WO2021083199A1 - 负极材料及其制备方法和锂离子电池 - Google Patents

负极材料及其制备方法和锂离子电池 Download PDF

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WO2021083199A1
WO2021083199A1 PCT/CN2020/124347 CN2020124347W WO2021083199A1 WO 2021083199 A1 WO2021083199 A1 WO 2021083199A1 CN 2020124347 W CN2020124347 W CN 2020124347W WO 2021083199 A1 WO2021083199 A1 WO 2021083199A1
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negative electrode
sio
electrode material
carbon
lithium
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PCT/CN2020/124347
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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
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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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Priority to EP20882730.3A priority Critical patent/EP3972014A4/en
Priority to KR1020217039398A priority patent/KR20220002639A/ko
Priority to US17/623,170 priority patent/US20220259053A1/en
Publication of WO2021083199A1 publication Critical patent/WO2021083199A1/zh

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    • H—ELECTRICITY
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    • 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
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    • C01B33/00—Silicon; Compounds thereof
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    • 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
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    • H01M4/0402—Methods of deposition of the material
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    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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    • 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

  • This application belongs to the technical field of battery materials, and relates to a negative electrode material and a preparation method thereof, and a lithium ion battery.
  • Lithium-ion batteries have been widely used in portable electronic products and electric vehicles because of their high working voltage, long cycle life, no memory effect, low 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 lithium-ion batteries in the future.
  • the theoretical capacity of the existing Si is as high as 4200mAh/g, its expansion reaches 300%, which affects the cycle performance and leads to restrictions on market promotion and application.
  • the corresponding silicon-oxygen material has better cycle performance but low efficiency for the first time.
  • an effective way to improve the first effect of silicon-oxygen materials is to dope it with lithium in advance so that the irreversible lithium-consuming phase in the silicon-oxygen materials can be reacted in advance.
  • the current industrialized method is to directly coat the surface of the pole piece with a lithium layer to achieve the effect of reducing the lithium consumption of the positive electrode.
  • this method has high requirements on the operating environment and has a large potential safety hazard, so it is difficult to realize industrialization.
  • the problem of poor processing performance generally exists by pre-lithium pre-lithium on the material side, mainly due to the serious gas production of water-based slurry, low viscosity, tailing during coating, and the appearance of pole pieces after drying.
  • a lithium ion battery, a nano-silicon material and a preparation method thereof include the steps of: mixing silicon dioxide, magnesium metal, and dopants uniformly according to a specified mass ratio to obtain a mixture; placing the mixture in a high-temperature reaction furnace, and After entering the inert gas, the temperature is raised to the specified temperature at the specified heating rate.
  • the temperature is naturally cooled to room temperature to obtain the reaction product; the reaction product is taken out for preliminary washing, acid washing, water washing, and drying to obtain Coarse-grained silicon:
  • the coarse-grained silicon and the dispersant are uniformly mixed according to a specified mass ratio, and then ground, dried, and sieved for a specified time according to a specified grinding process to obtain nano-silicon.
  • rate performance and cycle performance of this method are acceptable, the first-time efficiency and processing performance need to be improved.
  • Another method for improving the performance of silicon anode materials for lithium-ion batteries includes the following steps: (1) Preparation of anodes of siliceous oxide composite materials: 1) Weigh a certain amount of SiO powder, and pour it into a mass of SiO 10 2 times the deionized water, and then add a certain amount of graphite and glucose; 2) put the mixed solution into a high-energy ball mill for ball milling; 3) put the ball-milled precursor material into a tube furnace; 4) take it out
  • the prepared SiO/C composite material is mixed with the conductive agent acetylene black and the binder PVDF in a certain proportion; (2) the prelithiation treatment on the electrode.
  • the first time efficiency and processing performance of this method cannot meet the market demand.
  • the negative electrode coating of the silicon-based negative electrode sheet provided in the present application includes a first coating layer on the current collector and a second coating layer on the first coating layer, and the active material in the first coating layer includes a silicon-based negative electrode material
  • the active material in the second coating layer does not contain a silicon-based negative electrode material, and the surface of the second coating layer contains lithium.
  • the preparation method includes 1) coating a first slurry containing a silicon-based negative electrode material on a current collector to form a first coating; 2) using a second slurry that does not contain a silicon-based negative electrode material on the first coating Forming a second coating; 3) pre-doping the pole piece containing the second coating with lithium to obtain the silicon-based negative electrode piece.
  • This method has a long process and a cumbersome process, which is difficult to be applied in industry.
  • the purpose of the present application is to provide a negative electrode material with excellent processing performance after pre-lithium, a preparation method thereof, and a lithium ion battery.
  • the present application provides a negative electrode material, the negative electrode material includes SiO x and Li 2 Si 2 O 5 , and the SiO x is dispersed in Li 2 Si 2 O 5 , wherein 0 ⁇ x ⁇ 1.2.
  • the lithium-containing compound in the negative electrode material provided in this application is Li 2 Si 2 O 5. Since Li 2 Si 2 O 5 is insoluble in water, it can fundamentally solve the processing stability problems of pre-lithium materials, such as slurry gas production, Low viscosity, tailing during coating, pinholes, pores, etc. appear after the pole piece is dried. There is no need to perform additional surface treatment on the pre-lithium material, which can avoid the problems of reduced capacity and reduced initial efficiency of lithium batteries due to surface treatment.
  • the negative electrode material satisfies at least one of the following conditions a to d:
  • the pH value of the negative electrode material is 7 ⁇ PH ⁇ 10.7;
  • the average particle size of the negative electrode material is 5 ⁇ m to 50 ⁇ m;
  • the mass ratio of SiO x to Li 2 Si 2 O 5 in the negative electrode material is 1: (0.74 ⁇ 6.6);
  • the SiO x is uniformly dispersed in Li 2 Si 2 O 5 .
  • the negative electrode material satisfies at least one of the following conditions a to c:
  • a carbon coating layer is formed on the surface of the negative electrode material
  • a carbon coating layer is formed on the surface of the negative electrode material, and the thickness of the carbon coating layer is 10 nm to 2000 nm;
  • a carbon coating layer is formed on the surface of the negative electrode material, and the mass fraction of carbon element in the negative electrode material is 4% to 6%.
  • this application provides a method for preparing a negative electrode material, which includes the following steps:
  • the silicon oxide SiOy, the reductive lithium-containing compound and the auxiliary agent are mixed and heat-treated to obtain the negative electrode material, wherein the auxiliary agent includes a nucleation conversion agent or an endothermic agent, 0 ⁇ y ⁇ 2.
  • the preparation method provided in this application can realize that the final pre-lithium product has only Li 2 Si 2 O 5 but no Li 2 SiO 3 by adding a nucleation conversion agent or a heat absorption agent, which fundamentally solves the processing problem of pre-lithium materials. And the preparation process of the pre-lithium material is simplified, that is, no additional surface treatment of the pre-lithium material is required to prevent the occurrence of problems such as gas production. In addition, by adding a nucleation conversion agent or an endothermic agent, the resulting high-temperature crystalline phase Li 2 SiO 3 is directly converted into low-temperature crystalline phase Li 2 Si 2 O 5 , which can avoid the decrease in the capacity of the negative electrode material caused by the surface treatment. The first effect is reduced and other issues.
  • the negative electrode material satisfies at least one of the following conditions a to f:
  • the pH value of the negative electrode material is 7 ⁇ PH ⁇ 10.7;
  • the average particle size of the negative electrode material is 5 ⁇ m to 50 ⁇ m;
  • the mass ratio of SiO x to Li 2 Si 2 O 5 in the negative electrode material is 1: (0.74 to 6.6).
  • a carbon coating layer is formed on the surface of the negative electrode material
  • a carbon coating layer is formed on the surface of the negative electrode material, and the thickness of the carbon coating layer is 10 nm to 2000 nm;
  • a carbon coating layer is formed on the surface of the negative electrode material, and the mass fraction of carbon element in the negative electrode material is 4% to 6%.
  • the method satisfies at least one of the following conditions a to d:
  • the mass ratio of the silicon oxide and the reductive lithium-containing compound is 10: (0.08-1.2);
  • the silicon oxide is silicon monoxide
  • the reducing lithium compound includes at least one of lithium hydride, alkyl lithium, metal lithium, lithium aluminum hydride, lithium amide, and lithium borohydride.
  • the method satisfies at least one of the following conditions a to h:
  • the nucleation conversion agent includes at least one of phosphorus oxide and phosphate
  • the phosphorus oxide includes at least one of phosphorus pentoxide and phosphorus trioxide
  • the phosphate includes at least one of lithium phosphate, magnesium phosphate and sodium phosphate;
  • the nucleation conversion agent is phosphorus pentoxide
  • the melting point of the endothermic agent is less than 700°C;
  • the endothermic agent includes at least one of LiCl, NaCl, NaNO 3 , KNO 3 , KOH, BaCl, KCl, and LiF;
  • the mass ratio of the silicon oxide and the nucleation conversion agent is 100: (2-10);
  • the mass ratio of the silicon oxide and the endothermic agent is 100: (8-30).
  • the method satisfies at least one of the following conditions a to d:
  • the heat treatment is performed in a non-oxidizing atmosphere
  • the heat treatment is performed in a non-oxidizing atmosphere;
  • the non-oxidizing atmosphere includes at least one of hydrogen, nitrogen, helium, neon, argon, krypton, and xenon;
  • the temperature of the heat treatment is 300°C ⁇ 1000°C;
  • the heat treatment time is 1.5h to 2.5h.
  • the method before mixing the silicon oxide SiO y , the reducing lithium-containing compound, and the nucleation conversion agent or endothermic agent, the method further includes:
  • the raw material of silicon oxide is heated and gasified to generate silicon oxide gas, which is condensed and shaped to obtain silicon oxide SiO y , where 0 ⁇ y ⁇ 2.
  • the method satisfies at least one of the following conditions a to g:
  • the raw materials of the silicon oxide include silicon and silicon dioxide;
  • the mass ratio of the silicon to the silicon dioxide is 1:(1.8 ⁇ 2.2);
  • the temperature of the heating and gasification is 1200°C ⁇ 1400°C;
  • the heating and gasification time is 16h-20h;
  • the condensation temperature is 930°C ⁇ 970°C;
  • the heating and gasification are carried out in a protective atmosphere or in a vacuum;
  • the shaping includes at least one of crushing, ball milling and classification.
  • the method further includes:
  • the carbon-coated material is coated with carbon, and the carbon-coated material includes at least one of the silicon oxide and the negative electrode material.
  • the method satisfies at least one of the following conditions a to c:
  • the carbon coating includes at least one of gas-phase carbon-coated and solid-phase carbon-coated;
  • the carbon coating includes at least one of gas-phase carbon-coated carbon and solid-phase carbon-coated carbon, and the conditions for the gas-phase carbon coating are: heating the silicon oxide to 600°C to 1000°C in a protective atmosphere, Pass in organic carbon source gas, keep it warm for 0.5h-10h, and then cool; wherein, the organic carbon source gas includes hydrocarbons, and the hydrocarbons include at least one of methane, ethylene, acetylene, and benzene;
  • the carbon coating includes at least one of gas-phase carbon-coated carbon and solid-phase carbon-coated carbon, and the condition of the solid-phase carbon coating is: the silicon oxide and the carbon source are fused for 0.5h-2h to obtain The carbon mixture is carbonized at 600°C-1000°C for 2h-6h and cooled; wherein the carbon source includes at least one of polymers, sugars, organic acids and pitch.
