Negative electrode material, battery, manufacturing method of negative electrode material, and manufacturing method of battery

Abstract

It can improve the performance of the negative electrode material. The negative electrode material is the negative electrode material of the battery, which includes carbon, sodium tungstate disposed on the surface of carbon, and silicon disposed on the surface of carbon.

Description

[Technical Field]

[0001] This invention relates to a negative electrode material, a battery, a method for manufacturing the negative electrode material, and a method for manufacturing the battery. [Previous Technology]

[0002] Carbon is sometimes used as the negative electrode material in 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, the diffusion of lithium ions can be improved, thereby enhancing battery characteristics such as capacity. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-45904 [Summary of the Invention]

[0004] [The problem the invention aims to solve]

[0005] However, there is room for improvement in the performance of such anode materials.

[0006] This invention is based on the above and aims to provide a negative electrode material with improved performance, a battery, a method for manufacturing the negative electrode material, and a method for manufacturing the battery. [Means for solving the problem]

[0007] To solve the above problems and achieve the objective, the negative electrode material disclosed herein is a negative electrode material for a battery, which includes carbon, sodium tungstate disposed on the surface of the aforementioned carbon, and silicon disposed on the surface of the aforementioned carbon.

[0008] To address the above-mentioned issues and achieve the objectives, the battery system disclosed herein includes the aforementioned negative electrode material and positive electrode material.

[0009] In order to solve the above-mentioned problems and achieve the purpose, the method for manufacturing the negative electrode material disclosed herein includes the following steps: dissolving an surfactant, a first solution containing sodium, adding silicon, dispersing the silicon in the first solution to generate a second solution, adding carbon to the second solution, dispersing the carbon in the second solution to generate a third solution, mixing the third solution with a tungsten solution containing tungsten to generate a fourth solution, and removing the liquid components of the fourth solution to generate the negative electrode material.

[0010] To address the aforementioned issues and achieve the objectives, the battery manufacturing method disclosed herein includes the aforementioned method for manufacturing the negative electrode material and the steps for manufacturing the positive electrode material. [Effects of the Invention]

[0011] According to the present invention, the performance of the negative electrode material can be improved.

Implementation Method

[0013] Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to embodiments described below (hereinafter referred to as embodiments). Furthermore, the constituent elements of the following embodiments include those that are readily conceived by the art, substantially the same, and of the so-called equivalent scope. Moreover, the constituent elements disclosed in the following embodiments can be appropriately combined.

[0014] (Battery) Figure 1 is a partial cross-sectional view of a schematic battery according to this embodiment. The battery 1 of 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 an outer shell that houses the electrode group 12 and the electrolyte. Inside the casing 10, in addition to the electrode group 12, wiring or terminals connected to the electrode group 12 may be provided.

[0015] The electrode group 12 includes a negative electrode 14, a positive electrode 16, and a spacer 18. The electrode group 12 is configured such that the spacer 18 is disposed between the negative electrode 14 and the positive electrode 16. In the example of FIG1, the electrode group 12 is a stacked electrode group structure in which a rectangular spacer 18 is sandwiched between the rectangular negative electrode 14 and the rectangular positive electrode 16 are alternately stacked. However, the electrode group 12 is not limited to a stacked electrode group structure. For example, the electrode group 12 can also be a wound electrode group structure in which a strip-shaped spacer 18 is sandwiched between the strip-shaped negative electrode 14 and the strip-shaped positive electrode 16 are stacked.

[0016] (Negative Electrode) FIG2 is a schematic cross-sectional view of an example of the negative electrode of this embodiment. As shown in FIG2, the negative electrode 14 includes a current collector layer 20 and a negative electrode material layer 22. The current collector layer 20 is a layer composed of conductive members. Copper can be cited as an example of a conductive member of the current collector layer 20. The negative electrode material layer 22 is a layer containing the negative electrode material of this embodiment. The negative electrode material layer 22 is disposed on the surface of the current collector layer 20. The thickness of the current collector layer 20 can be, for example, 15 μm or more and 40 μm or less, and the thickness of the negative electrode material layer 22 can be, for example, 20 μm or more and 200 μm or less.

[0017] The negative electrode material layer 22 comprises a negative electrode material. The negative electrode material comprises carbon, sodium tungstate disposed on the surface of the carbon, and silicon disposed on the surface of the carbon. Sodium tungstate is a tungsten compound represented by NaxWOy, where x and y are numbers greater than 0. Details of NaxWOy will be described later.

[0018] However, sodium tungstate not only exists in crystal structure, but also in the form of Na xWO y, and can also take the form of Na 2WO 4 or Na 5W 14O 44. However, in the Na 2WO 4 system, the valence of Na is 2, the valence of W is 1, and the valence of O is 4, so it is represented by the chemical formula Na xWO y. Similarly, in the Na 5W 14O 44 system, when the valence of W is converted to 1, it is represented by the chemical formula Na 5 / 14WO 44 / 14 (i.e., the valence of Na is 5 / 14, the valence of W is 1, and the valence of O is 44 / 14), and can also be represented by the chemical formula Na xWO y. In other words, sodium tungstate represented by the chemical formula Na xWO y refers to sodium tungstate in which the ratio of the valence of Na to the valence of W to the valence of O is X:1:Y.

[0019] More specifically, the negative electrode material of the negative electrode material layer 22 comprises carbon particles 30 (carbon particles), sodium tungstate particles 32 (NaxWOy (sodium tungstate) particles), and silicon particles 33 (silicon particles). However, the particles are not limited to a spherical shape; they can be linear, sheet-like, or any other shape. Furthermore, the surface of the particles can be smooth or uneven. Also, the negative electrode material of this embodiment may contain unavoidable impurities in the residual portion.

[0020] The sodium tungstate disposed on the surface of carbon includes at least the following: sodium tungstate is directly fixed to carbon; sodium tungstate is indirectly fixed to carbon via silicon fixed to carbon; silicon is indirectly fixed to carbon via sodium tungstate fixed to carbon; or composite particles of sodium tungstate and silicon are directly or indirectly fixed to one side of carbon. However, it is preferable that the negative electrode material of this embodiment includes at least silicon and carbon with sodium tungstate fixed to it.

[0021] The negative electrode material of the negative electrode material layer 22 comprises a plurality of carbon particles 30. The carbon particles 30 comprise amorphous carbon or graphite.

