WO2022001880A1 - 硅氧复合负极材料、负极和锂离子电池及其制备方法 - Google Patents

硅氧复合负极材料、负极和锂离子电池及其制备方法 Download PDF

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WO2022001880A1
WO2022001880A1 PCT/CN2021/102416 CN2021102416W WO2022001880A1 WO 2022001880 A1 WO2022001880 A1 WO 2022001880A1 CN 2021102416 W CN2021102416 W CN 2021102416W WO 2022001880 A1 WO2022001880 A1 WO 2022001880A1
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silicon
negative electrode
lithium
electrode material
sio
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French (fr)
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屈丽娟
邓志强
庞春雷
任建国
贺雪琴
杜宁
杨德仁
肖称茂
何鹏
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贝特瑞新材料集团股份有限公司
惠州市鼎元新能源科技有限公司
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Publication of WO2022001880A1 publication Critical patent/WO2022001880A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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 disclosure belongs to the technical field of energy storage materials, and relates to a negative electrode material, a preparation method thereof, and a lithium ion battery, in particular to a silicon-oxygen composite negative electrode material, a negative electrode, a lithium ion battery, and a preparation method thereof.
  • Lithium-ion batteries have been widely used in portable electronic products and electric vehicles due to their advantages of high operating voltage, long cycle life, no memory effect, small self-discharge, and environmental friendliness.
  • commercial lithium-ion batteries mainly use graphite-based anode materials, but its theoretical specific capacity is only 372mAh/g, which cannot meet the demand for high energy density of future lithium-ion batteries.
  • the theoretical capacity of the existing Si is as high as 4200mAh/g, its expansion reaches 300%, which affects the cycle performance and restricts the market promotion and application.
  • the corresponding silicon-oxygen material has better cycle performance, but the first time efficiency is low. During the first charging, 20-50% of lithium needs to be consumed for SEI film formation, which greatly reduces the first Coulomb efficiency. Based on this, the most studied method to improve the first effect of silicon-oxygen materials is doping, among which lithium doping is more effective.
  • the first-efficiency improvement after lithium doping will also bring about a decrease in the capacity of the silicon-oxygen material.
  • Lithium doping consumes the irreversible phase in silicon and oxygen on the one hand, and also consumes part of the reversible phase. While improving the first effect of silicon-oxygen materials, reducing capacity loss is of great significance to the later use and commercialization of silicon-oxygen materials.
  • back-end batteries need higher energy density to meet the needs of use and development. Therefore, it is particularly important to improve the gram capacity of the front-end material itself.
  • the present disclosure provides a silicon-oxygen composite negative electrode material
  • the silicon-oxygen composite negative electrode material includes composite particles
  • the composite particles include lithium silicate and a silicon-containing material
  • the lithium silicate is Li 4 SiO 4
  • the silicon-containing material is A material is dispersed in the lithium silicate
  • the silicon-containing material includes at least one of elemental silicon, silicon oxide (144), silicon alloy, metal silicide, and silicate.
  • the grain size of Li 4 SiO 4 is below 60 nm.
  • the silicon-oxygen composite negative electrode material further includes a carbon layer formed on the surface of the composite particles.
  • the thickness of the carbon layer is 300nm-2000nm.
  • the silicon-oxygen composite negative electrode material further includes a hydrophobic layer formed on the surface of the carbon layer.
  • the hydrophobic layer has a thickness of 2 nm to 500 nm.
  • the material of the hydrophobic layer includes at least one of saturated fatty acid and amino acid.
  • the material of the hydrophobic layer includes at least one of lauric acid, stearic acid, leucine, methionine and phenylalanine.
  • the silicon-containing material includes nano-silicon and silicon oxide, and the nano-silicon is dispersed within the silicon oxide in the form of nano-silicon aggregates.
  • the nanosilicon aggregate includes a plurality of nanosilicon grains.
  • the nano-silicon grain size ranges from 0 nm to 10 nm, excluding 0 nm.
  • the chemical formula of the silicon oxide is SiO x, where 0 ⁇ x ⁇ 1.2.
  • the mass ratio of the lithium silicate to the silicon-containing material is 0.05-1.1;
  • the silicon alloy includes at least one of a silicon-lithium alloy, a silicon-sodium alloy, a silicon-magnesium alloy, and a silicon-aluminum alloy;
  • the elemental silicon includes at least one of nano-silicon, amorphous silicon, and crystalline silicon.
  • the present disclosure provides a preparation method of the silicon-oxygen composite negative electrode material, the method comprising the following steps:
  • the mixture containing the silicon source and the lithium-containing compound is calcined in a protective gas atmosphere and at a temperature of 300° C. to 600° C. to obtain the silicon-oxygen composite negative electrode material, wherein the general formula of the silicon source is SiO y , the The molar ratio of the silicon source to the lithium-containing compound is 1:1.2-1:3.
  • the silicon source is silicon monoxide.
  • the lithium-containing compound is a reducing lithium-containing compound.
  • the reducing lithium-containing compound includes at least one of lithium hydride, alkyl lithium, metallic lithium, lithium aluminum hydride, lithium amide, and lithium borohydride;
  • the mixture further includes at least one of a metal element and a metal oxide
  • the mixture is obtained by at least one of mixing, fusing and stirring in a VC mixer.
  • the protective gas includes at least one of hydrogen, nitrogen, helium, neon, argon, krypton, and xenon.
  • the roasting time is 2h-8h.
  • the preparation method of the silicon source includes: heating a raw material capable of generating silicon oxide gas under vacuum conditions or a protective gas atmosphere, and then cooling and shaping to obtain the silicon source after generating the silicon oxide gas.
  • the silicon oxide gas generating feedstock comprises a mixture of Si and SiO 2 .
  • the raw material capable of producing silicon oxide gas comprises a mixture of Si and O 2 , or a mixture of SiO 2 and carbon, or a mixture of at least two of silicon and silicon-containing oxide SiO m , wherein 1 ⁇ m ⁇ 6.
  • the shaping includes at least one of crushing, ball milling, and classification.
  • the heating temperature is 900°C-1500°C.
  • the protective gas includes at least one of hydrogen, nitrogen, helium, neon, argon, krypton, and xenon.
  • the surface of the silicon source is coated with a carbon layer.
  • the method for coating the surface of the silicon source with a carbon layer includes: reacting the silicon source with an organic carbon source gas under a protective gas atmosphere to obtain a silicon source coated with a carbon layer .
  • the protective gas includes at least one of hydrogen, nitrogen, helium, neon, argon, krypton, and xenon.
  • the organic carbon source gas is a hydrocarbon
  • the hydrocarbons include, but are not limited to, at least one of methane, ethylene, acetylene, acetone, and benzene.
  • the reaction temperature at which the reaction is performed is 600°C-1000°C.
  • the reaction time for the reaction is 0.5h-10.0h.
  • the preparation method further includes the step of: impregnating the silicon-oxygen composite negative electrode material in a hydrophobic solution.
  • the solute of the hydrophobic solution includes at least one of lauric acid, stearic acid, leucine, methionine and phenylalanine
  • the solvent of the hydrophobic solution includes water, At least one of methanol, ethanol, ether, benzene or formic acid.
  • the soaking time is 2h-6h.
  • the method comprises the following steps:
  • the mixture of Si and SiO 2 is heated at 900°C-1500°C under vacuum conditions or protective gas atmosphere to generate silicon oxide gas, then cooled and shaped to obtain silicon monoxide;
  • the silicon monoxide is heated to 600°C-1000°C, an organic carbon source gas is introduced, the temperature is kept for 0.5-10.0 h, and then cooled to obtain silicon monoxide coated with a carbon layer;
  • the carbon layer-coated silicon monoxide and the lithium-containing compound are mixed in a molar ratio of 1:1.2-1:3, calcined at 300°C-600°C for 2h-8h in a protective gas atmosphere, cooled to room temperature, and the The calcined product is immersed in a hydrophobic solution for 2h-6h to obtain the silicon-oxygen composite negative electrode material.
  • the present disclosure provides a negative electrode comprising the silicon-oxygen composite negative electrode material.
  • the present disclosure provides a lithium ion battery comprising the silicon-oxygen composite negative electrode material.
  • FIG. 1 is the first charge-discharge curve of the silicon-oxygen composite negative electrode material provided in Embodiment 1 of the present disclosure
  • Example 3 is an XRD image of the silicon-based composite material of Example 1 of the disclosure.
  • Example 5 is a SEM photograph of the silicon-oxygen composite negative electrode material provided in Example 2 of the present disclosure.
  • FIG. 8 is a schematic structural diagram of a silicon-oxygen composite negative electrode material in some embodiments of the disclosure.
  • FIG. 9 is a schematic structural diagram of a silicon-oxygen composite negative electrode material in some embodiments of the disclosure.
  • FIG. 10 is a schematic structural diagram of a silicon-oxygen composite negative electrode material in some embodiments of the disclosure.
  • Reference numerals 100-composite particle; 120-lithium silicate; 140-silicon-containing material; 142-nano-silicon grain; 144-silicon oxide; 160-carbon layer; 180-hydrophobic layer.
  • the silicon-oxygen composite negative electrode material includes composite particles 100, the composite particles 100 include lithium silicate 120 and a silicon-containing material 140, the lithium silicate 120 is Li 4 SiO 4 , and the silicon-containing material 140 is dispersed in In the lithium silicate 120, the silicon-containing material 140 includes at least one of elemental silicon, silicon oxide 144, silicon alloy, metal silicide and silicate.
  • the silicon-containing material 140 is uniformly dispersed in the lithium silicate 120 , in other words, the lithium silicate 120 wraps the silicon-containing material 140 therein.
  • the silicon-oxygen composite negative electrode material provided in this embodiment is a pre-lithium silicon negative electrode, which only contains Li 4 SiO 4 , a type of lithium silicate, so that the silicon-oxygen negative electrode material can still have a higher capacity after pre-lithiation, so that As a result, the silicon-oxygen composite negative electrode material provided by the embodiment of the present disclosure has the advantages of stable processing performance, high specific capacity, high initial efficiency, and long cycle life.
  • Pre-lithiation of the silicon oxide 144 will bring about a certain capacity loss.
  • Different types of lithium silicates are generated after pre-lithium, resulting in different capacity losses.
  • the amount of silicon monoxide consumed by different lithium silicates will be different. Only when Li 4 SiO 4 is generated, the least amount of silicon monoxide is consumed, and the capacity loss is the least.
  • the silicon-oxygen composite negative electrode material provided by the present disclosure only contains Li 4 SiO 4 , one type of lithium silicate, which can effectively reduce the capacity loss of the pre-lithium silicon-oxygen material.
  • the grain size of Li 4 SiO 4 is below 60 nm, for example, 60 nm, 50 nm, 40 nm, 30 nm, 20 nm, or 10 nm.
  • the grain size of Li 4 SiO 4 is in the range below 60 nm, which can further improve the good electrical conductivity of the negative electrode material, the cycle performance of the material, and the reversible capacity of the electrode material. The rate performance of the material is poor, the material cycle is poor, and the capacity decays quickly.
  • the silicon-oxygen composite negative electrode material further includes a carbon layer 160 formed on the surface of the composite particles 100 .
  • the surface of the composite particle 100 is coated with a carbon layer 160, which cooperates with the generation of only Li 4 SiO 4 , further improves the electrical conductivity of the material, and reduces the electronic conduction resistance between the particles.