  • the method includes the following steps:
  • silicon and silicon dioxide are heated and gasified in a vacuum at 1200°C ⁇ 1400°C for 16h ⁇ 20h, then condensed at 930°C ⁇ 970°C, and shaped to obtain silicon monoxide;
  • the carbon-coated silicon monoxide and phosphorus pentoxide are mixed, and then a reducing lithium-containing compound is added to mix, and the mixture is calcined at 450°C ⁇ 800°C in a non-oxidizing atmosphere for 1.5 h-2.5h to obtain a negative electrode material; wherein the mass ratio of the carbon-coated silicon monoxide and the reducing lithium-containing compound is 10: (0.08-1.2).
  • the present application provides a lithium ion battery, the lithium ion battery comprising the composite negative electrode material of the first aspect described above or the composite negative electrode material prepared according to the preparation method of the second aspect described above.
  • the preparation method provided by this application can realize that the final pre-lithium product has only low-temperature crystalline phase Li 2 Si 2 O 5 but no high-temperature crystalline phase Li 2 SiO 3 by adding a nucleation conversion agent or an endothermic agent.
  • the processing problem of the pre-lithium material is fundamentally solved, and the preparation process of the pre-lithium material is simplified, that is, no additional surface treatment of the pre-lithium material is required to prevent the occurrence of problems such as gas production.
  • the high-temperature crystalline phase Li 2 SiO 3 is directly converted into the low-temperature crystalline phase Li 2 Si 2 O 5 , which can avoid the reduction in the capacity of the negative electrode material and the first effect caused by the surface treatment. Decrease and other issues.
  • the negative electrode material provided by this application has the advantages of stable processing performance, high first-time efficiency, and long cycle life.
  • Fig. 1 is a process flow diagram of a method for preparing a negative electrode material provided by this application
  • 3b is a photo of the coating test of the negative electrode material prepared in Example 2 of the application.
  • Figure 4 is an XRD pattern of the negative electrode material prepared in Comparative Example 2;
  • Figure 5a is a gas production test photo of the negative electrode material prepared in Comparative Example 2;
  • FIG. 5b is a photo of the coating test of the negative electrode material prepared in Comparative Example 2.
  • an embodiment of the present application provides a negative electrode material.
  • the negative electrode material includes SiO x and Li 2 Si 2 O 5 , and the SiO x is dispersed in Li 2 Si 2 O 5 , where 0 ⁇ x ⁇ 1.2 .
  • the negative electrode material provided in this application only contains Li 2 Si 2 O 5, which is a lithium silicate phase. Since Li 2 Si 2 O 5 is insoluble in water, it can fundamentally solve the processing stability of the negative electrode material after pre-lithiation treatment. Sexual problems, such as slurry gas production, low viscosity, tailing during coating, pinholes, pores, etc. appear after the pole piece is dried. There is no need to perform additional surface treatment on the pre-lithium material, which can avoid the problems of reduced capacity and reduced initial efficiency of lithium batteries due to surface treatment.
  • the SiO x is uniformly dispersed in Li 2 Si 2 O 5 , for example, watermelon seeds (SiO x ) are dispersed in watermelon sacs (Li 2 Si 2 O 5 ).
  • SiO x in the SiO x , 0 ⁇ x ⁇ 1.2, and SiO x may be, for example, Si, SiO 0.2 , SiO 0.4 , SiO 0.6 , SiO 0.8 , SiO, or SiO 1.2 .
  • SiO x is SiO.
  • the composition of SiOx is relatively complicated, and can be understood as being formed by uniformly dispersing nano-silicon in SiO 2 .
  • the average particle size of the negative electrode material is 5 ⁇ m-50 ⁇ m; more specifically, it can be 5 ⁇ m, 10 ⁇ m, 15 ⁇ m, 20 ⁇ m, 25 ⁇ m, 30 ⁇ m, 35 ⁇ m, 40 ⁇ m, or 50 ⁇ m, but not limited to For the listed values, other unlisted values within the range of values are also applicable.
  • the average particle size of the silicon composite anode material is controlled within the above range, which is beneficial to the improvement of the cycle performance of the anode material.
  • the mass ratio of SiO x and Li 2 Si 2 O 5 in the negative electrode material is 1: (0.74 to 6.6); more specifically, it may be 1: 0.74, 1: 1.4, 1:1.6, 1:2.0, 1:2.3, 1:2.9, 1:3.5, 1:4, 1:5.0, 1:6.1 or 1:6.6, etc., but not limited to the numerical values listed, within the numerical range Other unlisted values also apply.
  • the mass ratio of SiO x and Li 2 Si 2 O 5 is too low, the content of Li 2 Si 2 O 5 in the material is too low, the slurry made of the negative electrode material is easy to generate gas, and pinholes and pinholes are likely to appear after the pole pieces are dried.
  • Air bubbles are not conducive to improving the processing performance of the negative electrode material; when the mass ratio of SiO x and Li 2 Si 2 O 5 is too high, the content of Li 2 Si 2 O 5 in the material is too high, and the lithium ion transmission efficiency is reduced, which is not conducive to the material Large rate charge and discharge.
  • the negative electrode material only contains Li 2 Si 2 O 5 .
  • the pH value of the negative electrode material is 7 ⁇ PH ⁇ 10.7.
  • the pH value may be 7.1, 8.0, 9.3, 9.8, 9.9, 10.0, 10.1, 10.2, 10.3, 10.4, 10.5 or 10.6, etc.
  • the material can be kept at a low alkalinity, the water system processing performance of the material can be improved, and the first effect of the negative electrode material can be improved.
  • the surface of the negative electrode material is coated with a carbon layer.
  • the thickness of the carbon layer is 10 nm to 2000 nm; more specifically, it can be 10 nm, 50 nm, 100 nm, 300 nm, 500 nm, 800 nm, 1000 nm, 1500 nm, 1800 nm or 2000 nm, but is not limited to the listed values, Other unlisted values within this value range also apply.
  • the carbon layer is too thick, the lithium ion transmission efficiency is reduced, which is not conducive to the large-rate charging and discharging of the material, and the overall performance of the negative electrode material is reduced.
  • the carbon layer is too thin, which is not conducive to increasing the conductivity of the negative electrode material and has a weak suppression performance on the volume expansion of the material. Lead to long cycle performance price difference.
  • the mass fraction of carbon element in the negative electrode material is 4% to 6%, more specifically, it can be 4%, 4.5%, 5%, 5.5 % Or 6%, etc., but are not limited to the listed values, and other unlisted values within the numerical range are also applicable.
  • the present application provides a method for preparing the negative electrode material, as shown in FIG. 1, including the following steps:
  • auxiliary agent includes a nucleation conversion agent or an endothermic agent, 0 ⁇ y ⁇ 2.
  • the preparation method provided in this application uses a nucleation conversion agent or an endothermic agent to cause the silicon oxide to react with the reductive lithium-containing compound (that is, to perform pre-lithiation), which can realize the production of only Li 2 Si 2 O 5
  • This kind of lithium silicate phase because Li 2 Si 2 O 5 is insoluble in water, it solves the processing stability problems of pre-lithium materials, such as slurry gas production, low viscosity, tailing during coating, and pinholes after drying of pole pieces , Stomata, etc.
  • the nucleation conversion agent can be used to accelerate the crystallization rate, increase the crystal density and promote the refinement of the crystal grain size.
  • silicon oxide SiO y and reductive lithium-containing compounds can generate Li 2 SiO 3 and Li 2 Si 2 O 5.
  • the added nucleation conversion agent can accelerate the crystallization rate and promote the formation of high-temperature crystal phase Li 2 SiO 3 is transformed into Li 2 Si 2 O 5 of low-temperature crystalline phase, thereby avoiding the problems of reduced capacity and reduced first effect caused by surface treatment.
  • the endothermic agent can be used to lower the reaction temperature.
  • silicon oxide SiO y and reductive lithium-containing compounds can produce Li 2 SiO 3 and Li 2 Si 2 O 5.
  • the added endothermic can lower the reaction temperature.
  • the silicon oxide SiO y wherein 0 ⁇ y ⁇ 2, for example, SiO y is SiO 0.2 , SiO 0.5 , SiO 0.8 , SiO, SiO 1.2 , SiO 1.5 or SiO 1.9, etc. .
  • the silicon oxide is SiO.
  • silicon monoxide is used as the silicon oxide, it can effectively solve the problem of unstable processing performance after the first effect is improved by doping lithium with silicon monoxide.
  • the silicon oxide particles have a particle size D10>1.0 ⁇ m and Dmax ⁇ 50 ⁇ m.
  • D10 is 1.0 ⁇ m, 1.5 ⁇ m, 2.0 ⁇ m, 2.5 ⁇ m, 3.0 ⁇ m, 4.0 ⁇ m, or 5.0 ⁇ m, etc.
  • Dmax is 49 ⁇ m, 45 ⁇ m, 30 ⁇ m, 35 ⁇ m, or 20 ⁇ m.
  • Dmax refers to the particle size of the largest particle.
  • the reducing lithium-containing compound includes at least one of lithium hydride, alkyl lithium, metal lithium, lithium aluminum hydride, lithium amide, and lithium borohydride.
  • the nucleation conversion agent includes at least one of phosphorus oxide and phosphate.
  • the phosphorus oxide includes at least one of phosphorus pentoxide and phosphorus trioxide.
  • the phosphate includes at least one of lithium phosphate, magnesium phosphate and sodium phosphate.
  • the nucleation conversion agent is phosphorus pentoxide.
  • the advantage of using phosphorus pentoxide is that the effect of converting Li 2 SiO 3 into Li 2 Si 2 O 5 is more obvious, and the nucleation conversion can be reduced.
  • the dosage of the agent can reduce the production cost on the one hand, and reduce the difficulty of production on the other hand.
  • the melting point of the endothermic agent is less than 700° C.; the endothermic agent includes at least one of LiCl, NaCl, NaNO3, KNO3, KOH, BaCl, KCl, and LiF.
  • the endothermic agent is KNO 3 .
  • KNO 3 is particularly preferred as the endothermic. Its advantages are: first, the use temperature of KNO 3 is low, and the promotion effect on the formation of Li 2 Si 2 O 5 is more obvious; second, the cost of KNO 3 is low, The raw materials are easily available, non-toxic and harmless, and environmentally friendly.
  • the mass ratio of the silicon oxide and the reductive lithium-containing compound is 10:(0.08 ⁇ 1.2), for example, 10:0.08, 10:0.2, 10:0.5, 10:0.8 or 10 : 1.2 etc., but not limited to the listed values, other unlisted values within this range of values also apply. Controlling within the above-mentioned mass ratio range is beneficial to increase the conversion rate of Li 2 SiO 3 into Li 2 Si 2 O 5.
  • the mass ratio of the silicon oxide to the nucleation conversion agent is 100: (2-10), for example, 100: 2, 100: 2.5 or 100: 3, 100: 5, 100: 7, 100:10, etc., but not limited to the listed values, other unlisted values within this range of values are also applicable. Understandably, when the amount of the nucleation conversion agent is too large, it will cause the Li 2 Si 2 O 5 crystal grains to be too large, which will affect the cycle performance; if the amount of the nucleation conversion agent is too small, it will result in residual Li 2 SiO 3 , which will affect the cycle performance.
  • the processing stability of the water-based slurry of the material is 100: 2, 100: 2.5 or 100: 3, 100: 5, 100: 7, 100:10, etc., but not limited to the listed values, other unlisted values within this range of values are also applicable. Understandably, when the amount of the nucleation conversion agent is too large, it will cause the Li 2 Si 2 O 5 crystal grains to be too large, which will affect the cycle performance; if the amount of the nucleation conversion
  • the mass ratio of the silicon oxide and the endothermic agent is 100: (8-30), for example, 100: 8, 100: 10, 100: 15, 100: 20, 100: 25 Or 100:30, etc., but not limited to the listed values, and other unlisted values within this range of values are also applicable.
  • the specific steps of mixing silicon oxide, reductive lithium-containing compound and nucleation conversion agent include: after mixing silicon oxide and nucleation conversion agent, adding the reductive conversion agent Lithium compound.