[0022] Amorphous carbon refers to amorphous carbon that does not possess a crystalline structure. Amorphous carbon is sometimes referred to as amorphous carbon or diamond-like carbon, and can be described as carbon containing a mixture of sp2 and sp3 bonds. Ideally, the carbon particles of amorphous carbon should be composed entirely of amorphous carbon, excluding unavoidable impurities, and should not contain any components other than amorphous carbon. Specifically, it is preferable that the carbon particles of amorphous carbon do not contain graphite.

[0023] Graphite is a carbon with a planar crystalline structure.

[0024] The average particle size of the carbon particles in the 30 series is preferably 1 μm to 50 μm, and more preferably 1 μm to 20 μm. When the average particle size is within this range, the strength of the electrode film can be maintained.

[0025] The negative electrode material system of the negative electrode material layer 22 further includes a plurality of Na xWO y particles 32 and silicon particles 33. More specifically, for each carbon particle 30, a plurality of Na xWO y particles 32 and silicon particles 33 are disposed. One of the plurality of Na xWO y particles 32 is disposed on the surface of the carbon particle 30. Another of the plurality of Na xWO y particles 32 is disposed on the surface of the silicon particle 33. More specifically, the silicon particle 33 is in close contact with the surface of the carbon particle 30, and the Na xWO y particles 32 are in close contact with the surface of the silicon particle 33. The carbon particle 30, Na xWO y particles 32, and silicon particles 33 can be composited. Furthermore, carbon particles 30 and silicon particles 33 can be composited, or carbon particles 30 can be composited with NaxWOy particles 32. Therefore, the negative electrode material of the negative electrode material layer 22 can be composed of composite carbon particles 30, NaxWOy particles 32, and silicon particles 33, or it can include at least one of the compositions of composite carbon particles 30 and silicon particles 33 and composite carbon particles 30 and NaxWOy particles 32. Moreover, sodium tungstate is not only in terms of crystal structure, but NaxWOy can also be in the form of Na2WO4 or Na5W14O44. However, because Na2WO4 has a valence of 2, W has a valence of 1, and O has a valence of 4, it is represented by the chemical formula NaxWOy. Furthermore, Na 5W 14O 44 is represented by the chemical formula Na 5 / 14WO 44 / 14 when the valence of W is converted to 1 (i.e., the valence of Na is 5 / 14, the valence of W is 1, and the valence of O is 44 / 14), and can be represented by the chemical formula Na xWO y. That is, sodium tungstate represented by the chemical formula Na xWO y refers to sodium tungstate in which the ratio of the valence of Na to the valence of W to the valence of O is X:1:Y.

[0026] Here, "composite" refers to a state in which, at least without the action of external force, it is impossible to separate silicon particles 33 from carbon particles 30, separate silicon particles 33 from Na x WO y particles 32, and separate Na x WO y particles 32 from carbon particles 30. For example, external force refers to the force exerted when the SEI (Solid Electrolyte Interphase) coating layer expands and contracts as a whole when the battery using the negative electrode material is operated.

[0027] For example, the composite system includes at least one of the following: a composite formed on the surface of carbon particles 30 and disposed on silicon particles 33, and disposed on the surface of silicon particles 33 and disposed on Na xWO y particles 32; a composite formed on the surface of carbon particles 30 and disposed on Na xWO y particles 32, and disposed on the surface of Na xWO y particles 32 and disposed on the surface of Na xWO y particles 32; a composite formed on the surface of carbon particles 30 and disposed on silicon particles 33; a composite formed on the surface of carbon particles 30 and disposed on Na xWO y particles 32; a composite formed on the surface of silicon particles 33 and disposed on Na xWO y particles 32; and a composite formed on the surface of carbon particles 30 and disposed on Na xWO y particles 32 and Si particles 33, wherein the Na xWO y particles 32 and Si particles 33 are also in close contact with each other.

[0028] It is preferable that the valence of O in the Na xWO y particles 32 contained in the negative electrode material layer 22 is 3, in other words, Na xWO 3 is preferable. Furthermore, it is preferable that the valence of Na in the Na xWO y particles 32 contained in the negative electrode material layer 22 is greater than 0 and less than 1, and the valence of O is greater than 2 and less than 4. Furthermore, it is preferable that the valence of Na xWO y particles 32 is 0.1 to 0.95 and y is 2.5 to 3.5; even more preferably, the valence of x is 0.1 to 0.95 and y is 2.8 to 3.2; and even more preferably, the valence of x is 0.3 to 0.7 and y is 2.8 to 3.2. When x and y are within this range, Na xWO y particles 32 can be appropriately disposed on the surface of the carbon particles 30. However, the negative electrode material system of the negative electrode material layer 22 may contain only one type of Na xWO y particles 32, or it may contain multiple types of Na xWO y particles 32.

[0029] Furthermore, the negative electrode material of the negative electrode material layer 22 is preferably NaxWOy particles 32, containing at least one of Na0.78WO3, Na0.48WO3, Na0.72WO3, Na0.48WO3, Na0.44WO3, Na0.48WO3, Na0.52WO3, Na2WO4, or Na5WO14O44. Thus, in this embodiment, the negative electrode material of the negative electrode material layer 22 is sodium tungstate, preferably containing at least one of Na 0.78WO3 and Na 0.48WO3, Na 0.72WO3 and Na 0.48WO3, Na 0.44WO3, Na 0.48WO3, Na 0.52WO3, Na 2WO4 or Na 5WO14O44.

[0030] Compounds such as Na xWO y particles 32 contained in the negative electrode material can be determined by XRD (X-Ray Diffraction). The XRD measurement conditions can be, for example, as follows: ・Measurement apparatus: Ultima IV manufactured by Rigaku Corporation ・Used tube: Cu ・Tube voltage: 40kV ・Tube current: 40mA ・Scan range: 5°~80° ・Scan speed: 2° / min To serve as a database for compound identification, the ICDD (PDF2.DAT) powder diffraction and crystal structure database can be used, i.e., the ICDD (International Center for Diffraction Data) PDF2.DAT. Then, for the crystal peaks detected by XRD, the compound specifically contained in the test sample (in this case, the negative electrode material) can be identified using PDXL2, a software that integrates powder X-ray diffraction. Specifically, using this software, compounds with a FOM (Form Factor) below the threshold value are extracted. These compounds with a FOM below the threshold value are then identified as compounds contained in the test sample (in this case, the anode material). The FOM value is taken from 0 to 100, with a smaller value indicating higher consistency. The threshold value for the FOM is 10. That is, for example, if the FOM of the diffraction peak of the anode material relative to the diffraction peak of Na 0.78WO3 in ICDD is below the threshold value (e.g., 10), it is determined that the anode material contains Na 0.78WO3. Another example is that although the peak waveform of the X-ray diffraction analysis results of the analyzed object shows a carbon peak waveform, if the (002) peak waveform of the known graphite structure is broad, it can be determined to be amorphous carbon.

