WO2022215498A1 - 負極材料、電池、負極材料の製造方法、及び電池の製造方法 - Google Patents
負極材料、電池、負極材料の製造方法、及び電池の製造方法 Download PDFInfo
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- WO2022215498A1 WO2022215498A1 PCT/JP2022/012756 JP2022012756W WO2022215498A1 WO 2022215498 A1 WO2022215498 A1 WO 2022215498A1 JP 2022012756 W JP2022012756 W JP 2022012756W WO 2022215498 A1 WO2022215498 A1 WO 2022215498A1
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- silicon
- negative electrode
- electrode material
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- 239000007773 negative electrode material Substances 0.000 title claims abstract description 132
- 238000004519 manufacturing process Methods 0.000 title claims description 54
- ZNOKGRXACCSDPY-UHFFFAOYSA-N tungsten trioxide Chemical compound O=[W](=O)=O ZNOKGRXACCSDPY-UHFFFAOYSA-N 0.000 claims abstract description 195
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 158
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 157
- 239000010703 silicon Substances 0.000 claims abstract description 157
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 106
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 98
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the present invention relates to a negative electrode material, a battery, a method for manufacturing a negative electrode material, and a method for manufacturing a battery.
- Patent Document 1 describes a negative electrode in which tungsten trioxide is arranged on the surface of graphite. By arranging tungsten trioxide on the surface of graphite, it becomes possible to improve the diffusibility of lithium ions, and the performance of the battery can be improved. Further, for example, Patent Document 2 describes a negative electrode containing silicon grains (silicon), tungsten, and carbon.
- the performance can be improved by providing tungsten trioxide or silicon, but there is room for improvement in improving the performance.
- the present invention has been made in view of the above, and an object of the present invention is to provide a negative electrode material and a battery with improved performance, a method for manufacturing the negative electrode material, and a method for manufacturing the battery.
- the present disclosure provides a negative electrode material for a battery, which contains carbon, tungsten trioxide, and a silicon material containing silicon, wherein the silicon In the material, the ratio of the Si amount of Si2p derived from simple silicon to the amount of Si2p derived from SiO2 in the surface layer is 3 or more on the basis of atomic concentration, when measured by X-ray photoelectron spectroscopy.
- the battery according to the present disclosure includes the negative electrode material and the positive electrode material.
- the method for producing a negative electrode material is a method for producing a negative electrode material for a battery, in which a silicon raw material is prepared in an atmosphere with an oxygen concentration of 5% or less. and using the silicon source material to produce a negative electrode material comprising carbon, tungsten trioxide, and a silicon material, wherein the silicon material has a surface layer thickness as measured by X-ray photoelectron spectroscopy.
- the ratio of the amount of Si in Si 2p derived from elemental silicon to the amount of Si in Si 2p derived from SiO 2 in is 3 or more on an atomic concentration basis.
- the method of manufacturing a battery according to the present disclosure includes the method of manufacturing the negative electrode material and the step of manufacturing the positive electrode material.
- the performance of the negative electrode material can be improved.
- FIG. 1 is a schematic partial cross-sectional view of a battery according to this embodiment.
- FIG. 2 is a schematic cross-sectional view of an example of the negative electrode according to this embodiment.
- FIG. 3 is a schematic cross-sectional view of a silicon material.
- FIG. 4 is a diagram showing an example of a survey spectrum showing the results of XPS measurement of a silicon material.
- FIG. 5 is a diagram showing an example of a Si2p narrow spectrum showing the result of XPS measurement of a silicon material.
- FIG. 6 is a diagram showing an example of peak separation of a Si2p narrow spectrum showing the result of XPS measurement of a silicon material.
- FIG. 1 is a schematic partial cross-sectional view of a battery according to this embodiment.
- FIG. 2 is a schematic cross-sectional view of an example of the negative electrode according to this embodiment.
- FIG. 3 is a schematic cross-sectional view of a silicon material.
- FIG. 4 is a diagram showing an example of
- FIG. 7 is a diagram showing an example of a narrow spectrum of O1s showing the result of XPS measurement of a silicon material.
- FIG. 8 is a flow chart illustrating the steps of preparing a silicon source.
- FIG. 9 is a flow chart illustrating an example of a method for manufacturing a battery according to this embodiment.
- FIG. 10 is a flow chart illustrating an example of a method for manufacturing a battery according to this embodiment.
- FIG. 11 is a table showing production conditions, properties of silicon particles, and evaluation results for each example.
- FIG. 1 is a schematic partial cross-sectional view of a battery according to this embodiment.
- a 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 electrolytic solution (not shown).
- the casing 10 is a case that accommodates the electrode group 12 and the electrolytic solution inside.
- the casing 10 may also include wiring, terminals, and the like connected to the electrode group 12 .
- the electrode group 12 includes a negative electrode 14, a positive electrode 16, and a separator 18.
- the electrode group 12 has a configuration in which a separator 18 is arranged between a negative electrode 14 and a positive electrode 16 .
- the electrode group 12 has a so-called laminated electrode group structure in which rectangular negative electrodes 14 and rectangular positive electrodes 16 are alternately laminated with rectangular separators 18 interposed therebetween.
- the electrode group 12 is not limited to the stacked electrode group structure.
- the electrode group 12 may have a wound electrode group structure in which a strip-shaped negative electrode 14 and a strip-shaped positive electrode 16 are laminated with a strip-shaped separator 18 interposed therebetween, and these are wound. good.
- FIG. 2 is a schematic cross-sectional view of an example of the negative electrode according to this embodiment.
- 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 member. Examples of the conductive member of the current collecting layer 20 include 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, about 15 ⁇ m to 40 ⁇ m, and the thickness of the negative electrode material layer 22 may be, for example, about 20 ⁇ m to 200 ⁇ m.
- the negative electrode 14 may include negative electrode material layers 22 on both sides of the current collecting layer 20 .
- the negative electrode material layer 22 contains a negative electrode material.
- Anode materials include carbon, tungsten trioxide, and silicon materials.
- tungsten trioxide is provided on the surface of carbon
- silicon material is provided on the surface of carbon. good.
- the negative electrode material of the negative electrode material layer 22 includes carbon particles 30 that are carbon particles, WO 3 (tungsten trioxide) particles 32 that are tungsten trioxide particles, and silicon particles that are particles containing silicon. and particles 33 .
- the shape of the particles here is not limited to a spherical shape, and may be of any shape such as a linear shape or a sheet shape.
- Tungsten trioxide provided on the surface of carbon means that tungsten trioxide is directly adhered to carbon, that tungsten trioxide is indirectly adhered to carbon through silicon that is adhered to carbon, and that tungsten trioxide is indirectly adhered to carbon. Silicon indirectly adheres to carbon through tungsten trioxide adhered to, and composite particles in which tungsten trioxide and silicon are directly adhered directly or indirectly adhere to carbon contains at least one
- the negative electrode material in this embodiment preferably contains at least carbon and a silicon material to which tungsten trioxide is adhered.
- the negative electrode material of the present embodiment is composed of carbon, tungsten trioxide, and a silicon material, and may contain only carbon, tungsten trioxide, and a silicon material, except for unavoidable impurities. In addition, the negative electrode material of the present embodiment may contain unavoidable impurities in the balance.
- the negative electrode material of the negative electrode material layer 22 contains a plurality of carbon particles 30 .
- the carbon particles 30 contain amorphous carbon or graphite.
- Amorphous carbon is amorphous carbon that does not have a crystal structure.
- Amorphous carbon is sometimes called amorphous carbon or diamond-like carbon, and can be said to be carbon in which sp2 bonds and sp3 bonds are mixed.
- Carbon particles of amorphous carbon preferably consist entirely of amorphous carbon and do not contain components other than amorphous carbon, except for inevitable impurities. Specifically, carbon particles of amorphous carbon preferably do not contain graphite.
- Amorphous carbon may also contain functional groups (eg, hydroxy groups, carboxyl groups) on the surface during treatment to place tungsten trioxide on the surface.
- this functional group enables proper trapping of tungsten trioxide on the surface of the amorphous carbon and proper arrangement of tungsten trioxide on the surface.
- this functional group fixes tungsten trioxide to the surface of the amorphous carbon, the adhesion of the tungsten trioxide to the surface of the amorphous carbon can be increased, and the tungsten trioxide is separated from the surface of the carbon. can be suppressed.
- the hard carbon raw material is produced at a lower temperature than, for example, graphite, the functional groups tend to remain without being removed, and tungsten trioxide and silicon can be appropriately arranged on the surface.
- Graphite is carbon with a planar crystal structure.
- the average particle diameter of the carbon particles 30 is preferably 1 ⁇ m or more and 50 ⁇ m or less, more preferably 1 ⁇ m or more and 20 ⁇ m or less. When the average particle diameter is within this range, the strength of the electrode film can be maintained.
- the negative electrode material of the negative electrode material layer 22 further includes a plurality of WO 3 particles 32 and silicon particles (silicon material) 33 . More specifically, a plurality of WO 3 particles 32 and silicon particles 33 are provided for each carbon particle 30 . One WO 3 particle 32 of the plurality of WO 3 particles 32 is provided on the surface of the carbon particle 30 . The other WO 3 particles 32 of the plurality of WO 3 particles 32 are provided on the surfaces of the silicon particles 33 . More specifically, the silicon particles 33 are in close contact with (contact with) the surfaces of the carbon particles 30 , and the WO 3 particles 32 are in close contact with (contact with) the surfaces of the silicon particles 33 .
- the carbon particles 30 , WO3 particles 32 and silicon particles 33 may be combined.
- the negative electrode material of the negative electrode material layer 22 has a structure in which the carbon particles 30 , the WO3 particles 32, and the silicon particles 33 are combined, and further, the structure in which the carbon particles 30 and the silicon particles 33 are combined. At least one of a structure in which carbon particles 30 and WO 3 particles 32 are combined may be included.
- Compositing here means separating the silicon particles 33 from the carbon particles 30, separating the silicon particles 33 from the WO3 particles 32 , and separating the WO3 particles 32 from the carbon particles 30, at least when no external force acts.
- the external force refers to the force when an SEI (Solid Electrolyte Interphase) film is formed covering the entire surface layer and expands and contracts when a battery using the negative electrode material is operated.
- compositing means forming a composite in which silicon particles 33 are arranged on the surfaces of carbon particles 30 and WO3 particles 32 are arranged on the surfaces of the silicon particles 33; is arranged to form a composite in which the silicon particles 33 are arranged on the surface of the WO 3 particles 32, to form a composite in which the silicon particles 33 are arranged on the surface of the carbon particles 30, and the surface of the carbon particles 30 forming a composite in which the WO3 particles 32 are arranged on the surface of the silicon particles 33; forming a composite in which the WO3 particles 32 are arranged on the surface of the silicon particles 33; At least one of the following: Particles 33 are arranged, and WO3 particles 32 and silicon particles 33 are also in close contact (contact) with each other.
- the WO 3 particles 32 include those with hexagonal crystal structures and those with monoclinic, triclinic, orthorhombic crystal structures. That is, the negative electrode material includes tungsten trioxide with a hexagonal crystal structure and tungsten trioxide with a monoclinic and triclinic crystal structure. However, the negative electrode material may include at least one of tungsten trioxide with a hexagonal crystal structure, tungsten trioxide with a monoclinic crystal structure, and tungsten trioxide with a triclinic crystal structure.
- the negative electrode material preferably comprises at least one of hexagonal, monoclinic and triclinic tungsten trioxide, wherein the hexagonal tungsten trioxide and the monoclinic or triclinic trioxide Tungsten, more preferably hexagonal, monoclinic and triclinic tungsten trioxide.
- the negative electrode material contains not only hexagonal tungsten trioxide but also tungsten trioxide with other crystal structures such as monoclinic and triclinic, , preferably with a maximum content of hexagonal tungsten trioxide.
- the crystal structure of tungsten trioxide contained in the negative electrode material is not limited to this, and for example, tungsten trioxide with other crystal structures may be included.
- the negative electrode material may also contain amorphous tungsten trioxide.
- the average particle size of the WO3 particles 32 is smaller than the average particle size of the carbon particles 30 .
- the average particle size of the WO 3 particles 32 is preferably 100 nm or more and 20 ⁇ m or less, more preferably 100 nm or more and 1 ⁇ m or less.
