WO y In the particles 32, it is preferable that x (the valence of Na) is greater than 0 and is equal to or less than 1, and y (the valence of O) is equal to or greater than 2 and is equal to or less than 4. x WO yIn the particles 32, the valence of x is more preferably 0.1 or more and 0.95 or less and y is 2.5 or more and 3.5 or less, more preferably the valence of x is more preferably 0.1 or more and 0.95 or less and y is 2.8 or more and 3.2 or less, and even more preferably the valence of x is more preferably 0.3 or more and 0.7 or less and y is 2.8 or more and 3.2 or less. When x and y are within these ranges, Na is formed on the surface of the carbon particles 30. x WO y The negative electrode material of the negative electrode material layer 22 is a single type of Na x WO y It may contain only particles 32 or multiple types of Na x WO y It may contain particles 32.

[0028] The negative electrode material of the negative electrode material layer 22 is Na x WO y As particle 32, Na 0.78 WO3 and Na 0.48 WO3, Na 0.72 WO3 and Na 0.48 WO3, Na 0.44 WO3, Na 0.48 WO3 and Na 0.52 WO3, Na2WO4 and Na5W 14 O 44 As described above, the negative electrode material of the negative electrode layer 22 in this embodiment preferably contains at least one of sodium tungstate, Na 0.78 WO3 and Na 0.48 WO3, Na 0.72 WO3 and Na 0.48 WO3, Na 0.44 WO3 and Na 0.48 WO3, Na 0.52 WO3, Na2WO4 and Na5W 14 O 44 It is preferable to include at least one of the following.

[0029] Na x WO yThe compounds contained in the negative electrode material, such as the particles 32, can be measured by XRD (X-ray diffraction). The measurement conditions for XRD may be, for example, as follows. Measurement equipment: Rigaku Corporation Ultima IV ·Tube used: Cu Tube voltage: 40kV ·Tube current: 40mA Scanning range: 5°~80° Scanning speed: 2° / min As a database for identifying compounds, the powder diffraction and crystal structure database ICDD (PDF2.DAT), i.e., PDF2.DAT from the ICDD (International Center for Diffraction Data), may be used. Then, for the crystal peaks detected by XRD, the integrated powder X-ray diffraction software PDXL2 may be used to identify the compounds contained in the measurement sample (here, the negative electrode material). Specifically, the software may be used to extract compounds whose FOM (figure of merit) is below a threshold, and the compounds whose FOM is below the threshold may be identified as compounds contained in the measurement sample (here, the negative electrode material). The FOM takes a value between 0 and 100, with the smaller the value, the higher the degree of match. The threshold for the FOM may be set to 10. For example, the diffraction peak of the negative electrode material may be identified as Na in ICDD. 0.78 When the FOM for the diffraction peak of WO3 is below a threshold value (e.g., 10), the negative electrode material contains Na. 0.78 For example, if the peak waveform in the X-ray diffraction analysis of the object to be analyzed shows the peak waveform of carbon, but the (002) peak waveform in the known graphite structure becomes broad, it can be determined that the object is amorphous carbon.

[0030] Na x WO y The average particle size of the particles 32 is smaller than the average particle size of the carbon particles 30. x WO y The average particle size of the particles 32 is preferably 100 nm or more and 20 μm or less, and more preferably 100 nm or more and 1 μm or less.

[0031] In this way, the negative electrode material is formed by disposing particulate sodium tungstate (Na x WO y The negative electrode material has a structure in which sodium tungstate and silicon (silicon particles 32) are provided on the surface of carbon, but is not limited thereto. The negative electrode material may have a structure in which sodium tungstate and silicon are provided on the surface of carbon, and the shapes of the sodium tungstate and silicon provided on the surface of carbon may be arbitrary. In this embodiment, sodium tungstate is used as the tungsten compound or tungsten oxide. Furthermore, although silicon is used in this embodiment, a silicon compound or silicon oxide may also be used.

[0032] Sodium tungstate (Na x WO y The content of sodium tungstate (Na tungstate particles 32) and silicon can be confirmed by measuring the content of Na, W, O, and Si by fluorescent X-ray analysis. That is, at least a part of the total amount of Na, W, O, and Si detected by fluorescent X-ray analysis is sodium tungstate (Na tungstate particles 32). x WO y Since the particles 32) and silicon are composed of sodium tungstate and silicon, the contents of Na, W, O, and Si can be confirmed.

[0033] The negative electrode material preferably has a Na content of 0.01% to 0.5% by mass, a W content of 1% to 20% by mass, an O content of 1% to 15% by mass, and a Si content of 1% to 15% by mass, as measured by X-ray fluorescence analysis.More preferably, the negative electrode material has a Na content of 0.02% to 0.5% by mass, a W content of 0.7% to 17% by mass, an O content of 2% to 13% by mass, and a Si content of 2% to 12% by mass, as measured by X-ray fluorescence analysis. Furthermore, it is more preferable that the negative electrode material has a Na content of 0.03% to 0.4% by mass, a W content of 1% to 15% by mass, an O content of 3% to 12% by mass, and a Si content of 3% to 10% by mass, as measured by X-ray fluorescence analysis. When the Na, W, O, and Si contents are within these ranges, sodium tungstate and silicon are contained in appropriate amounts, allowing the tungsten compound and silicon to be appropriately arranged on the carbon surface.

[0034] The negative electrode material preferably has a C content of 60% to 95%, more preferably 65% ​​to 95%, and even more preferably 70% to 92%, by mass, as measured by X-ray fluorescence analysis. When the C content is within this range, the tungsten compound can be appropriately arranged on the carbon surface.