  • the carbon layer 160 includes, but is not limited to, the carbon layer 160 formed for pyrolysis carbon.
  • the thickness of the carbon layer 160 is 300 nm-2000 nm, such as 300 nm, 500 nm, 1000 nm, 1500 nm or 2000 nm, and the like.
  • the thickness of the carbon layer is in the range of 300nm-2000nm, which can synergize with Li 4 SiO 4 and its grain size to further improve the conductivity of the material without reducing the capacity of the molecular material. If the carbon layer 160 is too thin, the conductivity of the material is not significantly improved, and if the carbon layer 160 is too thick, the capacity of the molecular material is low.
  • the silicon-oxygen composite negative electrode material further includes a hydrophobic layer 180 formed on the surface of the carbon layer 160 .
  • the silicon-oxygen composite negative electrode material is coated with the hydrophobic layer 180, which improves the water-based processing performance of the material, and effectively reduces the probability of gas generation in the water-based slurry.
  • the thickness of the hydrophobic layer 180 is 2 nm-500 nm, such as 2 nm, 5 nm, 10 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, or 500 nm, and the like.
  • the hydrophobic layer 180 in this range can tightly wrap the material, thereby further improving the processing performance of the negative electrode material. If the hydrophobic layer 180 is too thin, due to the uneven distribution of the hydrophobic layer 180, the internal coating is not tight, which will affect the processing performance of the material. .
  • the constituent materials of the hydrophobic layer 180 include, but are not limited to, any one of saturated fatty acids and amino acids, or a combination of at least two of them.
  • saturated fatty acid and amino acid are selected as the hydrophobic layer material, so that the coating integrity of the material to the electrode material is higher.
  • the saturated fatty acid has 8 or more carbon atoms.
  • the saturated fatty acid includes at least one of lauric acid, stearic acid, caprylic acid, nonanoic acid, capric acid, myristic acid, palmitic acid, pearlitic acid, stearic acid, arachidic acid, and behenic acid kind.
  • the amino acid includes at least one of leucine, methionine, tryptophan, valine, isoleucine, alanine, phenylalanine, and methionine.
  • the constituent material of the hydrophobic layer 180 includes at least one of lauric acid, stearic acid, leucine, methionine and phenylalanine.
  • the silicon-containing material 140 may be dispersed in the lithium silicate 120 .
  • the silicon-containing material 140 includes at least one of elemental silicon, silicon oxide 144, silicon alloys, metal suicides, and silicates.
  • the silicon-containing material 140 is a non-metallic silicon-containing material.
  • the non-metallic silicon-containing material includes at least one of elemental silicon, silicon oxide 144, silicon alloys, metal suicides, and silicates.
  • the silicon-containing material (or non-metallic silicon-containing material) includes at least one of nano-silicon and silicon oxide.
  • the elemental silicon includes at least one of nano-silicon, amorphous silicon, and crystalline silicon.
  • the silicon-containing material 140 includes nano-silicon and silicon oxide 144 , and the nano-silicon is dispersed inside the silicon oxide 144 in the form of nano-silicon aggregates.
  • the nano-silicon aggregate includes a plurality of nano-silicon crystal grains 142; the nano-silicon aggregate refers to an aggregate composed of several or even thousands of nano-silicon crystal grains 142 through physical or chemical binding force.
  • the nano-silicon grains 142 have a size of 0 nm to 10 nm, excluding 0 nm, such as 10 nm, 9 nm, 8 nm, 7 nm, 6 nm, or 5 nm, and the like. If the size of the nano-silicon crystal grains 142 is too large, it will cause the expansion of the material, thereby affecting the cycle performance of the material. When the size of nano-silicon grains 142 is controlled below 10 nm, on the one hand, it is beneficial to improve the overall distribution uniformity of nano-silicon in the particles, and on the other hand, it can better control the overall silicon-oxygen ratio of nano-silicon and silicon oxide.
  • the nano-silicon is not dispersed in the silicon oxide in the form of aggregates, its activity is high and it is more easily oxidized, resulting in a decrease in the specific capacity and first-efficiency of the material.
  • the crystallization rate of the nanosilicon was faster during the sintering process with the addition of the lithium source. If it exists in the form of aggregates, the crystallization rate will delay the growth rate of crystal nucleus due to the existence of more grain boundaries and mutual interference.
  • the silicon oxide 144 for the formula SiO x where 0 ⁇ x ⁇ 1.2, for example, x is 1.1 or the like 0.1,0.2,0.5,0.8,1.
  • x is in the range of 0 ⁇ x ⁇ 1.2, the expansion rate of the electrode material can be further reduced, the cycle performance of the battery can be improved, and the first effect can be improved.
  • x is 0, that is, there is no oxygen reaction, the expansion rate of the electrode material will increase, which will reduce the cycle performance of the material. If x is too large, the proportion of oxygen in the material will be large, and the material efficiency will be low, thereby reducing the initial efficiency.
  • the mass ratio of Li 4 SiO 4 and the silicon-containing material 140 is 0.05-1.1, eg, 0.05, 0.1, 0.5, 1, or 1.1, or the like.
  • the mass ratio is in the range of 0.05-1.1, which not only improves the first effect of the material, but also does not reduce the capacity of the material, thereby improving the rate of the material. If the proportion of Li 4 SiO 4 is too low, the first effect of the material will not be improved significantly. If the proportion of Li 4 SiO 4 is too high, the capacity of the material will be reduced, and the rate performance of the material will be reduced at the same time.
  • silicon alloys include, but are not limited to, at least one of silicon-lithium alloys, silicon-sodium alloys, silicon-magnesium alloys, and silicon-aluminum alloys; metal silicides include, but are not limited to, Mg 2 Si, Ca 2 Si, and Al 4 At least one of Si 3 ; silicates include but are not limited to K 2 SiO 3 , K 4 SiO 4 , K 2 Si 2 O 5 , Na 2 SiO 3 , Na 4 SiO 4 , Na 2 Si 2 O 5 , Mg At least one of 2 SiO 4 , MgSiO 3 , Ca 2 SiO 4 , CaSiO 3 , Al 4 (SiO 4 ) 3 and Al 2 (SiO 3 ) 3 . Wherein, at least one of silicon alloy, metal silicide and silicate is dispersed in lithium silicate.
  • One embodiment provides a method for preparing the silicon-oxygen composite negative electrode material, the method comprising the following steps:
  • the mixture containing the silicon source and the lithium-containing compound is calcined in a protective gas atmosphere and at a temperature of 300° C. to 600° C. to obtain a silicon-oxygen composite negative electrode material, wherein the general formula of the silicon source is SiO y , and the silicon source and the The molar ratio of the lithium compound is 1:1.2-1:3.
  • the molar ratio of silicon source to lithium-containing compound is 1:1.2, 1:1.23, 1:1.25, 1:1.27, 1:1.29, or 1:3, and the like.
  • the generated product when the molar ratio of the silicon source to the lithium-containing compound is in the range of 1:1.2-1:3, the generated product only contains Li 4 SiO 4 , but does not contain other lithium silicate composite materials. Good stability.
  • the molar ratio of silicon source SiO y to lithium-containing compounds is too high (that is, too much silicon source), which will lead to the formation of lithium-silicon alloys and reduce the stability of the material; the molar ratio of silicon source SiO y to lithium-containing compounds is too low (ie, lithium too much source), which will result in the inability to obtain Li 4 SiO 4 products.
  • the calcination temperature is 300°C-600°C, such as 300°C, 400°C, 500°C, or 600°C, and the like. If the calcination temperature is too high, the silicon grains will grow sharply and the cycle performance will be reduced; if the calcination temperature is too low, the reaction between the lithium-containing compound and the silicon source will be incomplete, and the expected pre-lithium effect will not be achieved.
  • the roasting time is 2h-8h, such as 2h, 3h, 4h, 5h, 6h, 7h or 8h, and the like.
  • this time range not only can the reaction be fully reacted, but only only Li 4 SiO 4 can be obtained, and the volume is moderate, and the expansion rate of the negative electrode material is further reduced in synergy. If the reaction time is too short, the reaction will not be sufficient, and one type of lithium silicate containing only Li 4 SiO 4 will not be obtained. The expansion rate of the material increases.
  • the molar ratio of the silicon source to the lithium-containing compound and the calcination temperature play a key role in obtaining a silicon-oxygen composite negative electrode material containing only Li 4 SiO 4 , a lithium silicate.
  • the silicon source includes silicon monoxide, SiO.
  • the lithium-containing compound is a reducing lithium-containing compound.
  • the reducing lithium-containing compound includes, but is not limited to, any one or a combination of at least two of lithium hydride, lithium alkyl, lithium metal, lithium aluminum hydride, lithium amide, or lithium borohydride.
  • the mixture is obtained by at least one of VC mixer, blending or stirring.
  • the protective gas includes at least one of hydrogen, nitrogen, helium, neon, argon, krypton, and xenon.
  • the mixture includes at least one of metal element and metal oxide; at this time, the obtained negative electrode material also contains at least one of silicon alloy, metal silicide and silicate;
  • the metal can be magnesium, aluminum, calcium, sodium, etc.
  • the silicon alloy can be silicon alloys such as silicon-magnesium alloys, silicon-aluminum alloys, etc.
  • metal silicides can be metal silicides such as Mg2Si, Ca2Si, Al4Si3, etc.
  • silicates can be K 2 SiO 3 , K 4 SiO 4 , K 2 Si 2 O 5 , Na 2 SiO 3 , Na 4 SiO 4 , Na 2 Si 2 O 5 , Mg 2 SiO 4 , MgSiO 3 , Ca 2 SiO 4 , CaSiO 3 , at least one of Al 4 (SiO 4 ) 3 or Al 2 (SiO 3 ) 3.
  • at least one of silicon alloy, metal silicide and silicate is dispersed in lithium silicate.
  • a method for preparing a silicon source includes: heating a raw material capable of generating silicon oxide gas under vacuum conditions or a protective gas atmosphere, generating silicon oxide gas, cooling and shaping to obtain a silicon source.
  • the raw material to produce the silicon oxide gas comprises a mixture of Si and O 2, or a mixture of SiO 2 and carbon, silicon, oxide of a mixture of at least two silicon-containing S i O m in which 1 ⁇ m ⁇ 6.
  • the silicon oxide gas generating feedstock includes a mixture of Si and SiO 2 .
  • shaping includes at least one of crushing, ball milling, or classification.
  • the heating temperature is 900°C-1500°C, such as 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C or 1500°C, and the like.
  • the protective gas includes at least one of hydrogen, nitrogen, helium, neon, argon, krypton, and xenon.
  • the surface of the silicon source is coated with a carbon layer 160 .
  • the method of coating the carbon layer 160 on the surface of the silicon source includes: reacting the silicon source with an organic carbon source gas under a protective gas atmosphere to obtain the silicon source coated with the carbon layer 160 .
  • the protective gas includes at least one of hydrogen, nitrogen, helium, neon, argon, krypton, and xenon.
  • the organic carbon source gas includes hydrocarbons.
  • the organic carbon source gas includes at least one of hydrocarbons and ketones.
  • the hydrocarbons include at least one of alkanes, alkenes, alkynes, and aromatic hydrocarbons.
  • the hydrocarbons include, but are not limited to, at least one of methane, ethylene, acetylene, acetone, and benzene.
  • the reaction temperature at which the reaction is performed is 600°C-1000°C, such as 600°C, 700°C, 800°C, 900°C, or 1000°C, and the like.