- the negative electrode material has a structure in which particulate tungsten trioxide (WO 3 particles 32) and silicon (silicon particles 33) are provided on the surface of the carbon particles 30, but the structure is not limited thereto.
- the negative electrode material may have a structure in which tungsten trioxide and a silicon material are provided on the surface of carbon, and the shape of the tungsten trioxide and silicon material provided on the surface of carbon may be arbitrary.
- tungsten trioxide is used as the tungsten compound or tungsten oxide.
- silicon is used as the silicon particles 33 in this embodiment, a silicon compound may be used.
- the negative electrode material layer 22 may contain substances other than the negative electrode material (the carbon particles 30 , the WO3 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, the negative electrode material layer 22, in other words, the negative electrode material, preferably does not contain graphite.
- PVDF polyvinylidene fluoride
- CMC carboxymethyl cellulose
- SBR styrene-butadiene rubber
- PAA polyacrylic acid
- Carbon, tungsten trioxide and silicon can be identified by X-ray diffraction.
- the peak waveform in the X-ray diffraction analysis result of the analyte shows the peak waveform of carbon, but the (002) peak waveform in the known graphite structure becomes broad, it can be determined to be amorphous carbon.
- the position (angle) indicating the peak in the X-ray diffraction analysis result of the analyte matches the known position indicating the peak in tungsten trioxide
- the analyte contains tungsten trioxide. can be judged.
- the positions (angles) of the peaks in the X-ray diffraction analysis result of the analyte match the known positions of the peaks in silicon, it can be determined that the analyte contains silicon.
- WO 3 particles 32 and the silicon particles 33 are arranged on the surface of the carbon particles 30 is confirmed by observation with an electron microscope such as a SEM (Scanning Electron Microscope) or a TEM (Transmission Electron Microscope). be able to.
- an electron microscope such as a SEM (Scanning Electron Microscope) or a TEM (Transmission Electron Microscope).
- the element ratio of carbon, tungsten trioxide, and silicon in the negative electrode material in this embodiment can be measured by emission spectrometry.
- the chemical components of silicon, tungsten, and oxygen are measured, and the remaining amount may be carbon.
- Silicon and tungsten were measured by the ICP-OES method (Inductivity Coupled Plasma Optical Emission Spectrometer, Inductively Coupled Plasma Emission Spectrometer) (manufacturer name "Agilent", equipment product name "720-ES”), and oxygen was measured by inert gas fusion- It can be measured by an infrared absorption method (manufacturer name “LECO”, equipment product name “ONH836”).
- the content of the silicon material is preferably 1% by weight or more and 10% by weight or less when the total of the three elements of the silicon material, tungsten trioxide, and carbon in the negative electrode material that is the product is 100% by weight. It is more preferably 1 wt% or more and 8 wt% or less, or 2 wt% or more and 8 wt% or less, and further preferably 1.5 wt% or more and 7 wt% or less, or 1.8 wt% or more and 7 wt% or less. preferable.
- the content of tungsten trioxide is preferably 1% by weight or more and 10% by weight or less when the total of the three elements of the silicon material, tungsten trioxide, and carbon is 100% by weight in the negative electrode material that is the product. , more preferably 2 wt % or more and 8 wt % or less, more preferably 3 wt % or more and 5 wt % or less.
- the content (% by weight) of the silicon material with respect to the content (% by weight) of tungsten trioxide ) is preferably 0.2 or more and 2.5 or less, more preferably 0.2 or more and 2.0 or less, or 0.5 or more and 2.0 or less, and 0.3 or more and 1.8 or less, or 0.4 or more and 1.7 or less.
- the silicon particles 33 may adhere (contact) the surfaces of the carbon particles 30 and the WO 3 particles 32 may adhere (contact) the surfaces of the carbon particles 30 .
- carbon particles 30 and silicon particles 33 may be combined, and carbon particles 30 and WO3 particles 32 may be combined.
- the negative electrode material has a structure in which particulate tungsten trioxide (WO 3 particles 32) and silicon particles 33 are provided on the surface of the carbon particles 30, but the structure is not limited to this.
- the negative electrode material may have a structure in which tungsten trioxide and a silicon material are provided on the surface of carbon, and the shape of the tungsten trioxide and silicon material provided on the surface of carbon may be arbitrary.
- FIG. 3 is a schematic cross-sectional view of silicon particles.
- silicon particle 33 includes Si layer 33A and oxide layer 33B.
- the Si layer 33A is a layer made of Si, and can be said to be a core portion of the silicon particles 33 .
- the Si layer 33A preferably does not contain elements other than Si, except for inevitable impurities.
- the oxide layer 33B is a layer formed on the surface of the Si layer 33A, and preferably covers the entire surface of the Si layer 33A.
- the oxide layer 33B can be said to be the outermost surface layer of the silicon particles 33 .
- the oxide layer 33B is a layer made of silicon oxide (SiO x ).
- the oxide layer 33B contains SiO 2 as a silicon oxide, but may contain silicon oxides other than SiO 2 , for example, SiO. It is preferable that the oxide layer 33B does not contain elements other than the elements constituting the oxide of silicon, except for unavoidable impurities.
- ⁇ Measuring device PHI5000 Versa Probe II (manufactured by ULVAC-PHI) ⁇ Excitation X-ray: Monochrome AlK ⁇ ray ⁇ Output: 50W ⁇ Pass energy: 187.85 eV (Survey), 46.95 eV (Narrow) ⁇ Measurement interval: 0.8 eV/step (Survey), 0.1 eV/step (Narrow) ⁇ Photoelectron extraction angle with respect to the sample surface: 45° ⁇ X-ray diameter: 200 ⁇ m
- the ratio of the amount of Si in Si2p derived from simple silicon to the amount of Si in Si2p derived from SiO2 in the surface layer when measured by X-ray photoelectron spectroscopy is 3.0 on an atomic concentration basis. , preferably 3.5 or more, more preferably 4 or more.
- surface layer refers to the range from the surface to the depth at which photoelectrons can escape from the sample.
- Si in Si2p refers to Si atoms from which 2p orbital electrons have been ejected by X-ray photoelectron spectroscopy.
- Si of Si2p derived from SiO2 refers to Si constituting SiO2 from which electrons in the 2p orbital have jumped out by X-ray photoelectron spectroscopy, and Si of Si2p derived from elemental silicon means 2p Si by X-ray photoelectron spectroscopy. It refers to Si that constitutes elemental silicon (metallic silicon) from which electrons in the orbit are ejected.
- the ratio of the amount of Si in Si2p derived from simple silicon to the amount of Si in Si2p derived from SiO2 in the surface layer is the surface layer (here, for example, from the outermost surface of the silicon particle 33 to a position approximately 6 angstroms deeper than the outermost surface. ), refers to the ratio of the atomic concentration of Si (Si atoms) derived from simple silicon from which 2p orbital electrons have popped to the atomic concentration of Si (Si atoms) derived from SiO 2 from which 2p orbital electrons have popped.
- the ratio of the amount of Si in Si2p derived from simple silicon to Si in Si2p derived from SiO2 is within this range (3.0 or more on the basis of atomic concentration), so that oxides near the surface The amount is reduced, and the capacity of the negative electrode material can be improved. In addition, since the oxide layer on the surface becomes thin, the intrusion and desorption of Li ions become easier, and the impedance decreases. In addition, in the silicon particles 33, the ratio of the amount of Si of Si2p derived from simple silicon to the amount of Si of Si2p derived from SiO2 in the surface layer when measured by X-ray photoelectron spectroscopy is 9 or less on the basis of atomic concentration.
- the ratio of the amount of Si in Si2p derived from simple silicon to the amount of Si in Si2p derived from SiO2 in the surface layer is the atomic concentration standard , preferably 3 or more and 9 or less, more preferably 3 or more and 19 or less, and even more preferably 3 or more and 99 or less.
- the ratio of the amount of Si in Si2p derived from simple silicon to the amount of Si in Si2p derived from SiO2 in the surface layer is, on an atomic concentration basis, It is preferably 3.5 or more and 9 or less, more preferably 3.5 or more and 19 or less, and even more preferably 3.5 or more and 99 or less.
- the ratio of the amount of Si in Si2p derived from simple silicon to the amount of Si in Si2p derived from SiO2 in the surface layer is, on an atomic concentration basis, It is preferably 4 or more and 9 or less, more preferably 4 or more and 19 or less, and even more preferably 4 or more and 99 or less.
- the amount of Si in Si2p derived from SiO2 is 1 %
- the amount of Si in Si2p derived from simple silicon is 99%.
- the ratio of the amount of Si to Si2p derived from elemental silicon is 99.
- the amount of Si in Si2p derived from SiO2 is 5 %
- the amount of Si in Si2p derived from simple silicon is 95%.
- the ratio of the amount of Si to Si2p derived from elemental silicon is 19.
- FIG. 4 is a diagram showing an example of a survey spectrum showing the XPS measurement results of a silicon material
- FIG. 5 is a diagram showing an example of a Si2p narrow spectrum showing the XPS measurement results of a silicon material
- FIG. 7 is a diagram showing an example of peak separation of the Si2p narrow spectrum showing the XPS measurement results of the silicon material
- FIG. 7 is a diagram showing an example of the O1s narrow spectrum showing the XPS measurement results of the silicon material. .
- FIG. 4 shows an example of the peak waveform P of the silicon particles 33 in wide scan analysis, and the peak waveform P1 near the binding energy of 100 eV indicates the peak of Si2p.
- FIG. 5 shows an example of the waveform of the silicon particles 33 in the narrow scan analysis near the peak waveform P1, in which the background is removed and the Si2p peak is extracted.
- Si of Si2p derived from SiO2 and Si of Si2p derived from elemental silicon differ in bond energy due to the difference in bond state. Therefore, as shown in FIG. 6, the peak waveform P1 can be separated into a peak waveform P1A indicating Si2p derived from elemental silicon and a peak waveform P1B indicating Si2p derived from SiO2 .
- the peak waveform P1A is a waveform having one peak near binding energy 99 eV
- the peak waveform P1B is a waveform having one peak near binding energy 103 eV. Background removal from the peak waveform was performed mainly by the Shirley method for baseline correction using Multipak version 9.9.0.8 attached to the X-ray photoelectron spectrometer as software.
- the ratio of the area of the peak waveform P1A to the area of the peak waveform P1B is calculated as the ratio of the amount of Si in Si2p derived from simple silicon to the amount of Si in Si2p derived from SiO 2 on the atomic concentration basis. .
- Si concentration ratio derived from Si the ratio of the atomic concentration of Si of Si2p derived from simple silicon to the atomic concentration of Si of all Si2p (all Si from which 2p orbital electrons have escaped) in the surface layer of the silicon particle 33 is defined as the Si concentration of Si derived from Si.
- the Si concentration ratio derived from Si can be calculated as the ratio of the area of the peak waveform P1A to the area of the peak waveform P1.
- the Si concentration ratio derived from Si is preferably 75% or more, more preferably 77% or more, and even more preferably 80% or more.
- the Si concentration ratio derived from Si is preferably 90% or less, more preferably 95% or less, and even more preferably 99% or less.
- concentration ratio of Si derived from Si is within this range, there is no need to prepare equipment or processes to prevent excessive oxidation of silicon particles, and the capacity of the negative electrode material is improved while suppressing a decrease in productivity. can.
- Si concentration ratio derived from SiO2 the ratio of the Si atomic concentration of Si 2p derived from SiO 2 to the atomic concentration of Si of all Si 2p in the surface layer of the silicon particles 33 is defined as the Si concentration ratio derived from SiO 2 .
- the Si concentration ratio derived from SiO 2 can be calculated as the ratio of the area of the peak waveform P1B to the area of the peak waveform P1.
- the Si concentration ratio derived from SiO 2 is preferably 25% or less, more preferably 23% or less, and even more preferably 20% or less. When the concentration ratio of Si derived from SiO 2 falls within this range, the amount of oxides in the vicinity of the surface is reduced, and the capacity of the negative electrode material can be improved.
- the Si concentration ratio derived from SiO 2 is preferably 10% or more, more preferably 5% or more, and even more preferably 1% or more.
- the Si concentration ratio derived from SiO2 is within this range, it becomes unnecessary to prepare facilities and processes for preventing excessive oxidation of silicon particles, and the capacity of the negative electrode material is improved, while reducing productivity. can be suppressed.