[0035] The negative electrode material preferably has a mass ratio of Na / W, which is the ratio of Na content to W content, as measured by X-ray fluorescence analysis, of 0.001 to 0.2, more preferably 0.005 to 0.15, and even more preferably 0.007 to 0.15. Furthermore, the negative electrode material preferably has a mass ratio of W / C, which is the ratio of W content to C content, as measured by X-ray fluorescence analysis, of 0.005 to 0.3, more preferably 0.008 to 0.25, and even more preferably 0.01 to 0.2. Furthermore, the negative electrode material preferably has a mass ratio of Si / O, which is the ratio of Si content to O content, as measured by X-ray fluorescence analysis, of 0.1 to 2, more preferably 0.2 to 1.5, and even more preferably 0.3 to 1.3. By ensuring that the content ratios fall within these ranges, the tungsten compound can be appropriately arranged on the carbon surface.

[0036] The negative electrode material preferably has a mass ratio of Si / W, which is the ratio of Si content to W content, measured by X-ray fluorescence analysis, of 0.1 to 15, more preferably 0.15 to 12, and even more preferably 0.2 to 10. Furthermore, the negative electrode material preferably has a mass ratio of Si / C, which is the ratio of Si content to C content, measured by X-ray fluorescence analysis, of 0.01 to 0.3, more preferably 0.02 to 0.25, and even more preferably 0.03 to 0.15. By ensuring that the content ratios fall within these ranges, the tungsten compound and silicon can be appropriately arranged on the carbon surface.

[0037] The X-ray fluorescence analysis may be carried out using a wavelength dispersive X-ray fluorescence analyzer, and the measurement conditions may be as follows. Measuring device: Rigaku ZSX PrimusIV Tube voltage: 30kV ·Tube current: 100mA The measurement method is the standardless fundamental parameter method, and the analysis can be performed using Rigaku's SQX scattered ray FP method.

[0038] The negative electrode material layer 22 is made of a negative electrode material (carbon particles 30, Na x WO y The negative electrode material layer 22 may contain a material other than the carbon particles 32 and the silicon particles 33. The negative electrode material layer 22 may contain, for example, a binder. Any material may be used for the binder, and examples thereof include polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), and polyacrylic acid (PAA). Only one type of binder may be used, or two or more types may be used in combination. However, when the carbon particles 30 are amorphous carbon, it is preferable that the negative electrode material layer 22, in other words, the negative electrode material, does not contain graphite.

[0039] Also, Na x WO y The arrangement of the particles 32 and silicon particles 33 on the surface of the carbon particles 30 can be confirmed by observing with an electron microscope such as a SEM (Scanning Electron Microscope) or a TEM (Transmission Electron Microscope).

[0040] (Modification of negative electrode) 3 is a schematic cross-sectional view of another example of the negative electrode according to this embodiment. The negative electrode material of the negative electrode material layer 22 is a silicon particle 33 that is in close contact with the surface of the carbon particle 30, and Na x WO y The particles 32 may be in close contact with (contact with) the surface of the carbon particles 30. In this case, the carbon particles 30 and the silicon particles 33 are composited, and the carbon particles 30 and the Na x WO y The particles 32 may be composited.

[0041] Na x WO yThe particles 32 include those with a cubic crystal structure and those with a tetragonal crystal structure. That is, the negative electrode material includes at least one of sodium tungstate with a cubic crystal structure and sodium tungstate with a tetragonal crystal structure. However, the crystal structure of the sodium tungstate included in the negative electrode material is not limited to this, and sodium tungstate with another crystal structure, such as a triclinic crystal, may also be included.

[0042] In this way, the negative electrode material is formed by disposing particulate sodium tungstate (Na x WO y The negative electrode material has a structure in which sodium tungstate and silicon are provided on the surface of carbon, but is not limited thereto. The negative electrode material may have a structure in which sodium tungstate and silicon are provided on the surface of carbon, and the sodium tungstate and silicon provided on the surface of carbon may have any shape.

[0043] (positive electrode) The positive electrode 16 includes a current collecting layer and a positive electrode material layer. The current collecting layer of the positive electrode 16 is a layer made of a conductive material, such as aluminum. The positive electrode material layer is a layer of a positive electrode material and is provided on the surface of the current collecting layer of the positive electrode 16. The thickness of the positive electrode current collecting layer may be, for example, about 10 μm to 30 μm, and the thickness of the positive electrode material layer may be, for example, about 10 μm to 100 μm.

[0044] The positive electrode material layer includes a positive electrode material. The positive electrode material includes particles of a lithium compound, which is a compound containing lithium. The lithium compound may be a lithium-containing metal oxide or a lithium-containing phosphate. More specifically, the lithium compound may be LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi a Co b Mn cO2 (where 0 < a < 1, 0 < b < 1, 0 < c < 1, and a + b + c = 1), LiFePO4, etc. may be mentioned. The lithium compound may contain only one type of material or may contain two or more types of materials. Further, the positive electrode material layer may contain substances other than the positive electrode material, for example, it may contain a binder. The material of the binder may be arbitrary, and for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PAA, etc. may be mentioned. Only one type of binder may be used, or two or more types may be used in combination.

[0045] (Separator) The separator 18 is an insulating member. In this embodiment, the separator 18 is, for example, a porous film made of resin, and examples of the resin include polyethylene (PE), polypropylene (PP), etc. Further, the separator 18 may have a structure in which films of different materials are laminated. Also, the separator 18, the separator 13 may have a heat-resistant layer. The heat-resistant layer is a layer containing a substance with a high melting point. The heat-resistant layer may contain, for example, particles of an inorganic material such as alumina.