[0031] The average particle size of Na xWO y particles 32 is smaller than that of carbon particles 30. The average particle size of Na xWO y particles 32 is preferably between 100 nm and 20 μm, and more preferably between 100 nm and 1 μm.

[0032] Thus, while the negative electrode material has a structure in which particulate sodium tungstate (Na₂xWO₃y particles 32) and silicon (silicon particles 33) are disposed on the surface of the carbon particles 30, it is not limited to this. The negative electrode material can be any structure in which sodium tungstate and silicon are disposed on the surface of carbon, and the shape of the sodium tungstate and silicon disposed on the surface of carbon can be arbitrary. In this embodiment, a tungsten compound or sodium tungstate as a tungsten oxide is used. Furthermore, although silicon is used in this embodiment, a silicon compound or silicon oxide can also be used.

[0033] The content of sodium tungstate (Na xWO y particles 32) and silicon in the negative electrode material can be confirmed by measuring the content of Na, W, O, and Si through fluorescence X-ray analysis. That is, at least a portion of the total amount of Na, W, O, and Si detected by fluorescence X-ray analysis constitutes sodium tungstate (Na xWO y particles 32) and silicon, and the content of sodium tungstate and silicon can be confirmed by measuring the content of Na, W, O, and Si.

[0034] Preferably, the anode material, as determined by fluorescence X-ray analysis, 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. Furthermore, it is preferable that the anode material, as determined by fluorescence X-ray analysis, has a Na content of 0.02% to 0.5% by mass, a W content of 0.7% to 17% by mass, a O content of 2% to 13% by mass, and a Si content of 2% to 12% by mass. Furthermore, when the negative electrode material is analyzed by fluorescence X-ray, it is preferable that the Na content is between 0.03% and 0.4% by mass, the W content is between 1% and 15% by mass, the O content is between 3% and 12% by mass, and the Si content is between 3% and 10% by mass. When the Na, W, O, and Si contents are within these ranges, sodium tungstate and silicon can be appropriately contained, and tungsten compounds and silicon can be appropriately configured on the surface of carbon.

[0035] Furthermore, the C content of the negative electrode material, as determined by fluorescence X-ray analysis, is preferably 60% to 95% by mass ratio, more preferably 65% ​​to 95%, and even more preferably 70% to 92%. When the C content is within these ranges, tungsten compounds can be appropriately configured on the surface of carbon.

[0036] The Na / W ratio, as determined by X-ray fluorescence analysis, is preferably 0.001 to 0.2 by mass, more preferably 0.005 to 0.15, and even more preferably 0.007 to 0.15 by mass. The W / C ratio, as determined by X-ray fluorescence analysis, is preferably 0.005 to 0.3 by mass, more preferably 0.008 to 0.25, and even more preferably 0.01 to 0.2 by mass. Furthermore, the Si / O ratio, as determined by X-ray fluorescence analysis, is preferably 0.1 to 2 by mass, more preferably 0.2 to 1.5, and even more preferably 0.3 to 1.3 by mass. When the content ratio falls within this range, tungsten compounds can be appropriately formulated on the surface of carbon.

[0037] The Si / W ratio, as determined by fluorescence X-ray analysis, is preferably 0.1 to 15 by mass, more preferably 0.15 to 12, and even more preferably 0.2 to 10. Furthermore, the Si / C ratio, as determined by fluorescence X-ray analysis, is preferably 0.01 to 0.3 by mass, more preferably 0.02 to 0.25, and even more preferably 0.03 to 0.15. When the content ratios are within these ranges, tungsten compounds and silicon can be appropriately configured on the surface of carbon.

[0038] Fluorescence X-ray analysis is performed using a wavelength-dispersive fluorescence X-ray analyzer, and the measurement conditions are as follows: • Measurement apparatus: Rigaku Corporation ZSX PrimusIV • Tube voltage: 30kV • Tube current: 100mA As the measurement method, the method without standard basic parameters is used. For resolution, Rigaku Corporation's SQX scattering FP method is sufficient.

[0039] However, the negative electrode material layer 22 may contain substances other than the negative electrode material (carbon particles 30, NaxWO3y particles 32, and silicon particles 33). The negative electrode material layer 22 may contain, for example, an adhesive. The adhesive material can be arbitrary, and examples include polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and polyacrylic acid (PAA). Only one type of adhesive 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 does not contain graphite.

[0040] Furthermore, the Na xWO y particles 32 and silicon particles 33 disposed on the surface of carbon particles 30 can be confirmed by observation using electron microscopes such as SEM (Scanning Electron Microscope) or TEM (Transmission Electron Microscope).

[0041] (Example of a modified negative electrode) Figure 3 is a schematic cross-sectional view of another example of the negative electrode of this embodiment. In the negative electrode material system of the negative electrode material layer 22, silicon particles 33 may be in close contact with the surface of carbon particles 30, and NaxWOy particles 32 may also be in close contact with the surface of carbon particles 30. In this case, carbon particles 30 and silicon particles 33 may be composited, or carbon particles 30 and NaxWOy particles 32 may be composited.

[0042] The NaxWOy particles 32 are those containing a cubic crystal structure and a tetragonal crystal structure. That is, the negative electrode material contains 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 contained in the negative electrode material is not limited to this, for example, it may contain sodium tungstate with other crystal structures such as triclinic crystals.

[0043] Thus, although the negative electrode material has a structure in which particulate sodium tungstate (Na xWO y particles 32) and silicon particles 33 are disposed on the surface of carbon particles 30, it is not limited to this. The negative electrode material can be any structure in which sodium tungstate and silicon are disposed on the surface of carbon, and the shape of the sodium tungstate and silicon disposed on the surface of carbon can be arbitrary.

[0044] (Positive Electrode) The positive electrode 16 comprises a current collector layer and a positive electrode material layer. The current collector layer of the positive electrode 16 is a layer composed of a conductive component, such as aluminum. The positive electrode material layer is a layer of positive electrode material disposed on the surface of the current collector layer of the positive electrode 16. The thickness of the current collector layer of the positive electrode can be, for example, between 10 μm and 30 μm, and the thickness of the positive electrode material layer can be, for example, between 10 μm and 100 μm.