- the ratio of the amount of Si in Si2p to the amount of O in O1s in the surface layer, when measured by X-ray photoelectron spectroscopy, is preferably 1.2 or more on the atomic concentration basis. It is more preferably 3 or more, and even more preferably 1.4 or more.
- the O in O1s refers to an O atom from which an electron in the 1s orbit is ejected by X-ray photoelectron spectroscopy.
- the ratio of the amount of Si in Si2p to the amount of O in O1s in the surface layer is the O of O1s (1s orbital Atomic concentration of Si of Si2p (Si atoms from which electrons in the 2p orbital have escaped) in the surface layer of the silicon particle 33 (for example, to a position approximately 6 angstroms deeper than the outermost surface) relative to the atomic concentration of O atoms from which electrons have escaped. refers to the ratio of In the silicon particles 33, when the ratio of the amount of Si in Si2p to the amount of O in O1s is within this range, the amount of oxide in the vicinity of the surface is reduced, and the capacity of the negative electrode material can be improved.
- silicon oxides other than SiO2 may act as a factor that suppresses the improvement of capacity.
- the ratio of the amount of Si to the amount of O is within the above range
- the amount of silicon oxides other than SiO 2 can be reduced, and the capacity can be appropriately improved.
- the ratio of the amount of Si in Si2p to the amount of O in O1s in the surface layer is preferably 4 or less, and 9 or less, based on the atomic concentration. is more preferable, and 99 or less is even more preferable.
- the ratio of the amount of Si to the amount of O of the silicon particles 33 is within this range, there is no need to prepare excessively pure Si, and the capacity of the negative electrode material can be improved while suppressing a decrease in productivity. .
- the ratio of Si in Si2p to the amount of O in O1s in the surface layer is 1.2 or more and 4 or less on an atomic concentration basis. is preferred, 1.2 to 9 is more preferred, and 1.2 to 99 is even more preferred.
- the ratio of Si in Si2p to the amount of O in O1s in the surface layer is preferably 1.3 or more and 4 or less on an atomic concentration basis. , is more preferably 1.3 or more and 9 or less, and more preferably 1.3 or more and 99 or less. Furthermore, when the silicon particles 33 are measured using X-ray photoelectron spectroscopy, the ratio of Si in Si2p to the amount of O in O1s in the surface layer is preferably 1.4 or more and 4 or less on an atomic concentration basis. , is more preferably 1.4 or more and 9 or less, and more preferably 1.4 or more and 99 or less.
- the ratio of Si in Si2p to the amount of O in O1s in the surface layer is 4, and when the O concentration is 5 at% and the Si concentration is 95%, the surface layer
- the ratio of Si in Si2p to the amount of O in O1s of is 19.
- FIG. 5 shows the narrow spectrum of Si2P and FIG. 7 shows the narrow spectrum of O1s. If there is a trace element other than this, the narrow spectrum of that element is similarly measured. Perform background correction for each narrow spectrum and determine the peak area.
- This peak area is multiplied by the sensitivity coefficient corresponding to the orbital level of each element to obtain the concentration (atomic concentration) of the element.
- a series of atomic concentration calculations can be obtained using analysis software Multi Pack attached to PHI5000 Versa Probe II. The results thus obtained are the Si concentration (second Si concentration) and O concentration in FIG. The Si/O ratio was obtained from this concentration. That is, the ratio of the Si concentration to the O concentration obtained as described above is the concentration ratio Si/O.
- the Si concentration is preferably 50 at % or higher, more preferably 55 at % or higher, even more preferably 60 at % or higher. When the Si concentration falls within this range, the amount of oxide in the vicinity of the surface is reduced, and the capacity of the negative electrode material can be improved. Also, the Si concentration is preferably 80 at % or less, more preferably 90 at % or less, and even more preferably 99 at % or less. When the Si concentration is within this range, it is not necessary to prepare equipment or processes for preventing excessive oxidation of silicon particles, and it is possible to suppress a decrease in productivity while improving the capacity of the negative electrode material.
- the O concentration is preferably 46 atomic % or less, more preferably 40 atomic % or less, and even more preferably 30 atomic % or less. When the O concentration falls within this range, the amount of oxide in the vicinity of the surface is reduced, and the capacity of the negative electrode material can be improved. Also, the O concentration is preferably 20 at % or more, more preferably 10 at % or more, and even more preferably 1 at % or more. When the O concentration is within this range, it is not necessary to prepare equipment or processes for preventing excessive oxidation of silicon particles, and the capacity of the negative electrode material can be improved while reducing productivity.
- the thickness of the oxide layer 33B of the silicon particles 33 is preferably 2.1 angstroms or less, more preferably 1.8 angstroms or less, and even more preferably 1.3 angstroms or less. By setting the thickness of the oxide layer 33B within this range, the amount of oxide in the vicinity of the surface is reduced, and the capacity of the negative electrode material can be improved.
- the thickness of the oxide layer 33B is preferably 0.7 angstroms or more, more preferably 0.3 angstroms or more, and even more preferably 0.06 angstroms or more. By setting the thickness of the oxide layer 33B within this range, it becomes unnecessary to prepare excessively pure Si, and it is possible to suppress a decrease in productivity while improving the capacity of the negative electrode material.
- the thickness of the oxide layer 33B is the ratio of the amount of Si in the Si 2p derived from SiO 2 to the amount of Si in the Si 2p derived from simple silicon (Si 2p derived from SiO 2 in the surface layer when measured by X-ray photoelectron spectroscopy). is calculated by multiplying the reciprocal of the ratio of the amount of Si in Si2p derived from elemental silicon to the amount of Si in Si2p by the photoelectron escape depth of Si in Si2p of 6 angstroms.
- volume average particle diameter volume-based average particle diameter of the silicon particles 33 measured by a laser diffraction scattering method is hereinafter referred to as volume average particle diameter.
- the ratio of the volume of the oxide layer 33B to the total volume of the silicon particles 33 is defined as the volume of the oxide layer 33B based on the volume average particle diameter.
- the volume ratio of the oxide layer 33B based on the volume average particle diameter is preferably 0.05% or less, more preferably 0.04% or less, and further preferably 0.035% or less. preferable. When the volume ratio falls within this range, the amount of oxide in the vicinity of the surface is reduced, and the capacity of the negative electrode material can be improved.
- the volume ratio of the oxide layer 33B based on the volume average particle diameter is preferably 0.015% or more, more preferably 0.01% or more, and even more preferably 0.001% or more. .
- the volume ratio falls within this range, there is no need to prepare equipment or processes for preventing excessive oxidation of the silicon particles, and it is possible to suppress a decrease in productivity while improving the capacity of the negative electrode material.
- the volume ratio of the oxide layer 33B based on the volume average particle diameter can be calculated as follows. That is, assuming that the silicon particles 33 are spherical (true spheres), the volume average particle diameter of the silicon particles 33 is used as the diameter of the silicon particles 33 to calculate the volume of the silicon particles 33 . Then, the thickness of the oxide layer 33B calculated as described above is subtracted from the volume average particle diameter to calculate the diameter of the Si layer 33A. is used to calculate the volume of the Si layer 33A. The volume of the oxide layer 33B is obtained by subtracting the volume of the Si layer 33A from the volume of the silicon particles 33 thus calculated. Then, the ratio of the volume of the oxide layer 33B to the volume of the silicon particles 33 is defined as the volume ratio of the oxide layer 33B based on the volume average particle size.
- D50 In the volume-based particle size distribution measured by the laser diffraction scattering method, the particle size with a cumulative frequency of 50% by volume is defined as D50.
- volume ratio of oxide layer based on D50 the ratio of the volume of the oxide layer 33B to the total volume of the silicon particles 33 when the silicon particles 33 are assumed to be spherical and the volume is calculated using D50 is defined as the volume ratio of the oxide layer 33B based on D50.
- the volume ratio of the oxide layer 33B based on D50 is preferably 0.4% or less, more preferably 0.3% or less, and even more preferably 0.25% or less. When the volume ratio falls within this range, the amount of oxide in the vicinity of the surface is reduced, and the capacity of the negative electrode material can be improved.
- the volume ratio of the oxide layer 33B based on D50 is preferably 0.13% or more, more preferably 0.05% or more, and even more preferably 0.01% or more. When the volume ratio falls within this range, there is no need to prepare equipment or processes for preventing excessive oxidation of the silicon particles, and it is possible to suppress a decrease in productivity while improving the capacity of the negative electrode material.
- the volume ratio of the oxide layer 33B based on D50 can be calculated as follows. That is, assuming that the silicon particles 33 are spherical (true spheres), D50 is used as the diameter of the silicon particles 33 to calculate the volume of the silicon particles 33 . Then, the diameter of the Si layer 33A is calculated by subtracting the thickness of the oxide layer 33B calculated as described above from D50. , the volume of the Si layer 33A is calculated. The volume of the oxide layer 33B is obtained by subtracting the volume of the Si layer 33A from the volume of the silicon particles 33 thus calculated. Then, the ratio of the volume of the oxide layer 33B to the volume of the silicon particles 33 is defined as the volume ratio of the oxide layer 33B based on D50.
- the positive electrode 16 shown in FIG. 1 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 member, and examples of the conductive member here include aluminum.
- the positive electrode material layer is a layer of positive electrode material and is provided on the surface of the current collecting layer of the positive electrode 16 .
- the thickness of the collector layer of the positive electrode may be, for example, about 10 ⁇ m to 30 ⁇ m, and the thickness of the positive electrode material layer may be, for example, about 10 ⁇ m to 100 ⁇ m.
- 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.
- a lithium compound may contain only one type of material, or may contain two or more types of materials.
- the positive electrode material layer may contain a substance other than the positive electrode material, for example, a binder.
- a binder Any material may be used for the binder, and examples thereof include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and PAA. Only one type of binder may be used, or two or more types may be used in combination.
- the separator 18 shown in FIG. 1 is an insulating member.
- the separator 18 is, for example, a porous film made of resin, and examples of resin include polyethylene (PE) and polypropylene (PP).
- the separator 18 may have a structure in which films of different materials are laminated.
- the separator 18 may have a heat-resistant layer.
- a heat-resistant layer is a layer containing a substance with a high melting point.
- the heat-resistant layer may contain particles of an inorganic material such as alumina, for example.
- Electrolyte The electrolyte provided in the battery 1 is a non-aqueous electrolyte.
- the electrolytic solution is impregnated into the voids in the electrode group 12 .
- Electrolyte solutions include, for example, lithium salts and aprotic solvents.
- the lithium salt is dispersed and dissolved in an aprotic solvent.
- Examples of lithium salts include LiPF 6 , LiBF 4 , Li[N(FSO 2 ) 2 ], Li[N(CF 3 SO 2 ) 2 ], Li[B(C 2 O 4 ) 2 ], LiPO 2 F 2 and the like.
- Aprotic solvents can be, for example, mixtures of cyclic and linear carbonates. Cyclic carbonates include, for example, EC, PC, and butylene carbonate. Chain carbonic acid esters include dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC) and the like.
- This production method includes the steps of preparing a silicon raw material in an atmosphere with an oxygen concentration of 5% or less, and using the silicon raw material to provide tungsten trioxide and a silicon material on the surface of carbon to produce a negative electrode material. and manufacturing the cathode material.
- FIG. 8 is a flow chart illustrating the steps of preparing a silicon source.
- the silicon raw material is the raw material of the silicon particles 33 .
- the step of preparing the silicon raw material includes a crushing step S1, a coarse crushing step S2, and a crushing step S3.
- the step of preparing the silicon raw material preferably prepares the silicon raw material by pulverizing the silicon base material in an atmosphere with an oxygen concentration of 5% or less, more preferably 3% or less, and the oxygen concentration is It is more preferably 1% or less, and even more preferably 0.1% or less. With such a low oxygen concentration, it is possible to suppress the oxidation of the new surface of silicon that appears after crushing and the thickening of the oxide layer formed on the surface before crushing, thereby suppressing the decrease in capacity.
- the oxygen concentration can be measured by an oxygen monitor OM-25MF01 manufactured by Taiei Engineering Co., Ltd., and when the oxygen concentration is lower than 1%, it can be measured by a low-concentration oxygen monitor JKO-O2LJD3 manufactured by Ichinen Jiko Co., Ltd.
- the oxygen concentration in the coarse pulverization step S2 and the pulverization step S3, it is preferable to set the oxygen concentration in the above range, and in all of the crushing step S1, the coarse pulverization step S2, and the pulverization step S3, the oxygen concentration is set in the above range. is more preferable.