  • the reaction time is 0.5h-10.0h, such as 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, or 10h, and the like.
  • the preparation method further includes the steps of: immersing the silicon-oxygen composite negative electrode material in a hydrophobic solution and separating solid-liquid.
  • the solute of the hydrophobic solution includes at least one of lauric acid, stearic acid, leucine, methionine and phenylalanine
  • the solvent of the hydrophobic solution includes water, methanol, ethanol, At least one of ether and formic acid.
  • the time of immersion is 2h-6h, such as 2h, 3h, 4h, 5h or 6h, and the like.
  • the parameters of the structure in which nano-silicon is formed in the form of nano-silicon aggregates dispersed inside the silicon oxide 144 in this embodiment include: (1) the molar ratio of the silicon source to the lithium-containing compound, and (2) the baking temperature and time after mixing with the lithium source. , 3 immersion time in hydrophobic solution.
  • the synergy of these three elements to obtain the structure is indispensable.
  • These parameters are within the disclosed range, which can prevent the size of the nano-silicon aggregates from being too large or too small, so as to form the above-mentioned structure and achieve the optimal technical effect. If the size of nano-silicon aggregates is too large, the volume expansion of the material will be large, and the capacity of the cell will decay rapidly.
  • the preparation method of composite negative electrode material comprises the following steps:
  • the mixture of Si and SiO 2 is heated at 900°C-1500°C under vacuum conditions or protective gas atmosphere to generate silicon oxide gas, then cooled and shaped to obtain silicon monoxide;
  • the silicon monoxide is heated to 600°C-1000°C, an organic carbon source gas is introduced, the temperature is kept for 0.5-10.0 h and then cooled to obtain a silicon monoxide coated with a carbon layer 160;
  • the silicon monoxide coated with the carbon layer 160 and the lithium-containing compound are mixed in a molar ratio of 1:1.2-1:3, calcined at 300-600° C. for 2-8 hours in a protective gas atmosphere, cooled to room temperature, and the calcined product It is immersed in a hydrophobic solution for 2h-6h to obtain a silicon-oxygen composite negative electrode material.
  • the silicon-oxygen composite anode material can be used as an anode active material, such as an anode active material in a lithium ion battery.
  • An embodiment provides a negative electrode material, and the negative electrode material includes the above-mentioned silicon-oxygen composite negative electrode material.
  • the negative electrode material includes a silicon-oxygen composite negative electrode material, a conductive agent, and a binder.
  • the negative electrode material further comprises graphite.
  • graphite accounts for 20-97% of the total mass percentage of the silicon-oxygen composite negative electrode material and graphite.
  • One embodiment provides a method for preparing a negative electrode material, comprising: mixing a silicon-oxygen composite negative electrode material, a conductive agent and a binder.
  • One embodiment provides a negative electrode including a silicon-oxygen composite negative electrode material.
  • One embodiment provides a lithium-ion battery, comprising the above-mentioned silicon-oxygen composite negative electrode material.
  • the silicon-oxygen composite negative electrode material provided by some embodiments of the present disclosure only contains Li 4 SiO 4 , one type of lithium silicate, and does not contain other types of lithium silicate, which makes the silicon-oxygen composite negative electrode material provided by the present disclosure have The advantages of stable processing performance, high specific capacity, high first-time efficiency and long cycle life.
  • the first reversible capacity of the silicon-oxygen composite negative electrode material provided by the present disclosure can reach 1540 mAh/g, the first coulombic efficiency can reach 87.2%, and the capacity retention rate for 50 deduction cycles can reach 89.2%.
  • the preparation method provided by some embodiments of the present disclosure ensures that only Li 4 SiO 4 is contained in the product by controlling the molar ratio of the silicon source to the lithium-containing compound and the calcination temperature, and the preparation method is simple to operate. , the process is short, and it is easy to carry out industrialized large-scale production.
  • the silicon-oxygen composite negative electrode material is coated with a carbon layer, so that the conductivity of the negative electrode material is enhanced, and the electron conduction resistance between particles is reduced.
  • the silicon-oxygen composite negative electrode material is coated with a hydrophobic layer, so that the processing performance of the negative electrode material is improved, and the probability of gas generation in the aqueous slurry is reduced, thereby cooperating with the generation of only Li 4 SiO 4 in the embodiment of the present disclosure, and further improving the first time of the negative electrode material. Reversible capacity, first coulombic efficiency, and capacity retention over 50 electrical cycles.
  • the surface of the silicon-oxygen composite negative electrode material is covered with a carbon layer, and the surface of the carbon layer also includes a lauric acid hydrophobic layer. The thickness of the carbon layer is 300 nm, the thickness of the hydrophobic layer is 2 nm, and the mass ratio of Li 4 SiO 4 and silicon-containing material is 1:1.0.
  • FIG. 2 is an SEM photo of the silicon-oxygen composite negative electrode material provided in this example. From this figure, it can be seen that the particles of the composite material are evenly distributed, and there is no residual lithium source. At the same time, no other substances other than particles are found. The hydrophobic substances in the material are uniformly wrapped on the surface of the particles.
  • the surface of the silicon-oxygen composite negative electrode material is covered with a carbon layer, and the surface of the carbon layer further includes a stearic acid hydrophobic layer.
  • the thickness of the carbon layer is 800 nm
  • the thickness of the hydrophobic layer is 500 nm
  • the mass ratio of Li 4 SiO 4 and silicon-containing material is 1:1.1.
  • FIG. 5 is an SEM photo of the silicon-oxygen composite negative electrode material provided in this example. From this figure, it can be seen that the composite material particles are also uniformly distributed, there is no residual lithium source, and other substances other than particles are not found.
  • the surface of the silicon-oxygen composite negative electrode material is covered with a carbon layer, and the surface of the carbon layer further includes a phenylalanine hydrophobic layer.
  • the thickness of the carbon layer is 2000 nm
  • the thickness of the hydrophobic layer is 100 nm
  • the mass ratio of Li 4 SiO 4 and silicon-containing material is 1:0.6.
  • FIG. 7 is an SEM photo of the silicon-oxygen composite negative electrode material provided in this embodiment. From this figure, it can be seen that the composite material particles are also uniformly distributed, there is no residual lithium source, and other substances other than particles are not found.
  • the method for preparing a silicon-oxygen composite negative electrode material provided in this example is the same as Example 1 except that the operation of step (2) is not performed, that is, the carbon layer coating is not performed.
  • the silicon-oxygen composite negative electrode material provided in this example does not contain a carbon layer.
  • the method for preparing a silicon-oxygen composite negative electrode material provided in this example is the same as Example 1 except that the dipping operation in step (3) is not performed.
  • the silicon-oxygen composite negative electrode material provided in this example does not contain a hydrophobic layer.
  • the method for preparing a silicon-oxygen composite negative electrode material provided in this example is the same as Example 1 except that the operation of step (2) and the impregnation operation of step (3) are not performed.
  • the silicon-oxygen composite negative electrode material provided in this example does not contain a carbon layer and a hydrophobic layer.
  • SiO2 and Si (1) take the Si powder 1kg, 2kg SiO 2 powder, VC into the mixer for 30 min; the mixture was put into a vacuum furnace; vacuum degree is under negative pressure 5Pa heated to 1300 °C And keep it for 18h, generate SiO vapor in the furnace and then rapidly condense (the condensation temperature is 950 °C) to generate SiOy block; the SiOy block is crushed, ball milled, classified and other processes to control the median particle size to 6 ⁇ m to obtain monoxide Silicon powder material;
  • the silicon-oxygen composite negative electrode material provided in this embodiment includes Li4SiO4 and a silicon-containing material.
  • the silicon-containing material is dispersed in Li4SiO4.
  • the bulk form is dispersed inside the silicon oxide, and the grain size (average grain size) of the nano-silicon is 8.8 nm; the grain size (average grain size) of Li 4 SiO 4 is 500 nm.
  • the surface of the silicon-oxygen composite negative electrode material is covered with a carbon layer, and the surface of the carbon layer also includes a lauric acid hydrophobic layer.
  • the thickness of the carbon layer was 300nm, the thickness of the hydrophobic layer is 2nm, Li4SiO 4 and the mass ratio of silicon-containing material is 1: 1.0.
  • Example 8 Compared with Example 8, the magnesium oxide was changed to Al, the added mass was 100 g, and other operations were the same as those of the newly added Example 1.
  • the surface of the silicon-oxygen composite negative electrode material is covered with a carbon layer, and the surface of the carbon layer also includes a lauric acid hydrophobic layer.
  • the thickness of the carbon layer is 300 nm
  • the thickness of the hydrophobic layer is 2 nm
  • the mass ratio of Li 4 SiO 4 and silicon-containing material is 1:1.0.
  • This comparative example is the same as Example 1 except that the amount of lithium hydride used in step (3) is 120 g (the molar ratio of silicon monoxide containing carbon layer and lithium hydride is 1:0.4).
  • silicon-oxygen composite anode materials prepared in each example and comparative example were tested by the following methods
  • the silicon-oxygen composite negative electrode materials prepared in Examples and Comparative Examples were used as active materials; Homogeneous solution, the mass percentage is controlled to be 1.2%, as the binder; the conductive carbon black is used as the conductive agent; the active material, the conductive agent, and the binder are mixed in a mass ratio of 85:15:10, and the mixture is coated on the On the copper foil negative electrode current collector, the total solid content of the slurry is controlled to be 50%, and finally, a negative electrode pole piece is obtained by drying and rolling, and a negative electrode active material layer is formed on the upper layer of the negative electrode pole piece.
  • metal lithium sheet (diameter 10cm, thickness 1.2cm, Jiangxi Ganfeng Lithium Industry) as the counter electrode (ie positive electrode), PP (polypropylene) (diaphragm thickness 16um, Shanghai Enjie) as the separator, LiPF6/EC+DEC+DMC (1:1:1 volume ratio of EC, DEC, and DMC) was used as the electrolyte, while a simulated battery was assembled in an argon-filled glove box (Braun glove box) using the outer casing.
  • PP polypropylene
  • LiPF6/EC+DEC+DMC (1:1:1 volume ratio of EC, DEC, and DMC
  • the first reversible specific capacity (mAh/g) the data is obtained by the following blue power 5V/10mA battery tester;
  • the test method is as follows: use the blue electric 5V/10mA battery tester (CT2001A, Wuhan Jinnuo Electronics Co., Ltd. LAND battery test system) to test the electrochemical performance of the button battery, the charging voltage is 1.5V, discharge to 0.01V, charge and discharge The rate was 0.1C, and the first charge specific capacity (mAh/g) when charged and discharged with a 0.1C rate current and the first discharge specific capacity (mAh/g) when charged and discharged with a 0.1C rate current were measured.
  • the silicon-oxygen composite negative electrode material and graphite prepared by embodiment and comparative example are mixed as active material by mass ratio 1:9; SBR (styrene-butadiene rubber)+CMC (carboxymethyl cellulose) is equally mixed with mass ratio 1:9: 1 Mix, add water to dissolve to form a uniform solution, and control the mass percentage to 1.2% as a binder; use conductive carbon black as a conductive agent; where the active material, conductive agent, and binder are mixed in a mass ratio of 92:4:4 , Coating the mixed slurry on the copper foil negative current collector, controlling the total solid content of the slurry to be 50%, and finally drying and rolling to obtain a negative electrode sheet, and the upper layer of the negative electrode electrode sheet is the negative electrode active material layer.