[0046] (Electrolyte) The electrolyte provided in the battery 1 is a non-aqueous electrolyte. The electrolyte is impregnated in the voids in the electrode group 12. The electrolyte contains, for example, a lithium salt and an aprotic solvent. The lithium salt is dispersed and dissolved in the aprotic solvent. Examples of the lithium salt include LiPF6, LiBF4, Li[N(FSO2)2], Li[N(CF3SO2)2], Li[B(C2O4)2], LiPO2F2, etc. The aprotic solvent may be, for example, a mixture of a cyclic carbonate and a chain carbonate. Examples of the cyclic carbonate include EC, PC, butylene carbonate, etc. Examples of the chain carbonate include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), etc.

[0047] (Method for manufacturing a battery) Next, an example of a method for manufacturing the battery 1 according to this embodiment will be described. Fig. 4 is a flowchart illustrating an example of a method for manufacturing the battery according to this embodiment. As shown in Fig. 4, in this manufacturing method, the negative electrode 14 is formed in steps S10 to S22.

[0048] Specifically, a surfactant is dissolved in a solvent to generate a first solution (step S10). The first solution is a solution in which the surfactant is dissolved and which contains Na (Na in an ionic state). The surfactant is used to disperse carbon and silicon. Any surfactant capable of dispersing carbon may be used, but in this embodiment, a surfactant containing Na is used. For example, sodium dodecyl sulfate (SDS) may be used as a surfactant containing Na. The solvent of the first solution may be any solvent capable of dissolving the surfactant, but for example, water may be used.

[0049] The surfactant is not limited to one containing Na. In this case, for example, a surfactant not containing Na and a compound containing Na may be dissolved in a solvent to produce the first solution. As the surfactant not containing Na, for example, poly(oxyethylene) alkyl ether, polyoxyethylene nonylphenyl ether, etc. may be used. As the poly(oxyethylene) alkyl ether, it is preferable to use one having an alkyl group with 12 to 15 carbon atoms, for example, C 12 H 25 O(C2H4) n H(poly(oxyethylene) dodecyl ether), C 13 H 27 O(C2H4) n H(poly(oxyethylene) tridecyl ether), C 13 H 27 O(C2H4) n H(poly(oxyethylene) isotridecyl ether), C 14 H 25 O(C2H4) n H(poly(oxyethylene)tetradecyl ether), C 155 H 25 O(C2H4)n H(poly(oxyethylene)pentadecyl ether), etc., may be used. Here, n is an integer of 1 or more. Examples of polyoxyethylene nonylphenyl ether include CH 19 C6(CH2CH2O)8H, C9H 19 C6(CH2CH2O) 10 H, C9H 19 C6(CH2CH2O) 12 H, etc. Examples of compounds containing Na include sodium sulfate, sodium stearate, sodium hyaluronate, and sodium hypochlorite.

[0050] The content of the surfactant in the first solution, i.e., the amount of surfactant added, is preferably 0.1% to 10% by mass, more preferably 0.5% to 7% by mass, and even more preferably 1% to 5% by mass, relative to the amount of carbon raw material added in the subsequent step S14. By setting it within this range, the amount of surfactant added is reduced. x WO y This can appropriately improve the affinity with

[0051] Next, a silicon raw material is added to the first solution to generate a second solution (step S12). The silicon raw material is silicon used as a raw material. In step S12, first, the silicon raw material is put into a solvent to generate a silicon solution. In this embodiment, water is used as the solvent. Then, the silicon solution is put into the first solution and stirred to generate a second solution.

[0052] The silicon content in the first solution, i.e., the amount of silicon added, is preferably 1% or more and 10% or less, more preferably 2% or more and 8% or less, and even more preferably 3% or more and 6% or less, in mass ratio relative to the amount of carbon raw material added in the subsequent step S14.

[0053] Next, a carbon raw material is added to the second solution to produce a third solution (step S14). The carbon raw material is amorphous carbon used as a raw material. The carbon raw material preferably has an average particle size of 1 μm or more and 50 μm or less, and more preferably 1 μm or more and 20 μm or less. By setting the average particle size of the carbon raw material within this range, it is possible to increase the capacity of the battery. In step S14, the second solution to which the carbon raw material has been added, i.e., the third solution, is stirred to disperse the carbon raw material in the second solution. In other words, the third solution can be said to be the second solution in which the carbon raw material has been dispersed.

[0054] The carbon raw material may be produced, for example, by an oil furnace method. In the oil furnace method, for example, a raw material oil is sprayed into a high-temperature atmosphere to cause thermal decomposition, and then rapidly cooled to produce a particulate amorphous carbon raw material. However, the method for producing the carbon raw material is not limited to this and may be any method.

[0055] Next, the third solution and the tungsten solution are mixed to generate a fourth solution (step S16). The tungsten solution is a solution containing W and O. The tungsten solution is, for example, a solution generated by dissolving a tungsten oxide raw material in a solvent. The tungsten oxide raw material here is Na x WO y The raw material of the particles 32 is, for example, tungsten trioxide. As the solvent, for example, an alkaline liquid is used, and in this embodiment, an aqueous ammonia solution is used. Therefore, in this embodiment, the tungsten solution is an alkaline solution containing W and O, or more specifically, ammonium tungstate. However, the tungsten solution may be any solution containing W and O.