- the crushing step S1 is a step of crushing silicon lumps to obtain crushed silicon substances.
- the size of the silicon lumps is not particularly limited.
- the shape of the silicon mass is not particularly limited, and may be columnar, plate-like, or granular, for example. Silicon chunks, polycrystalline silicon other than chunks, lumps of single crystal silicon and columnar crystal silicon ingots, monitor silicon wafers, dummy silicon wafers, and granular silicon can be used as the silicon lumps.
- a crushing device for crushing silicon lumps is not particularly limited, and for example, a hammer crusher, jaw crusher, gyratory crusher, cone crusher, roll crusher, and impact crusher can be used.
- the size of the crushed silicon obtained by crushing the lumps of silicon is preferably in the range of more than 1 mm and 5 mm or less in longest diameter.
- the coarse pulverization step S2 is a step of coarsely pulverizing the silicon crushed material to obtain silicon coarse particles.
- the silicon coarse particles obtained in the coarse pulverization step S2 preferably have a maximum particle size of 1000 ⁇ m or less when separated by a sieve method. Therefore, the coarse pulverization step S2 preferably includes a step of classifying the coarsely pulverized material obtained by the coarse pulverization using a sieve with an opening of 1000 ⁇ m to collect coarse particles having a maximum particle size of 1000 ⁇ m or less. If the size of the silicon coarse particles exceeds 1000 ⁇ m, the silicon coarse particles may not be sufficiently pulverized in the subsequent pulverization step S3 and the particles may be mixed. It is particularly preferable that the maximum particle size of the silicon coarse particles is 500 ⁇ m or less.
- Coarse pulverization may be performed by either dry or wet method, but dry method is preferred.
- the pulverizing device for coarsely pulverizing the crushed silicon material is not particularly limited, and for example, ball mills (planetary ball mills, vibrating ball mills, rolling ball mills, stirring ball mills), jet mills, and three-dimensional ball mills can be used.
- the pulverizing step S3 is a step of pulverizing silicon coarse particles to obtain a silicon raw material (silicon microparticles).
- a ball mill planetary ball mill, vibrating ball mill, rolling ball mill, stirring ball mill, or three-dimensional ball mill can be used.
- a three-dimensional ball mill manufactured by Nagao System Co., Ltd. is preferably used as the pulverizer.
- zirconia (ZrO 2 ) balls and alumina (Al 2 O 3 ) balls can be used as hard balls.
- the particle diameter of the hard balls is preferably in the range of 0.1 mm or more and 20 mm or less. When the particle size of the hard balls is within this range, coarse silicon particles can be efficiently pulverized.
- the amount of the hard balls used is preferably in the range of 500 parts by mass or more and 2500 parts by mass or less relative to 100 parts by mass of the coarse silicon particles. When the amount of hard balls used is within this range, coarse silicon particles can be pulverized efficiently.
- the amount of hard balls used is more preferably in the range of 1000 parts by mass to 2000 parts by mass, and particularly preferably in the range of 1100 parts by mass to 1500 parts by mass.
- the filling rate of the coarse silicon particles and hard balls in the container of the three-dimensional ball mill is preferably in the range of 3% or more and 35% or less as the total volume of the coarse silicon particles and hard balls with respect to the capacity of the container. If the filling rate is too low, the pulverization efficiency may decrease and the manufacturing cost may increase. On the other hand, if the filling rate is too high, pulverization will be difficult to proceed, and the average particle size of the resulting silicon raw material may increase, or silicon coarse particles may not be sufficiently pulverized and remain.
- the filling rate of the silicon coarse particles and the hard balls is more preferably in the range of 15% to 30%, particularly preferably in the range of 20% to 30%.
- the filling rate is the volume assuming 100% when the inside of the container is filled with the raw material and the balls without gaps. For example, 50% if the spherical container is half-filled with raw material and hard balls, and half the height of the hemispherical container (one of the two half-containers forming the container). 15.6% if filled with hard balls without gaps.
- no gap as used herein means a macroscopic gap, meaning a state in which a plurality of balls are missing, and is not a gap formed between balls.
- the container is preferably filled with a non-oxidizing gas.
- a container filled with a non-oxidizing gas it is possible to suppress aggregation of particles due to moisture absorption of the silicon fine particles and oxidation of the silicon fine particles.
- Argon, nitrogen, and carbon dioxide can be used as the non-oxidizing gas.
- silicon coarse particles having a maximum particle size of 1000 ⁇ m or less as measured by a sieve method are prepared in the coarse pulverization step S2, and a three-dimensional ball mill is used in the next pulverization step S3. and pulverize the silicon coarse particles under predetermined conditions. For this reason, it is possible to industrially produce a silicon raw material that is less likely to form fine and coarse aggregated particles and has high dispersibility when mixed with other raw material particles.
- the manufacturing method is not limited to the above and may be arbitrary.
- FIG. 9 is a flow chart illustrating an example of a method for manufacturing a battery according to this embodiment. As shown in FIG. 9, in this manufacturing method, the negative electrode 14 is formed in steps S10 to S28.
- the WO3 raw material is added to the dissolving solution to dissolve the WO3 raw material in the dissolving solution (step S10; dissolving step).
- the WO3 raw material is tungsten trioxide , which is used as the raw material for the negative electrode material.
- the dissolving solution is a solution in which the WO3 raw material , ie tungsten trioxide, can be dissolved.
- an alkaline solution is used, and in this embodiment, an aqueous ammonia solution is used.
- the dissolution solution preferably has a concentration of ammonia of 5% or more and 30% or less by weight with respect to the entire dissolution solution.
- dissolution is not limited to a state in which everything is dissolved, and includes a state in which a portion remains.
- Dissolving also includes mixing and dissolving.
- the WO 3 raw material is produced, for example, by reacting CaWO 4 with hydrochloric acid, dissolving it with ammonia, and calcining the crystallized ammonium paratungstate, but it may be produced by any method.
- WO3 is tungsten trioxide , tungsten (VI) oxide, and tungstic anhydride.
- the ratio of the amount of WO3 raw material added to the amount of ammonia contained in the solution for dissolution is preferably 1% or more and 10% or less in mol%.
- the ratio of the amount of the WO3 raw material added is set to 10 % or less.
- the WO3 raw material is added to the dissolving solution and stirred for a predetermined time to dissolve the WO3 raw material in the dissolving solution.
- the predetermined time here is preferably 6 hours or more and 24 hours or less.
- the process of step S10 may be a preparatory process in which a dissolving solution in which the WO3 raw material is dissolved is prepared in advance before proceeding to step S12, which will be described later.
- the silicon raw material is added to and dissolved in the dissolving solution (here, ammonium tungstate solution) in which the WO 3 raw material is dissolved (step S12; addition step).
- the dissolving solution here, ammonium tungstate solution
- step S12 the dissolving solution in which the WO3 raw material is dissolved is stirred to disperse the silicon raw material in the dissolving solution.
- a surfactant may be added to the dissolving solution in which the silicon raw material and WO3 are dispersed in order to improve the affinity between the silicon raw material and WO3.
- SDS sodium dodecyl sulfate
- Na-free surfactants examples include poly(oxyethylene) alkyl ethers and polyoxyethylene nonylphenyl ethers.
- poly ( oxyethylene ) alkyl ether it is preferable to use an alkyl group having 12 or more and 15 or less carbon atoms.
- ether C13H27O ( C2H4 ) nH (poly(oxyethylene)tridecyl ether), C13H27O ( C2H4 ) nH ( poly ( oxyethylene)isotridecyl ether ), C 14 H 25 O(C 2 H 4 ) n H (poly(oxyethylene) tetradecyl ether), C 155 H 25 O(C 2 H 4 ) n H (poly(oxyethylene) pentadecyl ether), etc.
- n is an integer of 1 or more.
- polyoxyethylene nonylphenyl ether examples include C9H19C6 ( CH2CH2O ) 8H , C9H19C6 ( CH2CH2O ) 10H , C9H19C6 ( CH2CH2O ) 12H and the like may be used.
- the amount of the surfactant to be added is preferably 2% or more and 8% or less in weight % with respect to the amount of the WO3 raw material added to the dissolving solution. This numerical range appropriately improves the affinity between the silicon raw material and WO 3 .
- a primary intermediate material is generated by removing the liquid component of the dissolving solution (primary intermediate material generating step).
- steps S14 and S16 are executed as primary intermediate material steps.
- the dissolution solution is dried to produce a primary intermediate (step S14; drying step).
- the dissolving solution is dried at 80° C. for 12 hours in the air or inert gas to remove, ie, evaporate, the liquid component contained in the dissolving solution. Oxidation of Si can be suppressed by using an inert gas.
- the primary intermediate can be said to contain solid components remaining after the liquid component of the dissolution solution has been removed.
- a primary intermediate material is produced by heat-treating the dried primary intermediate (step S16; heating step). Heating the primary intermediate forms a primary intermediate material having WO 3 particles 32 on the surface of silicon particles 33 .
- the temperature for heating the primary intermediate is preferably 500° C. or higher and 900° C. or lower in an inert gas. By setting the temperature for heating the primary intermediate within this range, the primary intermediate material can be properly formed.
- the time for heating the primary intermediate is preferably 1 hour or more and 10 hours or less. By setting the heating time of the primary intermediate within this range, the primary intermediate material can be properly formed.
- the steps S12 to S16 may be a preparatory step in which the primary intermediate material (or primary intermediate) is prepared in advance before proceeding to step S18, which will be described later.
- the primary intermediate and the carbon raw material (here, hard carbon) are mixed and dispersed in the liquid (here, water) (step S18; addition step).
- the carbon raw material is hard carbon used as a raw material.
- the carbon raw material may be produced, for example, by an oil furnace method.
- oil furnace method for example, raw material oil is sprayed in a high-temperature atmosphere to thermally decompose, followed by rapid cooling to produce particulate carbon raw material.
- the method for producing the carbon raw material is not limited to this and may be arbitrary.
- the silicon raw material addition ratio is set to 1% by weight or more and 10% by weight or less, preferably 2% by weight or more and 8% by weight or less, more preferably 5% by weight or more and 8% by weight or less.
- the silicon particles 33 can be appropriately formed on the surfaces of the carbon particles 30, and the capacity of the battery can be increased as a negative electrode.
- the WO3 raw material addition ratio is 1 % by weight or more and 10% by weight or less, preferably 2% by weight or more and 8% by weight or less, more preferably 5% by weight or more and 8% by weight or less. preferable.
- a step S18 stirs the liquid (here, water) to disperse the primary intermediate material and the carbon raw material in the liquid.
- a surfactant may be added to the liquid in order to improve the affinity between the carbon raw material , silicon and WO3.
- SDS sodium dodecyl sulfate
- Na-free surfactant may be used.
- the amount of the surfactant to be added is preferably 2% or more and 8% or less in weight % with respect to the amount of the carbon raw material added to the liquid. This numerical range appropriately improves the affinity between the carbon raw material , silicon and WO3.
- the negative electrode material is generated by removing the liquid component of the solution in which the primary intermediate material and the carbon raw material are dispersed in the liquid (negative electrode material generating step).
- steps S20 and S22 are performed as negative electrode material generation steps.
- the solution is dried to produce a negative electrode intermediate (step S20; drying step).
- step S20 the liquid component contained in the solution is removed, that is, evaporated by drying the solution at 80° C. for 12 hours in the air or inert gas. It can be said that the negative electrode intermediate contains the solid component remaining after the liquid component of the solution has been removed.
- the negative electrode material is produced by heating the negative electrode intermediate (step S22; heating step).
- a negative electrode material having WO 3 particles 32 and silicon particles 33 provided on the surface of carbon particles 30 is formed.
- the temperature for heating the negative electrode intermediate is preferably 500° C. or higher and 900° C. or lower in an inert gas. By setting the temperature for heating the negative electrode intermediate within this range, the negative electrode material can be properly formed.
- the time for heating the negative electrode intermediate is preferably 1 hour or more and 10 hours or less. By setting the heating time of the negative electrode intermediate within this range, the negative electrode material can be properly formed.
- the formed negative electrode material is used to form the negative electrode 14 (step S24). That is, the negative electrode 14 is formed by forming the negative electrode material layer 22 containing the negative electrode material on the surface of the current collecting layer 20 .
- the positive electrode 16 is formed (step S26).