  • SBR styrene-butadiene rubber
  • CMC carboxymethyl cellulose
  • a metal lithium sheet (diameter 10cm, thickness 1.2cm, Jiangxi Ganfeng Lithium Industry) was used as the counter electrode, PP/PE (diaphragm thickness 16um, Shanghai Enjie) was used as the separator, LiPF 6 /EC+DEC+DMC (EC, DEC and The volume ratio of DMC was 1:1:1) as the electrolyte, and the coin cells were assembled in an argon-filled glove box (Braun glove box).
  • 50-cycle cycle retention rate (%) discharge specific capacity in the 50th cycle/discharge specific capacity in the 1st cycle ⁇ 100% (Formula 1);
  • the instrument setting parameters are: the charging voltage is 1.5V, the discharge is 0.01V, the charging and discharging rate is 0.1C, and the battery is measured. The discharge specific capacity at the 1st and 50th cycle of the cycle was calculated to calculate the electrochemical performance. .
  • the test data of the silicon-oxygen composite negative electrode materials of Examples 1-7 and Comparative Example 1 are shown in Table 1.
  • Figure 1 is the first charge-discharge curve of the silicon-oxygen composite negative electrode material provided in Example 1. From this figure, it can be seen that the specific charge capacity of the composite material is above 1700mAh/g, and the reversible specific capacity is above 1450mAh/g.
  • Fig. 3 is the XRD image of the silicon-based composite material of Example 1. There are only peaks of Si and Li 4 SiO 4 in the image, and the peak positions of Li 4 SiO 4 are 23-26° and 36-38°.
  • Example 2-9 is, XRD image, only image peaks of Si and Li4SiO4, and Li 4 SiO can get the same peak position 4.
  • Figure 4 is the first charge-discharge curve of the silicon-oxygen composite negative electrode material provided in Example 2.
  • Figure 6 is the first charge-discharge curve of the silicon-oxygen composite negative electrode material provided in Example 3. From this figure, it can be seen that the specific charge capacity of the composite material is above 1680mAh/g, and the reversible specific capacity is above 1450mAh/g.
  • the silicon-oxygen composite negative electrode materials prepared in Examples 1-4 only contain Li 4 SiO 4 which is a kind of lithium silicate and do not contain other kinds of lithium silicates.
  • the silicon-oxygen composite anode material has the advantages of stable processing performance, high specific capacity, high initial efficiency and long cycle life.
  • Example 1 and Example 5 Compared with Example 1 and Example 5, a carbon layer is contained, so that compared with Example 1 and Example 5, the electrical conductivity of the material is improved, the electron conduction resistance between particles is reduced, and the Coulombic efficiency is improved.
  • Example 1 and Example 6 Compared with Example 1 and Example 6, the hydrophobic layer is contained, so that compared with Example 1 and Example 6, the processability of the material is improved, and the probability of gas generation in the aqueous slurry is reduced.
  • Example 7 does not contain a carbon layer and a hydrophobic layer, so that compared to Example 1, the material has poor electrical conductivity and processability.
  • Comparative Example 1 because the amount of added lithium source is small, it is not enough to generate Li 4 SiO 4 , resulting in no Li 4 SiO 4 in the prepared negative electrode material.
  • the lithium silicate in the product of this comparative example is Li 2 SiO 3 , which is obviously reduced.
  • the first reversible capacity of the product of Comparative Example 1 was obtained.
  • the present disclosure illustrates the detailed process equipment and process flow of the present disclosure through the above-mentioned embodiments, but the present disclosure is not limited to the above-mentioned detailed process equipment and process flow, that is, it does not mean that the present disclosure must rely on the above-mentioned detailed process equipment and process flow. Process flow can be implemented. Those skilled in the art should understand that any improvement of the present disclosure, equivalent replacement of each raw material of the disclosed product, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present disclosure.

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Abstract

本公开提供了硅氧复合负极材料、负极和锂离子电池及其制备方法。本公开提供的硅氧复合负极材料包括复合粒子，所述复合粒子包括硅酸锂和含硅材料，所述硅酸锂为Li 4SiO 4，所述含硅材料分散在所述硅酸锂中，所述含硅材料包括纳米硅及硅氧化物中的至少一种。本公开提供的制备方法包括：将含有硅源与含锂化合物的混合物，在保护性气体气氛下焙烧，得到所述硅氧复合负极材料，其中所述硅源的通式为SiO y；所述硅源与含锂化合物的摩尔比为1:1.2-1:3。本公开提供的硅氧复合负极材料中仅含有Li 4SiO 4这一种硅酸锂，这使得本公开提供的硅氧复合负极材料容量较高。制备的负极和锂离子电池具有加工性能稳定、比容量高、首次效率高、循环寿命长等优点。

Description

硅氧复合负极材料、负极和锂离子电池及其制备方法
相关申请的交叉引用
本申请要求于2020年06月28日提交中国专利局的申请号为202010597112.5、名称为“硅氧复合负极材料及其制备方法和锂离子电池”的中国专利申请的优先权，其全部内容通过引用结合在本公开中。
技术领域
本公开属于储能材料技术领域，涉及一种负极材料及其制备方法和锂离子电池，特别涉及硅氧复合负极材料、负极和锂离子电池及其制备方法。