  • the nucleation conversion agent adheres to the surface of the silicon oxide, and when the reducing lithium-containing compound reacts with the silicon oxide, it adheres to the surface of the silicon oxide
  • the nucleation conversion agent can convert part of the high-temperature crystal phase Li 2 SiO 3 generated by the reaction into low-temperature crystal phase Li 2 Si 2 O 5 in time , that is, as the reaction proceeds, the phase change of lithium silicate is also at the same time In progress, the nucleation conversion agent promotes the shift of the crystallization of lithium silicate to the low-temperature crystal phase of Li 2 Si 2 O 5 and transforms the crystal phase structure of lithium silicate.
  • the heat treatment is performed in a non-oxidizing atmosphere
  • the non-oxidizing atmosphere includes at least one of hydrogen, nitrogen, helium, neon, argon, krypton, or xenon.
  • the heat treatment may be performed in a firing furnace, so that the heat treatment is fully performed.
  • the temperature of the heat treatment is 300°C to 1000°C, such as 300°C, 400°C, 450°C, 480°C, 500°C, 600°C, 700°C, 800°C, 900°C or 1000°C, etc., but not It is not limited to the listed values, and other unlisted values within this range of values are also applicable. Understandably, when the heat treatment temperature is too high, the reaction will be violent, the silicon crystal grains will grow up sharply, silicon monoxide will be disproportionated, performance degradation, and the cycle performance of the material will be affected; when the heat treatment temperature is too low, the reaction will be difficult to proceed, resulting in Li 2 Si 2 O 5 cannot be formed.
  • the temperature of the heat treatment is 450°C to 800°C.
  • the heat treatment time is 1.5h to 2.5h, such as 1.5h, 1.7h, 2h, 2.3h or 2.5h, etc., but it is not limited to the listed values, and other unlisted values within this range are the same Be applicable. Understandably, sufficient firing can fully convert Li 2 SiO 3 into Li 2 Si 2 O 5 .
  • step S100 the method further includes:
  • the raw material of silicon oxide is heated and gasified to generate silicon oxide gas, which is condensed and shaped to obtain silicon oxide SiO y , where 0 ⁇ y ⁇ 2.
  • the raw material of the silicon oxide includes Si and SiO 2 .
  • the specific ratio of Si and SiO 2 can be adjusted according to the required y value of SiO y , which is not limited here.
  • the mass ratio of silicon to silicon dioxide is 1:(1.8-2.2), for example, 1:1.8, 1:1.9, 1:2.0, 1:2.1 or 1:2.2, etc., however, it is not limited to the listed values, and other unlisted values within this range of values are also applicable.
  • the heating temperature is 1200°C to 1400°C, such as 1200°C, 1250°C, 1300°C, 1350°C or 1400°C, etc., but is not limited to the listed values, and other unlisted values within this range of values are equally applicable.
  • the heating and gasification time is 16h-20h, such as 16h, 17h, 18h, 19h or 20h, etc., but it is not limited to the listed values, and other unlisted values within this range of values are also applicable.
  • the condensation temperature is 930°C to 970°C, such as 930°C, 940°C, 950°C, 960°C or 970°C, etc., but is not limited to the listed values, and other unlisted values within the range of values The values also apply.
  • the shaping includes at least one of crushing, ball milling or classification.
  • the silicon oxide SiO y particles have D10>1.0 ⁇ m and Dmax ⁇ 50 ⁇ m, for example, D10 is 1.1 ⁇ m, 1.5 ⁇ m, 2.0 ⁇ m, 2.5 ⁇ m, 3.0 ⁇ m, 4.0 ⁇ m or 5.0 ⁇ m, etc. , Dmax is 49 ⁇ m, 45 ⁇ m, 30 ⁇ m, 35 ⁇ m or 20 ⁇ m, etc. It should be noted that Dmax refers to the particle size of the largest particle.
  • the heating gasification is performed in a protective atmosphere or a vacuum.
  • the protective atmosphere can be selected according to the prior art, such as a nitrogen atmosphere and/or an argon atmosphere.
  • the vacuum degree of the vacuum can be selected according to the prior art, for example, 5 Pa.
  • the method further includes:
  • Carbon coating is performed on a carbon-coated material, the carbon-coated material includes at least one of the silicon oxide and the negative electrode material; the carbon coating includes at least one of gas-phase carbon-coated and solid-phase carbon-coatedkind.
  • the silicon oxide when using vapor-phase carbon coating, is heated to 600°C to 1000°C in a protective atmosphere, such as 600°C, 700°C, 800°C, 900°C, or 1000°C, etc. , Pass the organic carbon source gas, keep it for 0.5h-10h and then cool it down, for example keep it for 0.5h, 1h, 2h, 5h, 8h or 10h.
  • a protective atmosphere such as 600°C, 700°C, 800°C, 900°C, or 1000°C, etc.
  • the protective atmosphere can be selected according to the prior art, such as a nitrogen atmosphere and/or an argon atmosphere.
  • the organic carbon source gas includes hydrocarbons.
  • the hydrocarbons include at least one of methane, ethylene, acetylene, and benzene.
  • the resulting carbon mixture is carbonized at 600° C. to 1000° C. for 2 h to 6 hours, and cooled.
  • the fusion time is more than 0.5h, such as 0.5h, 0.6h, 0.7h, 0.8h, 1h, 1.5h or 2h, etc.
  • the carbonization temperature can be 600°C, 700°C, 800°C, 900°C or 1000°C, etc., carbonization
  • the time can be, for example, 2h, 3h, 4h, 5h, or 6h.
  • the silicon oxide is first coated with carbon and then subjected to the lithiation reaction, which can effectively reduce the preparation process and reduce the cost; and a carbon layer is formed on the surface of the silicon oxide, the carbon layer is relatively loose, and there are a large number of micropores.
  • the subsequent reducing lithium-containing compounds can pass through the micropores of the carbon layer, penetrate the carbon layer and react on the surface of the silicon oxide, which can appropriately suppress the severity of the reaction, so that a uniform Li 2 Si is formed on the surface of the silicon oxide. 2 O 5 layers to improve the electrochemical performance of the material.
  • the fusion is performed in a fusion machine, and the speed of the fusion machine is 500-3000r/min, such as 500r/min, 1000r/min, 1500r/min, 2000r/min, 2500r/min, or 3000r/min, etc. .
  • the cutter gap width of the fusion machine can be selected according to the prior art, for example, 0.5 cm.
  • the carbon source includes at least one of polymers, sugars, organic acids, and pitch.
  • the above-mentioned carbonization treatment temperature, time, and fusion are used to cooperate with each other to form a carbon layer on the surface of the silicon oxide.
  • the carbon layer is relatively loose and has a large number of micropores, and the subsequent reducing lithium-containing compound Both can pass through the micro pores of the carbon layer, penetrate the carbon layer and react on the surface of the silicon oxide. Therefore, in the obtained negative electrode material, the carbon layer is still located in the outermost layer, which can better improve the performance of the product.
  • the method includes the following steps:
  • silicon and silicon dioxide are heated and gasified in a vacuum at 1200°C ⁇ 1400°C for 16h ⁇ 20h, then condensed at 930°C ⁇ 970°C, and shaped to obtain silicon monoxide;
  • the carbon-coated silicon monoxide and phosphorus pentoxide are mixed, and then a reducing lithium-containing compound is added to mix, and the mixture is calcined at 450°C ⁇ 800°C in a non-oxidizing atmosphere for 1.5 h-2.5h to obtain a negative electrode material; wherein the mass ratio of the carbon-coated silicon monoxide and the reducing lithium-containing compound is 10: (0.08-1.2).
  • the present application provides a lithium ion battery, the lithium ion battery comprising the silicon-oxygen composite negative electrode material described in the first aspect or the silicon-oxygen composite negative electrode material obtained by the preparation method described in the second aspect.
  • the negative electrode material was prepared according to the following method:
  • the anode material prepared in this embodiment includes SiO 0.8 and Li 2 Si 2 O 5 , and the SiO 0.8 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 0.8 and Li 2 Si 2 O 5 is 1:2.6, and the pH value of the negative electrode material is 10.5.
  • the negative electrode material was prepared according to the following method:
  • the anode material prepared in this embodiment includes SiO 0.8 and Li 2 Si 2 O 5 , and the SiO 0.8 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 0.8 and Li 2 Si 2 O 5 is 1:2.1.
  • the pH value of the negative electrode material is 10.2, the surface of the negative electrode material is coated with a carbon layer, and the thickness of the carbon layer is 205 nm.
  • Fig. 2 is an XRD pattern of the negative electrode material prepared in this embodiment. From the figure, it can be seen that only the characteristic peaks of the material Li 2 Si 2 O 5 and silicon.
  • Figure 3a is a gas production test photo of the negative electrode material prepared in this embodiment. It can be seen from the figure that the aluminum-plastic film bag has no bulges or protrusions, and the surface is flat, indicating that the material does not produce gas.
  • Figure 3b is a photo of the coating test of the negative electrode material prepared in this embodiment, and it can be seen from the figure that the pole piece is smooth and flat.
  • the anode material prepared in this embodiment includes SiO 0.5 and Li 2 Si 2 O 5 , and the SiO 0.5 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 0.5 and Li 2 Si 2 O 5 is 1:1.4, and the pH value of the negative electrode material is 10.3.
  • the surface of the negative electrode material is coated with a carbon layer, and the thickness of the carbon layer is 200 nm.
  • the negative electrode material was prepared according to the following method:
  • the anode material prepared in this embodiment includes SiO 0.86 and Li 2 Si 2 O 5 , and the SiO 0.86 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 0.86 and Li 2 Si 2 O 5 is 1:2.2, and the pH value of the negative electrode material is 10.0.
  • the surface of the negative electrode material is coated with a carbon layer, and the thickness of the carbon layer is 220 nm.
  • the negative electrode material was prepared according to the following method:
  • the anode material prepared in this embodiment includes SiO 0.7 and Li 2 Si 2 O 5 , and the SiO 0.7 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 0.7 and Li 2 Si 2 O 5 is 1:2.0, and the pH value of the negative electrode material is 10.6.
  • the surface of the negative electrode material is coated with a carbon layer, and the thickness of the carbon layer is 199 nm.
  • the negative electrode material was prepared according to the following method:
  • the negative electrode material prepared in this embodiment includes SiO 1.2 and Li 2 Si 2 O 5 , and the SiO 1.2 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 1.2 and Li 2 Si 2 O 5 is 1:2.1
  • the pH value of the negative electrode material is 9.8.
  • the surface of the negative electrode material is coated with a carbon layer, and the thickness of the carbon layer is 204 nm.
  • the negative electrode material was prepared according to the following method:
  • the negative electrode material prepared in this embodiment includes SiO 0.6 and Li 2 Si 2 O 5 , and the SiO 0.6 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 0.6 and Li 2 Si 2 O 5 is 1:3.0, and the pH value of the negative electrode material is 10.2.
  • the surface of the negative electrode material is coated with a carbon layer, and the thickness of the carbon layer is 210 nm.
  • the negative electrode material was prepared according to the following method:
  • the negative electrode material prepared in this embodiment includes SiO 0.2 and Li 2 Si 2 O 5 , and the SiO 0.2 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 0.2 and Li 2 Si 2 O 5 is 1:1.6, and the pH value of the negative electrode material is 10.6.
  • the surface of the negative electrode material is coated with a carbon layer, and the thickness of the carbon layer is 198 nm.
  • the negative electrode material was prepared according to the following method:
  • the negative electrode material prepared in this embodiment includes SiO 0.9 and Li 2 Si 2 O 5 , and the SiO 0.9 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 0.9 and Li 2 Si 2 O 5 is 1:2.3, and the pH value of the negative electrode material is 10.1.