- the positive electrode material is formed in the same manner as steps S10 to S24, 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 a positive electrode material is formed on the surface of the collector layer for the positive electrode 16 to form the positive electrode 16 .
- the battery 1 is manufactured using the negative electrode 14 and the positive electrode 16 (step S28).
- the electrode group 12 is formed by stacking the negative electrode 14 , the separator 18 and the positive electrode 16 , and the electrode group 12 and the electrolytic solution are accommodated in the casing 10 to manufacture the battery 1 .
- steps S10 to S24 after silicon is added to the dissolution solution in which tungsten trioxide is dissolved and the liquid component is removed to generate the primary intermediate material,
- the negative electrode material is produced by adding the primary intermediate material and hard carbon to the liquid and then removing the liquid component.
- a solution method such a method for producing a negative electrode material is appropriately referred to as a solution method.
- the above manufacturing method using SDS as the surfactant is referred to as the first manufacturing method.
- a surfactant may be added to the solution to improve the affinity between the carbon raw material , silicon and WO3.
- a surfactant containing no Na may be used.
- silicon is added to the dissolution solution in which tungsten trioxide is dissolved, and then the liquid component is removed to produce the primary intermediate material.
- the negative electrode material is produced by adding the primary intermediate material and the hard carbon to the liquid and then removing the liquid component.
- a solution method such a method for producing a negative electrode material is appropriately referred to as a solution method.
- said manufacturing method is called a 2nd manufacturing method.
- FIG. 10 is a flow chart illustrating an example of a method for manufacturing a battery according to this embodiment.
- the negative electrode 14 is formed in steps S30 to S44. Steps S30, S32, S40, S42, and S44 are the same as steps S10, S12, S24, S26, and S28.
- the carbon raw material is added and dissolved in the dissolving solution in which the WO3 raw material and the silicon raw material are dissolved (step S34; addition step).
- the carbon raw material is hard carbon used as a raw material.
- a step S34 stirs the dissolving solution to mix and disperse the WO3 raw material , the silicon raw material and the carbon raw material in the solution. Further, in step S34, a surfactant may be added to the solution in order to improve the affinity between the carbon raw material , silicon and WO3.
- steps S36 and S38 are performed as negative electrode material generation steps.
- the dissolution solution is dried to produce the negative electrode intermediate (step S36; drying step).
- the dissolving solution is dried at 80° C. for 12 hours in the air or inert gas to remove, ie, evaporate, the liquid component contained in the dissolving solution. It can be said that the negative electrode intermediate contains the solid component remaining after the liquid component of the dissolving solution is removed.
- a negative electrode material is produced (step S38; heating step).
- a negative electrode material having WO 3 particles 32 and silicon particles 33 provided on the surface of carbon particles 30 is formed.
- the temperature for heating the negative electrode intermediate is preferably 500° C. or higher and 900° C. or lower in an inert gas. By setting the temperature for heating the negative electrode intermediate within this range, the negative electrode material can be properly formed.
- the time for heating the negative electrode intermediate is preferably 1 hour or more and 10 hours or less. By setting the heating time of the negative electrode intermediate within this range, the negative electrode material can be properly formed.
- the negative electrode material is manufactured by adding silicon and hard carbon to the dissolving solution in which tungsten trioxide is dissolved and then removing the liquid component.
- a method for producing a negative electrode material is also referred to as a solution method as appropriate.
- said manufacturing method is called the 3rd manufacturing method.
- the manufacturing method is not limited to the above and may be arbitrary.
- the negative electrode material according to this embodiment is a negative electrode material for a battery, and contains carbon, tungsten trioxide, and silicon particles 33 containing silicon.
- the ratio of the amount of Si in Si2p derived from simple silicon to the amount of Si in Si2p derived from SiO2 in the surface layer is 3 or more on the atomic concentration basis when measured by X-ray photoelectron spectroscopy. .
- the performance of the battery can be improved by providing tungsten trioxide or Si as the negative electrode material.
- Si tungsten trioxide or Si
- the present inventor discovered that oxides of Si suppress the improvement in capacity.
- the ratio of the amount of Si in Si2p derived from elemental silicon to the amount of Si in Si2p derived from SiO2 in the surface layer is 3 or more on an atomic concentration basis. Therefore, according to the present embodiment, it is possible to reduce the amount of oxides of silicon and improve the performance of the battery.
- the ratio of the amount of Si in Si2p to the amount of O in O1s in the surface layer, when measured by X-ray photoelectron spectroscopy, is preferably 1.2 or more on the basis of atomic concentration.
- the ratio of the amount of Si in Si2p to the amount of O in O1s of the silicon particles 33 is within this range, so that the amount of oxide in the vicinity of the surface is reduced, and the battery performance can be improved.
- silicon oxides other than SiO2 may also act as a factor that suppresses the improvement in capacity, and in such cases, the ratio of the amount of Si in Si2p to the amount of O in O1s is within the above range, the amount of silicon oxides other than SiO 2 can be reduced, and the performance of the battery can be appropriately improved.
- the silicon particles 33 include a Si layer 33A made of Si and an oxide layer 33B formed on the surface of the Si layer 33A and made of silicon oxide.
- the volume of the oxide layer 33B is preferably 0.05% or less of the total volume of the silicon particles 33 .
- the silicon particles 33 include a Si layer 33A made of Si and an oxide layer 33B formed on the surface of the Si layer 33A and made of silicon oxide.
- the volume of the silicon particles 33 is calculated using the particle diameter D50 with a cumulative frequency of 50% by volume in the volume-based particle size distribution measured by the laser diffraction scattering method, the volume of the oxide layer 33B is equal to that of the silicon particles 33. It is preferably 0.4% or less with respect to the total volume. By setting the volume ratio of the oxide layer 33B within this range, the amount of oxide in the vicinity of the surface is reduced, and the performance of the battery can be improved.
- the negative electrode material when the total content of carbon, tungsten trioxide, and silicon particles 33 is 100% by weight, the negative electrode material preferably has a content of silicon particles 33 of 1% by weight or more and 10% by weight or less. By setting the content of the silicon particles 33 within this range, the performance of the battery can be improved.
- the method for producing a negative electrode material includes a step of preparing a silicon raw material in an atmosphere with an oxygen concentration of 5% or less, and carbon, tungsten trioxide, and silicon particles 33 using the silicon raw material. including the step of producing a negative electrode material, wherein the silicon particles 33 are such that the ratio of the amount of Si2p of elemental silicon to the amount of Si2p of elemental silicon due to SiO2 in the surface layer, as measured by X-ray photoelectron spectroscopy, is equal to the atomic concentration As a standard, it is preferably 3 or more.
- Example 1 Preparation of silicon raw materials
- a scale-like polycrystalline silicon chunk (purity: 99.999999999% by mass, length: 5-15 mm, width: 5-15 mm, thickness: 2-10 mm) was crushed using a hammer mill.
- the obtained pulverized material was dry-classified using a sieve with an opening of 5 mm to obtain a silicon pulverized material under the sieve.
- the obtained silicon crushed material, hard balls (zirconia balls, diameter: 10 mm), and a container divisible into one container and the other container were each housed in a glove box filled with Ar gas. In the glove box, 30 parts by mass of crushed silicon and 380 parts by mass of hard balls were put into one of the containers.
- one container containing the crushed silicon and hard balls was combined with the other container, and the two containers were screwed and sealed in a glove box filled with Ar gas.
- the mating surfaces of the two containers are ground surfaces so as to maintain airtightness.
- the filling ratio of crushed silicon and hard balls in the container was 28%.
- a container filled with crushed silicon and hard balls was taken out from the glove box and set in a three-dimensional ball mill. Then, coarse pulverization was carried out under the conditions of rotation speed of the first rotating shaft: 300 rpm, rotation speed of the second rotating shaft: 300 rpm, and pulverization time: 0.33 hours.
- the coarsely pulverized silicon material and the hard balls were dry-classified using a sieve with an opening of 1000 ⁇ m to obtain coarse silicon particles having a maximum particle size of 1000 ⁇ m or less.
- the obtained silicon coarse particles, hard balls (zirconia balls, diameter: 10 mm), and hemispherical containers were each housed in a glove box filled with Ar gas.
- 15 parts by mass of crushed silicon and 200 parts by mass of hard balls were put into one of the hemispherical containers in the glove box (the amount of hard balls was 1333 parts by mass with respect to 100 parts by mass of coarse silicon particles).
- one hemispherical container containing the crushed silicon and hard balls is combined with the other hemispherical container so as to form a spherical container, and the two containers are screwed together in a glove box filled with Ar gas. and sealed.
- the filling rate of crushed silicon and hard balls in the container was 15%.
- a container filled with silicon coarse particles and hard balls was taken out from the glove box and set in a three-dimensional ball mill. Then, pulverization was performed under the conditions of rotation speed of the first rotating shaft: 300 rpm, rotation speed of the second rotating shaft: 300 rpm, pulverization time: 3 hours, and a silicon raw material was obtained.
- Example 1 (Preparation of negative electrode material)
- hard carbon, tungsten trioxide, and silicon were used to produce a negative electrode material by the first production method using the solution method described in the embodiment.
- 5 ml of an ammonia solution with a concentration of 28% by weight and 0.05 g of a WO3 raw material were added to a beaker with a capacity of 50 ml, and stirred at 40° C. for 12 hours to add WO to the ammonia solution.
- 3 raw materials were dissolved.
- 0.05 g of SDS was added to this ammonia solution so that the weight ratio with the WO 3 raw material was 1:1, and the mixture was stirred at room temperature for 4 hours to dissolve SDS in the ammonia solution.
- the silicon raw material was added to the ammonia solution so that the weight ratio with the WO3 raw material was 1 :1, and the silicon raw material was dissolved in the ammonia solution by stirring at room temperature for 4 hours. . After stirring this ammonia solution, it was dried by heating at 80° C. for 12 hours to produce a primary intermediate material. Then, this primary intermediate material is introduced into a tubular furnace, under a nitrogen atmosphere, at room temperature for 2 hours, and then, while still under the nitrogen atmosphere, the temperature is raised at a rate of 3 ° C./min to 200 ° C., and then at a rate of 1 ° C./min.
- Example 1 the ratio of the silicon raw material, that is, the amount of the silicon raw material added to the total value of the added amount of the carbon raw material, the added amount of the WO3 raw material , and the added amount of the silicon raw material was set to 5% by weight. .
- the added amount of the WO3 raw material was set to 0.05 g
- the added amount of the silicon raw material was set to 0.05 g
- the added amount of the carbon raw material was set to 0.95 g.
- Example 2 a negative electrode material was produced in the same manner as in Example 1, except that the final pulverization time in obtaining the silicon raw material was 6 hours.
- Example 3 Poly(oxyethylene) alkyl ether (C 12 H 25 O(C 2 H 4 ) n H (poly(oxyethylene) dodecyl ether)) was used as the surfactant, and the second production method was carried out. It was made using The amount of hard carbon, tungsten trioxide, silicon raw material, and surfactant additive were the same as in Example 1.
- Example 4 polyoxyethylene nonylphenyl ether ( C9H19C6 ( CH2CH2O )8H) was used as the surfactant, and the final pulverization time for obtaining the silicon raw material was 6 hours.
- a negative electrode material was produced in the same manner as in Example 3, except that
- Comparative example 1 a negative electrode material was produced in the same manner as in Example 1, except that air was filled indoors when obtaining the silicon raw material, and the final pulverization time was set to 1 hour.
- Comparative example 2 In Comparative Example 2, a negative electrode material was produced in the same manner as in Example 1, except that the room was filled with air when the silicon raw material was obtained, and the final pulverization time was set to 1.5 hours.
- the glove box is filled with argon, and the oxygen concentration is 5% or less when obtaining the silicon raw material, but in Comparative Examples 1 and 2, the glove box is filled with air. Therefore, the oxygen concentration in obtaining the silicon raw material becomes higher than 5%.
- FIG. 11 is a table showing production conditions, properties of silicon particles, and evaluation results for each example. As shown in FIG. 11, the properties of the silicon particles of each example were measured based on XPS measurement.