[0045] The cathode material layer system includes a cathode material. The cathode material system includes lithium compound particles containing lithium compounds. As a lithium compound, it can be a lithium metal oxide or a lithium phosphate, etc. More specifically, examples of lithium compounds include LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi aCo bMn cO2 (where 0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1), LiFePO4, etc. The lithium compound system may contain only one type of material or may contain two or more types of materials. Furthermore, the cathode material layer system may contain substances other than the cathode material, such as binders. The binder material can be arbitrary, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PAA, etc. Only one type of binder may be used, or two or more types may be used in combination.

[0046] (Spacer) Spacer 18 is an insulating component. In this embodiment, spacer 18 is, for example, a porous membrane made of resin, such as polyethylene (PE) or polypropylene (PP). Furthermore, spacer 18 can be a structure consisting of films laminated with different materials. Also, spacer 18 may have a heat-resistant layer, as per spacer 13. The heat-resistant layer is a layer containing a substance with a high melting point. For example, the heat-resistant layer may contain particles of inorganic materials such as alumina.

[0047] (Electrolyte) The electrolyte provided in battery 1 is a non-aqueous electrolyte. The electrolyte is contained within the voids of electrode group 12. The electrolyte may contain, for example, a lithium salt and an aprotic solvent. The lithium salt is dispersed and dissolved in the aprotic solvent. Examples of lithium salts 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 cyclic carbonates and chain carbonates. Examples of cyclic carbonates include EC, PC, butene carbonate, etc. Examples of chain carbonates include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), etc.

[0048] (Method for Manufacturing a Battery) Next, an example of a method for manufacturing the battery 1 according to this embodiment will be described. Figure 4 is a flowchart illustrating an example of a method for manufacturing the battery according to this embodiment. As shown in Figure 4, in this manufacturing method, a negative electrode 14 is formed in steps S10 to S22.

[0049] Specifically, the surfactant is dissolved in a solvent to generate a first solution (step S10). The first solution is a solution containing Na (Na in ionic form) after dissolving the surfactant. The surfactant is used to disperse carbon and silicon. Although any substance capable of dispersing carbon can be used as the surfactant, in this embodiment, a substance containing Na is used. For example, sodium dodecyl sulfate (SDS) can be used as a Na-containing surfactant. The solvent for the first solution can be any substance that dissolves the surfactant, such as water.

[0050] However, the surfactant is not limited to those containing Na. In this case, for example, a Na-free surfactant and a Na-containing compound can be dissolved in a solvent to form a first solution. As a Na-free surfactant, for example, poly(oxyethylene) alkyl ethers or nonylphenol polyoxyethylene ethers can be used. As for poly(ethylene oxide) alkyl ethers, it is preferable to use those with 12 to 15 carbon atoms in the alkyl group. Examples include C12H25O(C2H4)nH (poly(ethylene oxide) dodecane ether), C13H27O(C2H4)nH (poly(ethylene oxide) tridecane ether), C13H27O(C2H4)nH (poly(ethylene oxide) isotridecane ether), C14H25O(C2H4)nH (poly(ethylene oxide) tetradecane ether), and C155H25O(C2H4)nH (poly(ethylene oxide) pentadecane ether). Here, n is an integer greater than or equal to 1. For example, nonylphenol polyoxyethylene ethers can be made using C9H19C6(CH2CH2O)8H, C9H19C6(CH2CH2O)10H, C9H19C6(CH2CH2O)12H, etc. For compounds containing sodium, examples include sodium sulfate, sodium stearate, sodium hyaluronate, sodium hypochlorite, etc.

[0051] The amount of surfactant in the first solution, i.e., the amount of surfactant added, is preferably 0.1% to 10% by mass ratio, more preferably 0.5% to 7%, and even more preferably 1% to 5%, in relation to the amount of carbon raw material added in the subsequent step S14. By achieving this range, the affinity between carbon and NaxWO3y can be appropriately improved.

[0052] Next, silicon raw material is added to the first solution to generate the second solution (step S12). The silicon raw material is silicon used as a raw material. In step S12, firstly, silicon raw material is added to a solvent to generate a silicon solution. In this embodiment, water is used as the solvent. Then, the silicon solution is added to the first solution and stirred to generate the second solution.

[0053] The amount of silicon in the first solution, i.e. the amount of silicon added, is preferably 1% to 10% by mass ratio, more preferably 2% to 8%, and even more preferably 3% to 6%, in relation to the amount of carbon raw material added in the subsequent step S14.

[0054] Next, carbon raw material is added to the second solution to generate the third solution (step S14). The carbon raw material used is amorphous carbon. It is preferable, for example, to have an average particle size of 1 μm to 50 μm, more preferably 1 μm to 20 μm. Achieving this average particle size range for the carbon raw material can improve the battery capacity. In step S14, the second solution of carbon raw material is added, i.e., the third solution is stirred, and the carbon raw material is dispersed in the second solution. That is, the third solution can be referred to as the second solution dispersing the carbon raw material.

[0055] The carbon raw material can be manufactured, for example, by an oil furnace method. In the oil furnace method, for example, raw material oil is sprayed in a high-temperature environment, thermally decomposed, and then rapidly cooled to produce particulate amorphous carbon raw material. However, the method of manufacturing carbon raw material is not limited to this and can be any method.

[0056] Next, the third solution and the tungsten solution are mixed to generate the 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 tungsten oxide raw material in a solvent. The tungsten oxide raw material here is a raw material of NaxWOy particles 32, for example, tungsten trioxide is used. As the solvent, for example, an alkaline liquid is used, and in this embodiment, an 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 can be any solution containing W and O.

[0057] The amount of W contained in the tungsten solution added to the second solution, i.e., the amount of W added, is preferably 0.5% to 20% by mass ratio, more preferably 1% to 15%, and even more preferably 1.3% to 10%, relative to the amount of carbon raw material added in step S14. By achieving this range, the affinity between carbon and NaxWOy can be appropriately improved. Furthermore, by achieving this range, NaxWOy particles 32 can be appropriately formed on the surface of the carbon particles 30, serving as a negative electrode, thereby increasing the battery capacity.

[0058] Next, the liquid components of the fourth solution are removed to generate a negative electrode material (negative electrode material generation step). In this embodiment, steps S18 and S20 are performed as the negative electrode material generation step. Specifically, the fourth solution is dried to generate a negative electrode intermediate (step S18; drying step). In step S18, for example, the fourth solution is dried at 80°C for 12 hours in the atmosphere to remove the liquid components contained in the added fourth solution, i.e., by evaporation. However, the drying conditions can be arbitrary. The negative electrode intermediate can be referred to as containing the solid components remaining after removing the liquid components of the fourth solution.