[0056] The content of W in the tungsten solution added to the second solution, i.e., the amount of W added, is preferably 0.5% or more and 20% or less, more preferably 1% or more and 15% or less, and even more preferably 1.3% or more and 10% or less, by mass ratio relative to the amount of carbon raw material added in step S14. By setting it within this range, the amount of W added to the tungsten solution is reduced. x WO y In addition, by setting the content in this range, the surface of the carbon particle 30 can be formed with Na. x WO y By properly forming the particles 32, it is possible to increase the capacity of the battery by using them as a negative electrode.

[0057] Next, the liquid component of the fourth solution is removed to produce a negative electrode material (negative electrode material production step). In this embodiment, steps S18 and S20 are executed as the negative electrode material production step. Specifically, the fourth solution is dried to produce a negative electrode intermediate (step S18; drying step). In step S18, for example, the fourth solution is dried in the atmosphere at 80°C for 12 hours to remove, i.e., evaporate, the liquid component contained in the fourth solution. However, the drying conditions may be arbitrary. It can be said that the negative electrode intermediate contains the solid component remaining after the liquid component of the fourth solution has been removed.

[0058] Next, the dried negative electrode intermediate is subjected to a heat treatment to produce a negative electrode material (step S20; heating step). By heating the negative electrode intermediate, Na is formed on the surface of the silicon particles 33. x WO y The negative electrode material is formed by dissolving the carbon particles 32 on the surface of the carbon particles 30 dispersed in the fourth solution. That is, the ionic states of Na, W, and O contained in the third solution are dissolved in Na x WO y It precipitates as particles 32 to form the negative electrode material.

[0059] The conditions for heating the negative electrode intermediate in the heating step may be arbitrary, but are preferably performed as follows: That is, the heating step preferably includes a step of placing the negative electrode intermediate in a furnace and creating an inert atmosphere inside the furnace, a first heating step of heating the negative electrode intermediate to a first temperature at a first heating rate, and a second heating step of heating the negative electrode intermediate heated to the first temperature to a second temperature at a second heating rate.

[0060] The inert atmosphere in the step of creating an inert atmosphere inside the furnace may be, for example, a nitrogen atmosphere or a rare gas atmosphere such as Ar, and the inert atmosphere may be created by, for example, replacing oxygen in the furnace with nitrogen or a rare gas. Note that this step is not essential.

[0061] The first heating step is a step for removing metals, organic substances, and the like contained in the negative electrode intermediate. The first heating temperature in the first heating step is, for example, 550°C, but is not limited thereto. The first heating temperature is preferably 150°C to 625°C, more preferably 175°C to 600°C, and more preferably 200°C to 575°C. The first heating rate may be any rate, but is, for example, preferably 45°C / hour to 75°C / hour, more preferably 50°C / hour to 70°C / hour, and even more preferably 55°C / hour to 65°C / hour. By setting the first heating temperature and the first heating rate within these ranges, metals, organic substances, and the like contained in the negative electrode intermediate can be appropriately removed.

[0062] The second heating step is performed after the first heating step. x WO yIn the second heating step, the second heating temperature is higher than the first heating temperature, for example, 700°C, but is not limited thereto, and is preferably 680°C or higher and 750°C or lower, preferably 685°C or higher and 740°C or lower, and more preferably 690°C or higher and 730°C or lower. The second heating rate may be any rate, but is preferably higher than the first heating rate, for example, preferably 165°C / hour or higher and 195°C / hour or lower, more preferably 170°C / hour or higher and 190°C / hour or lower, and even more preferably 175°C / hour or higher and 185°C / hour or lower. By setting the second heating temperature and the second heating rate within these ranges, it is possible to shorten the time required for the process while increasing the amount of Na. x WO y can be generated properly.

[0063] In the second heating step, the negative electrode intermediate heated to the second heating temperature is preferably held at the second heating temperature for a predetermined time, preferably from 1.25 hours to 2.75 hours, more preferably from 1.5 hours to 2.5 hours, and even more preferably from 1.75 hours to 2.25 hours.

[0064] Note that, prior to the first heating step (and in this embodiment, after the step of creating an inert atmosphere), a step of heating the negative electrode intermediate to a third temperature at a third heating rate and holding the negative electrode intermediate at the third temperature for a predetermined time may be provided. The third temperature is lower than the first temperature, for example, 100°C, but is not limited thereto. It is preferably 80°C to 120°C, more preferably 85°C to 115°C, and more preferably 90°C to 110°C. The third heating rate may also be any rate, for example, preferably 165°C / hour to 195°C / hour, more preferably 170°C / hour to 190°C / hour, and even more preferably 175°C / hour to 185°C / hour. The predetermined time for holding the negative electrode intermediate at the third heating temperature may also be any rate, for example, preferably 0.5 hours to 1.75 hours, more preferably 0.75 hours to 1.5 hours, and even more preferably 1.0 hour to 1.25 hours. By providing this step, moisture can be appropriately removed.

[0065] Next, the negative electrode 14 is formed using the formed negative electrode material (step S22). That is, the negative electrode 14 is formed by forming a negative electrode material layer 22 containing the negative electrode material on the surface of the current collecting layer 20.

[0066] This manufacturing method also includes forming the positive electrode 16 (step S24). In step S24, the positive electrode material may be formed by the same method as steps S10 to S20, except that a lithium compound raw material, which is a lithium compound, is used instead of the carbon raw material. Then, a positive electrode material layer containing the positive electrode material is formed on the surface of the current collecting layer for the positive electrode 16, thereby forming the positive electrode 16.