- the Si concentration in FIG. 11 corresponds to the Si concentration described in this embodiment
- the O concentration in FIG. 11 corresponds to the O concentration described in this embodiment
- the ratio of the Si concentration derived from SiO2 in FIG. corresponds to the ratio of Si concentration derived from SiO 2 described in this embodiment
- the ratio of Si derived from Si in FIG. 11 corresponds to the ratio of Si derived from Si described in this embodiment
- Si 2 corresponds to the ratio of the amount of Si in Si2p derived from simple silicon to the amount of Si in Si2p derived from SiO2 in the surface layer described in this embodiment, and Si/O in FIG. 11 is described in this embodiment.
- 11 corresponds to the ratio of the amount of Si in Si2p to the amount of O in O1s in the surface layer
- the oxide film thickness in FIG. 11 corresponds to the thickness of the oxide layer 33B described in this embodiment.
- the X-ray photoelectron spectroscopy in each example used the apparatus and conditions described in this embodiment. Further, as shown in FIG. 11, the silicon particles of each example were measured for properties based on the volume average particle size and D50.
- a silicon fine particle dispersion liquid was prepared by putting silicon particles into a surfactant aqueous solution and dispersing the silicon fine particles by ultrasonic treatment.
- the particle size distribution of the silicon fine particles in the resulting silicon fine particle dispersion was measured using a laser diffraction/scattering particle size distribution analyzer (MT3300EX II, manufactured by Microtrack Bell Co., Ltd.). From the obtained particle size distribution, the volume average particle size, D50, was obtained.
- the SiO2 volume in FIG. 11 corresponds to the volume of the oxide layer 33B calculated using the volume average particle diameter (or D50) in this embodiment, and the particle volume in FIG. It corresponds to the volume of the silicon particles 33 calculated using the average particle size (or D50), and the SiO2 volume/particle volume in FIG. It corresponds to the volume ratio of the layer 33B.
- the capacity of the negative electrode using the negative electrode material was measured. Specifically, the current value (mAh/g) per 1 g when the C rate is 0.2 and the current value (mAh/g) per 1 g when the C rate is 3.2 are measured. did.
- the current value of the negative electrode per 1 g when the C rate is 0.2 refers to the current value that consumes the rated capacity in 0.2 hours.
- FIG. 11 shows the evaluation results. As shown in FIG. 11, in Examples 1 and 2 in which Si/SiO 2 is 3 or more, the amount of silicon oxide is small, so the current value at a C rate of 0.2 is sufficiently maintained, and the C rate is 3. It can be seen that the current value in the case of .2 is sufficiently maintained, and lithium flows into the negative electrode and lithium is released from the negative electrode, so that the performance of the battery can be improved.
- the embodiment of the present invention has been described above, the embodiment is not limited by the content of this embodiment.
- the components described above include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within the so-called equivalent range.
- the components described above can be combined as appropriate.
- various omissions, replacements, or modifications of components can be made without departing from the gist of the above-described embodiments.
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Abstract
Description
図1は、本実施形態に係る電池の模式的な一部断面図である。本実施形態に係る電池1は、リチウムイオン二次電池である。電池1は、ケーシング10と、電極群12と、図示しない電解液と、を備える。ケーシング10は、内部に電極群12及び電解液を収納するケースである。ケーシング10内には、電極群12以外にも、電極群12に接続される配線や端子などを備えていてよい。
図2は、本実施形態に係る負極の一例の模式的な断面図である。図2に示すように、負極14は、集電層20と、負極材料層22と、を備える。集電層20は、導電性部材で構成される層である。集電層20の導電性部材としては、例えば銅が挙げられる。負極材料層22は、本実施形態に係る負極材料を含む層である。負極材料層22は、集電層20の表面に設けられる。集電層20の厚みは、例えば、15μm以上40μm以下程度であってよく、負極材料層22の厚みは、例えば20μm以上200μm以下程度であってよい。なお、負極14は、集電層20の両面に、負極材料層22を備えてもよい。
また、アモルファスカーボンは、表面に三酸化タングステンを配置する処理の際に、表面に官能基(例、ヒドロキシ基、カルボキシル基)を含むことができる。そのため、この官能基によって、アモルファスカーボンの表面に三酸化タングステンを適切にトラップすることが可能となり、表面に三酸化タングステンを適切に配置できる。また、この官能基によって三酸化タングステンがアモルファスカーボンの表面に定着されるために、アモルファスカーボンの表面への三酸化タングステンの密着性を高くすることができ、三酸化タングステンがカーボンの表面から切り離されることを抑制できる。特に、ハードカーボン原料は、例えば黒鉛に比べて低温で製造されるため、官能基が除去されずに残りやすく、表面に三酸化タングステン及びシリコンを適切に配置できる。
図3は、シリコン粒子の模式的な断面図である。図3に示すように、シリコン粒子33は、Si層33Aと酸化層33Bとを含む。Si層33Aは、Siで構成される層であり、シリコン粒子33のコアとなる部分といえる。Si層33Aは、不可避的不純物を除き、Si以外の元素を含まないことが好ましい。酸化層33Bは、Si層33Aの表面に形成される層であり、Si層33Aの表面の全域を覆っていることが好ましい。酸化層33Bは、シリコン粒子33の最も外側の表面となる層といえる。酸化層33Bは、シリコンの酸化物(SiOx)で構成される層である。酸化層33Bは、シリコン酸化物としてSiO2を含むが、SiO2以外のシリコン酸化物を含んでよく、例えばSiOを含んでもよい。酸化層33Bは、不可避的不純物を除き、シリコンの酸化物を構成する元素以外の元素を含まないことが好ましい。
次に、X線光電子分光法(XPS:X-ray Photoelectron Spectroscopy)を用いて測定した場合における、シリコン粒子33の特性について説明する。以降においては、特に断りが無い限り、X線光電子分光法の測定条件を、以下とする。
・測定装置:PHI5000 Versa ProbeII (アルバック・ファイ社製)
・励起X線:モノクロAlKα線
・出力:50W
・パスエネルギー:187.85eV(Survey)、46.95eV(Narrow)
・測定間隔:0.8eV/step(Survey)、0.1eV/step(Narrow)
・試料面に対する光電子取り出し角:45°
・X線径:200μm
シリコン粒子33は、X線光電子分光法で測定した場合の、表層におけるSiO2由来のSi2pのSiの量に対する、単体シリコン由来のSi2pのSiの量の比率が、原子濃度基準で、3.0以上であり、3.5以上であることが好ましく、4以上であることがより好ましい。
ここでの表層とは、表面から、光電子が試料内から脱出できる深さまでの範囲のことで、例えば、論文J.D.Lee et al.,Journal surface analysisVol16,No.1 (2009)PP.42-63の図5に記載されている。また、シリコン粒子33を、上記の測定条件でX線光電子分光法により測定した場合に、光電子が観測できる深さ範囲を、表層といってもよい。
試料面に対する光電子の取り出し角が45°であるので、Siウエハのような平面の場合には、検出される光電子の測定深さd´=dcosθ(θは試料面に対する光電子取り出し角度、dは光電子の脱出深さ)より、θ=90°の場合の0.71倍になる。しかし、今回は粒子状のシリコンを平板の上に敷き詰めて測定を行ったので、検出器に向いている個々の粒子の面からの光電子が主と考えられるので、試料面に対する光電子取り出し角度の補正は行わなかった。
また、Si2pのSiとは、X線光電子分光法によって2p軌道の電子が飛び出したSi原子を指す。SiO2由来のSi2pのSiとは、X線光電子分光法によって2p軌道の電子が飛び出した、SiO2を構成するSiを指し、単体シリコン由来のSi2pのSiとは、X線光電子分光法によって2p軌道の電子が飛び出した、単体シリコン(金属シリコン)を構成するSiを指す。