  • the surface of the negative electrode material is coated with a carbon layer, and the thickness of the carbon layer is 207 nm.
  • the negative electrode material was prepared according to the following method:
  • the negative electrode material prepared in this embodiment includes SiO 0.92 and Li 2 Si 2 O 5 , and the SiO 0.92 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 0.92 and Li 2 Si 2 O 5 is 1:2.9, and the pH value of the negative electrode material is 9.9.
  • the surface of the negative electrode material is coated with a carbon layer, and the thickness of the carbon layer is 250 nm.
  • the negative electrode material was prepared according to the following method:
  • the anode material prepared in this embodiment includes SiO 0.9 and Li 2 Si 2 O 5 , and the SiO 0.9 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 0.9 and Li 2 Si 2 O 5 is 1:3.5, and the pH value of the negative electrode material is 10.3.
  • the surface of the negative electrode material is coated with a carbon layer, and the thickness of the carbon layer is 180 nm.
  • the negative electrode material was prepared according to the following method:
  • the anode material prepared in this embodiment includes SiO 0.3 and Li 2 Si 2 O 5 , and the SiO 0.3 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 0.3 and Li 2 Si 2 O 5 is 1:0.2, and the pH value of the negative electrode material is 10.3.
  • the surface of the negative electrode material is coated with a carbon layer, and the thickness of the carbon layer is 800 nm.
  • the negative electrode material prepared in this embodiment includes SiO 0.8 , Li 2 SiO 3 and Li 2 Si 2 O 5 , and the SiO 0.8 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 0.8 and Li 2 Si 2 O 5 is 1:2.6
  • the pH value of the negative electrode material is 11.3.
  • the negative electrode material was prepared according to the following method:
  • the anode material prepared in this embodiment includes SiO 0.86 , Li 2 SiO 3 and Li 2 Si 2 O 5 , and the SiO 0.86 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 0.86 and Li 2 Si 2 O 5 is 1:2.2, and the pH value of the negative electrode material is 11.2.
  • the surface of the negative electrode material is coated with a carbon layer, and the thickness of the carbon layer is 220 nm.
  • Figure 4 is the XRD pattern of the negative electrode material prepared in the comparative example. It can be seen from this figure that in addition to the characteristic peaks of silicon and the characteristic peaks of Li 2 Si 2 O 5 , there are characteristic peaks of Li 2 SiO 3 .
  • Figure 5a is a gas production test photo of the negative electrode material prepared in the comparative example. It can be seen from the figure that the sealed aluminum plastic film bag bulges, indicating that gas production has occurred inside.
  • Figure 5b is a photo of the coating test of the negative electrode material prepared in the comparative example. It can be seen from the figure that the pole piece is full of pinholes.
  • the negative electrode material was prepared according to the following method:
  • the anode material prepared in this embodiment includes SiO 0.95 and Li 2 Si 2 O 5 , and the SiO 0.95 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 0.95 and Li 2 Si 2 O 5 is 1:6.1, and the pH value of the negative electrode material is 11.0.
  • the surface of the negative electrode material is coated with a carbon layer, and the thickness of the carbon layer is 200 nm.
  • the negative electrode material was prepared according to the following method:
  • the anode material prepared in this embodiment includes SiO 0.88 and Li 2 Si 2 O 5 , and the SiO 0.88 is uniformly dispersed in Li 2 Si 2 O 5 .
  • the mass ratio of SiO 0.88 and Li 2 Si 2 O 5 is 1:5.0, and the pH value of the negative electrode material is 11.1.
  • the surface of the negative electrode material is coated with a carbon layer, and the thickness of the carbon layer is 190 nm.
  • the negative electrode materials prepared in each of the examples and comparative examples were used as the active material, SBR+CMC was used as the binder, conductive carbon black was added, then the slurry was stirred and then coated on the copper foil, and finally the negative electrode was made by drying and rolling.
  • Active material: conductive agent: binder 85:15:10.
  • the electrochemical performance of the button cell is tested with the blue power 5V/10mA battery tester.
  • the charging voltage is 1.5V
  • the discharge 0.01V
  • the charge and discharge rate is 0.1C.
  • the negative electrode materials prepared in the respective examples and comparative examples and graphite were mixed uniformly at a mass ratio of 1:9 as the active material, lithium metal sheets were used as the counter electrode, PP/PE as the separator, and LiPF6/EC+DEC+DMC (EC The volume ratio of DEC and DMC is 1:1:1)
  • the button battery is assembled in a glove box filled with argon gas, and the electrochemical performance of the battery after 50 cycles of 50-week cycle is tested by the blue power 5V/10mA battery tester. , Charging voltage is 1.5V, discharging to 0.01V, charging and discharging rate is 0.1C.
  • Example 1 Discharge capacity mAh/g First effect% 50-week capacity retention rate%
  • Example 1 1308 86.5 88.8
  • Example 2 1417 88.9 89.1
  • Example 3 1420 89.5 90.5
  • Example 4 1411 88.6 90.0
  • Example 5 1400 88.3 89.1
  • Example 6 1404 86.5 89.4
  • Example 7 1415 88.4 90.2
  • Example 8 1407 90.5 90.1
  • Example 9 1388 87.0 88.8
  • Example 10 1380 87.2 88.9
  • Example 11 1394 88.8 90.0
  • Example 12 1405 89.7 91.8 Comparative example 1 1720 76.8 75.8 Comparative example 2 1720 76.8 75.8 Comparative example 3 1401 86.7 82.2 Comparative example 4 1421 86.5 84.6
  • Example 2 Comparative Example 3, and Comparative Example 4 that as the amount of P 2 O 5 increases, the content of Li 2 SiO 3 gradually decreases, and when the amount of addition reaches 2 %, there is no Li 2 SiO 3 and the processing performance of the material is improved. It can be seen from Examples 1, 2 and 4 that the pre-lithiation reaction is carried out after the carbon is coated, and the nucleation conversion agent is added to obtain a better conversion effect, and the type of carbon source has no effect on the conversion effect of Li 2 SiO 3 .