[0067] After the negative electrode 14 and the positive electrode 16 are formed, the negative electrode 14 and the positive electrode 16 are used to manufacture the battery 1 (step S26). Specifically, the negative electrode 14, the separator 18, and the positive electrode 16 are stacked together to form the electrode group 12, and the electrode group 12 and the electrolyte are housed in the casing 10 to manufacture the battery 1.

[0068] As described above, in this embodiment, as shown in steps S10 to S20, a fourth solution containing Na, O, W, and Si and having dispersed therein carbon is produced, and the liquid component is removed from the fourth solution to produce a negative electrode material. Hereinafter, this method of producing a negative electrode material will be referred to as a solution method, as appropriate. The above-described method of production will also be referred to as a first production method.

[0069] As described above, the negative electrode material of the battery according to this embodiment includes carbon, sodium tungstate provided on the surface of the carbon, and silicon provided on the surface of the carbon. By providing sodium tungstate and silicon on the surface of the carbon, the negative electrode material according to this embodiment can improve battery characteristics such as capacity.

[0070] It is known that the inclusion of silicon in a battery anode material improves battery performance. However, it is known that it is difficult to provide silicon on the carbon surface of the anode material. In this embodiment, a silicon-containing anode material provided on the carbon surface can be produced by a solution method using raw materials including carbon, sodium tungstate, and silicon.

[0071] Furthermore, in a negative electrode material in which sodium tungstate is provided on the surface of carbon, it is necessary to appropriately arrange the sodium tungstate on the surface of the carbon. If the sodium tungstate cannot be appropriately arranged on the surface of the carbon, i.e., if the sodium tungstate is not provided on the surface of the carbon or if the sodium tungstate is detached from the surface of the carbon, the battery characteristics cannot be appropriately improved. In contrast, the negative electrode material according to this embodiment uses amorphous carbon as the carbon, and sodium tungstate is provided on the surface of the amorphous carbon. The amorphous carbon can contain functional groups on its surface during the treatment to arrange the sodium tungstate on its surface. Therefore, these functional groups enable the sodium tungstate to be appropriately trapped on the surface of the amorphous carbon, allowing the sodium tungstate to be appropriately arranged on the surface. Furthermore, the amorphous carbon can contain functional groups (e.g., hydroxyl groups, carboxyl groups) on its surface during the treatment to arrange the sodium tungstate on its surface. Therefore, this functional group makes it possible to appropriately trap sodium tungstate on the surface of the amorphous carbon, thereby allowing tungsten trioxide to be appropriately arranged. Furthermore, because this functional group fixes sodium tungstate to the surface of the amorphous carbon, the adhesion of sodium tungstate to the surface of the amorphous carbon can be increased, and separation of sodium tungstate from the carbon surface can be suppressed. In particular, since hard carbon raw materials are produced at lower temperatures than, for example, graphite, the functional groups are more likely to remain without being removed, allowing sodium tungstate and silicon to be appropriately arranged on the surface.

[0072] The negative electrode material according to this embodiment is preferably a composite of carbon, sodium tungstate, and silicon, and in this embodiment, the sodium tungstate and silicon can be appropriately arranged on the surface of the carbon.

[0073] In the negative electrode material according to this embodiment, sodium tungstate is Nax WO y It is preferable that x is greater than 0 and less than or equal to 1, and y is greater than or equal to 2 and less than or equal to 4. By including sodium tungstate of this chemical formula, it is possible to appropriately arrange sodium tungstate on the surface of the carbon.

[0074] Furthermore, the negative electrode material according to this embodiment preferably has a sodium content of 0.01% to 0.5% by mass, a tungsten content of 0.5% to 20% by mass, and an oxygen content of 1% to 15% by mass, as measured by X-ray fluorescence analysis. When Na, W, and O are within these ranges, sodium tungstate is contained in appropriate amounts, allowing the sodium tungstate to be appropriately arranged on the carbon surface.

[0075] Furthermore, the negative electrode material according to this embodiment preferably has a ratio of sodium to tungsten, Na / W, of 0.001 to 0.2, as measured by fluorescent X-ray analysis. When Na / W is in this range, an appropriate amount of sodium tungstate is contained, and the sodium tungstate can be appropriately arranged on the surface of the carbon.

[0076] In the negative electrode material according to this embodiment, the carbon is preferably amorphous carbon or graphite. According to this embodiment, sodium tungstate and silicon can be appropriately arranged on the surface of the amorphous carbon or graphite.

[0077] The negative electrode material according to this embodiment contains sodium tungstate having at least one of a tetragonal, a cubic, and an orthorhombic crystal structure, which allows the sodium tungstate to be appropriately arranged on the surface of the carbon.

[0078] In the negative electrode material according to this embodiment, sodium tungstate is Na x WO ywhere x is greater than 0 and less than or equal to 1, and y is greater than or equal to 2 and less than or equal to 4. By including sodium tungstate of this chemical formula, it is possible to properly arrange the sodium tungstate on the surface of the carbon.

[0079] The negative electrode material according to this embodiment preferably has a sodium content of 0.01% to 0.5% by mass, a tungsten content of 1% to 20% by mass, an oxygen content of 1% to 15% by mass, and a silicon content of 1% to 15% by mass, as measured by X-ray fluorescence analysis. By ensuring that Na, W, O, and Si fall within these ranges, sodium tungstate is contained in appropriate amounts, allowing the sodium tungstate to be appropriately disposed on the carbon surface.

[0080] In the negative electrode material according to this embodiment, the ratio of sodium to tungsten, Na / W, is 0.001 to 0.2, as measured by fluorescent X-ray analysis. When Na / W is in this range, an appropriate amount of sodium tungstate is contained, and the sodium tungstate can be appropriately arranged on the surface of the carbon.