表層におけるSiO2由来のSi2pのSiの量に対する、単体シリコン由来のSi2pのSiの量の比率とは、表層(ここでは例えば、シリコン粒子33の最表面から、最表面よりもおよそ6オングストローム深い位置まで)における、2p軌道の電子が飛び出したSiO2由来のSi(Si原子)の原子濃度に対する、2p軌道の電子が飛び出した単体シリコン由来のSi(Si原子)の原子濃度の比率を指す。シリコン粒子33は、SiO2由来のSi2pのSiに対する単体シリコン由来のSi2pのSiの量の比率がこの範囲(原子濃度基準で、3.0以上)となることで、表面近傍での酸化物の量が少なくなり、負極材料の容量を向上できる。また、表面の酸化層が薄くなるので、Liイオンの侵入と脱離が容易になり、インピーダンスが低下する。また、シリコン粒子33は、X線光電子分光法で測定した場合の、表層におけるSiO2由来のSi2pのSiの量に対する単体シリコン由来のSi2pのSiの量の比率が、原子濃度基準で、9以下であることが好ましく、19以下であることがより好ましく、99以下であることがさらに好ましい。シリコン粒子33は、SiO2の量に対するSiの量の比率がこの範囲(99以下)となることで、過度にシリコン粒子の酸化を防止するための設備やプロセスを準備する必要がなくなり、負極材料の容量を向上させつつ、生産性の低下を抑制できる。このように、X線光電子分光法で用いてシリコン粒子33を測定した場合において、表層におけるSiO2由来のSi2pのSiの量に対する、単体シリコン由来のSi2pのSiの量の比率が、原子濃度基準で、3以上9以下であることが好ましく、3以上19以下であることがより好ましく、3以上99以下であることがさらに好ましい。また、X線光電子分光法で用いてシリコン粒子33を測定した場合において、表層におけるSiO2由来のSi2pのSiの量に対する、単体シリコン由来のSi2pのSiの量の比率が、原子濃度基準で、3.5以上9以下であることが好ましく、3.5以上19以下であることがより好ましく、3.5以上99以下であることがさらに好ましい。さらに、X線光電子分光法で用いてシリコン粒子33を測定した場合において、表層におけるSiO2由来のSi2pのSiの量に対する、単体シリコン由来のSi2pのSiの量の比率が、原子濃度基準で、4以上9以下であることが好ましく、4以上19以下であることがより好ましく、4以上99以下であることがさらに好ましい。
なお例えば、SiO2由来のSi2pのSiの量が1%のとき、単体シリコン由来のSi2pのSiは99%になるので、その比をとると、表層におけるSiO2由来のSi2pのSiの量に対する、単体シリコン由来のSi2pのSiの量の比率が、99となる。同様に、SiO2由来のSi2pのSiの量が5%のとき、単体シリコン由来のSi2pのSiは95%になるので、その比をとると、表層におけるSiO2由来のSi2pのSiの量に対する、単体シリコン由来のSi2pのSiの量の比率が、19となる。
また、シリコン粒子33の表層における、全てのSi2pのSi(2p軌道の電子が飛び出した全てのSi)の原子濃度に対する、単体シリコン由来のSi2pのSiの原子濃度の比率を、Si由来のSi濃度割合(第1Si濃度)とする。Si由来のSi濃度割合は、ピーク波形P1の面積に対するピーク波形P1Aの面積の比率として算出できる。Si由来のSi濃度割合は、75%以上であることが好ましく、77%以上であることがより好ましく、80%以上であることがさらに好ましい。Si由来のSi濃度割合がこの範囲となることで、表面近傍での酸化物の量が少なくなり、負極材料の容量を向上できる。またSi由来のSi濃度割合度は、90%以下であることが好ましく、95%以下であることがより好ましく、99%以下であることがさらに好ましい。Si由来のSi濃度割合がこの範囲となることで、過度にシリコン粒子の酸化を防止するための設備やプロセスを準備する必要がなくなり、負極材料の容量を向上させつつ、生産性の低下を抑制できる。
また、シリコン粒子33の表層における、全てのSi2pのSiの原子濃度に対する、SiO2由来のSi2pのSiの原子濃度の比率を、SiO2由来のSi濃度割合とする。SiO2由来のSi濃度割合は、ピーク波形P1の面積に対するピーク波形P1Bの面積の比率として算出できる。SiO2由来のSi濃度割合は、25%以下であることが好ましく、23%以下であることがより好ましく、20%以下であることがさらに好ましい。SiO2由来のSi濃度割合がこの範囲となることで、表面近傍での酸化物の量が少なくなり、負極材料の容量を向上できる。また、SiO2由来のSi濃度割合は、10%以上であることが好ましく、5%以上であることがより好ましく、1%以上であることがさらに好ましい。SiO2由来のSi濃度割合がこの範囲となることで、過度にシリコン粒子の酸化を防止するための設備やプロセスを準備する必要がなくなり、負極材料の容量を向上させつつ、生産性の低下を抑制できる。
シリコン粒子33は、X線光電子分光法で測定した場合の、表層のO1sのOの量に対するSi2pのSiの量の比率が、原子濃度基準で、1.2以上であることが好ましく、1.3以上であることがより好ましく、1.4以上であることがさらに好ましい。
O1sのOとは、X線光電子分光法によって1s軌道の電子が飛び出したO原子を指す。
表層におけるO1sのOの量に対するSi2pのSiの量の比率とは、シリコン粒子33の表層(例えば、最表面から、最表面よりもおよそ10オングストローム深い位置まで)における、O1sのO(1s軌道の電子が飛び出したO原子)の原子濃度に対する、シリコン粒子33の表層(例えば、最表面よりもおよそ6オングストローム深い位置まで)における、Si2pのSi(2p軌道の電子が飛び出したSi原子)の原子濃度の比率を指す。シリコン粒子33は、O1sのOの量に対するSi2pのSiの量の比率がこの範囲となることで、表面近傍での酸化物の量が少なくなり、負極材料の容量を向上できる。特に、SiO2以外のシリコン酸化物(例えばSiOなど)も、容量の向上を抑制する因子として作用する可能性があり、そのような場合に、Oの量に対するSiの量の比率が上記範囲となることで、SiO2以外のシリコン酸化物の量も少なくして、容量を適切に向上できる。また、シリコン粒子33は、X線光電子分光法で測定した場合の、表層におけるO1sのOの量に対するSi2pのSiの量の比率が、原子濃度基準で、4以下であることが好ましく、9以下であることがより好ましく、99以下であることがさらに好ましい。シリコン粒子33は、Oの量に対するSiの量の比率がこの範囲となることで、過度に純粋なSiを準備する必要がなくなり、負極材料の容量を向上させつつ、生産性の低下を抑制できる。このように、X線光電子分光法を用いてシリコン粒子33を測定した場合において、表層のO1sのOの量に対するSi2pのSiの比率が、原子濃度基準で、1.2以上4以下であることが好ましく、1.2以上9以下であることがより好ましく、1.2以上99以下であることがさらに好ましい。また、X線光電子分光法を用いてシリコン粒子33を測定した場合において、表層のO1sのOの量に対するSi2pのSiの比率が、原子濃度基準で、1.3以上4以下であることが好ましく、1.3以上9以下であることがより好ましく、1.3以上99以下であることがさらに好ましい。さらに、X線光電子分光法を用いてシリコン粒子33を測定した場合において、表層のO1sのOの量に対するSi2pのSiの比率が、原子濃度基準で、1.4以上4以下であることが好ましく、1.4以上9以下であることがより好ましく、1.4以上99以下であることがさらに好ましい。
なお例えば、O濃度が20at%でSi濃度が80%のとき、表層のO1sのOの量に対するSi2pのSiの比率は、4となり、O濃度が5at%でSi濃度が95%のとき、表層のO1sのOの量に対するSi2pのSiの比率は、19となる。
すなわち、上記のように求めたO濃度に対するSi濃度の比率が、濃度比Si/Oとなる。
Si濃度は、50at%以上であることが好ましく、55at%以上であることがより好ましく、60at%以上であることがさらに好ましい。Si濃度がこの範囲となることで、表面近傍での酸化物の量が少なくなり、負極材料の容量を向上できる。また、Si濃度は、80at%以下であることが好ましく、90at%以下であることがより好ましく、99at%以下であることがさらに好ましい。Si濃度がこの範囲となることで、過度にシリコン粒子の酸化を防止するための設備やプロセスを準備する必要がなくなり、負極材料の容量を向上させつつ、生産性の低下を抑制できる。
O濃度は、46at%以下であることが好ましく、40at%以下であることがより好ましく、30at%以下であることがさらに好ましい。O濃度がこの範囲となることで、表面近傍での酸化物の量が少なくなり、負極材料の容量を向上できる。また、O濃度は、20at%以上であることが好ましく、10at%以上であることがより好ましく、1at%以上であることがさらに好ましい。O濃度がこの範囲となることで、過度にシリコン粒子の酸化を防止するための設備やプロセスを準備する必要がなくなり、負極材料の容量を向上させつつ、生産性の低下を抑制できる。
シリコン粒子33は、酸化層33Bの厚みが、2.1オングストローム以下であることが好ましく、1.8オングストローム以下であることがより好ましく、1.3オングストローム以下であることがさらに好ましい。酸化層33Bの厚みがこの範囲となることで、表面近傍での酸化物の量が少なくなり、負極材料の容量を向上できる。また、酸化層33Bの厚みは、0.7オングストローム以上であることが好ましく、0.3オングストローム以上であることがより好ましく、0.06オングストローム以上であることがさらに好ましい。酸化層33Bの厚みがこの範囲となることで、過度に純粋なSiを準備する必要がなくなり、負極材料の容量を向上させつつ、生産性の低下を抑制できる。なお、酸化層33Bの厚みは、X線光電子分光法で測定した場合の、表層における、単体シリコン由来のSi2pのSiの量に対するSiO2由来のSi2pのSiの量の比率(SiO2由来のSi2pのSiの量に対する単体シリコン由来のSi2pのSiの量の比率の逆数)に、Si2pのSiの光電子の脱出深さ6オングストロームを乗じることで算出される。
次に、体積平均粒径に基づくシリコン粒子33の特性について説明する。
シリコン粒子33の、レーザ回折散乱法によって測定される体積平均粒子径(体積基準の平均粒子径)を、以下、体積平均粒子径と記載する。
シリコン粒子33を球形と仮定し体積平均粒子径を用いて体積を算出した場合の、シリコン粒子33の全体の体積に対する酸化層33Bの体積の比率を、体積平均粒子径に基づく酸化層33Bの体積比率とする。この場合、体積平均粒子径に基づく酸化層33Bの体積比率は、0.05%以下であることが好ましく、0.04%以下であることがより好ましく、0.035%以下であることがさらに好ましい。体積比率がこの範囲となることで、表面近傍での酸化物の量が少なくなり、負極材料の容量を向上できる。また、体積平均粒子径に基づく酸化層33Bの体積比率は、0.015%以上であることが好ましく、0.01%以上であることがより好ましく、0.001%以上であることがさらに好ましい。体積比率がこの範囲となることで、過度にシリコン粒子の酸化を防止するための設備やプロセスを準備する必要がなくなり、負極材料の容量を向上させつつ、生産性の低下を抑制できる。
次に、D50に基づくシリコン粒子33の特性について説明する。
レーザ回折散乱法によって測定される体積基準の粒度分布において、累積度数が50体積%の粒子径を、D50とする。
ここで、シリコン粒子33を球形と仮定しD50を用いて体積を算出した場合の、シリコン粒子33の全体の体積に対する酸化層33Bの体積の比率を、D50に基づく酸化層33Bの体積比率とする。この場合、D50に基づく酸化層33Bの体積比率は、0.4%以下であることが好ましく、0.3%以下であることがより好ましく、0.25%以下であることがさらに好ましい。体積比率がこの範囲となることで、表面近傍での酸化物の量が少なくなり、負極材料の容量を向上できる。また、D50に基づく酸化層33Bの体積比率は、0.13%以上であることが好ましく、0.05%以上であることがより好ましく、0.01%以上であることがさらに好ましい。体積比率がこの範囲となることで、過度にシリコン粒子の酸化を防止するための設備やプロセスを準備する必要がなくなり、負極材料の容量を向上させつつ、生産性の低下を抑制できる。
図1に示す正極16は、集電層と正極材料層とを備える。正極16の集電層は、導電性部材で構成される層であり、ここでの導電性部材としては、例えばアルミニウムが挙げられる。正極材料層は、正極材料の層であり、正極16の集電層の表面に設けられる。正極の集電層の厚みは、例えば、10μm以上30μm以下程度であってよく、正極材料層の厚みは、例えば10μm以上100μm以下程度であってよい。
図1に示すセパレータ18は、絶縁性の部材である。本実施形態では、セパレータ18は、例えば、樹脂製の多孔質膜であり、樹脂としては、ポリエチレン(PE)、ポリプロピレン(PP)などが挙げられる。また、セパレータ18は、異なる材料の膜が積層された構造であってもよい。また、セパレータ18は、耐熱層を有していてもよい。耐熱層は、高融点の物質を含有する層である。耐熱層は、たとえば、アルミナ等の無機材料の粒子を含有してもよい。
電池1に設けられる電解液は、非水電解液である。電解液は、電極群12内の空隙に含浸されている。電解液は、例えば、リチウム塩および非プロトン性溶媒を含む。リチウム塩は、非プロトン性溶媒に分散、溶解している。リチウム塩としては、たとえば、LiPF6、LiBF4、Li[N(FSO2)2]、Li[N(CF3SO2)2]、Li[B(C2O4)2]、LiPO2F2などが挙げられる。非プロトン性溶媒は、例えば、環状炭酸エステルおよび鎖状炭酸エステルの混合物であってよい。環状炭酸エステルとしては、たとえば、EC、PC、ブチレンカーボネート等が挙げられる。鎖状炭酸エステルとしては、ジメチルカーボネート(DMC)、エチルメチルカーボネート(EMC)、ジエチルカーボネート(DEC)等が挙げられる。
次に、本実施形態に係る電池1の製造方法の一例を説明する。本製造方法は、酸素濃度が5%以下の雰囲気下でシリコン原料を準備するステップと、シリコン原料を用いて、カーボンの表面に、三酸化タングステンとシリコン材料とを設けて負極材料を製造するステップと、正極材料を製造するステップとを含む。
図8は、シリコン原料を準備するステップを説明するフローチャートである。シリコン原料は、シリコン粒子33の原料である。図8に示すように、シリコン原料を準備するステップは、破砕工程S1と、粗粉砕工程S2と、粉砕工程S3と、を含む。
破砕工程S1は、シリコン塊状物を破砕してシリコン破砕物を得る工程である。シリコン塊状物のサイズは、特に制限はない。シリコン塊状物の形状は、特に制限はなく、例えば、柱状、板状、粒状であってもよい。シリコン塊状物としては、シリコンチャンク、チャンク以外の多結晶シリコン、単結晶シリコンと柱状晶シリコンインゴットの塊、モニター用シリコンウエハ、ダミー用シリコンウエハ、粒状シリコンを用いることができる。