  • the cycle performance of the anode material is significantly improved; when all Li 2 SiO 3 is converted into Li 2 Si 2 O 5 , the material The cycle retention rate is stable above 88%.
  • Examples 9-10 did not use the nucleation conversion agent P 2 O 5 , but used other types of nucleation conversion agents. Compared with Example 4, the capacity and circulation of the materials prepared in Examples 9 and 10 are worse than those with P 2 O 5 added, which may be caused by different types of transforming agents. Because P 2 O 5 has a more significant effect on the conversion of Li 2 SiO 3 to Li 2 Si 2 O 5 , the content of Li 2 Si 2 O 5 in the material after adding P 2 O 5 is also more, which will increase the expansion of the cycle process. The inhibitory effect is stronger.
  • the endothermic agent is added in Examples 11-12.
  • the endothermic agent promotes the conversion of Li 2 SiO 3 in the high temperature phase to Li 2 Si 2 O 5 in the low temperature phase, and can also make the final product only Li 2 Si 2 O 5 , and show Good first-time coulombic efficiency and cycle performance.
  • Comparative Example 1 On the basis of Example 1, no nucleation conversion agent was added, resulting in higher Li 2 SiO 3 content, poor processing performance, more gas production, obvious pinholes after coating, and obvious first effect and cycle performance Inferior to Example 1.
  • the situation of Comparative Example 2 is the same as that of Comparative Example 1, and no nucleation conversion agent is added, resulting in poor product processing performance, excessive gas production, obvious pinholes after coating, and first effect and cycle performance inferior to Example 4.
  • Comparative Example 3 and Comparative Example 4 were based on Example 2, respectively, with the addition amount of the nucleation converting agent changed.
  • the mass ratios of silicon oxide to the nucleation converting agent were 100:0.5 and 100:1, respectively.
  • Comparative Example 3 The nucleation conversion agent in ⁇ 4 is insufficient to completely convert Li 2 SiO 3 into Li 2 Si 2 O 5 , resulting in poor material processing performance, gas production after placement, and pinholes during coating.

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Abstract

本申请提供了一种负极材料及其制备方法和锂离子电池。所述负极材料包括SiO x及Li 2Si 2O 5，所述SiO x分散在Li 2Si 2O 5中，其中，0≤x≤1.2。所述制备方法包括：将硅氧化物SiO y、还原性含锂化合物和助剂进行混合，热处理，得到所述负极材料，其中，所述助剂包括成核转化剂或吸热剂，0＜y＜2。本申请提供的制备方法通过使用成核转化剂或吸热剂，使得制备得到的产品中硅酸锂仅为Li 2Si 2O 5而没有其他硅酸锂相，由于Li 2Si 2O 5不溶于水，解决了预锂材料的加工稳定性问题，如浆料产气、粘度低，涂布时拖尾，极片干燥后出现针孔、气孔等。

Description

负极材料及其制备方法和锂离子电池
本申请要求于2019年10月30日提交中国专利局，申请号为2019110465972、发明名称为“一种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申请中。
技术领域
本申请属于电池材料技术领域，涉及负极材料及其制备方法和锂离子电池。
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。随着正极材料首效越来越高，提升硅氧材料的首次效率显得尤为重要。
目前，提升硅氧材料首效行之有效的方式是预先对其掺杂锂，使之提前将硅氧材料中的不可逆耗锂相反应掉。现已工业化的方法是直接在极片表面涂覆锂层，以此达到减少正极锂消耗的效果。但是该方法对操作环境要求高，且存在较大安全隐患，因此难以实现产业化推广。当前技术发展状态下，通过在材料端进行预锂获得首效提升普遍存在加工性能差的问题，主要表现为：水系浆料产气严重、粘度低，涂布时拖尾，极片干燥后出现针孔、气孔等。出现这一问题的主要原因是：预锂后材料中存在大量的Li 2SiO 3、Li 4SiO 4相，甚至Li 2O、Li xSi，而这些成分均易溶于水，显示出强碱性导致加工性能差。
因此，加工性能差仍是预锂材料普遍存在的问题，也是技术难点。
一种锂离子电池、纳米硅材料及制备方法，包括步骤：将二氧化硅、镁金属、掺杂剂按照指定的质量比混合均匀，得到混合物；将所述混合物置于高温反应炉中，通入惰性气体后，在指定的升温速率下升至指定温度，高温反应一段时间后，自然降温至室温，得到反应产物；取出所述反应产物进行初步水洗、酸洗、再水洗，烘干，得到粗颗粒硅；所述粗颗粒硅与分散剂按照指定的质量比混合均匀，然后按照指定研磨工艺研磨指定时间、干燥、过筛，得到纳米硅。该方法虽然倍率性能和循环性能尚可，但是首次效率和加工性能还有待提高。
另一种提高锂离子电池硅负极材料性能的方法，包括有以下步骤：(一)氧化亚硅复合材料的负极制备：1)称取一定量的SiO粉末，将其倒入质量为SiO质量10倍的去离子水中，然后再加入一定量的石墨与葡萄糖；2)将混合好的溶液放入高能球磨机中进行球磨；3)将球磨好的前驱体材料放入管式炉中；4)取出制备好的SiO/C 复合材料，通过将其与导电剂乙炔黑、粘结剂PVDF按一定比例混合；(二)电极上的预锂化处理。该方法的首次效率和加工性能无法满足市场需求。
又一种硅基负极片及其制备方法和锂离子电池。本申请提供的硅基负极片的负极涂层包括位于集流体上的第一涂层和位于第一涂层上的第二涂层，所述第一涂层中的活性物质包括硅基负极材料，所述第二涂层中的活性物质不包含硅基负极材料，所述第二涂层表面含有锂。所述制备方法包括1)用含有硅基负极材料的第一浆料涂布在集流体上形成第一涂层；2)用不包含硅基负极材料的第二浆料在第一涂层上形成第二涂层；3)对含有第二涂层的极片进行预掺锂，得到所述硅基负极片。该方法流程长，工艺繁琐，难以在产业上进行应用。
申请内容
基于此，本申请的目的在于提供一种预锂后加工性能优异的负极材料及其制备方法和锂离子电池。
为达此目的，本申请采用以下技术方案：
第一方面，本申请提供一种负极材料，所述负极材料包括SiO x及Li 2Si 2O 5，所述SiO x分散在Li 2Si 2O 5中，其中，0≤x≤1.2。
本申请提供的负极材料中的含锂化合物为Li 2Si 2O 5，由于Li 2Si 2O 5不溶于水，可从根本上解决预锂材料的加工稳定性问题，如浆料产气、粘度低，涂布时拖尾，极片干燥后出现针孔、气孔等。不需要额外的对预锂后材料进行表面处理，可以避免锂电池因为表面处理带来的容量降低、首效降低等问题。
在一种可行的实施方式中，所述负极材料满足以下条件a～d的至少一者：
a.所述负极材料的的PH值为7＜PH＜10.7；
b.所述负极材料的平均粒径为5μm～50μm；
c.所述负极材料中的SiO x与Li 2Si 2O 5的质量比为1：(0.74～6.6)；
d.所述SiO x均匀分散在Li 2Si 2O 5中。
在一种可行的实施方式中，所述负极材料满足以下条件a～c的至少一者：
a.所述负极材料的表面形成有碳包覆层；
b.所述负极材料的表面形成有碳包覆层，所述碳包覆层的厚度为10nm～2000nm；
c.所述负极材料的表面形成有碳包覆层，所述负极材料中的碳元素的质量分数为4％～6％。
第二方面，本申请提供一种负极材料的制备方法，包括以下步骤：
将硅氧化物SiOy、还原性含锂化合物和助剂进行混合，热处理，得到所述负极材料，其中，所述助剂包括成核转化剂或吸热剂，0＜y＜2。
本申请提供的制备方法通过添加成核转化剂或吸热剂可实现使最终的预锂产物只有Li 2Si 2O 5而没有Li 2SiO 3，从根本上解决了预锂材料的加工问题，且简化了预锂材料的制备工艺，即不需要额外的对预锂后材料进行表面处理，防止产气等问题的出现。此外，通过添加成核转化剂或吸热剂直接将生成的高温晶相的Li 2SiO 3转化为低温晶相的Li 2Si 2O 5，可避免因为表面处理带来的负极材料容量降低、首效降低等问题。
在一种可行的实施方式中，所述负极材料满足以下条件a～f的至少一者：
a.所述负极材料的的PH值为7＜PH＜10.7；
b.所述负极材料的平均粒径为5μm～50μm；
c.所述负极材料中的SiO x与Li 2Si 2O 5的质量比为1：(0.74～6.6)。
d.所述负极材料的表面形成有碳包覆层；
e.所述负极材料的表面形成有碳包覆层，所述碳包覆层的厚度为10nm～2000nm；
f.所述负极材料的表面形成有碳包覆层，所述负极材料中的碳元素的质量分数为4％～6％。
在一种可行的实施方式中，所述方法满足以下条件a～d的至少一者：
a.所述硅氧化物和还原性含锂化合物的质量比为10：(0.08～1.2)；
b.所述硅氧化物为一氧化硅；
c.所述硅氧化物的D10＞1.0μm且Dmax＜50μm；
d.所述还原性锂化合物包括氢化锂、烷基锂、金属锂、氢化铝锂、氨基锂和硼氢化锂中的至少一种。
在一种可行的实施方式中，所述方法满足以下条件a～h的至少一者：
a.所述成核转化剂包括磷的氧化物和磷酸盐中的至少一种；
b.所述磷的氧化物包括五氧化二磷和三氧化二磷中的至少一种；
c.所述磷酸盐包括磷酸锂、磷酸镁和磷酸钠中的至少一种；
d.所述成核转化剂为五氧化二磷；
e.所述吸热剂的熔点小于700℃；
f.所述吸热剂包括LiCl、NaCl、NaNO 3、KNO 3、KOH、BaCl、KCl和LiF中的至少一种；
g.所述硅氧化物和所述成核转化剂的质量比为100：(2～10)；
h.所述硅氧化物和所述吸热剂的质量比为100：(8～30)。
在一种可行的实施方式中，所述方法满足以下条件a～d的至少一者：
a.所述热处理在非氧化性气氛下进行；
b.所述热处理在非氧化性气氛下进行；所述非氧化性气氛包括氢气、氮气、氦气、氖气、氩气、氪气和氙气中的至少一种；
c.所述热处理的温度为300℃～1000℃；
d.所述热处理的时间为1.5h～2.5h。
在一种可行的实施方式中，在将硅氧化物SiO y、还原性含锂化合物和成核转化剂或吸热剂进行混合之前，所述方法还包括：
将硅氧化物的原料进行加热气化，产生硅氧化物气体，并进行冷凝、整形得到硅氧化物SiO y，其中，0＜y＜2。
在一种可行的实施方式中，所述方法满足以下条件a～g的至少一者：
a.所述硅氧化物的原料包括硅和二氧化硅；
b.所述硅和所述二氧化硅的质量比为1:(1.8～2.2)；
c.所述加热气化的温度为1200℃～1400℃；
d.所述加热气化的时间为16h～20h；
e.所述冷凝的温度为930℃～970℃；
f.所述加热气化在保护性气氛或真空中进行；
g.所述整形包括破碎、球磨和分级中的至少一种。
在一种可行的实施方式中，所述方法还包括：
对待包碳材料进行碳包覆，所述待包碳材料包括所述硅氧化物和所述负极材料中的至少一种。
在一种可行的实施方式中，所述方法满足以下条件a～c的至少一者：
a.所述碳包覆包括气相包碳和固相包碳中的至少一种；
b.所述碳包覆包括气相包碳和固相包碳中的至少一种，所述气相包碳的条件为：将所述硅氧化物在保护性气氛下升温至600℃～1000℃，通入有机碳源气体，保温0.5h～10h后冷却；其中，所述有机碳源气体包括烃类，所述烃类包括甲烷、乙烯、乙炔和苯中的至少一种；
c.所述碳包覆包括气相包碳和固相包碳中的至少一种，所述固相包碳的条件为：将所述硅氧化物与碳源融合0.5h～2h后，将得到的碳混合物在600℃～1000℃下碳化2h～6h，冷却；其中，所述碳源包括聚合物、糖类、有机酸和沥青中的至少一种。
在一种可行的实施方式中，所述方法包括以下步骤：
按照质量比为1：(1.8～2.2)将硅和二氧化硅在真空中1200℃～1400℃加热气化16h～20h，再在930℃～970℃下冷凝，整形，得到一氧化硅；
对所述一氧化硅进行碳包覆，得到包碳的一氧化硅；
按照质量比为100：(2～10)将所述包碳的一氧化硅和五氧化二磷混合后，再加入还原性含锂化合物混合，在非氧化气氛下450℃～800℃下焙烧1.5h～2.5h，得到负极材料；其中，所述包碳的一氧化硅和所述还原性含锂化合物的质量比为10：(0.08～1.2)。