背景技术
锂离子电池因具有工作电压高、循环使用寿命长、无记忆效应、自放电小、环境友好等优点，已被广泛应用于便携式电子产品和电动汽车中。目前，商业化的锂离子电池主要采用石墨类负极材料，但它的理论比容量仅为372mAh/g，无法满足未来锂离子电池对高能量密度的需求。现有的Si虽然理论容量高达4200mAh/g，但其膨胀达300％，使循环性能受到影响，导致市场推广和应用受到约束。与之相对应的硅氧材料，循环性能更好，但是首次效率低。在首次充电时，需要消耗20～50％的锂用于SEI膜形成，这就大大降低了首次库伦效率。基于此，研究较多的提升硅氧材料首效的方法是掺杂，其中掺锂是效果比较明显的。
但是，掺锂后获得首效提升的同时会带来硅氧材料的容量下降。掺锂一方面会消耗硅氧中的不可逆相，同时也会消耗一部分可逆相。在提升硅氧材料首效的同时，减少容量损失对硅氧材料的后期使用以及商业化都具有重要意义。尤其是在当下环境，后端电池需要更高的能量密度来满足使用和发展需求。因此，提升前端材料自身的克容量显得尤为重要。
发明内容
本公开提供一种硅氧复合负极材料，所述硅氧复合负极材料包括复合粒子，所述复合粒子包括硅酸锂和含硅材料，所述硅酸锂为Li 4SiO 4，所述含硅材料分散在所述硅酸锂中，所述含硅材料包括单质硅、硅氧化物(144)、硅合金、金属硅化物及硅酸盐中的至少一种。
在一些实施方式中，所述硅氧复合负极材料中，Li 4SiO 4的晶粒尺寸在60nm以下。
在一些实施方式中，所述硅氧复合负极材料还包括形成于所述复合粒子表面的碳层。
在一些实施方式中，所述碳层的厚度为300nm-2000nm。
在一些实施方式中，所述硅氧复合负极材料还包括形成于所述碳层的表面的疏水层。
在一些实施方式中，所述疏水层的厚度为2nm-500nm。
在一些实施方式中，所述疏水层的材料包括饱和脂肪酸及氨基酸中的至少一种。
在一些实施方式中，所述疏水层的材料包括月桂酸、硬脂酸、亮氨酸、甲硫氨酸及苯丙氨酸中的至少一种。
在一些实施方式中，所述含硅材料包括纳米硅和硅氧化物，所述纳米硅以纳米硅聚集体形式分散在硅氧化物内部。
在一些实施方式中，所述纳米硅聚集体包括多个纳米硅晶粒。
在一些实施方式中，所述纳米硅晶粒尺寸在0nm～10nm，且不包括0nm。
在一些实施方式中，所述硅氧化物的化学式为SiO x，其中0＜x＜1.2。
在一些实施方式中，所述硅酸锂和含硅材料的质量比为0.05-1.1；
在一些实施方式中，所述硅合金包括硅锂合金、硅钠合金、硅镁合金及硅铝合金中的至少一种；
在一些实施方式中，所述单质硅包括纳米硅、非晶硅及结晶硅中的至少一种。
本公开提供一种如所述硅氧复合负极材料的制备方法，所述方法包括以下步骤：
将含有硅源与含锂化合物的混合物，在保护性气体气氛及温度为300℃～600℃下焙烧，得到所述硅氧复合负极材料，其中所述硅源的通式为SiO y，所述硅源与含锂化合物的摩尔比为1:1.2-1:3。
在一些实施方式中，0＜y＜2。
在一些实施方式中，所述硅源为一氧化硅。
在一些实施方式中，所述含锂化合物为还原性含锂化合物。
在一些实施方式中，所述还原性含锂化合物包括氢化锂、烷基锂、金属锂、氢化铝锂、氨基锂及硼氢化锂中的至少一种；
在一些实施方式中，所述混合物还包括金属单质及金属氧化物中的至少一种；
在一些实施方式中，所述混合物通过VC混合机混合、融合及搅拌中至少一种方法混合得到。
在一些实施方式中，所述保护性气体包括氢气、氮气、氦气、氖气、氩气、氪气及氙气中的至少一种。
在一些实施方式中，所述焙烧的时间为2h-8h。
在一些实施方式中，所述硅源的制备方法包括：在真空条件或保护性气体气氛下对能产生硅氧化物气体的原料进行加热，产生硅氧化物气体后冷却、整形得到硅源。
在一些实施方式中，所述能产生硅氧化物气体的原料包括Si和SiO 2的混合物。
在一些实施方式中，所述能产生硅氧化物气体的原料包括Si和O 2的混合物，或者SiO 2和碳的混合物，或者硅、含有硅的氧化物SiO m中的至少两种混合物，其中1≤m≤6。
在一些实施方式中，所述整形包括破碎、球磨及分级中的至少一种。
在一些实施方式中，所述加热的温度为900℃-1500℃。
在一些实施方式中，所述保护性气体包括氢气、氮气、氦气、氖气、氩气、氪气及氙气中的至少一种。
在一些实施方式中，所述硅源的表面包覆有碳层。
在一些实施方式中，在所述硅源的表面包覆碳层的方法包括：在保护性气体气氛下，将所述硅源与有机碳源气体进行反应，得到包覆有碳层的硅源。
在一些实施方式中，所述保护性气体包括氢气、氮气、氦气、氖气、氩气、氪气及氙气中的至少一种。
在一些实施方式中，所述有机碳源气体为烃类。
在一些实施方式中，所述烃类包括但不限于甲烷、乙烯、乙炔、丙酮及苯中的至少一种。
在一些实施方式中，所述进行反应的反应温度为600℃-1000℃。
在一些实施方式中，所述进行反应的反应时间为0.5h-10.0h。
在一些实施方式中，所述制备方法还包括步骤：将所述硅氧复合负极材料在疏水性溶液中进行浸渍。
在一些实施方式中，所述疏水性溶液的溶质包括月桂酸、硬脂酸、亮氨酸、甲硫氨酸及苯丙氨酸中的至少一种，所述疏水性溶液的溶剂包括水、甲醇、乙醇、乙醚、苯或甲酸中的至少一种。
在一些实施方式中，所述浸渍的时间为2h-6h。
作为本公开所述制备方法的可选的技术方案，所述方法包括以下步骤：
在真空条件或保护性气体气氛下对Si和SiO 2的混合物进行900℃-1500℃加热，产生硅氧化物气体后冷却、整形得到一氧化硅；
在保护性气体氛围下，将所述一氧化硅升温至600℃-1000℃，通入有机碳源气体，保温0.5-10.0h后冷却，得到包覆有碳层的一氧化硅；
将所述包覆有碳层的一氧化硅与含锂化合物以摩尔比1:1.2-1:3进行混合，在保护性气体气氛下300℃-600℃焙烧2h-8h，冷却至室温，将焙烧产物置于疏水性溶液中浸渍2h-6h，得到所述硅氧复合负极材料。
本公开提供一种负极，所述负极包括所述硅氧复合负极材料。
本公开提供一种锂离子电池，所述锂离子电池包含所述的硅氧复合负极材料。
附图说明
为了更清楚地说明本公开实施方式的技术方案，下面将对实施方式中所需要使用的附图作简单地介绍，应当理解，以下附图仅示例地表征本公开的实施方式，图中尺寸比例与实施方式的真实比例并不能直接对应，同时以下附图仅示出了本公开的某些实施方式，因此不应被看作是对范围的限定。
图1为本公开实施例1提供的硅氧复合负极材料的首次充放电曲线；
图2为本公开实施例1提供的硅氧复合负极材料的SEM照片；
图3为本公开实施例1硅基复合材料的XRD图像；
图4为本公开实施例2提供的硅氧复合负极材料的首次充放电曲线；
图5为本公开实施例2提供的硅氧复合负极材料的SEM照片；
图6为本公开实施例3提供的硅氧复合负极材料的首次充放电曲线；
图7为本公开实施例3提供的硅氧复合负极材料的SEM照片；
图8为本公开一些实施方式中的硅氧复合负极材料的结构示意图；
图9为本公开一些实施方式中的硅氧复合负极材料的结构示意图；
图10为本公开一些实施方式中的硅氧复合负极材料的结构示意图；
附图标记：100-复合粒子；120-硅酸锂；140-含硅材料；142-纳米硅晶粒；144-硅氧化物；160-碳层；180-疏水层。
实施方式
下面结合附图并通过具体实施方式来进一步说明本公开的技术方案。
为了使本公开的目的、技术方案及优点更加清楚明白，以下对本公开进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本公开，并不用于限定本公开。此外，下面所描述的本公开各个实施方式中所涉及的技术特征只要彼此之间未构成冲突就可以相互组合。在不脱离本公开实施例原理的前提 下，还可以做出若干改进和润饰，这些改进和润饰也视为本公开实施例的保护范围。
I.硅氧复合负极材料
一实施方式的硅氧复合负极材料，硅氧复合负极材料包括复合粒子100，复合粒子100包括硅酸锂120和含硅材料140，硅酸锂120为Li 4SiO 4，含硅材料140分散在硅酸锂120中，含硅材料140包括单质硅、硅氧化物144、硅合金、金属硅化物及硅酸盐中的至少一种。
实施方式中提供的硅氧复合负极材料中，含硅材料140均匀分散在硅酸锂120中，换言之，硅酸锂120将含硅材料140包裹其中。
本实施方式中提供的硅氧复合负极材料是预锂后的硅负极，其仅含有Li 4SiO 4这一种硅酸锂，这样可以实现硅氧负极材料预锂后仍具有较高容量，从而使得本公开实施方式提供的硅氧复合负极材料具有加工性能稳定、比容量高、首次效率高、循环寿命长的优点。
将硅氧化物144进行预锂，均会带来一定的容量损失。预锂后生成不同种类的硅酸锂，带来的容量损失也不同。消耗相同数量锂源，不同的硅酸锂消耗的一氧化硅量也会不同，只有生成Li 4SiO 4时消耗的一氧化硅最少，同时带来的容量损失最少。本公开提供的硅氧复合负极材料中，仅含有Li 4SiO 4这一种硅酸锂，可有效降低预锂硅氧材料的容量损失。
以下作为实施方式中可选的技术方案，但不作为对本公开提供的技术方案的限制。
(A)Li 4SiO 4的晶粒
在一些实施方式中，硅氧复合负极材料中，Li 4SiO 4的晶粒尺寸在60nm以下，例如60nm、50nm、40nm、30nm、20nm或10nm等。Li 4SiO 4的晶粒尺寸在60nm以下的范围，可以进一步提高负极材料良好的导电性能、材料的循环性能，提高电极材料的可逆容量，而晶粒尺寸过大，则会导致材料导电性差，材料的倍率性能差，材料循环性差，容量衰减快。
(B)碳层和疏水层
如图9所示，在一些实施方式中，硅氧复合负极材料还包括形成于复合粒子100表面的碳层160。复合粒子100表面包覆碳层160，协同仅Li 4SiO 4的生成，进一步提高材料的导电性，减少颗粒间的电子传导阻力。
碳层160包括但不限于为裂解碳形成的碳层160。
在一些实施方式中，碳层160的厚度为300nm-2000nm，例如300nm、500nm、1000nm、1500nm或2000nm等。碳层的厚度在300nm-2000nm的范围内，可以协同Li 4SiO 4及其晶粒尺寸进一步提高材料的导电性，同时不会降低分子材料的容量。该碳层160过薄，材料的导电性提升不明显，碳层160过厚，分子材料的容量较低。
如图10所示，在一些实施方式中，硅氧复合负极材料还包括形成于碳层160的表面的疏水层180。
硅氧复合负极材料经疏水层180的包覆，提升了材料的水系加工性能，有效降低了水系浆料中产气的几率。在一些实施方式中，疏水层180的厚度为2nm-500nm，例如2nm、5nm、10nm、50nm、100nm、200nm、300nm、400nm或500nm等。在该范围的疏水层180，可以将材料严密包裹，从而进一步提高负极材料的加工性能。疏水层180过薄，由于疏水层180分布不均匀等问题，使得内部包覆不严密，会影响材料的加工性能，疏水层180过厚，则不溶于水，加工性能不好，同时影响调浆。
在一些实施方式中，疏水层180的组成材料包括但不限于饱和脂肪酸、氨基酸中的任意一种或至少两 种的组合。在实施方式中，选择饱和脂肪酸和氨基酸作为疏水层材料，使得该材料对于电极材料的包覆完整性更高。
在一些实施方式中，饱和脂肪酸的碳原子数大于等于8。
在一些实施方式中，饱和脂肪酸包括月桂酸、硬脂酸、辛酸、壬酸、癸酸、肉豆蔻酸、软脂酸、珠光脂酸、硬脂酸、花生酸及山嵛酸中的至少一种。
在一些实施方式中，氨基酸包括亮氨酸、甲硫氨酸、色氨酸、缬氨酸、异亮氨酸、丙氨酸、苯丙氨酸及蛋氨酸中的至少一种。