[0081] The negative electrode material according to this embodiment has a silicon to carbon ratio Si / C of 0.01 to 0.3 as measured by fluorescent X-ray analysis. When Si / C is in this range, an appropriate amount of sodium tungstate is contained, and the sodium tungstate can be appropriately arranged on the surface of the carbon.

[0082] The negative electrode material according to this embodiment has a tungsten to carbon ratio W / C of 0.005 to 0.3, as measured by fluorescent X-ray analysis. When W / C is in this range, an appropriate amount of sodium tungstate is contained, allowing the sodium tungstate to be appropriately disposed on the surface of the carbon.

[0083] In the negative electrode material according to this embodiment, the Si / W ratio, which is the content ratio of silicon to tungsten, as measured by X-ray fluorescence analysis, is 0.1 or more and 15 or less. When Si / W is in this range, an appropriate amount of sodium tungstate is contained, and sodium tungstate can be appropriately arranged on the surface of the carbon.

[0084] In the negative electrode material according to this embodiment, the Si / O ratio, which is the silicon to oxygen content ratio as measured by X-ray fluorescence analysis, is 0.1 or more and 2 or less. When the Si / O ratio is in this range, an appropriate amount of sodium tungstate is contained, and the sodium tungstate can be appropriately arranged on the surface of the carbon.

[0085] The method for producing a negative electrode material according to this embodiment includes the steps of: adding silicon to a first solution containing sodium and a surfactant dissolved therein to produce a second solution in which silicon is dispersed in the first solution; adding amorphous carbon to the second solution to produce a third solution in which amorphous carbon is dispersed in the second solution; mixing the third solution with a tungsten solution containing oxygen and tungsten to produce a fourth solution; and removing the liquid components of the fourth solution to produce a negative electrode material. By producing a negative electrode material according to this embodiment, it is possible to properly arrange sodium tungstate and silicon on the surface of the carbon.

[0086] Furthermore, in the method for producing a negative electrode material according to this embodiment, the amount of W added is preferably 0.5% to 20% by mass, more preferably 1% to 15%, and even more preferably 1.3% to 10% by mass, relative to the amount of carbon raw material added in step S14. By setting the amount of W added within this range, sodium tungstate can be appropriately formed on the surface of the hard carbon, and the negative electrode can improve battery characteristics.

[0087] The negative electrode material producing step preferably includes a drying step of drying the fourth solution to produce a negative electrode intermediate, and a heating step of heating the negative electrode intermediate. By producing the negative electrode material by heating the negative electrode intermediate formed by drying the fourth solution, sodium tungstate is appropriately formed on the surface of the carbon, which can be used as a negative electrode to improve battery characteristics.

[0088] The heating step preferably includes the steps of heating the negative electrode intermediate to a first temperature of 150°C or more and 625°C or less at a first heating rate, heating the negative electrode intermediate heated to the first temperature at a second heating rate higher than the first heating rate to a second temperature of 680°C or more and 750°C or less, and holding the negative electrode intermediate at the second temperature. By producing the negative electrode material through the first heating step and the second heating step, sodium tungstate can be appropriately formed on the surface of the carbon.

[0089] (Example) Next, an example will be described.

[0090] Example 1 In Example 1, a negative electrode material was manufactured using the solution method described in the embodiment. Specifically, a first solution was prepared using water as a solvent and SDS dissolved as a surfactant. The concentration of SDS in the first solution was 4.85%. A silicon raw material was added to the first solution and stirred so that the mass ratio of the silicon raw material in the first solution to the amorphous carbon raw material to be added was 4.85%. This resulted in a second solution. An amorphous carbon raw material was added to the second solution and stirred so that the mass ratio of SDS in the second solution to the amorphous carbon raw material to be added was 3%. This resulted in a third solution. Ammonium tungstate (tungsten solution) was added to the third solution so that the amount of W contained in the ammonium tungstate (tungsten solution) relative to the amorphous carbon raw material in the third solution was 5% by mass. This resulted in a fourth solution. The fourth solution was stirred and then dried by heating to evaporate the water, producing a negative electrode intermediate. The negative electrode intermediate was then placed in a tubular furnace (sintering furnace) and heated to 550°C (first heating temperature) at a first heating rate of 60°C / hour under an argon atmosphere. After reaching the first heating temperature, the temperature was increased to 700°C (second heating temperature) at a second heating rate of 180°C / hour and maintained at this temperature for 2 hours. After maintaining the temperature for 2 hours, heating was stopped and the temperature was allowed to naturally decrease to 50°C, producing the negative electrode material.

[0091] In Example 1, the silicon raw material was prepared as follows. First, high-purity silicon chunks of several mm (purity: 11N) were crushed using a jaw crusher, and the crushed silicon particles were then separated using a sieve with 0.5 mm openings. Next, the silicon particles that passed through the 0.5 mm opening sieve were placed in a spherical ball mill and crushed for 6 hours to obtain silicon microparticles (silicon raw material). The particle size distribution of the obtained silicon microparticles was determined using a laser diffraction scattering particle size distribution measurement method (device product name "Microtrac MT3300EXII"). The volume average particle size of the silicon microparticles was 1.92 μm, and the d50 (median diameter) was 0.31 μm. The maximum volume diameter of the silicon microparticles was 32.23 μm, and the minimum volume diameter was 0.066 μm.

[0092] Example 2 In Example 2, a negative electrode material was produced in the same manner as in Example 1, except that the grinding time was 3 hours and the amounts of silicon, tungsten, and SDS added were 4 wt%, 2 wt%, and 1 wt%, respectively.