第三方面，本申请提供一种锂离子电池，所述锂离子电池包含如上述第一方面的复合负极材料或根据上述第二方面的制备方法制得的复合负极材料。
与现有技术相比，本申请具有以下有益效果：
(1)本申请提供的制备方法通过添加成核转化剂或吸热剂可实现使最终的预锂产物只有低温晶相的Li 2Si 2O 5而没有高温晶相的Li 2SiO 3，从根本上解决了预锂材料的加工问题，且简化了预锂材料的制备工艺，即不需要额外的对预锂后材料进行表面处理，防止产气等问题的出现。此外，通过添加成核转化剂或吸热剂直接将高温晶相的Li 2SiO 3转化为低温晶相的Li 2Si 2O 5，可避免因为表面处理带来的负极材料容量降低、首效降低等问题。
(2)本申请提供的负极材料具有加工性能稳定、首次效率高、循环寿命长的优点。
附图说明
图1为本申请提供的负极材料的制备方法的工艺流程图；
图2为本申请实施例2制备的负极材料的XRD图谱；
图3a为本申请实施例2制备的负极材料的产气测试照片；
图3b为本申请实施例2制备的负极材料的涂布测试照片；
图4为对比例2制备的负极材料的XRD图谱；
图5a为对比例2制备的负极材料的产气测试照片；
图5b为对比例2制备的负极材料的涂布测试照片。
具体实施方式
为更好地说明本申请，便于理解本申请的技术方案，下面对本申请进一步详细说明。但下述的实施例仅仅是本申请的简易例子，并不代表或限制本申请的权利保护范围，本申请保护范围以权利要求书为准。
以下为本申请典型但非限制性实施例：
多数硅基/硅氧基材料在首次嵌锂过程中会产生一定量的不可逆相(如:Li 4SiO 4、Li 2O等)，导致电池首次库伦效率较低。通过预锂化处理，在负极材料中掺杂锂元素。从而在电池化成过程中，负极界面形成的SEI膜会消耗掉从负极材料中的锂，而不是正极脱嵌的锂离子，从而最大限度的保留从正极脱嵌的锂离子，提高全电池的容量。目前，预锂后材料中存在大量的Li 2SiO 3、Li 4SiO 4相，甚至Li 2O、Li xSi，这些物质会消耗电解液以及从正极脱出的Li，且此过程不可逆，造成首次可逆容量的严重丢失，并且这些成分均易溶于水，显示出强碱性导致加工性能差。
第一方面，本申请实施例提供一种负极材料，所述负极材料包括SiO x及Li 2Si 2O 5，所述SiO x分散在Li 2Si 2O 5中，其中，0≤x≤1.2。
本申请提供的负极材料中仅含有Li 2Si 2O 5这一种硅酸锂相，由于Li 2Si 2O 5不溶于水，可从根本上解决预锂化处理后的负极材料的加工稳定性问题，如浆料产气、粘度低，涂布时拖尾，极片干燥后出现针孔、气孔等。不需要额外的对预锂后材料进行表面处理，可以避免锂电池因为表面处理带来的容量降低、首效降低等问题。作为本申请可选的技术方案，所述SiO x均匀分散在Li 2Si 2O 5中，例如西瓜籽(SiO x)分散在西瓜囊(Li 2Si 2O 5)内。
作为本申请可选的技术方案，所述SiO x中，0≤x≤1.2，SiO x例如可以为Si、SiO 0.2、SiO 0.4、SiO 0.6、SiO 0.8、SiO或SiO 1.2等。优选地，SiO x为SiO。可以理解地，SiOx的组成比较复杂，可以理解为由纳米硅均匀分散在SiO 2中形成。
作为本申请可选的技术方案，所述负极材料的平均粒径5μm～50μm；更具体地，可以是5μm、10μm、15μm、20μm、25μm、30μm、35μm、40μm或50μm等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。硅复合物负极材料的平均粒径控制在上述范围内，有利于负极材料循环性能的提升。
作为本申请可选的技术方案，所述负极材料中的SiO x和Li 2Si 2O 5的质量比为1：(0.74～6.6)；更具体地，可以是1：0.74、1:1.4、1：1.6、1:2.0、1：2.3、1:2.9、1：3.5、1：4、1：5.0、1：6.1或1：6.6等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。当SiO x和Li 2Si 2O 5的质量比过低时，材料中的Li 2Si 2O 5含量过低，负极材料制成的浆料容易产气，极片干燥后容易出现针孔、气泡，不利于提高负极材料的加工性能；当SiO x和Li 2Si 2O 5的质量比过高时，材料中的Li 2Si 2O 5含量过高，锂离子传输效率降低，不利于材料大倍率充放电。
在具体实施例中，所述负极材料中只含有Li 2Si 2O 5。
作为本申请可选的技术方案，所述负极材料的PH值为7＜PH＜10.7，示例性地，PH值例如可以是7.1、8.0、9.3、9.8、9.9、10.0、10.1、10.2、10.3、10.4、10.5或10.6等等。可以理解地，可以使得材料保持在较低的碱性，提高材料水系加工性能，提高负极材料的首效。
作为本申请可选的技术方案，所述负极材料的表面包覆有碳层。
可选地，所述碳层的厚度为10nm～2000nm；更具体地，可以是10nm、50nm、100nm、300nm、500nm、800nm、1000nm、1500nm、1800nm或2000nm，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。碳层过厚，锂离子传输效率降低，不利于材料大倍率充放电，降低负极材料的综合性能，碳层过薄，不利于增加负极材料的导电性且对材料的体积膨胀抑制性能较弱，导致长循环性能价差。
优选地，所述负极材料的表面包覆有碳层时，所述负极材料中的碳元素的质量分数为4％～6％，更具体地，可以是4％、4.5％、5％、5.5％或6％等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
第二方面，本申请提供一种所述负极材料的制备方法，如图1所示，包括以下步骤：
S100，将硅氧化物SiO y、还原性含锂化合物和助剂进行混合，热处理，得到所述负极材料，其中，所述助剂包括成核转化剂或吸热剂，0＜y＜2。
本申请提供的制备方法通过使用成核转化剂或吸热剂，使得硅氧化物与还原性含锂化合物发生反应(即进行预锂化)后，可以实现只生成Li 2Si 2O 5这一种硅酸锂相，因为Li 2Si 2O 5不溶于水，解决了预锂材料的加工稳定性问题，如浆料产气、粘度低，涂布时拖尾，极片干燥后出现针孔、气孔等。
需要说明的是，成核转化剂可以用于加快结晶速率、增加结晶密度和促使晶粒尺寸微细化。在制备过程中，硅氧化物SiO y与还原性含锂化合物可以生成Li 2SiO 3和Li 2Si 2O 5，加入的成核转化剂可以加速结晶速率，促进生成的高温晶相的Li 2SiO 3转化为低温晶相的Li 2Si 2O 5，从而避免因为表面处理带来的容量降低、首效降低等问题。
需要说明的是，吸热剂可以用于降低反应温度。在制备过程中，硅氧化物SiO y与还原性含锂化合物可以生成Li 2SiO 3和Li 2Si 2O 5，加入的吸热剂可以降低反应温度，随着反应温度的降低，有利于促进生成的硅酸锂的结晶相向低温晶相的Li 2Si 2O 5相偏移，即促进生成的高温晶相的Li 2SiO 3转化为低温晶相的Li 2Si 2O 5，从而避免因为表面处理带来的容量降低、首效降低等问题。
以下作为本申请优选的技术方案，但不作为对本申请提供的技术方案的限制，通过以下优选的技术方案，可以更好的达到和实现本申请的技术目的和有益效果。
作为本申请可选的技术方案，所述硅氧化物SiO y，其中，0＜y＜2，例如SiO y例如为SiO 0.2、SiO 0.5、SiO 0.8、SiO、SiO 1.2、SiO 1.5或SiO 1.9等。优选地，所述硅氧化物为SiO，当硅氧化物使用一氧化硅时，可以有效解决一氧化硅掺锂提升首效后加工性能不稳定的问题。
优选地，所述硅氧化物颗粒的粒径D10＞1.0μm且Dmax＜50μm。例如D10为 1.0μm、1.5μm、2.0μm、2.5μm、3.0μm、4.0μm或5.0μm等，Dmax为49μm、45μm、30μm、35μm或20μm等。这里，Dmax是指最大的颗粒的粒径。
作为本申请可选的技术方案，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、氨基锂和硼氢化锂中的至少一种。
作为本申请可选的技术方案，所述成核转化剂包括磷的氧化物和磷酸盐中的至少一种。可选地，所述磷的氧化物包括五氧化二磷和三氧化二磷中的至少一种。
作为本申请可选的技术方案，所述磷酸盐包括磷酸锂、磷酸镁和磷酸钠中的至少一种。
优选地，所述成核转化剂为五氧化二磷。本申请中，特别优选使用五氧化二磷作为成核转化剂，采用五氧化二磷的好处在于：使得Li 2SiO 3转化为Li 2Si 2O 5的效果更明显，且可以减少成核转化剂的用量，实现一方面降低生产成本，另一方面降低生产难度。
作为本申请可选的技术方案，所述吸热剂的熔点小于700℃；所述吸热剂包括LiCl、NaCl、NaNO3、KNO3、KOH、BaCl、KCl和LiF中的至少一种。
优选地，所述吸热剂为KNO 3。本申请中，特别优选KNO 3作为吸热剂，其优势在于：第一，KNO 3的使用温度低，且对生成Li 2Si 2O 5的促进作用更明显；第二，KNO 3成本低，原料易得，无毒无害，环境友好。
作为本申请可选的技术方案，所述硅氧化物和还原性含锂化合物的质量比为10:(0.08～1.2)，例如10:0.08、10:0.2、10:0.5、10:0.8或10:1.2等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。控制在上述质量比范围内，有利于提高Li 2SiO 3转化成Li 2Si 2O 5的转化率。
作为本申请可选的技术方案，所述硅氧化物和成核转化剂的质量比为100:(2～10)，例如100:2、100:2.5或100:3、100:5、100:7、100:10等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。可以理解地，当成核转化剂的用量过多，会导致Li 2Si 2O 5晶粒过大，影响循环性能；如果成核转化剂的用量过少，会导致有残留Li 2SiO 3，影响材料的水系浆料加工稳定性。
作为本申请可选的技术方案，所述硅氧化物和吸热剂的质量比为100：(8～30)，例如100:8、100:10、100:15、100:20、100:25或100:30等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
作为本申请可选的技术方案，所述将硅氧化物、还原性含锂化合物和成核转化剂混合的具体步骤，包括：将硅氧化物和成核转化剂混合后，再加入还原性含锂化合物。
可以理解地，将硅氧化物与成核转化剂混合后，成核转化剂粘附于硅氧化物的表面，当还原性含锂化合物与硅氧化物发生反应时，粘附在硅氧化物表面的成核转化剂就能及时地将反应生成的部分高温晶相的Li 2SiO 3转化为低温晶相的Li 2Si 2O 5，即随着反应进行，硅酸锂的相变也在同时进行，成核转化剂促使硅酸锂的结晶向低温晶相的Li 2Si 2O 5偏移，转变硅酸锂的晶相结构。
可选地，所述热处理在非氧化性气氛下进行，所述非氧化性气氛包括氢气、氮气、氦气、氖气、氩气、氪气或氙气中的至少一种。
在一些具体实施方式中，所述热处理可以在烧成炉中进行，使得热处理充分进行。
可选地，所述热处理的温度为300℃～1000℃，例如300℃、400℃、450℃、480℃、500℃、600℃、700℃、800℃、900℃或1000℃等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。可以理解地，当热处理温度过高，会导致反应剧烈，硅晶粒急剧长大，一氧化硅歧化，性能劣化，影响材料的循环性能；当热处理的温度过低，反应难以进行，导致Li 2Si 2O 5无法生成。优选地，所述热处理的温度为450℃～800℃。
优选地，所述热处理的时间为1.5h～2.5h，例如1.5h、1.7h、2h、2.3h或2.5h等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。可以理解地，充分焙烧，可以使得Li 2SiO 3充分转化成Li 2Si 2O 5，。
进一步地，在步骤S100之前，所述方法还包括：
将硅氧化物的原料进行加热气化，产生硅氧化物气体，并进行冷凝、整形得到硅氧化物SiO y，其中，0＜y＜2。
作为本申请可选的技术方案，所述硅氧化物的原料包括Si和SiO 2。Si和SiO 2的具体比例可以根据所需的SiO y的y值进行调整，在此不做限定。
作为本申请可选的技术方案，所述硅和二氧化硅的质量比为1:(1.8～2.2)，例如1:1.8、1:1.9、1:2.0、1:2.1或1:2.2等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
所述加热的温度为1200℃～1400℃，例如1200℃、1250℃、1300℃、1350℃或1400℃等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
可选地，所述加热气化的时间为16h～20h，例如16h、17h、18h、19h或20h等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
可选地，所述冷凝的温度为930℃～970℃，例如930℃、940℃、950℃、960℃或970℃等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
可选地，所述整形包括破碎、球磨或分级中的至少一种。
作为本申请可选的技术方案，硅氧化物SiO y颗粒的D10＞1.0μm，且Dmax＜50μm，例如D10为1.1μm、1.5μm、2.0μm、2.5μm、3.0μm、4.0μm或5.0μm等，Dmax为49μm、45μm、30μm、35μm或20μm等。需要说明的是，Dmax是指最大的颗粒的粒径。
优选地，所述加热气化在保护性气氛或真空中进行。本申请中，所述保护性气氛可根据现有技术进行选择，例如氮气气氛和/或氩气气氛。所述真空的真空度可根据现有技术进行选取，例如5Pa。
进一步地，所述方法还包括：
对待包碳材料进行碳包覆，所述待包碳材料包括所述硅氧化物和所述负极材料中的至少一种；所述碳包覆包括气相包碳和固相包碳中的至少一种。
作为本申请可选的技术方案，采用气相包碳时，将所述硅氧化物在保护性气氛下升温至600℃～1000℃，例如600℃、700℃、800℃、900℃或1000℃等，通入有机碳源气体，保温0.5h～10h后冷却，例如保温0.5h、1h、2h、5h、8h或10h等。本 申请中，所述保护性气氛可根据现有技术进行选择，例如氮气气氛和/或氩气气氛。
优选地，所述有机碳源气体包括烃类。所述烃类包括甲烷、乙烯、乙炔和苯中的至少一种。