[0059] Next, the dried negative electrode intermediate is heated to generate a negative electrode material (step S20; heating step). By heating the negative electrode intermediate, a negative electrode material with NaxWOy particles 32 disposed thereon is formed on the surface of the silicon particles 33. That is, on the surface of the carbon particles 30 dispersed in the fourth solution, Na, W, and O contained in the ionic state of the third solution are precipitated as NaxWOy particles 32 to form the negative electrode material.

[0060] In the heating step, the conditions for heating the negative electrode intermediate can be arbitrary, but it is preferable to perform the heating step as follows: that is, the heating step preferably includes a step of putting the negative electrode intermediate into the furnace to make the furnace an inactive environment, 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.

[0061] The inactive environment in the step of making the furnace an inactive environment can be, for example, a nitrogen environment or a rare gas environment such as Ar. For example, the oxygen in the furnace can be replaced with nitrogen or a rare gas to make it an inactive environment. However, this step is not necessary.

[0062] The first heating step is a step to remove metals or organic matter contained in the negative electrode intermediate. The first heating temperature of the first heating step is, for example, 550°C, but is not limited to this; 150°C to 625°C is preferred, more preferably 175°C to 600°C, and even more preferably 200°C to 575°C. The first heating rate can be any rate, but for example, 45°C / hour to 75°C / hour is preferred, more preferably 50°C / hour to 70°C / hour, and even more preferably 55°C / hour to 65°C / hour. When the first heating temperature or the first heating rate is within this range, metals or organic matter contained in the negative electrode intermediate can be effectively removed.

[0063] The second heating step is a step that generates NaxWOy after the first heating step. The second heating temperature in the second heating step is higher than the first heating temperature, for example, 700°C, but not limited to this; preferably 680°C to 750°C, more preferably 685°C to 740°C, and even more preferably 690°C to 730°C. The second heating rate can be any rate, but preferably higher than the first heating 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. When the second heating temperature or the second heating rate is within this range, the required process time can be shortened, and NaxWOy can be generated appropriately.

[0064] In the second heating step, it is preferable to maintain the negative electrode intermediate heated to the second heating temperature at the second heating temperature for a specific time. The maintenance time is preferably 1.25 hours to 2.75 hours, more preferably 1.5 hours to 2.5 hours, and even more preferably 1.75 hours to 2.25 hours.

[0065] However, before the first heating step (and, in this embodiment, after the step of creating an inactive environment), a step may be provided in which the negative electrode intermediate is heated to a third temperature at a third heating rate and maintained at the third temperature for a specific time. The third temperature is lower than the first temperature, for example, 100°C, but is not limited thereto; 80°C to 120°C is preferred, more preferably 85°C to 115°C, and even more preferably 90°C to 110°C. The third heating rate may also be arbitrary; for example, 165°C / hour to 195°C / hour is preferred, more preferably 170°C / hour to 190°C / hour, and even more preferably 175°C / hour to 185°C / hour. Furthermore, the specific time for maintaining the third heating temperature can be arbitrary, 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 setting this step, moisture can be appropriately removed.

[0066] Next, the negative electrode 14 is formed using the formed negative electrode material (step S22). That is, a negative electrode material layer 22 containing the negative electrode material is formed on the surface of the current collector layer 20 to form the negative electrode 14.

[0067] Furthermore, this manufacturing method forms the positive electrode 16 (step S24). In step S24, except for a portion of the lithium compound raw material used instead of carbon raw material, the positive electrode material is formed using the same method as in steps S10 to S20. Then, a positive electrode material layer containing the positive electrode material is formed on the surface of the current collector layer used in the positive electrode 16, thereby forming the positive electrode 16.

[0068] After forming the negative electrode 14 and the positive electrode 16, the negative electrode 14 and the positive electrode 16 are used to manufacture the battery 1 (step S26). Specifically, the negative electrode 14, the spacer 18 and the positive electrode 16 are laminated to form an electrode group 12, and the electrode group 12 and the electrolyte are housed in the casing 10 to manufacture the battery 1.

[0069] Thus, in this embodiment, as shown in steps S10 to S20, a fourth solution containing Na, O, W, and Si, and with dispersed carbon, is generated. The liquid components are removed from the fourth solution to produce a negative electrode material. This method for producing the negative electrode material will be appropriately described below as a solution method. Furthermore, the above-described manufacturing method will be referred to as the first manufacturing method.

[0070] As explained above, the negative electrode material of the battery in this embodiment includes carbon, sodium tungstate disposed on the surface of the carbon, and silicon disposed on the surface of the carbon. By disposing sodium tungstate and silicon on the surface of the carbon, the negative electrode material of this embodiment can improve battery characteristics such as capacity.

[0071] It is known that the presence of silicon in the negative electrode material of a battery can improve battery characteristics. However, it is known that silicon is difficult to deposit on the surface of carbon in the negative electrode material. In this embodiment, a negative electrode material containing silicon deposited on the surface of carbon can be manufactured by using raw materials containing carbon, sodium tungstate, and silicon via a solution method.

[0072] Furthermore, in a negative electrode material in which sodium tungstate is disposed on the surface of carbon, it is required that sodium tungstate be appropriately disposed on the surface of carbon. If sodium tungstate cannot be appropriately disposed on the surface of carbon, that is, if sodium tungstate cannot be disposed on the surface of carbon, or if sodium tungstate detaches from the surface of carbon, the battery characteristics cannot be adequately improved. In this regard, the negative electrode material of this embodiment is carbon, specifically amorphous carbon, on which sodium tungstate is disposed. When amorphous carbon is treated to dispose of sodium tungstate on its surface, it may contain functional groups on the surface. Therefore, through these functional groups, sodium tungstate can be appropriately captured on the surface of amorphous carbon, and sodium tungstate can be appropriately disposed on the surface. Furthermore, when amorphous carbon is treated to dispose of sodium tungstate on its surface, it may contain functional groups (e.g., hydroxyl, carboxyl groups). Therefore, through these functional groups, sodium tungstate can be appropriately captured on the surface of amorphous carbon, and tungsten trioxide can be appropriately disposed. Furthermore, because sodium tungstate is fixed to the surface of amorphous carbon via this functional group, the adhesion of sodium tungstate to the surface of amorphous carbon is high, which can prevent sodium tungstate from detaching from the carbon surface. In particular, hard carbon raw materials, compared to graphite, can be manufactured at low temperatures, so the functional groups can be easily retained without being removed, allowing for the appropriate configuration of sodium tungstate and silicon on the surface.