[0093] Example 3 In Example 3, a negative electrode material was produced in the same manner as in Example 1, except that the grinding time was 4 hours and the amounts of silicon, tungsten, and SDS added were 4 wt%, 15 wt%, and 5 wt%, respectively.

[0094] Example 4 In Example 4, a negative electrode material was produced in the same manner as in Example 1, except that the shape of the container used for crushing was a long-bodied container, the crushing time was 2 hours, and the amounts of silicon, tungsten, and SDS added were 4 wt%, 10 wt%, and 5 wt%, respectively.

[0095] Example 5 In Example 5, a negative electrode material was produced in the same manner as in Example 1, except that the shape of the container used for crushing was a long-bodied container, the crushing time was 1 hour, and the amounts of silicon, tungsten, and SDS added were 10 wt%, 2 wt%, and 2 wt%, respectively.

[0096] Example 6 In Example 6, a negative electrode material was produced in the same manner as in Example 1, except that the shape of the container used for crushing was a long-bodied container, the crushing time was 3 hours, and the amounts of silicon, tungsten, and SDS added were 3 wt%, 4 wt%, and 10 wt%, respectively.

[0097] Example 7 In Example 7, the shape of the container used for grinding was a spherical container, the grinding time was 2 hours, and the C of the surfactant in the first solution 12 H 25 O(C2H4) n A negative electrode material was produced in the same manner as in Example 1, except that H(poly(oxyethylene) dodecyl ether) was added at a concentration of 4% and sodium stearate was added at a concentration of 1%.

[0098] (Comparative Example 1) In Comparative Example 1, only carbon was used as the negative electrode material.

[0099] (Identification of negative electrode material) Fig. 5 is a table showing the identification results of the negative electrode material of each example. Fluorescent X-ray analysis was performed on the negative electrode material produced in each example to measure the content of elements contained in the negative electrode material, as well as Na / W, Si / C, W / C, Si / W, and Si / O. The measurement results of the content of elements are shown in Fig. 5. The measurement conditions for fluorescent X-ray analysis were the same as those described in the above embodiment. The negative electrode materials of Examples 1 to 7 contain elements other than C derived from carbon, Na, W, and O derived from sodium tungstate, and Si derived from silicon (here, S), which are impurities. Furthermore, they may contain unavoidable impurities other than the elements listed in FIG. 5.

[0100] XRD was performed on the negative electrode materials produced in each example to identify the chemical formula and crystalline structure of the sodium tungstate contained in the negative electrode material. The XRD measurement results are shown in Figure 6. The XRD measurement conditions were the same as those described in the above embodiment.

[0101] 6 shows the results of XRD measurement of the negative electrode material of Example 2. As shown in FIG. 6, the XRD measurement revealed that the negative electrode material of Example 2 is composed of cubic Na 0.72 WO3 and tetragonal Na 0.48 It can be seen that the negative electrode material of Example 1 contains WO3. It can also be seen that the negative electrode material of Example 1 contains Si. Although Si is also contained in samples other than Example 2, it will be omitted in the following description. Similarly, by XRD measurement, it can be seen that the negative electrode material of Example 1 contains cubic Na 0.78 WO3 and tetragonal Na 0.48 It was found that the negative electrode material of Example 3 contains cubic Na 0.44 WO3 and triclinic Na5(W 14 O 44 ), and the negative electrode material of Example 4 contains cubic Na 0.49 WO3 and tetragonal Na 0.33 It was found that the negative electrode materials of Examples 5 and 6 contain tetragonal Na0.48 The negative electrode material of Example 7 was found to contain cubic Na2WO4.

[0102] The negative electrode materials produced in each example were observed by SEM. As shown in the SEM observation results, it was found that in Examples 1 to 7, sodium tungstate was provided on the surface of the carbon.

[0103] (Evaluation results) To evaluate the negative electrode material of each example, the capacity of the negative electrode using the negative electrode material was measured. Specifically, the current value per 1g (mAh / g) was measured when the C rate was 0.2, and the current value per 1g (mAh / g) was measured when the C rate was 3.2. For example, the current value per 1g of the negative electrode when the C rate was 0.2 refers to the current value that consumes the rated capacity in 5 hours.

[0104] The evaluation results are shown in Figure 5. As shown in Figure 5, in Examples 1 to 7 in which sodium tungstate was provided on the surface of carbon, the battery characteristics at 0.2 C and 3.2 C were improved compared to Comparative Example 1 which did not contain sodium tungstate.

[0105] 7 to 10 show SEM photographs and elemental analysis results of the negative electrode material of Example 1. As shown in FIGS. 7 to 10, the SEM photographs reveal that the surfaces of the carbon particles 30 are scaly. In each of FIGS. 7 to 10, (A) on the left side is the SEM photograph, and (C) on the middle left is the sodium distribution image, (D) on the top right is the oxygen distribution image, (E) on the middle right is the silicon distribution image, and (F) on the bottom right is the carbon distribution image.

[0106] 7, tungsten and silicon do not overlap on the surface of carbon particle 30. The sodium concentration is slightly higher at the position of tungsten in the center of the photograph.

[0107] 8 and 9, tungsten and silicon overlap on the surface of carbon particle 30. In Fig. 9, the sodium concentration is slightly higher at the upper right position where the tungsten concentration is high.

[0108] 10 shows that many particles other than tungsten and silicon are attached to the surface of carbon particle 30. On the surface of carbon particle 30, there is a mixture of particles where tungsten and silicon overlap and particles where they do not. The sodium concentration is slightly higher at the lower left position where the tungsten concentration is high.