在一些实施方式中，疏水层180的组成材料包括月桂酸、硬脂酸、亮氨酸、甲硫氨酸及苯丙氨酸中的至少一种。
(C)含硅材料
在一些实施方式中，含硅材料140可以分散在所述硅酸锂120中。
在一些实施方式中，含硅材料140包括单质硅、硅氧化物144、硅合金、金属硅化物及硅酸盐中的至少一种。
在一些实施方式中，含硅材料140为非金属含硅材料。
在一些实施方式中，非金属含硅材料包括单质硅、硅氧化物144、硅合金、金属硅化物及硅酸盐中的至少一种。
在一些实施方式中，含硅材料(或非金属含硅材料)包括纳米硅及硅氧化物中的至少一种。
一实施方式中，所述单质硅包括纳米硅、非晶硅及结晶硅中的至少一种。
一实施方式中，如图8所示，含硅材料140包括纳米硅和硅氧化物144，纳米硅是以纳米硅聚集体的形式分散在硅氧化物144内部。纳米硅聚集体包括多个纳米硅晶粒142；纳米硅聚集体是指由几个乃至上千个纳米硅晶粒142通过物理或化学结合力组成的聚集体。
由于硅的膨胀各向同性，小尺寸的硅晶粒形成聚集体时，可以利用相互作用力抵消部分膨胀，因此纳米硅聚集体的膨胀更小，循环寿命更长，从而能够有利于提高负极材料的循环性能、倍率性能。
在一些实施方式中，纳米硅晶粒142尺寸为0nm～10nm，且不包括0nm，例如10nm、9nm、8nm、7nm、6nm或5nm等。纳米硅晶粒142尺寸过大，则会引起材料的膨胀，从而影响材料的循环性能。当纳米硅晶粒142尺寸控制在10nm以下，一方面有利于提升纳米硅在颗粒中的整体分布均匀性，另一方面还可以更好的控制纳米硅与硅氧化物整体的硅氧比。如果纳米硅未以聚集体形式分散在硅氧化物内部，其活性高，更容易被氧化，导致材料的比容量和首效降低。此外，如果纳米硅未形成聚集体，在加入锂源烧结过程中，纳米硅结晶速率更快。如果是以聚集体的形式存在，结晶速率会因为较多的晶界存在，相互干扰而延缓晶核生长速率。
在一些实施方式中，硅氧化物144的化学式为SiO x，其中0＜x＜1.2，例如x为0.1、0.2、0.5、0.8、1或1.1等。x在0＜x＜1.2的范围内，可进一步降低电极材料的膨胀率，提高电池的循环性能，提高首效。x为0，即没有氧反应，会导致电极材料的膨胀率增加，使得材料循环性能降低，x过大，则材料中氧占比大，材料效率低，从而降低首效率。
在一些实施方式中，Li 4SiO 4和含硅材料140的质量比为0.05-1.1，例如0.05、0.1、0.5、1或1.1等。质量比在0.05-1.1范围内，不仅提高了材料的首效，而且不降低材料的容量，从而提高了材料的倍率性。 Li 4SiO 4占比过低，对材料首效提升不明显，Li 4SiO 4占比过高，则会使得材料的容量降低，同时降低材料的倍率性能。
在一些实施方式中，硅合金包括但不限于硅锂合金、硅钠合金、硅镁合金及硅铝合金中的至少一种；金属硅化物包括但不限于Mg 2Si、Ca 2Si及Al 4Si 3中的至少一种；硅酸盐包括但不限于K 2SiO 3、K 4SiO 4、K 2Si 2O 5、Na 2SiO 3、Na 4SiO 4、Na 2Si 2O 5、Mg 2SiO 4、MgSiO 3、Ca 2SiO 4、CaSiO 3、Al 4(SiO 4) 3及Al 2(SiO 3) 3中的至少一种。其中，硅合金、金属硅化物及硅酸盐中的至少一种分散在硅酸锂中。
II.硅氧复合负极材料的制备
一实施方式提供一种所述硅氧复合负极材料的制备方法，所述方法包括以下步骤：
将含有硅源与含锂化合物的混合物，在保护性气体气氛及温度为300℃-600℃下焙烧，得到硅氧复合负极材料，其中硅源的通式为SiO y，所述硅源与含锂化合物的摩尔比为1:1.2-1:3。
在一些实施方式中，硅源与含锂化合物的摩尔比为1:1.2、1:1.23、1:1.25、1:1.27、1:1.29或1:3等。
该实施方式中，在硅源与含锂化合物的摩尔比在1:1.2-1:3的范围下，生成的产物仅含有Li 4SiO 4，而不含其它硅酸锂的复合材料，材料的稳定性好。硅源SiO y与含锂化合物的摩尔比过高(即硅源过多)，会导致锂硅合金生成，降低材料的稳定性；硅源SiO y与含锂化合物的摩尔比过低(即锂源过多)，会导致不能获得Li 4SiO 4产物。
在一些实施方式中，焙烧的温度为300℃-600℃，例如300℃、400℃、500℃或600℃等。焙烧温度过高，会导致硅晶粒急剧长大，使循环性能降低；焙烧温度过低，会导致含锂化合物与硅源反应不完全，达不到预期的预锂效果。
在一些实施方式中，焙烧的时间为2h-8h，例如2h、3h、4h、5h、6h、7h或8h等。在该时间范围下，不仅可以反应充分，而且仅能获得唯一的Li 4SiO 4，且体积适中，协同进一步降低的负极材料的膨胀率。若反映时间过短，则反应不充分，得不到仅含有Li 4SiO 4这一种硅酸锂，若时间过长，则硅酸锂种类发生变化，且生成的产物体积变大，从而导致材料的膨胀率增大。
该实施方式提供的制备方法中，硅源与含锂化合物的摩尔比以及焙烧的温度，对于得到仅含有Li 4SiO 4这一种硅酸锂的硅氧复合负极材料起到了关键作用。
在一些实施方式中，0＜y＜2，0.1＜y＜1.9，或1.5＜y＜1.5，例如y为0.1、0.5、1、1.5或1.9等。
在一些实施方式中，硅源包括一氧化硅SiO。
在一些实施方式中，含锂化合物为还原性含锂化合物。
在一些实施方式中，还原性含锂化合物包括但不限于氢化锂、烷基锂、金属锂、氢化铝锂、氨基锂或硼氢化锂中的任意一种或至少两种的组合。
在一些实施方式中，混合物通过VC混合机、融合或搅拌中至少一种方法混合得到。
在一些实施方式中，保护性气体包括氢气、氮气、氦气、氖气、氩气、氪气及氙气中的至少一种。
在一些实施方式中，所述混合物包括金属单质及金属氧化物中的至少一种；此时得到负极材料还含有硅合金、金属硅化物及硅酸盐中的至少一种；
具体地，金属可以为镁、铝、钙、钠等，则硅合金可以为硅镁合金、硅铝合金等硅合金；金属硅化物可以为Mg2Si、Ca2Si、Al4Si3等金属硅化物；硅酸盐可以为K 2SiO 3、K 4SiO 4、K 2Si 2O 5、Na 2SiO 3、Na 4SiO 4、Na 2Si 2O 5、Mg 2SiO 4、MgSiO 3、Ca 2SiO 4、CaSiO 3、Al 4(SiO 4) 3或Al 2(SiO 3) 3中的至少一种。其中，硅合金、 金属硅化物及硅酸盐中的至少一种分散在硅酸锂中。
(A)硅源的制备
在一些实施方式中，硅源的制备方法包括：在真空条件或保护性气体气氛下对能产生硅氧化物气体的原料进行加热，产生硅氧化物气体后冷却、整形得到硅源。
在一些实施方式中，能产生硅氧化物气体的原料包括Si和O 2的混合物，或者SiO 2和碳的混合物，硅、含有硅的氧化物S iO m中的至少两种混合物，其中1≤m≤6。
在一些实施方式中，能产生硅氧化物气体的原料包括Si和SiO 2的混合物。
在一些实施方式中，整形包括破碎、球磨或分级中的至少一种。
在一些实施方式中，加热的温度为900℃-1500℃，例如900℃、1000℃、1100℃、1200℃、1300℃、1400℃或1500℃等。
在一些实施方式中，保护性气体包括氢气、氮气、氦气、氖气、氩气、氪气及氙气中的至少一种。
(B)碳层的包覆
在一些实施方式中，如图9所示，硅源的表面包覆有碳层160。
在一些实施方式中，在硅源的表面包覆碳层160的方法包括：在保护性气体气氛下，将硅源与有机碳源气体进行反应，得到包覆有碳层160的硅源。
在一些实施方式中，保护性气体包括氢气、氮气、氦气、氖气、氩气、氪气及氙气中的至少一种。
在一些实施方式中，有机碳源气体包括烃类。
在一些实施方式中，有机碳源气体包括烃类及酮类中的至少一种。
在一些实施方式中，烃类包括烷烃、烯烃、炔烃及芳香烃中的至少一种。
在一些实施方式中，烃类包括但不限于甲烷、乙烯、乙炔、丙酮及苯中的至少一种。
在一些实施方式中，进行反应的反应温度为600℃-1000℃，例如600℃、700℃、800℃、900℃或1000℃等。
在一些实施方式中，进行反应的反应时间为0.5h-10.0h，例如0.5h、1h、2h、3h、4h、5h、6h、7h、8h、9h或10h等。
(C)疏水层的包覆
作为本实施方式可选的技术方案，制备方法还包括步骤：将硅氧复合负极材料在疏水性溶液中进行浸渍并固液分离。
在一些实施方式中，疏水性溶液的溶质包括月桂酸、硬脂酸、亮氨酸、甲硫氨酸及苯丙氨酸中的至少一种，疏水性溶液的溶剂包括水、甲醇、乙醇、乙醚及甲酸中的至少一种。
在一些实施方式中，浸渍的时间为2h-6h，例如2h、3h、4h、5h或6h等。
本实施方式形成纳米硅是以纳米硅聚集体的形式分散在硅氧化物144内部的结构的参数包括：①硅源与含锂化合物的摩尔比，②与锂源混合后的焙烧的温度、时间，③疏水溶液浸渍时间。这三个要素的协同作用下获得该结构，缺一不可。这些参数在公开范围内，可避免纳米硅聚集体尺寸过大或者过小，从而形成上述的结构，达到最优的技术效果。如果纳米硅聚集体尺寸过大，会导致材料的体积膨胀大，电芯容量衰减快。
(D)复合负极材料的制备
复合负极材料的制备方法包括以下步骤：
在真空条件或保护性气体气氛下对Si和SiO 2的混合物进行900℃-1500℃加热，产生硅氧化物气体后冷却、整形得到一氧化硅；
在保护性气体氛围下，将一氧化硅升温至600℃-1000℃，通入有机碳源气体，保温0.5-10.0h后冷却，得到包覆有碳层160的一氧化硅；
将包覆有碳层160的一氧化硅与含锂化合物以摩尔比1:1.2-1:3进行混合，在保护性气体气氛下300-600℃焙烧2-8h，冷却至室温，将焙烧产物置于疏水性溶液中浸渍2h-6h，得到硅氧复合负极材料。
III.负极材料及负极
硅氧复合负极材料可以用作负极活性材料，例如锂离子电池中的负极活性材料。
一实施方式提供了负极材料，负极材料包含上述硅氧复合负极材料。
在一些实施方式中，负极材料包含硅氧复合负极材料、导电剂和粘结剂。
在一些实施方式中，负极材料还包含石墨。
在一些实施方式中，石墨占比硅氧复合负极材料与石墨总质量百分比的20-97％。
一实施方式提供了制备负极材料的方法，包括：将硅氧复合负极材料以及导电剂和粘结剂混合。
一实施方式提供了负极，包括硅氧复合负极材料。
IV.锂离子电池
一实施方式提供了锂离子电池，包含上述的硅氧复合负极材料。
与其他方式相比，本公开的实施方式具有以下有益效果：
(1)本公开一些实施方式提供的硅氧复合负极材料中仅含有Li 4SiO 4这一种硅酸锂而不含其它种类的硅酸锂，这使得本公开提供的硅氧复合负极材料具有加工性能稳定、比容量高、首次效率高、循环寿命长的优点。本公开提供的硅氧复合负极材料的首次可逆容量可达1540mAh/g，首次库伦效率可达87.2％，50次扣电循环容量保持率可达89.2％。
(2)本公开一些实施方式提供的制备方法通过控制硅源与含锂化合物的摩尔比以及焙烧的温度，保证了产品中仅含有Li 4SiO 4这一种硅酸锂，并且制备方法操作简单，流程短，易于进行产业化大规模生产。
(3)本公开一些实施方式中，硅氧复合负极材料通过包覆碳层，使得负极材料导电性增强，颗粒间的电子传导阻力降低。同时硅氧复合负极材料通过包覆疏水层，使得负极材料的加工性能提高，降低水系浆料中产气的概率，从而协同本公开实施方式中仅Li 4SiO 4的生成，进一步提高负极材料的首次可逆容量、首次库伦效率以及50次电循环容量保持率。