作为本申请可选的技术方案，采用固相包碳时，将所述硅氧化物与碳源融合0.5h以上后，将得到的碳混合物在600℃～1000℃下碳化2h～6h，冷却。融合时间在0.5h以上，例如0.5h、0.6h、0.7h、0.8h、1h、1.5h或2h等，碳化温度例如可以是600℃、700℃、800℃、900℃或1000℃等，碳化时间例如可以是2h、3h、4h、5h或6h等。
可以理解地，将硅氧化物先进行碳包覆，再进行锂化反应，可以有效缩减制备工艺，降低成本；并且在硅氧化物表面形成碳层，碳层较为疏松，存在大量微孔道，而后续的还原性含锂化合物均可以通过碳层的微孔道，渗透过碳层而在硅氧化物表面进行反应，可以适当抑制反应的剧烈程度，使得硅氧化物表面形成均匀的Li 2Si 2O 5层，提高材料的电化学性能。
可选地，所述融合在融合机中进行，所述融合机转速为500-3000r/min，例如500r/min、1000r/min、1500r/min、2000r/min、2500r/min或3000r/min等。融合机的刀具间隙宽度可根据现有技术进行选取，例如为0.5cm。
在一些实施例中，所述碳源包括聚合物、糖类、有机酸和沥青中的至少一种。
本申请中，采用上述碳化处理温度、时间以及融合等这些操作条件相互配合，有利于在硅氧化物表面形成碳层，碳层较为疏松，存在大量微孔道，而后续的还原性含锂化合物均可以通过碳层的微孔道，渗透过碳层而在硅氧化物表面进行反应，故得到的负极材料中，碳层依然是位于最外层，可以更好地提升产品的性能。
进一步地，作为本申请所述制备方法的进一步优选技术方案，所述方法包括以下步骤：
按照质量比为1：(1.8～2.2)将硅和二氧化硅在真空中1200℃～1400℃加热气化16h～20h，再在930℃～970℃下冷凝，整形，得到一氧化硅；
对所述一氧化硅进行碳包覆，得到包碳的一氧化硅；
按照质量比为100：(2～10)将所述包碳的一氧化硅和五氧化二磷混合后，再加入还原性含锂化合物混合，在非氧化气氛下450℃～800℃下焙烧1.5h～2.5h，得到负极材料；其中，所述包碳的一氧化硅和所述还原性含锂化合物的质量比为10：(0.08～1.2)。
第三方面，本申请提供一种锂离子电池，所述锂离子电池包含上述第一方面所述的硅氧复合负极材料或上述第二方面所述的制备方法制得的硅氧复合负极材料。
下面分多个实施例对本申请实施例进行进一步的说明。其中，本申请实施例不限定于以下的具体实施例。在保护范围内，可以适当的进行变更实施。
实施例1
本实施例按照如下方法制备负极材料：
(1)取1kg Si粉与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块体；将SiO块体经过破碎、球磨、分级等工艺处理，得到SiO粉体材料，其中值粒径控制在6μm左右(D10为1.2μm，Dmax为28μm)。
(2)取1kg SiO粉体材料、20g五氧化二磷，投入VC混合机内混合40min取出，得到SiO与五氧化二磷的混合物，然后将混合物放入球磨罐中，加入100g氢化锂球磨20min取出，得到预锂前驱体；将预锂前驱体置于氮气保护下热处理，热处理温度800℃，热处理时间2h，自然降温至室温取出物料、经筛分、除磁得到负极材料。
本实施例制备的负极材料包括SiO 0.8和Li 2Si 2O 5，所述SiO 0.8均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 0.8和Li 2Si 2O 5的质量比为1：2.6，所述负极材料的PH值为10.5。
本实施例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
实施例2
本实施例按照如下方法制备负极材料：
(1)取1kg Si粉与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块体；将SiO块体经过破碎、球磨、分级等工艺处理，得到SiO粉体材料，其中值粒径控制在6μm左右(D10为1.3μm，Dmax为25μm)。
(2)取1.5kg SiO粉体材料置于CVD回转炉中，通入乙炔作为碳源，通入氮气作为保护气，800℃沉积70min，冷却出料得SiO/C材料。
(3)取1kg SiO/C材料与20g五氧化二磷投入VC混合机内混合40min取出，得到SiO/C材料与五氧化二磷的混合物，然后将混合物放入球磨罐中，加入100g氢化锂球磨20min取出，得到预锂前驱体；将预锂前驱体置于氮气保护下热处理，热处理温度800℃，热处理时间2h，自然降温至室温取出物料、经筛分、除磁得到负极材料。
本实施例制备的负极材料中，包括SiO 0.8和Li 2Si 2O 5，所述SiO 0.8均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 0.8和Li 2Si 2O 5的质量比为1：2.1。所述负极材料的PH值为10.2，所述负极材料的表面包覆有碳层，所述碳层厚度为205nm。
图2为本实施例制备的负极材料的XRD图谱，由该图可以看出只有物质Li 2Si 2O 5和硅的特征峰。
图3a为本实施例制备的负极材料的产气测试照片，由该图可以看出铝塑膜袋无鼓包或者突起，表面平整，说明材料未发生产气现象。
图3b为本实施例制备的负极材料的涂布测试照片，由该图可以看出极片光滑、平整。
本实施例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见 表2。
实施例3
(1)取1kg Si粉与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块体；将SiO块体经过破碎、球磨、分级等工艺处理，得到SiO粉体材料，其中值粒径控制在6μm左右(D10为1.3μm，Dmax为25μm)。
(2)取1.5kg SiO粉体材料置于CVD回转炉中，通入乙炔作为碳源，通入氮气作为保护气，800℃沉积70min，冷却出料得SiO/C材料。
(3)取1kg SiO/C材料与30g五氧化二磷投入VC混合机内混合40min取出，得到SiO/C材料与五氧化二磷的混合物，然后将混合物放入球磨罐中，加入120g氢化锂球磨20min取出，得到预锂前驱体；将预锂前驱体置于氮气保护下热处理，热处理温度800℃，热处理时间2h，自然降温至室温取出物料、经筛分、除磁得到负极材料。
本实施例制备的负极材料中，包括SiO 0.5和Li 2Si 2O 5，所述SiO 0.5均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 0.5和Li 2Si 2O 5的质量比为1：1.4，所述负极材料的PH值为10.3。所述负极材料的表面包覆有碳层，所述碳层厚度为200nm。
本实施例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
实施例4
本实施例按照如下方法制备负极材料：
(1)取1kg Si粉与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块体；将SiO块体经过破碎、球磨、分级等工艺处理，得到SiO粉体材料，其中值粒径控制在6μm左右(D10为1.5μm，Dmax为29μm)。
(2)取1.5kg SiO粉体材料、113g沥青置于VC机中混合30min，转速800rpm，出料后置于高温箱式炉中900℃烧成3h，箱式炉中通入氮气保护。自然冷却至室温出料得SiO/C材料。
(3)取1kg SiO/C材料与20g五氧化二磷投入VC混合机内混合40min取出，得到SiO/C材料与五氧化二磷的混合物，然后将混合物放入球磨罐中，加入100g氢化锂球磨20min取出，得到预锂前驱体；将预锂前驱体置于氮气保护下热处理，热处理温度800℃，热处理时间2h，自然降温至室温取出物料、经筛分、除磁，得到负极材料。
本实施例制备的负极材料包括SiO 0.86和Li 2Si 2O 5，所述SiO 0.86均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 0.86和Li 2Si 2O 5的质量比为1：2.2，所述负极材料的PH值为10.0。所述负极材料的表面包覆有碳层，所述碳层厚度为220nm。
本实施例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
实施例5
本实施例按照如下方法制备负极材料：
(1)取1kg Si粉与1.8kg 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1200℃并保温20h，在炉内生成SiO蒸汽经过迅速凝结(凝结的温度为930℃)生成SiO 0.92块体；将SiO 0.92块体经过破碎、球磨、分级等工艺处理，得到SiO 0.92粉体材料，其中值粒径控制在6μm左右(D10为1.5μm，Dmax为26μm)。
(2)取1.5kg SiO 0.92粉体材料置于CVD回转炉中，通入甲烷作为碳源，通入氮气作为保护气，600℃沉积10h，冷却出料得SiO 0.92/C材料。
(3)取1kg SiO 0.92/C材料与70g五氧化二磷投入VC混合机内混合40min取出，得到SiO 0.92/C材料与五氧化二磷的混合物，然后将混合物放入球磨罐中，加入100g氢化锂球磨20min取出，得到预锂前驱体；将预锂前驱体置于氮气保护下热处理，热处理温度600℃，热处理时间2h，自然降温至室温取出物料、经筛分、除磁，得到负极材料。
本实施例制备的负极材料包括SiO 0.7和Li 2Si 2O 5，所述SiO 0.7均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 0.7和Li 2Si 2O 5的质量比为1：2.0，所述负极材料的PH值为10.6。所述负极材料的表面包覆有碳层，所述碳层厚度为199nm。
本实施例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
实施例6
本实施例按照如下方法制备负极材料：
(1)取1kg Si粉与2.2kg 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1400℃并保温16h，在炉内生成SiO蒸汽经过迅速凝结(凝结的温度为970℃)生成SiO 1.3块体；将SiO 1.3块体经过破碎、球磨、分级等工艺处理，得到SiO 1.3粉体材料，其中值粒径控制在6μm左右(D10为1.6μm，Dmax为25μm)。
(2)取1.5kg SiO 1.3粉体材料置于CVD回转炉中，通入乙烯作为碳源，通入氮气作为保护气，1000℃沉积30min，冷却出料得SiO 1.3/C材料。
(3)取1kg SiO 1.3/C材料与100g五氧化二磷投入VC混合机内混合40min取出，得到SiO 1.3/C材料与五氧化二磷的混合物，然后将混合物放入球磨罐中，加入100g氢化锂球磨20min取出，得到预锂前驱体；将预锂前驱体置于氮气保护下热处理，热处理温度450℃，热处理时间2h，自然降温至室温取出物料、经筛分、除磁，得到负极材料。
本实施例制备的负极材料包括SiO 1.2和Li 2Si 2O 5，所述SiO 1.2均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 1.2和Li 2Si 2O 5的质量比为1：2.1，所述负极材 料的PH值为9.8。所述负极材料的表面包覆有碳层，所述碳层厚度为204nm。
本实施例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
实施例7
本实施例按照如下方法制备负极材料：
(1)取1kg Si粉与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块体；将SiO块体经过破碎、球磨、分级等工艺处理，得到SiO粉体材料，其中值粒径控制在6μm左右(D10为1.1μm，Dmax为27μm)。
(2)取1.5kg SiO粉体材料、113g沥青置于VC机中混合40min，转速500rpm，出料后置于高温箱式炉中600℃烧成6h，箱式炉中通入氮气保护，自然冷却至室温出料得SiO/C材料。
(3)取1kg SiO/C材料与20g五氧化二磷投入VC混合机内混合40min取出，得到SiO/C材料与五氧化二磷的混合物，然后将混合物放入球磨罐中，加入120g硼氢化锂球磨20min取出，得到预锂前驱体；将预锂前驱体置于氩气保护下热处理，热处理温度300℃，热处理时间2.5h，自然降温至室温取出物料、经筛分、除磁，得到负极材料。
本实施例制备的负极材料包括SiO 0.6和Li 2Si 2O 5，所述SiO 0.6均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 0.6和Li 2Si 2O 5的质量比为1：3.0，所述负极材料的PH值为10.2。所述负极材料的表面包覆有碳层，所述碳层厚度为210nm。
本实施例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
实施例8
本实施例按照如下方法制备负极材料：
(1)取1kg Si粉与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块体；将SiO块体经过破碎、球磨、分级等工艺处理，得到SiO粉体材料，其中值粒径控制在6μm左右(D10为1.5μm，Dmax为26μm)。
(2)取1.5kg SiO粉体材料、113g沥青置于VC机中混合50min，转速3000rpm，出料后置于高温箱式炉中1000℃烧成2h，箱式炉中通入氮气保护，自然冷却至室温出料得SiO/C材料。
(3)取1kg SiO/C材料与20g五氧化二磷投入VC混合机内混合40min取出，得到SiO/C材料与五氧化二磷的混合物，然后将混合物放入球磨罐中，加入150g金属锂球磨20min取出，得到预锂前驱体；将预锂前驱体置于氮气保护下热处理，热处理温度1000℃，热处理时间1.5h，自然降温至室温取出物料、经筛分、除磁，得 到负极材料。
本实施例制备的负极材料包括SiO 0.2和Li 2Si 2O 5，所述SiO 0.2均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 0.2和Li 2Si 2O 5的质量比为1：1.6，所述负极材料的PH值为10.6。所述负极材料的表面包覆有碳层，所述碳层厚度为198nm。
本实施例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
实施例9
本实施例按照如下方法制备负极材料：
(1)取1kg Si粉与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块体；将SiO块体经过破碎、球磨、分级等工艺处理，得到SiO粉体材料，其中值粒径控制在6μm左右(D10为1.5μm，Dmax为29μm)。