[0073] In this embodiment, the negative electrode material is preferably a composite of carbon, sodium tungstate, and silicon. In this embodiment, sodium tungstate and silicon can be appropriately disposed on the surface of carbon.

[0074] Furthermore, regarding the negative electrode material of this embodiment, sodium tungstate is represented by the chemical formula NaxWOy, where x is greater than 0 and less than 1, and y is preferably more than 2 and less than 4. Using sodium tungstate containing such a chemical formula, sodium tungstate can be appropriately deposited on the surface of carbon.

[0075] Furthermore, regarding the negative electrode material of this embodiment, the sodium content, as determined by fluorescence X-ray analysis, is preferably 0.01% to 0.5% by mass, the tungsten content is 0.5% to 20% by mass, and the oxygen content is 1% to 15% by mass. By ensuring that Na, W, and O contain appropriate amounts of sodium tungstate within this range, sodium tungstate can be appropriately deposited on the surface of carbon.

[0076] Furthermore, regarding the negative electrode material of this embodiment, the sodium content ratio (Na / W) relative to tungsten, as determined by fluorescence X-ray analysis, is preferably 0.001 to 0.2 or less. By having a suitable amount of sodium tungstate within this Na / W range, sodium tungstate can be appropriately disposed on the surface of carbon.

[0077] In this embodiment, the anode material is preferably amorphous carbon or graphite. According to this embodiment, sodium tungstate and silicon can be appropriately disposed on the surface of amorphous carbon or graphite.

[0078] The negative electrode material of this embodiment is sodium tungstate, which has at least one crystal structure of tetragonal, cubic, or orthorhombic crystal. With such a crystal structure, sodium tungstate can be appropriately disposed on the surface of carbon.

[0079] Regarding the negative electrode material of this embodiment, sodium tungstate is represented by the chemical formula Na xWO y, where x is greater than 0 and less than 1, and y is greater than 2 and less than 4. Using sodium tungstate containing this chemical formula, sodium tungstate can be appropriately deposited on the surface of carbon.

[0080] Regarding the negative electrode material of this embodiment, the sodium content, as determined by fluorescence X-ray analysis, is preferably 0.01% to 0.5% by mass, the tungsten content is 1% to 20% by mass, the oxygen content is 1% to 15% by mass, and the silicon content is 1% to 15% by mass. By including an appropriate amount of sodium tungstate in Na, W, O, and Si within this range, sodium tungstate can be appropriately deposited on the surface of carbon.

[0081] Regarding the negative electrode material of this embodiment, the sodium content ratio (Na / W) relative to tungsten, as determined by fluorescence X-ray analysis, is 0.001 to 0.2 or less. By having a suitable amount of sodium tungstate within this Na / W range, sodium tungstate can be appropriately deposited on the surface of carbon.

[0082] Regarding the negative electrode material of this embodiment, the silicon content ratio (Si / C) relative to carbon, as determined by fluorescence X-ray analysis, is 0.01 to 0.3 or less. With Si / C within this range and containing an appropriate amount of sodium tungstate, sodium tungstate can be appropriately disposed on the surface of carbon.

[0083] Regarding the negative electrode material of this embodiment, the tungsten content ratio (W / C) relative to carbon, as determined by fluorescence X-ray analysis, is 0.005 to 0.3 or less. By having a suitable amount of sodium tungstate within this W / C range, sodium tungstate can be appropriately deposited on the surface of carbon.

[0084] Regarding the negative electrode material of this embodiment, the silicon content ratio (Si / W) relative to tungsten, as determined by fluorescence X-ray analysis, is 0.1 to 15 or less. With Si / W within this range and containing an appropriate amount of sodium tungstate, sodium tungstate can be appropriately disposed on the surface of carbon.

[0085] Regarding the negative electrode material of this embodiment, the silicon content ratio (Si / O) relative to oxygen, as determined by fluorescence X-ray analysis, is 0.1 to 2 or less. With Si / O within this range and containing an appropriate amount of sodium tungstate, sodium tungstate can be appropriately disposed on the surface of carbon.

[0086] Furthermore, the method for manufacturing the negative electrode material of this embodiment includes the steps of dissolving an surfactant, a first solution containing sodium, adding silicon, dispersing silicon in the first solution to generate a second solution, adding amorphous carbon to the second solution, dispersing amorphous carbon in the second solution to generate a third solution, mixing the third solution with a tungsten solution containing oxygen and tungsten to generate a fourth solution, and removing the liquid components of the fourth solution to generate the negative electrode material. The negative electrode material manufactured by the method of this embodiment can appropriately deposit sodium tungstate and silicon on the surface of carbon.

[0087] Furthermore, regarding the manufacturing method of the negative electrode material in this embodiment, the amount of W added is preferably 0.5% to 20% by mass ratio, more preferably 1% to 15%, and even more preferably 1.3% to 10% by mass ratio, in relation to the amount of carbon raw material added in step S14. By ensuring that the amount of W added is within this range, sodium tungstate is appropriately formed on the surface of hard carbon to serve as a negative electrode, thereby improving battery characteristics.

[0088] Furthermore, the negative electrode material generation step preferably includes a drying step of drying the fourth solution to generate a negative electrode intermediate and a heating step of heating the negative electrode intermediate. By drying the fourth solution and heating the formed negative electrode intermediate, a negative electrode material is generated. Sodium tungstate is appropriately formed on the surface of carbon to serve as a negative electrode, which can improve battery characteristics.

[0089] Furthermore, the heating step preferably includes the steps of heating the negative electrode intermediate to a first temperature of 150°C to 625°C at a first heating rate, heating the negative electrode intermediate heated to the first temperature to a second temperature of 680°C to 750°C at a second heating rate faster than the first heating rate, and maintaining the negative electrode intermediate at the second temperature. Through the first heating step and the second heating step, a negative electrode material is generated, and sodium tungstate can be appropriately formed on the surface of carbon.

[0090] (Example) Next, the example will be described.