[0109] Although the embodiments of the present invention have been described above, the embodiments are not limited to the contents of these embodiments. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the scope of what is called equivalents. Furthermore, the above-described components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-described embodiments. [Explanation of symbols]

[0110] 1 battery 14 Negative electrode 22 Negative electrode material layer 30 carbon particles 32 Na x WO y 33 Silicon particles

Claims

1. A battery negative electrode material, A negative electrode material comprising: amorphous carbon; sodium tungstate provided on a surface of the amorphous carbon; and silicon provided on the surface of the amorphous carbon, wherein the sodium tungstate is represented by a chemical formula Na x WO y , where x is greater than 0 and less than or equal to 1, and y is greater than or equal to 2 and less than or equal to 4.

2. The negative electrode material according to claim 1 , wherein the amorphous carbon, the sodium tungstate, and the silicon are composited together.

3. 3. The negative electrode material according to claim 1, wherein the amorphous carbon and the sodium tungstate are composited, and the amorphous carbon and the silicon are composited.

4. The negative electrode material according to claim 1 , comprising the sodium tungstate having at least one of a tetragonal crystal structure and a cubic crystal structure.

5. 5. The negative electrode material of claim 4 comprising said sodium tungstate in a triclinic crystal structure.

6. 6. The negative electrode material according to claim 1, wherein the sodium content is from 0.01% to 0.5% by mass, the tungsten content is from 1% to 20% by mass, the oxygen content is from 1% to 15% by mass, and the silicon content is from 1% to 15% by mass, as measured by X-ray fluorescence analysis.

7. 7. The negative electrode material according to claim 1, wherein a content ratio of sodium to tungsten, Na / W, is 0.001 or more and 0.2 or less in mass ratio, as measured by fluorescent X-ray analysis.

8. 8. The negative electrode material according to claim 1, wherein the Si / C content ratio of silicon to amorphous carbon is 0.01 or more and 0.3 or less in mass ratio when measured by fluorescent X-ray analysis.

9. 9. The negative electrode material according to claim 1, wherein the W / C content ratio of tungsten to amorphous carbon, as measured by fluorescent X-ray analysis, is 0.005 or more and 0.3 or less in mass ratio.

10. 10. The negative electrode material according to claim 1, wherein the Si / W content ratio of silicon to tungsten, as measured by fluorescent X-ray analysis, is 0.1 to 15 in mass ratio.

11. 11. The negative electrode material according to claim 1, wherein a silicon to oxygen content ratio Si / O is 0.1 or more and 2 or less in mass ratio when measured by fluorescent X-ray analysis.

12. The sodium tungstate may be Na ０．７８ WO ３ , Na ０．４８ WO ３ , Na ０．７２ WO ３ , Na ０．４４ WO ３ , Na ０．５２ WO ３ , Na ２ WO ４、 and Na ５ W １４ O ４４ The negative electrode material according to claim 1 , comprising at least one of:

13. A battery anode material comprising:

1. A negative electrode material comprising: amorphous carbon; sodium tungstate provided on a surface of the amorphous carbon; and silicon provided on the surface of the amorphous carbon, wherein the sodium tungstate has at least one of a tetragonal crystal structure and a cubic crystal structure.

14. A battery anode material comprising:

1. A negative electrode material comprising: amorphous carbon; sodium tungstate provided on a surface of the amorphous carbon; and silicon provided on the surface of the amorphous carbon, wherein a content ratio of sodium to tungsten, Na / W, is equal to or greater than 0.001 and equal to or less than 0.2 by mass when measured by X-ray fluorescence analysis.

15. A battery anode material comprising: A negative electrode material comprising: amorphous carbon; sodium tungstate provided on a surface of the amorphous carbon; and silicon provided on the surface of the amorphous carbon, wherein the sodium tungstate includes at least one of Na0.78WO3, Na0.48WO3, Na0.72WO3, Na0.44WO3, Na0.52WO3, Na2WO4, and Na5W14O44.

16. A battery comprising the anode material according to any one of claims 1 to 15 and a cathode material.

17. A method for producing a negative electrode material for a battery, comprising: adding silicon to a first solution containing sodium and a surfactant dissolved therein to generate a second solution in which the silicon is dispersed in the first solution; adding amorphous carbon to the second solution to form a third solution in which the amorphous carbon is dispersed in the second solution; mixing the third solution with a tungsten solution containing oxygen and tungsten to generate a fourth solution; removing a liquid component of the fourth solution to produce a negative electrode material including amorphous carbon, silicon provided on a surface of the amorphous carbon, and sodium tungstate provided on a surface of the amorphous carbon; A method for producing a negative electrode material, comprising:

18. 18. The method for producing a negative electrode material according to claim 17, wherein a ratio of the amount of silicon added in the first solution to the amount of amorphous carbon added in the second solution is set to 1% or more and 10% or less in mass ratio.

19. The step of producing the negative electrode material includes: drying the fourth solution to form a negative electrode intermediate; and a heating step of heating the negative electrode intermediate.

20. The heating step comprises: heating the negative electrode intermediate at a first heating rate to a first temperature of 150° C. or greater and 625° C. or less; heating the negative electrode intermediate heated to the first temperature at a second heating rate higher than the first heating rate to a second temperature of 680°C or higher and 750°C or lower; and maintaining the negative electrode intermediate at the second temperature.

21. A method for manufacturing a battery, comprising the method for manufacturing an anode material according to any one of claims 17 to 20, and manufacturing a cathode material.

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