为更好地说明本公开，便于理解本公开的技术方案，下面对本公开进一步详细说明。但下述的实施例仅仅是本公开的简易例子，并不代表或限制本公开的权利保护范围，本公开保护范围以权利要求书为准。
以下为本公开典型但非限制性实施例：
实施例1
本实施例按照如下方法制备硅氧复合负极材料：
(1)取1kg Si粉，2kg SiO 2粉，投入VC混合机内混合30min后得到SiO 2和Si的混合物；将该混合物投入真空炉内；在真空度为5Pa的负压条件下加热到1300℃并保温18h，在炉内生成SiO蒸汽经过迅速 凝结(凝结的温度为950℃)生成SiO y块体；将SiO y块体经过破碎、球磨、分级等工艺将其中值粒径控制在6μm，得到一氧化硅粉体材料；
(2)将1kg一氧化硅粉体材料置于回转炉中，通入保护性气体N 2，升温至1000℃，通入有机碳源气体丙酮，保温4h后冷却，得含有碳层的一氧化硅颗粒；
(3)取含有碳层一氧化硅2kg，氢化锂250g(含有碳层的一氧化硅与氢化锂的摩尔比为1:1.2)放入卧式球磨罐中，球磨2h，球磨机转数为500rpm，取出装入石墨坩埚中，放入箱式炉中在氩气气氛下600℃焙烧2h，冷却至室温得只含Li 4SiO 4而不含其它硅酸锂的复合材料；然后将上述复合材料置于月桂酸与乙醚(质量比为复合材料：月桂酸：乙醚＝1:0.005:0.005)形成的溶液中浸渍5h，过滤后烘干即为所述硅氧复合负极材料。
本实施例提供的硅氧复合负极材料包括Li 4SiO 4和含硅材料，含硅材料分散在Li 4SiO 4中，含硅材料由纳米硅和硅氧化物(SiO x，x＝0.65)组成，纳米硅以聚集体形式分散在硅氧化物内部，所述纳米硅的晶粒尺寸(平均粒径)为8.8nm；Li 4SiO 4的晶粒尺寸(平均粒径)为500nm。硅氧复合负极材料的表面包覆有碳层，碳层的表面还包含月桂酸疏水层。碳层的厚度为300nm，疏水层的厚度为2nm，Li 4SiO 4和含硅材料的质量比为1:1.0。
图2为本实施例提供的硅氧复合负极材料的SEM照片，由该图可以看出所述复合材料颗粒形貌分布均匀，无残余的锂源，同时未发现除颗粒以外的其他物质，说明材料中的疏水物质均匀包裹在颗粒表面。
实施例2
本实施例按照如下方法制备硅氧复合负极材料：
(1)取1kg Si粉，2kg SiO 2粉，投入VC混合机内混合30min后得到SiO 2和Si的混合物；将该混合物投入反应炉内；在氮气气氛下加热到1500℃并保温16h，在炉内生成SiO蒸汽经过迅速凝结(凝结的温度为1300℃)生成SiO y块体；将SiO y块体经过破碎、球磨、分级等工艺将其中值粒径控制在6μm，得到SiO y(y＝1.0)粉体材料；
(2)将1kg SiO y粉体材料置于回转炉中，通入保护性气体N 2，升温至800℃，通入有机碳源气体甲烷，保温0.5h后冷却，得含有碳层的SiO y颗粒；
(3)取含有碳层的SiO y与金属锂(含有碳层的SiO y与金属锂的摩尔比为1:3)放入卧式球磨罐中，球磨2h，球磨机转数为500rpm，取出装入石墨坩埚中，放入箱式炉中在氩气气氛下450℃焙烧2h，冷却至室温得只含Li 4SiO 4而不含其它硅酸锂的复合材料；然后将上述复合材料置于硬脂酸与苯(质量比为复合材料：硬脂酸：苯＝1:0.05:0.03)形成的溶液中浸渍10h，过滤后烘干即为所述硅氧复合负极材料。
本实施例提供的硅氧复合负极材料包括Li 4SiO 4和含硅材料，含硅材料分散在Li 4SiO 4中，含硅材料由纳米硅和硅氧化物(SiO x，x＝0.2)组成，纳米硅以聚集体形式分散在硅氧化物内部，纳米硅的晶粒尺寸(平均粒径)为5nm；Li 4SiO 4的晶粒尺寸(平均粒径)为80nm。硅氧复合负极材料的表面包覆有碳层，碳层的表面还包含硬脂酸疏水层。碳层的厚度为800nm，疏水层的厚度为500nm，Li 4SiO 4和含硅材料的质量比为1:1.1。
图5为本实施例提供的硅氧复合负极材料的SEM照片，由该图可以看出所述复合材料颗粒同样分布均匀，无残余的锂源，同时未发现除颗粒以外的其他物质。
实施例3
本实施例按照如下方法制备硅氧复合负极材料：
(1)取1kg Si粉，2kg SiO 2粉，投入VC混合机内混合30min后得到SiO 2和Si的混合物；将该混合物投入反应炉内；在氩气气氛下加热到900℃并保温20h，在炉内生成SiO蒸汽经过迅速凝结(凝结的温度为1300℃)生成SiO y块体；将SiO y块体经过破碎、球磨、分级等工艺将其中值粒径控制在6μm，得到SiO y(y＝1.0)粉体材料；
(2)将1kg SiO y粉体材料置于回转炉中，通入保护性气体氩气，升温至600℃，通入有机碳源气体乙烯，保温10h后冷却，得含有碳层的SiO y颗粒；
(3)取含有碳层的SiO y与硼氢化锂(含有碳层的SiO y与硼氢化锂的摩尔比为1:1.2)放入卧式球磨罐中，球磨2h，球磨机转数为500rpm，取出装入石墨坩埚中，放入箱式炉中在氩气气氛下300℃焙烧8h，冷却至室温得只含Li 4SiO 4而不含其它硅酸锂的复合材料；然后将上述复合材料置于苯丙氨酸与乙醇(质量比为复合材料：苯丙氨酸：乙醇＝1:0.02:0.05)形成的溶液中浸渍2h，过滤后烘干即为所述硅氧复合负极材料。
本实施例提供的硅氧复合负极材料包括Li 4SiO 4和含硅材料，含硅材料分散在Li 4SiO 4中，含硅材料由纳米硅和硅氧化物(SiOx，x＝0.98)组成，纳米硅以聚集体形式分散在硅氧化物内部，纳米硅的晶粒尺寸(平均粒径)为3nm；Li 4SiO 4的晶粒尺寸(平均粒径)为20nm。硅氧复合负极材料的表面包覆有碳层，碳层的表面还包含苯丙氨酸疏水层。碳层的厚度为2000nm，疏水层的厚度为100nm，Li 4SiO 4和含硅材料的质量比为1:0.6。
图7为本实施例提供的硅氧复合负极材料的SEM照片，由该图可以看出所述复合材料颗粒同样分布均匀，无残余的锂源，同时未发现除颗粒以外的其他物质。
实施例4
本实施例按照如下方法制备硅氧复合负极材料：
(1)取1kg Si粉，2kg SiO 2粉，投入VC混合机内混合30min后得到SiO 2和Si的混合物；将该混合物投入真空炉内；在真空度为5Pa的负压条件下加热到1300℃并保温18h，在炉内生成SiO蒸汽经过迅速凝结(凝结的温度为950℃)生成SiO y块体；将SiO y块体经过破碎、球磨、分级等工艺将其中值粒径控制在6μm，得到一氧化硅粉体材料；
(2)将1kg一氧化硅粉体材料置于回转炉中，通入保护性气体氩气，升温至800℃，通入有机碳源气体苯，保温7h后冷却，得含有碳层的一氧化硅颗粒；
(3)取含有碳层一氧化硅和氢化锂(含有碳层的一氧化硅与氢化锂的摩尔比为1:2)，放入卧式球磨罐中，球磨1.5h，球磨机转数为800rpm，取出装入石墨坩埚中，放入箱式炉中在氩气气氛下500℃焙烧2.5h，冷却至室温得只含Li 4SiO 4而不含其它硅酸锂的复合材料；然后将上述复合材料置于月桂酸与水(质量比为复合材料：月桂酸：水＝1:0.05:0.06)形成的溶液中浸渍4h，过滤后烘干即为所述硅氧复合负极材料。
本实施例提供的硅氧复合负极材料包括Li 4SiO 4和含硅材料，含硅材料分散在Li 4SiO 4中，含硅材料由纳米硅和硅氧化物(SiO x，x＝0.6)组成，纳米硅以聚集体形式分散在硅氧化物内部，纳米硅的晶粒尺寸(平均粒径)为7nm；Li 4SiO 4的晶粒尺寸(平均粒径)为210nm。硅氧复合负极材料的表面包覆有碳层，碳层的表面还包含月桂酸疏水层。碳层的厚度为1300nm，疏水层的厚度为300nm，Li 4SiO 4和含硅材料的质量 比为1:0.9。
实施例5
本实施例提供的制备硅氧复合负极材料的方法除了不进行步骤(2)的操作，即不进行碳层包覆之外，其他操作均与实施例1相同。
本实施例提供的硅氧复合负极材料相比于实施例1的产品不含碳层。
实施例6
本实施例提供的制备硅氧复合负极材料的方法除了不进行步骤(3)的浸渍操作之外，其他操作均与实施例1相同。
本实施例提供的硅氧复合负极材料相比于实施例1的产品不含疏水层。
实施例7
本实施例提供的制备硅氧复合负极材料的方法除了不进行步骤(2)的操作并且不进行步骤(3)的浸渍操作之外，其他操作均与实施例1相同。
本实施例提供的硅氧复合负极材料相比于实施例1的产品不含碳层和疏水层。
实施例8
(1)取1kg Si粉，2kg SiO 2粉，投入VC混合机内混合30min后得到SiO2和Si的混合物；将该混合物投入真空炉内；在真空度为5Pa的负压条件下加热到1300℃并保温18h，在炉内生成SiO蒸汽经过迅速凝结(凝结的温度为950℃)生成SiOy块体；将SiOy块体经过破碎、球磨、分级等工艺将其中值粒径控制在6μm，得到一氧化硅粉体材料；
(2)将1kg一氧化硅粉体材料置于回转炉中，通入保护性气体N2，升温至1000℃，通入有机碳源气体丙酮，保温4h后冷却，得含有碳层的一氧化硅颗粒；
(3)取含有碳层一氧化硅2kg，氢化锂250g、(含有碳层的一氧化硅与氢化锂的摩尔比为1:1.2)、氧化镁80g放入卧式球磨罐中，球磨2h，球磨机转数为500rpm，取出装入石墨坩埚中，放入箱式炉中在氩气气氛下600℃焙烧2h，冷却至室温得只含Li4SiO4而不含其它硅酸锂的复合材料；然后将上述复合材料置于月桂酸与乙醚(质量比为复合材料：月桂酸：乙醚＝1:0.005:0.005)形成的溶液中浸渍5h，过滤后烘干即为所述硅氧复合负极材料。
本实施例提供的硅氧复合负极材料包括Li4SiO4和含硅材料，含硅材料分散在Li4SiO4中，含硅材料由纳米硅和硅氧化物(SiOx，x＝0.65)、MgSiO3组成，纳米硅以聚集体形式分散在硅氧化物内部，所述纳米硅的晶粒尺寸(平均粒径)为8.8nm；Li 4SiO 4的晶粒尺寸(平均粒径)为500nm。硅氧复合负极材料的表面包覆有碳层，碳层的表面还包含月桂酸疏水层。碳层的厚度为300nm，疏水层的厚度为2nm，Li4SiO 4和含硅材料的质量比为1:1.0。
实施例9
与实施例8相比，将氧化镁改为Al，添加质量为100g，其他操作与新增实施例1相同。
本实施例提供的硅氧复合负极材料包括Li4SiO4和含硅材料，含硅材料分散在Li4SiO4中，含硅材料由纳米硅和硅氧化物(SiOx，x＝0.52)、Al 2(SiO 3)3、Al 4Si 3组成，纳米硅以聚集体形式分散在硅氧化物内部，所述纳米硅的晶粒尺寸(平均粒径)为8.8nm；Li 4SiO 4的晶粒尺寸(平均粒径)为500nm。硅氧复合负极材料的表面包覆有碳层，碳层的表面还包含月桂酸疏水层。碳层的厚度为300nm，疏水层的厚度为 2nm，Li 4SiO 4和含硅材料的质量比为1:1.0。
对比例1
本对比例除了步骤(3)中氢化锂使用量为120g(含有碳层的一氧化硅与氢化锂的摩尔比为1:0.4)之外，其他操作均与实施例1相同。
本对比例制备的负极材料中没有Li 4SiO 4，其中的硅酸锂为Li 2SiO 3。
本对比例制备的硅氧复合负极材料的性能测试结果见表1。
性能测试：
采用以下方法对各实施例和对比例制备的硅氧复合负极材料进行测试
1、采用日立公司S4800扫描电子显微镜观察样品的表面形貌、颗粒大小等。
2、采用德国布鲁型号为D2 PHASER的X射线衍射仪对样品进行X射线衍测定。
3、扣电首次充放电性能测试：
I、锂离子模拟电池的制备