[0091] (Example 1) In Example 1, a negative electrode material was manufactured using a solution method as described in the embodiment. Specifically, as the first solution, a solution in which SDS is dissolved using water as a solvent and as a surfactant was prepared. The concentration of SDS in the first solution was 4.85%. Then, the mass ratio of silicon raw material in the first solution relative to the added amorphous carbon raw material was set to 4.85%, and silicon raw material was added to the first solution and stirred to obtain the second solution. Then, the mass ratio of SDS in the second solution relative to the added amorphous carbon raw material was set to 3%, and amorphous carbon raw material was added to the second solution and stirred to obtain the third solution. Then, the amount of W contained in ammonium tungstate (tungsten solution) relative to the amorphous carbon raw material in the third solution was set to 5% by mass ratio, and ammonium tungstate (tungsten solution) was added to the third solution to obtain the fourth solution. Then, after stirring the fourth solution, the water was dried by heating and evaporation to generate a negative electrode intermediate. Then, this negative electrode intermediate is introduced into a tubular furnace (curing 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 is increased to 700°C (second heating temperature) at a second heating rate of 180°C / hour and held for 2 hours. After holding for 2 hours, heating is stopped, and the material is allowed to cool naturally to 50°C to generate the negative electrode material.

[0092] Furthermore, in Example 1, the silicon raw material was prepared as follows. First, a high-purity silicon block (purity 11N) several mm in size was crushed using a jaw crusher, and the crushed silicon particles were separated using a sieve with a mesh size of 0.5 mm. Next, the silicon particles that passed through the 0.5 mm mesh sieve were placed into a 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 by laser diffraction particle size distribution measurement method (device product name "Microtrac MT3300EX II"). The volume average particle size of the silicon microparticles was 1.92 μm, and the d50 (median diameter) was 0.31 μm. Furthermore, the maximum volume diameter of the silicon microparticles was 32.23 μm, and the minimum volume diameter was 0.066 μm.

[0093] (Example 2) In Example 2, the pulverization time is 3 hours, and the amount of silicon, tungsten and SDS added is 4wt%, 2wt% and 1wt% respectively. The negative electrode material is generated in the same way as in Example 1.

[0094] (Example 3) In Example 3, the pulverization time was 4 hours, and the amount of silicon, tungsten and SDS added was 4 wt%, 15 wt% and 5 wt% respectively. The negative electrode material was generated in the same way as in Example 1.

[0095] (Example 4) In Example 4, the container used for crushing is a long container, the crushing time is 2 hours, and the amount of silicon, tungsten and SDS added is 4wt%, 10wt% and 5wt% respectively. The negative electrode material is generated in the same way as in Example 1.

[0096] (Example 5) In Example 5, the container used for crushing is a long container, the crushing time is 1 hour, and the amount of silicon, tungsten and SDS added is 10wt%, 2wt% and 2wt% respectively. The negative electrode material is generated in the same way as in Example 1.

[0097] (Example 6) In Example 6, the container used for crushing is a long container, the crushing time is 3 hours, and the amount of silicon, tungsten and SDS added is 3wt%, 4wt% and 10wt% respectively. The negative electrode material is generated in the same way as in Example 1.

[0098] (Example 7) In Example 7, the container used for pulverization is spherical, the pulverization time is 2 hours, the concentration of the surfactant C12H25O(C2H4)nH (poly(oxyethylene)dodecane ether) in the first solution is 4%, the concentration of sodium stearate is 1%, and the negative electrode material is generated in the same way as in Example 1.

[0099] (Comparative Example 1) In Comparative Example 1, only carbon was used as the negative electrode material.

[0100] (Identification of Anode Materials) Figure 5 is a table showing the identification results of the anode materials in each example. For the anode materials manufactured in each example, fluorescence X-ray analysis was performed to determine the content of elements contained in the anode materials, and the ratios of Na / W, Si / C, W / C, Si / W, and Si / O. The results of the element content determination are shown in Figure 5. However, the fluorescence X-ray analysis was performed under the conditions described in the above embodiments. Although the anode materials of Examples 1 to 7 contain elements other than carbon (C), sodium tungstate (Na, W, O), and silicon (Si), these are impurities. In addition to the elements listed in Figure 5, unavoidable impurities may also be present.

[0101] For each example of manufactured negative electrode material, XRD was performed to identify the chemical formula and crystal structure of sodium tungstate contained in the negative electrode material. The XRD measurement results are shown in Figure 6. However, the XRD measurement conditions were those described in the above embodiments.

[0102] Figure 6 shows the XRD results of the negative electrode material of Example 2. As shown in Figure 6, the XRD measurement of the negative electrode material of Example 2 shows that it contains cubic Na 0.72WO3 and tetragonal Na 0.48WO3. It also shows that it contains Si. Although samples other than those from Example 2 also contain Si, this will be omitted in the following description. Similarly, XRD measurements showed that the negative electrode material of Example 1 contained cubic Na 0.78WO3 and tetragonal Na 0.48WO3; the negative electrode material of Example 3 contained cubic Na 0.44WO3 and triclinic Na 5 (W 14O 44); the negative electrode material of Example 4 contained cubic Na 0.49WO3 and tetragonal Na 0.33WO3; the negative electrode materials of Examples 5 and 6 contained tetragonal Na 0.48WO3; and the negative electrode material of Example 7 contained cubic Na 2WO4.

[0103] The negative electrode materials manufactured in each example were observed by SEM. As shown in the SEM observation results, sodium tungstate was found on the surface of carbon in Examples 1 to 7.

[0104] (Evaluation Results) As an evaluation of the negative electrode materials in each example, the capacity of the negative electrode using the negative electrode material was measured. Specifically, the current value per 1g (mAh / g) when the C ratio is 0.2 and the current value per 1g (mAh / g) when the C ratio is 3.2 were measured. For example, the current value per 1g of negative electrode when the C ratio is 0.2 refers to the current value that consumes the rated capacity in 5 hours.

[0105] Figure 5 shows the evaluation results. As shown in Figure 5, in Examples 1-7 where sodium tungstate is disposed on the surface of carbon, compared with Comparative Example 1 which does not contain sodium tungstate, it can be seen that the battery characteristics at 0.2C and 3.2C are improved.

[0106] Figures 7 to 10 show SEM photographs and elemental analysis results of the negative electrode material of Example 1. As shown in Figures 7 to 10, the surface of carbon particles 30 can be seen to be scaly from the SEM photographs. In each of Figures 7 to 10, the left side (A) is the SEM photograph, and the right side is the elemental analysis result. The upper left (B) of the elemental analysis results is the distribution image of tungsten, the middle left (C) is the distribution image of sodium, the upper right (D) is the distribution image of oxygen, the middle right (E) is the distribution image of silicon, and the lower right (F) is the distribution image of carbon.

[0107] Figure 7 is taken on the surface of carbon particles 30, without overlapping tungsten and silicon. Sodium is located in the center of the image where tungsten is, with a slightly higher concentration.