粗粉砕工程S2は、シリコン破砕物を粗粉砕してシリコン粗粒子を得る工程である。粗粉砕工程S2で得られるシリコン粗粒子は、ふるい法により分別される最大粒子径が1000μm以下であることが好ましい。このため、粗粉砕工程S2は、粗粉砕によって得られた粗粉砕物を目開き1000μmのふるいを用いて分級して、最大粒子径が1000μm以下の粗粒子を回収する工程を含むことが好ましい。シリコン粗粒子のサイズが1000μmを超えると、次の粉砕工程S3でシリコン粗粒子が十分に粉砕されずに、その粒子が混入するおそれがある。シリコン粗粒子の最大粒子径は、500μm以下であることが特に好ましい。
粉砕工程S3は、シリコン粗粒子を粉砕してシリコン原料(シリコン微粒子)を得る工程である。粉砕工程S3では、例えば、ボールミル(遊星ボールミル、振動ボールミル、転動ボールミル、撹拌ボールミル)、ジェットミル、三次元ボールミルを用いることができる。粉砕装置として、株式会社ナガオシステムの三次元ボールミルを用いることが好ましい。
図9は、本実施形態の電池の製造方法の一例を説明するフローチャートである。図9に示すように、本製造方法においては、ステップS10からステップS28の工程で、負極14を形成する。
Naを含有しない界面活性剤としては、例えば、ポリ(オキシエチレン)アルキルエーテルや、ポリオキシエチレンノニルフェニールエーテルなどを用いてよい。ポリ(オキシエチレン)アルキルエーテルとしては、アルキル基の炭素数が12以上15以下の物を用いることが好ましく、例えば、C12H25O(C2H4)nH(ポリ(オキシエチレン)ドデシルエーテル)、C13H27O(C2H4)nH(ポリ(オキシエチレン)トリデシルエーテル)、C13H27O(C2H4)nH(ポリ(オキシエチレン)イソトリデシルエーテル)、C14H25O(C2H4)nH(ポリ(オキシエチレン)テトラデシルエーテル)、C155H25O(C2H4)nH(ポリ(オキシエチレン)ペンタデシルエーテル)などを用いてよい。ここでnは1以上の整数である。ポリオキシエチレンノニルフェニールエーテルとしては、例えば、C9H19C6(CH2CH2O)8H、C9H19C6(CH2CH2O)10H、C9H19C6(CH2CH2O)12Hなどを用いてよい。
界面活性剤の添加量は、溶解用溶液に対するWO3原料の添加量に対して、重量%で、2%以上8%以下とすることが好ましい。この数値範囲とすることで、シリコン原料とWO3との親和性を適切に向上させる。
次に、本実施形態に係る電池1の製造方法の他の例を説明する。図10は、本実施形態の電池の製造方法の一例を説明するフローチャートである。図10に示すように、本製造方法においては、ステップS30からステップS44の工程で、負極14を形成する。ステップS30、ステップS32、ステップS40、ステップS42、ステップS44は、ステップS10、ステップS12、ステップS24、ステップS26、ステップS28と同様の処理を行う。
以上説明したように、本実施形態に係る負極材料は、電池の負極材料であって、カーボンと、三酸化タングステンと、シリコンを含むシリコン粒子33と、を含む。シリコン粒子33は、X線光電子分光法で測定した場合の、表層におけるSiO2由来のSi2pのSiの量に対する単体シリコン由来のSi2pのSiの量の比率が、原子濃度基準で、3以上である。
次に、実施例について説明する。
(シリコン原料の準備)
鱗片状多結晶シリコンチャンク(純度:99.999999999質量%、縦:5~15mm、横:5~15mm、厚さ:2~10mm)を、ハンマーミルを用いて破砕した。次いで、得られた粉砕物を、目開き5mmのふるいを用いて乾式分級して、ふるい下のシリコン破砕物を得た。
得られたシリコン破砕物と、硬質ボール(ジルコニアボール、直径:10mm)と、一方の容器と他方の容器とに分割可能な容器とを、それぞれArガスが充填されたグローブボックスに収容した。グローブボックス内にて、容器の一方にシリコン破砕物30質量部と硬質ボール380質量部とを投入した。次いで、シリコン破砕物と硬質ボールを投入した一方の容器と、他方の容器とを組み合わせ、Arガスが充填されたグローブボックス内で、二つの容器をねじ止めして密封した。二つの容器の合わせ面は、気密が保たれるようにすり合わせ面となっている。容器中のシリコン破砕物と硬質ボールの充填率は28%とした。
シリコン破砕物と硬質ボールとを充填した容器を、グローブボックスから取り出して、三次元ボールミル装置にセットした。そして、第1回転軸の回転速度:300rpm、第2回転軸の回転速度:300rpm、粉砕時間:0.33時間の条件で粗粉砕した。粗粉砕後のシリコン粗粉砕物と硬質ボールとを、目開き1000μmのふるいを用いて乾式分級して、最大粒子径が1000μm以下のシリコン粗粒子を得た。
得られたシリコン粗粒子と、硬質ボール(ジルコニアボール、直径:10mm)と、半球状容器とを、それぞれArガスが充填されたグローブボックスに収容した。次いで、グローブボックス内にて、半球容器の一方にシリコン破砕物15質量部と硬質ボール200質量部とを投入した(シリコン粗粒子100質量部に対する硬質ボールの量は1333質量部)。次いで、球状容器を形成するように、シリコン破砕物と硬質ボールを投入した一方の半球容器と、他方の半球容器とを組み合わせ、Arガスが充填されたグローブボックス内で、二つの容器をねじ止めして密封した。容器中のシリコン破砕物と硬質ボールの充填率は15%であった。
シリコン粗粒子と硬質ボールとを充填した容器を、グローブボックスから取り出して、三次元ボールミル装置にセットした。そして、第1回転軸の回転速度:300rpm、第2回転軸の回転速度:300rpm、粉砕時間:3時間の条件で粉砕して、シリコン原料を得た。
実施例1においては、ハードカーボンと三酸化タングステンとシリコンとを用いて、実施形態で説明した溶液法を使用した第1の製造方法で、負極材料を製造した。具体的には、50ml容量のビーカー内に、濃度が28重量%のアンモニア溶液を5mlと、WO3原料を0.05gとを添加して、40℃で12時間撹拌して、アンモニア溶液にWO3原料を溶解させた。さらに、このアンモニア溶液に、WO3原料との重量比が1:1となるように、SDSを0.05g添加して、室温で4時間撹拌して、アンモニア溶液にSDSを溶解させた。そして、このアンモニア溶液に、WO3原料との重量比が1:1となるように、シリコン原料を0.05g添加して、室温で4時間撹拌して、アンモニア溶液にシリコン原料を溶解させた。そして、このアンモニア溶液を撹拌した後、80℃で12時間加熱して乾燥させて、一次中間材料を生成した。そして、この一次中間材料を、管状炉内に導入し、窒素雰囲気下で、室温で2時間、その後、窒素雰囲気下のまま、昇温スピード3℃/minで200℃まで、1℃/minで550℃まで、3℃/minで700℃まで連続加熱して2時間保持して、一次中間材料を生成した。そして、生成された一次中間材料と5mlの純水と0.053gのSDSと0.95gのカーボン原料とを順番に添加した。そして、カーボン原料が純水に分散するまで、この液体を4時間撹拌した後、80℃で12時間加熱して乾燥させて、負極中間物を生成した。そして、この負極中間物を、管状炉内に導入し、窒素雰囲気下で、室温で2時間、その後、窒素雰囲気下のまま、昇温スピード3℃/minで200℃まで、1℃/minで550℃まで、3℃/minで700℃まで連続加熱して2時間保持して、負極材料を製造した。
実施例2においては、シリコン原料を得る際の最後の粉砕時間を6時間とした以外は、実施例1と同じ方法で、負極材料を製造した。
実施例3においては、界面活性剤にポリ(オキシエチレン)アルキルエーテル(C12H25O(C2H4)nH(ポリ(オキシエチレン)ドデシルエーテル))を用いて第2の製造方法を用いて作製した。ハードカーボン、三酸化タングステン、シリコン原料の量、界面活性剤の添加剤の量は、実施例1と同じとした。
実施例4においては、界面活性剤にポリオキシエチレンノニルフェニールエーテル(C9H19C6(CH2CH2O)8H)を用いて、シリコン原料を得る際の最後の粉砕時間を6時間とした以外は、実施例3と同じ方法で、負極材料を製造した。
比較例1においては、シリコン原料を得る際に、屋内で空気を充填し、最後の粉砕時間を1時間とした以外は、実施例1と同じ方法で、負極材料を製造した。
比較例2においては、シリコン原料を得る際に屋内で空気を充填し、最後の粉砕時間を1.5時間とした以外は、実施例1と同じ方法で、負極材料を製造した。
図11は、各例の製造条件、シリコン粒子の特性、及び評価結果を示す表である。図11に示すように、各例のシリコン粒子について、XPS測定に基づく特性を測定した。図11におけるSi濃度は、本実施形態で説明したSi濃度に相当し、図11におけるO濃度は、本実施形態で説明したO濃度に相当し、図11におけるSiO2由来のSi濃度の割合は、本実施形態で説明したSiO2由来のSi濃度の割合に相当し、図11におけるSi由来のSi割合は、本実施形態で説明したSi由来のSi割合に相当し、図11のSi/SiO2は、本実施形態で説明した、表層におけるSiO2由来のSi2pのSiの量に対する単体シリコン由来のSi2pのSiの量の比率に相当し、図11のSi/Oは、本実施形態で説明した、表層におけるO1sのOの量に対するSi2pのSiの量の比率に相当し、図11の酸化膜厚は、本実施形態で説明した酸化層33Bの厚みに相当する。各例でのX線光電子分光法は、本実施形態で説明した装置及び条件を用いた。
また、図11に示すように、各例のシリコン粒子について、体積平均粒径及びD50に基づく特性を測定した。シリコン粒子を界面活性剤水溶液に投入し、超音波処理によりシリコン微粒子を分散させてシリコン微粒子分散液を調製した。次いで、得られたシリコン微粒子分散液中のシリコン微粒子の粒度分布を、レーザ回折・散乱式粒子径分布測定装置(MT3300EX II、マイクロトラック・ベル株式会社製)を用いて測定した。得られた粒度分布から、体積平均粒径、D50を求めた。図11におけるSiO2体積は、本実施形態での、体積平均粒子径(又はD50)を用いて算出した酸化層33Bの体積に相当し、図11における粒子体積は、本実施形態での、体積平均粒子径(又はD50)を用いて算出したシリコン粒子33の体積に相当し、図11でのSiO2体積/粒子体積は、本実施形態での、体積平均粒子径(又はD50)に基づく酸化層33Bの体積比率に相当する。
各例の負極材料の評価として、負極材料を用いた負極の容量を測定した。具体的には、Cレートを0.2とした場合の1g当たりの電流値(mAh/g)と、Cレートを3.2とした場合の1g当たりの電流値(mAh/g)とを測定した。例えばCレートを0.2とした場合の1g当たりの負極の電流値とは、0.2時間で定格容量を消費する電流値を指す。
また、各例の負極材料の評価として、負極のSiにリチウムが流入するか、負極のSiからリチウムが放出されるかについても確認した。負極のSiにリチウムが流入する場合を〇、流入しない場合を×とし、負極のSiからリチウムが放出される場合を〇、放出されない場合を×とした。
図11に評価結果を示す。図11に示すように、Si/SiO2が3以上となる実施例1、2では、シリコンの酸化物が少ないため、Cレート0.2の場合の電流値が十分に保たれ、Cレート3.2の場合の電流値が十分に保たれ、かつ、負極にリチウムが流入し、負極からリチウムが放出されるため、電池の性能を向上できることが分かる。
一方、Si/SiO2が3未満となる比較例1、2では、シリコンの酸化物が多くなるため、Cレート3.2の場合の電流値が低くなり、負極のSiからはリチウムが放出されず、電池の性能を適切に向上できないことが分かる。
14 負極
22 負極材料層
30 カーボン粒子
32 WO3粒子
33 シリコン粒子
Claims (8)
- 電池の負極材料であって、
カーボンと、三酸化タングステンと、シリコンを含むシリコン材料と、を含み、
前記シリコン材料は、X線光電子分光法で測定した場合の、表層におけるSiO2由来のSi2pのSiの量に対する単体シリコン由来のSi2pのSiの量の比率が、原子濃度基準で、3以上である、
負極材料。 - 前記シリコン材料は、X線光電子分光法で測定した場合の、表層におけるO1sのOの量に対するSi2pのSiの量の比率が、原子濃度基準で、1.2以上である、請求項1に記載の負極材料。
- 前記シリコン材料は、Siで構成されるSi層と、Si層の表面に形成されてシリコンの酸化物で構成される酸化層と、を含み、前記シリコン材料を球形と仮定し、体積平均粒子径を用いて前記シリコン材料の体積を算出した場合に、前記酸化層の体積は、前記シリコン材料の全体の体積に対して、0.04%以下である、請求項1又は請求項2に記載の負極材料。
- 前記シリコン材料は、Siで形成されるSi層と、Si層の表面に形成されてSiとOとを含む酸化層と、を含み、前記シリコン材料を球形と仮定し、レーザ回折散乱法によって測定される体積基準の粒度分布において累積度数が50体積%の粒子径D50を用いて前記シリコン材料の体積を算出した場合に、前記酸化層の体積は、前記シリコン材料の全体の体積に対して、0.4%以下である、請求項1から請求項3のいずれか1項に記載の負極材料。
- 前記カーボンと前記三酸化タングステンと前記シリコン材料との合計含有量を100重量%とした場合に、前記シリコン材料の含有量は1重量%以上10重量%以下である、請求項1から請求項4のいずれか1項に記載の負極材料。
- 請求項1から請求項5のいずれか1項に記載の負極材料と、正極材料とを含む、電池。
- 電池の負極材料の製造方法であって、
酸素濃度が5%以下の雰囲気下でシリコン原料を準備するステップと、
前記シリコン原料を用いて、カーボンと、三酸化タングステンと、シリコン材料とを含む負極材料を生成するステップを含み、
前記シリコン材料は、X線光電子分光法で測定した場合の、表層におけるSiO2由来のSi2pのSiの量に対する単体シリコン由来のSi2pのSiの量に対する比率が、原子濃度基準で、3以上である、
負極材料の製造方法。 - 請求項7に記載の負極材料の製造方法と、正極材料を製造するステップと、を含む、電池の製造方法。
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