如图12所示，将实施例和对比例制备的硅氧复合负极材料作为活性物质；将SBR(丁苯橡胶)+CMC(羧甲基纤维素)以质量比1:1混合加入水中溶解形成均匀溶液，控制质量百分比为1.2％，作为粘结剂；将导电炭黑作为导电剂；其中将活性物质、导电剂、粘结剂按照质量比85:15:10混合，将混合料涂覆在铜箔负极集流体上，控制浆料的总固体含量为50％，最后经过烘干碾压制得负极极片，负极极片上层形成负极活性材料层。以金属锂片(直径10cm，厚度1.2cm，江西赣峰锂业)作为对电极(即正极)，PP(聚丙烯)(隔膜厚度16um，上海恩捷)作为隔膜，LiPF6/EC+DEC+DMC(EC、DEC和DMC的体积比为1:1:1)作为电解液，同时利用外壳在充氩气的手套箱(布劳恩手套箱)中装配模拟电池。
II、首次充放电性能测试
首次可逆比容量(mAh/g)：由以下蓝电5V/10mA型电池测试仪测定得出数据；
首次库伦效率(％)公式参照：《硅炭》GB/T 38823-2020中D6.1中的公式D.3。其中，由以下测试方法和仪器测定。
测试方法为：采用蓝电5V/10mA型电池测试仪(CT2001A，武汉金诺电子有限公司LAND电池测试系统)测试扣式电池的电化学性能，充电电压为1.5V，放电至0.01V，充放电速率为0.1C，测定以0.1C倍率电流充放电时首次充电比容量(mAh/g)以及以0.1C倍率电流充放电时首次放电比容量(mAh/g)。
4、循环测试
I、锂离子扣式电池的制备
将实施例和对比例制备的硅氧复合负极材料与石墨按质量比1:9混合均匀后作为活性物质；同样将SBR(丁苯橡胶)+CMC(羧甲基纤维素)以质量比1:1混合，加入水中溶解形成均匀溶液，控制质量百分比为1.2％，作为粘结剂；将导电炭黑作为导电剂；其中将活性物质、导电剂、粘结剂按照质量比92:4:4混合，将混合浆料涂覆在铜箔负极集流体上，控制浆料的总固体含量为50％，最后经过烘干碾压制得负极片，负极极片上层即为负极活性材料层。以金属锂片(直径10cm，厚度1.2cm，江西赣峰锂业)作为对电极，PP/PE(隔膜厚度16um，上海恩捷)作为隔膜，LiPF 6/EC+DEC+DMC(EC、DEC和DMC的体积比为1:1:1)作为电解液，在充氩气的手套箱(布劳恩手套箱)中组装扣式电池。
II、扣电首次充放电性能测试
50周扣电循环效率(％)：
50周循环保持率(％)＝第50周的放电比容量/第1周的放电比容量×100％   (公式1)；
采用蓝电5V/10mA型电池测试仪(CT2001A，武汉金诺电子有限公司LAND电池测试系统)，仪器设置参数为：充电电压为1.5V，放电至0.01V，充放电速率为0.1C，测定电池循环第1周和第50周的放电比容量，从而计算得出电化学性能。。实施例1-7及对比例1的硅氧复合负极材料的测试数据如表1所示。
表1
Figure PCTCN2021102416-appb-000001
图1为实施例1提供的硅氧复合负极材料的首次充放电曲线，由该图可以看出所述复合材料的充电比容量1700mAh/g以上，可逆比容量达1450mAh/g以上。图3为实施例1硅基复合材料的XRD图像，图像中仅有Si和Li 4SiO 4的峰，其中Li 4SiO 4的出峰位置为23-26°、36-38°，需要说明的是实施例2-9中，XRD图像，图像中仅有Si和Li4SiO4的峰，且均能获得Li 4SiO 4相同的出峰位置。图4为实施例2提供的硅氧复合负极材料的首次充放电曲线，由该图可以看出所述复合材料的充电比容量1766mAh/g以上，可逆比容量达1540mAh/g以上。图6为实施例3提供的硅氧复合负极材料的首次充放电曲线，由该图可以看出所述复合材料的充电比容量1680mAh/g以上，可逆比容量达1450mAh/g以上。
综合上述实施例和对比例可知，实施例1-4制备的硅氧复合负极材料中仅含有Li 4SiO 4这一种硅酸锂而不含其它种类的硅酸锂，这使得本公开提供的硅氧复合负极材料具有加工性能稳定、比容量高、首次效率高、循环寿命长的优点。
实施例1和实施例5相比，含有碳层，使得实施例1与实施例5相比，提高了材料的导电性，降低了颗粒间的电子传导阻力，从而提高了库伦效率。
实施例1和实施例6相比，含有疏水层，使得实施例1和实施例6相比，提高了材料的加工性能，降低了水系浆料中产气的概率。
实施例7不含碳层和疏水层，使得其相比实施例1，材料的导电性和加工性能均差。
对比例1因为添加锂源量较少，不足以生成Li 4SiO 4，导致其制备的负极材料中没有Li 4SiO 4，该对比例的产品中硅酸锂为Li 2SiO 3，这明显降低了对比例1产品的首次可逆容量。
申请人声明，本公开通过上述实施例来说明本公开的详细工艺设备和工艺流程，但本公开并不局限于上述详细工艺设备和工艺流程，即不意味着本公开必须依赖上述详细工艺设备和工艺流程才能实施。所属技术领域的技术人员应该明了，对本公开的任何改进，对本公开产品各原料的等效替换及辅助成分的添加、具体方式的选择等，均落在本公开的保护范围和公开范围之内。
工业实用性
本公开提供了硅氧复合负极材料及其制备方法和锂离子电池。本公开提供的硅氧复合负极材料中仅含有Li 4SiO 4这一种硅酸锂，这使得本公开提供的硅氧复合负极材料容量较高、首次库伦效率较高，循环性能较好。

Claims (14)

  1. 一种硅氧复合负极材料，所述硅氧复合负极材料包括复合粒子(100)，所述复合粒子(100)包括硅酸锂(120)和含硅材料(140)，所述硅酸锂(120)为Li 4SiO 4，所述含硅材料分散在所述硅酸锂(120)中，所述含硅材料(140)包括单质硅、硅氧化物(144)、、硅合金、金属硅化物及硅酸盐中的至少一种。
  2. 根据权利要求1所述的硅氧复合负极材料，其中，所述硅氧复合负极材料包括以下特征(1)～(5)中的至少一个：
    (1)所述硅酸锂(120)的晶粒尺寸在60nm以下；
    (2)所述硅氧复合负极材料还包括形成于所述复合粒子(100)表面的碳层(160)；
    (3)所述碳层(160)的厚度为300nm-2000nm；
    (4)所述硅氧复合负极材料还包括形成于所述碳层(160)的表面的疏水层(180)；
    (5)所述疏水层(180)的厚度为2nm-500nm。
  3. 根据权利要求2所述的硅氧复合负极材料，其中，所述疏水层(180)的材料包括饱和脂肪酸及氨基酸中的至少一种；及/或
    所述疏水层(180)的材料包括月桂酸、硬脂酸、亮氨酸、甲硫氨酸及苯丙氨酸中的至少一种。
  4. 根据权利要求1-3任一所述的硅氧复合负极材料，其中，所述硅氧复合负极材料包括以下特征(1)～(7)中的至少一个：
    (1)所述含硅材料(140)包括纳米硅和硅氧化物(144)，所述纳米硅以纳米硅聚集体形式分散在硅氧化物(144)内部；
    (2)所述纳米硅是以纳米硅聚集体的形式分散在硅氧化物内部，所述纳米硅聚集体包括多个纳米硅晶粒(142)；
    (3)所述纳米硅晶粒(142)尺寸在0nm～10nm，且不包括0nm；
    (4)所述硅氧化物(144)的化学式为SiO x，其中0＜x＜1.2；
    (5)所述硅酸锂(120)和含硅材料(140)的质量比为0.05-1.1；
    (6)所述硅合金包括硅锂合金、硅钠合金、硅镁合金及硅铝合金中的至少一种；
    (7)所述单质硅包括纳米硅、非晶硅及结晶硅中的至少一种。
  5. 一种如权利要求1-4任一项所述的硅氧复合负极材料的制备方法，其中，所述方法包括以下步骤：
    将含有硅源与含锂化合物的混合物，在保护性气体气氛及温度为300℃-600℃下焙烧，得到所述硅氧复合负极材料，其中所述硅源的通式为SiO y，所述硅源与含锂化合物的摩尔比为1:1.2-1:3。
  6. 根据权利要求5所述的硅氧复合负极材料的制备方法，其中，所述制备方法包括以下特征(1)～(8)中的至少一个：
    (1)0＜y＜2；
    (2)所述硅源为一氧化硅；
    (3)所述含锂化合物为还原性含锂化合物；
    (4)所述还原性含锂化合物包括氢化锂、烷基锂、金属锂、氢化铝锂、氨基锂及硼氢化锂中的至少一种；
    (5)所述混合物还包括金属单质及金属氧化物中的至少一种；
    (6)所述混合物包括VC混合机、融合或搅拌中的至少一种方法混合得到；
    (7)所述保护性气体包括氢气、氮气、氦气、氖气、氩气、氪气及氙气中至少一种；
    (8)所述焙烧的时间为2h-8h。
  7. 根据权利要求5-6任一所述的制备方法，其中，所述硅源的制备方法包括：在真空条件或保护性气体气氛下对能产生硅氧化物气体的原料进行加热，产生硅氧化物气体后冷却、整形得到硅源。
  8. 根据权利要求7所述的制备方法，其中，所述制备方法包括以下特征(1)～(5)中的至少一个：
    (1)所述能产生硅氧化物气体的原料包括Si和SiO 2的混合物；
    (2)所述能产生硅氧化物气体的原料包括下述混合中的至少一种：Si和O 2的混合物，或者SiO 2和碳的混合物，或者硅、含有硅的氧化物SiO m中的至少两种混合物，其中1≤m≤6；
    (3)所述整形包括破碎、球磨或分级中的任意一种或至少两种的组合；
    (4)所述加热的温度为900℃-1500℃；
    (5)所述保护性气体包括氢气、氮气、氦气、氖气、氩气、氪气及氙气中至少一种。
  9. 根据权利要求5-8任一项所述的制备方法，其中，所述硅源的表面包覆有碳层(160)；及/或
    在所述硅源的表面包覆碳层(160)的方法包括：在保护性气体气氛下，将所述硅源与有机碳源气体进行反应，得到包覆有碳层(160)的硅源。
  10. 根据权利要求9所述的制备方法，所述制备方法包括以下特征(1)～(5)中的至少一个：
    (1)所述保护性气体包括氢气、氮气、氦气、氖气、氩气、氪气及氙气中至少一种；
    (2)所述有机碳源气体为烃类；
    (3)所述烃类包括甲烷、乙烯、乙炔、丙酮及苯中的至少一种；
    (4)所述进行反应的反应温度为600℃-1000℃；
    (5)所述进行反应的反应时间为0.5h-10.0h。
  11. 根据权利要求5-10任一项所述的制备方法，其中，所述制备方法还包括步骤：将所述硅氧复合负极材料在疏水性溶液中进行浸渍；及/或
    所述疏水性溶液的溶质包括月桂酸、硬脂酸、亮氨酸、甲硫氨酸或苯丙氨酸中的至少一种；所述疏水性溶液的溶剂包括水、甲醇、乙醇、乙醚、苯或甲酸中的至少一种；及/或
    所述浸渍的时间为2-6h。
  12. 根据权利要求5-11任一项所述的制备方法，其中，所述方法包括以下步骤：
    在真空条件或保护性气体气氛下对Si和SiO 2的混合物进行900-1500℃加热，产生硅氧化物气体后冷却、整形得到一氧化硅；
    在保护性气体氛围下，将所述一氧化硅升温至600-1000℃，通入有机碳源气体，保温0.5-10.0h后冷却，得到包覆有碳层(160)的一氧化硅；
    将所述包覆有碳层(160)的一氧化硅与含锂化合物以摩尔比1:1.2-1:3进行混合，在保护性气体气氛下300-600℃焙烧2-8h，冷却至室温，将焙烧产物置于疏水性溶液中浸渍2-6h，得到所述硅氧复合负极材料。
  13. 一种负极，所述负极包括：如权利要求1-4任一所述的硅氧复合负极材料。
  14. 一种锂离子电池，所述锂离子电池包含如权利要求1-4任一项所述的硅氧复合负极材料。
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