[0108] Figures 8 and 9 are attached to the surface of carbon particles 30, with tungsten and silicon superimposed. In Figure 9, the concentration of sodium is slightly higher in the upper right position where the concentration of tungsten is higher.

[0109] Figure 10 shows the surface of carbon particles 30, which are covered with most particles other than tungsten and silicon. On the surface of carbon particles 30, there is a mixture of overlapping tungsten and silicon particles and non-overlapping particles. At the lower left position where the tungsten concentration is high, the sodium concentration is slightly higher.

[0110] While the embodiments of the present invention have been described above, they are not limited to the content of these embodiments. Furthermore, the aforementioned constituent elements include those readily conceived by the industry, those that are substantially the same, and so on, within a range of equality. Moreover, the aforementioned constituent elements can be appropriately combined. Furthermore, various omissions, substitutions, or changes to the constituent elements can be made without departing from the essence of the aforementioned embodiments. [Simplified Explanation of the Diagram]

[0012] [Figure 1] Figure 1 is a partial cross-sectional view of a battery according to this embodiment. [Figure 2] Figure 2 is a cross-sectional view of an example of the negative electrode according to this embodiment. [Figure 3] Figure 3 is a cross-sectional view of another example of the negative electrode according to this embodiment. [Figure 4] Figure 4 is a flowchart illustrating an example of a method for manufacturing the battery according to this embodiment. [Figure 5] Figure 5 is a table showing the identification results of the negative electrode materials in each example. [Figure 6] Figure 6 is a graph showing the XRD measurement results of the negative electrode material of the embodiment. [Figure 7] Figure 7 is a graph of the negative electrode material of the photographic embodiment. [Figure 8] Figure 8 is a graph of the negative electrode material of the photographic embodiment. [Figure 9] Figure 9 is a graph of the negative electrode material of the photographic embodiment. [Figure 10] Figure 10 is a graph of the negative electrode material of the photographic embodiment.

Claims

1. A negative electrode material, which is a negative electrode material of a battery, characterized in that it comprises carbon, sodium tungstate disposed on the surface of the aforementioned carbon, and silicon disposed on the surface of the aforementioned carbon, wherein the aforementioned sodium tungstate is represented by the chemical formula NaxWOy, where x is greater than 0 and less than 1, and y is greater than 2 and less than 4.

2. The negative electrode material as described in claim 1, wherein, The aforementioned carbon, sodium tungstate, and silicon are combined.

3. The negative electrode material as described in claim 1 or 2, wherein, The aforementioned carbon-based amorphous carbon or graphite.

4. The negative electrode material as described in claim 1 or 2, wherein, Sodium tungstate, comprising at least one of the crystal structures of tetragonal and cubic crystals as described above.

5. The negative electrode material as described in claim 4, wherein, Sodium tungstate, which has a triclinic crystal structure, was described above.

6. The negative electrode material as described in claim 1 or 2, wherein, Furthermore, the sodium content determined by fluorescence X-ray analysis is between 0.01% and 0.5% by mass, the tungsten content is between 1% and 20% by mass, the oxygen content is between 1% and 15% by mass, and the silicon content is between 1% and 15% by mass.

7. The negative electrode material as described in claim 1 or 2, wherein, The sodium content ratio (Na / W) relative to tungsten, as determined by fluorescence X-ray analysis, is between 0.001 and 0.2 by mass.

8. The negative electrode material as described in claim 1 or 2, wherein, The silicon content ratio (Si / C) relative to carbon, as determined by fluorescence X-ray analysis, is 0.01 to 0.3 by mass.

9. The negative electrode material as described in claim 1 or 2, wherein, The tungsten content ratio (W / C) relative to carbon, as determined by fluorescence X-ray analysis, is 0.005 to 0.3 by mass.

10. The negative electrode material as described in claim 1 or 2, wherein, The silicon content ratio (Si / W) relative to tungsten, as determined by fluorescence X-ray analysis, is 0.1 to 15 by mass.

11. The negative electrode material as described in claim 1 or 2, wherein, The silicon content ratio (Si / O) relative to oxygen, as determined by fluorescence X-ray analysis, is 0.1 to 2 by mass.

12. The negative electrode material as described in claim 1 or 2, wherein, The aforementioned sodium tungstate contains at least one of Na0.78WO3, Na0.48WO3, Na0.72WO3, Na0.44WO3, Na0.52WO3, and Na5WO14O44.

13. A negative electrode material, which is a negative electrode material for a battery, characterized in that it comprises carbon, sodium tungstate disposed on the surface of the aforementioned carbon, and silicon disposed on the surface of the aforementioned carbon, wherein the sodium content ratio Na / W relative to tungsten, as determined by fluorescence X-ray analysis, is 0.001 to 0.2 by mass, the silicon content ratio Si / C relative to carbon, as determined by fluorescence X-ray analysis, is 0.01 to 0.3 by mass, and the tungsten content ratio W / C relative to carbon, as determined by fluorescence X-ray analysis, is 0.005 to 0.3 by mass.

14. A battery characterized by comprising a negative electrode material and a positive electrode material as described in claim 1 or 2.

15. A method for manufacturing a negative electrode material, which is a method for manufacturing a negative electrode material for a battery, characterized by comprising the steps of dissolving an surfactant in a first solution containing sodium, adding silicon, dispersing the silicon in the first solution to generate a second solution, adding carbon to the second solution, dispersing the carbon in the second solution to generate a third solution, mixing the third solution with a tungsten solution containing oxygen and tungsten to generate a fourth solution, and removing the liquid components of the fourth solution to generate the negative electrode material.

16. A method for manufacturing the negative electrode material as described in claim 15, wherein, The ratio of the amount of carbon added to the second solution to the amount of silicon added to the first solution, by mass ratio, is 1% to 10%.

17. A method for manufacturing the negative electrode material as described in claim 15 or 16, wherein, The steps for generating the aforementioned negative electrode material include drying the aforementioned fourth solution, drying the negative electrode intermediate, and heating the aforementioned negative electrode intermediate.

18. A method for manufacturing the negative electrode material as described in claim 17, wherein, The aforementioned heating step includes the steps of heating the aforementioned negative electrode intermediate to a first temperature of 150°C to 625°C at a first heating rate, heating the aforementioned negative electrode intermediate to a second temperature of 680°C to 750°C at a second heating rate that is faster than the aforementioned first heating rate, and maintaining the aforementioned negative electrode intermediate at the aforementioned second temperature.

19. A method for manufacturing a battery, characterized by comprising a method for manufacturing a negative electrode material as described in claim 15 or 16, and a step for manufacturing a positive electrode material.

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