(2)取1.5kg SiO粉体材料、沥青113g置于VC机中混合30min，转速800rpm，出料后置于高温箱式炉中900℃烧成3h，箱式炉中通入氮气保护。自然冷却至室温出料得SiO/C材料。
(3)取1kg SiOy/C材料与20g三氧化二磷投入VC混合机内混合40min取出，得到SiO/C材料与三氧化二磷的混合物，然后将混合物放入球磨罐中，加入100g氢化锂球磨20min取出，得到预锂前驱体；将预锂前驱体置于氮气保护下热处理，热处理温度800℃，热处理时间2h，自然降温至室温取出物料、经筛分、除磁，得到负极材料。
本实施例制备的负极材料包括SiO 0.9和Li 2Si 2O 5，所述SiO 0.9均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 0.9和Li 2Si 2O 5的质量比为1：2.3，所述负极材料的PH值为10.1。所述负极材料的表面包覆有碳层，所述碳层厚度为207nm。
本实施例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
实施例10
本实施例按照如下方法制备负极材料：
(1)取1kg Si粉与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块体；将SiO块体经过破碎、球磨、分级等工艺处理，得到SiO粉体材料，其中值粒径控制在6μm左右(D10为1.5μm，Dmax为29μm)。
(2)取1.5kg SiO粉体材料、沥青113g置于VC机中混合30min，转速800rpm，出料后置于高温箱式炉中900℃烧成3h，箱式炉中通入氮气保护。自然冷却至室温出料得SiO/C材料。
(3)取1kg SiO/C材料与20g磷酸锂投入VC混合机内混合40min取出，得到 SiO/C材料与磷酸锂的混合物，然后将混合物放入球磨罐中，加入100g氢化锂球磨20min取出，得到预锂前驱体；将预锂前驱体置于氮气保护下热处理，热处理温度800℃，热处理时间2h，自然降温至室温取出物料、经筛分、除磁，得到负极材料。
本实施例制备的负极材料包括SiO 0.92和Li 2Si 2O 5，所述SiO 0.92均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 0.92和Li 2Si 2O 5的质量比为1：2.9，所述负极材料的PH值为9.9。所述负极材料的表面包覆有碳层，所述碳层厚度为250nm。
本实施例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
实施例11
本实施例按照如下方法制备负极材料：
(1)取1kg Si粉与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块体；将SiO块体经过破碎、球磨、分级等工艺处理，得到SiO粉体材料，其中值粒径控制在6μm左右(D10为1.3μm，Dmax为25μm)。
(2)取1.5kg SiO粉体材料置于CVD回转炉中，通入乙炔作为碳源，通入氮气作为保护气，800℃沉积70min，冷却出料得SiO/C材料。
(3)取1kg SiO/C材料与8gNaCl投入VC混合机内混合40min取出，得到SiO/C材料与NaCl的混合物，然后将混合物放入球磨罐中，加入100g氢化锂球磨20min取出，得到预锂前驱体；将预锂前驱体置于氮气保护下热处理，热处理温度800℃，热处理时间2h，自然降温至室温取出物料、经筛分、除磁得到负极材料。
本实施例制备的负极材料中，包括SiO 0.9和Li 2Si 2O 5，所述SiO 0.9均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 0.9和Li 2Si 2O 5的质量比为1:3.5，所述负极材料的PH值为10.3。所述负极材料的表面包覆有碳层，所述碳层厚度为180nm。
本实施例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
实施例12
本实施例按照如下方法制备负极材料：
(1)取1kg Si粉与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块体；将SiO块体经过破碎、球磨、分级等工艺处理，得到SiO粉体材料，其中值粒径控制在6μm左右(D10为1.3μm，Dmax为25μm)。
(2)取1.5kg SiO粉体材料置于CVD回转炉中，通入乙炔作为碳源，通入氮气作为保护气，800℃沉积70min，冷却出料得SiO/C材料。
(3)取1kg SiO/C材料与30gNaCl投入VC混合机内混合40min取出，得到SiO/C材料与NaCl的混合物，然后将混合物放入球磨罐中，加入100g氢化锂球磨 20min取出，得到预锂前驱体；将预锂前驱体置于氮气保护下热处理，热处理温度800℃，热处理时间2h，自然降温至室温取出物料、经筛分、除磁得到负极材料。
本实施例制备的负极材料中，包括SiO 0.3和Li 2Si 2O 5，所述SiO 0.3均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 0.3和Li 2Si 2O 5的质量比为1:0.2，所述负极材料的PH值为10.3。所述负极材料的表面包覆有碳层，所述碳层厚度为800nm。
本实施例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
对比例1
(1)取1kg Si粉与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块体；将SiO块体经过破碎、球磨、分级等工艺处理，得到SiO粉体材料，其中值粒径控制在6μm左右(D10为1.2μm，Dmax为28μm)。
(2)取1kg SiO粉体材料、20g五氧化二磷，得到SiO与五氧化二磷的混合物，然后将混合物放入球磨罐中，加入100g氢化锂球磨20min取出，得到预锂前驱体；将预锂前驱体置于氮气保护下热处理，热处理温度800℃，热处理时间2h，自然降温至室温取出物料、经筛分、除磁得到负极材料。
本实施例制备的负极材料包括SiO 0.8、Li 2SiO 3和Li 2Si 2O 5，所述SiO 0.8均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 0.8和Li 2Si 2O 5的质量比为1：2.6，所述负极材料的PH值为11.3。
本实施例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
本对比例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
对比例2
本实施例按照如下方法制备负极材料：
(1)取1kg Si粉与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块体；将SiO块体经过破碎、球磨、分级等工艺处理，得到SiO粉体材料，其中值粒径控制在6μm左右(D10为1.5μm，Dmax为29μm)。
(2)取1.5kg SiO粉体材料、沥青113g置于VC机中混合30min，转速800rpm，出料后置于高温箱式炉中900℃烧成3h，箱式炉中通入氮气保护。自然冷却至室温出料得SiO/C材料。
(3)取1kg SiO/C材料与20g五氧化二磷，得到SiO/C材料与五氧化二磷的混合物，然后将混合物放入球磨罐中，加入100g氢化锂球磨20min取出，得到预锂前 驱体；将预锂前驱体置于氮气保护下热处理，热处理温度800℃，热处理时间2h，自然降温至室温取出物料、经筛分、除磁，得到负极材料。
本实施例制备的负极材料包括SiO 0.86、Li 2SiO 3和Li 2Si 2O 5，所述SiO 0.86均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 0.86和Li 2Si 2O 5的质量比为1：2.2，所述负极材料的PH值为11.2。所述负极材料的表面包覆有碳层，所述碳层厚度为220nm。
本实施例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
图4为本对比例制备的负极材料的XRD图谱，由该图可以看出图谱中除了硅特征峰和Li 2Si 2O 5特征峰以外，还有Li 2SiO 3的特征峰存在。
图5a为本对比例制备的负极材料的产气测试照片，由该图可以看出密封的铝塑膜袋鼓起，说明内部出现了产气现象。
图5b为本对比例制备的负极材料的涂布测试照片，由该图可以看出极片上布满针孔。
本对比例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
对比例3
本实施例按照如下方法制备负极材料：
(1)取1kg Si粉与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块体；将SiO块体经过破碎、球磨、分级等工艺处理，得到SiO粉体材料，其中值粒径控制在6μm左右(D10为1.3μm，Dmax为25μm)。
(2)取1.5kg SiO粉体材料置于CVD回转炉中，通入乙炔作为碳源，通入氮气作为保护气，800℃沉积70min，冷却出料得SiO/C材料。
(3)取1kg SiO/C材料与5g五氧化二磷投入VC混合机内混合40min取出，得到SiO/C材料与五氧化二磷的混合物，然后将混合物放入球磨罐中，加入100g氢化锂球磨20min取出，得到预锂前驱体；将预锂前驱体置于氮气保护下热处理，热处理温度800℃，热处理时间2h，自然降温至室温取出物料、经筛分、除磁得到负极材料。
本实施例制备的负极材料中，包括SiO 0.95和Li 2Si 2O 5，所述SiO 0.95均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 0.95和Li 2Si 2O 5的质量比为1:6.1，所述负极材料的PH值为11.0。所述负极材料的表面包覆有碳层，所述碳层厚度为200nm。
本对比例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
对比例4
本实施例按照如下方法制备负极材料：
(1)取1kg Si粉与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块体；将SiO块体经过破碎、球磨、分级等工艺处理，得到SiO粉体材料，其中值粒径控制在6μm左右(D10为1.3μm，Dmax为25μm)。
(2)取1.5kg SiO粉体材料置于CVD回转炉中，通入乙炔作为碳源，通入氮气作为保护气，800℃沉积70min，冷却出料得SiO/C材料。
(3)取1kg SiO/C材料与10g五氧化二磷投入VC混合机内混合40min取出，得到SiO/C材料与五氧化二磷的混合物，然后将混合物放入球磨罐中，加入100g氢化锂球磨20min取出，得到预锂前驱体；将预锂前驱体置于氮气保护下热处理，热处理温度800℃，热处理时间2h，自然降温至室温取出物料、经筛分、除磁得到负极材料。
本实施例制备的负极材料中，包括SiO 0.88和Li 2Si 2O 5，所述SiO 0.88均匀分散在Li 2Si 2O 5中。所述负极材料中，SiO 0.88和Li 2Si 2O 5的质量比为1:5.0，所述负极材料的PH值为11.1。所述负极材料的表面包覆有碳层，所述碳层厚度为190nm。
本对比例制备的负极材料的常规性能测试结果见表1，电化学性能测试结果见表2。
测试方法
1、XRD测试：
添加10wt％的氧化镁作为标准物质，均匀混合至各实施例和对比例制备的待测试负极材料中，制片，进行测试。角度范围：10～90°，扫描模式：步进扫描，选择狭缝宽度1.0，并设置电压40kW，电流40mA。测得数据再通过Jade6.5计算各组分相对含量。
2、加工性能测试
(1)产气测试。分别将各实施例和对比例制备的负极材料作为活性物质，SBR+CMC作为粘结剂，加入导电炭黑，按活性物质：导电剂：粘结剂＝95:2:3配比高速搅拌混合均匀，得到浆料，将其装入铝塑膜袋中密封、静置，然后监测铝塑膜袋的形状变化，监测周期1个月。
(2)涂布测试。将产气测试中配置好的浆料均匀涂覆在铜箔上，烘干后观察极片表面是否有针孔、气孔、凹坑存在。
3、扣电测试
分别将各实施例和对比例制备的负极材料作为活性物质，SBR+CMC作为粘结剂，加入导电炭黑后搅拌制浆涂覆在铜箔上，最后经过烘干碾压制得负极片，活性物质：导电剂：粘结剂＝85:15:10。以金属锂片作为对电极，PP/PE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，在充氩气的手套箱中装配模拟电池。采用蓝电5V/10mA型电池测试仪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。
4、循环测试
分别将各实施例和对比例制备的负极材料与石墨按质量比1：9混合均匀后作为 活性物质，以金属锂片作为对电极，PP/PE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，在充氩气的手套箱中组装扣式电池，采用蓝电5V/10mA型电池测试仪测试电池循环50周的电化学性能，充电电压为1.5V，放电至0.01V，充放电速率为0.1C。
上述测试的结果见表1和表2。
表1
Figure PCTCN2020124347-appb-000001
Figure PCTCN2020124347-appb-000002
表2
实验 放电容量mAh/g 首效％ 50周容量保持率％
实施例1 1308 86.5 88.8
实施例2 1417 88.9 89.1
实施例3 1420 89.5 90.5
实施例4 1411 88.6 90.0
实施例5 1400 88.3 89.1
实施例6 1404 86.5 89.4
实施例7 1415 88.4 90.2
实施例8 1407 90.5 90.1
实施例9 1388 87.0 88.8
实施例10 1380 87.2 88.9
实施例11 1394 88.8 90.0
实施例12 1405 89.7 91.8
对比例1 1720 76.8 75.8
对比例2 1720 76.8 75.8
对比例3 1401 86.7 82.2
对比例4 1421 86.5 84.6
根据表1及表2，从实施例2、实施例3、对比例3、对比例4可以看出，随着 P 2O 5添加量增加，Li 2SiO 3含量逐渐减少，当添加量达到2％时，已经没有Li 2SiO 3存在，材料的加工性能得到改善。从实施例1、2和4可以看出，包碳后再进行预锂化反应，并添加成核转化剂可获得更好的转化效果，并且碳源种类对Li 2SiO 3的转化效果没有影响。
总体上看，添加成核转化剂后，随着负极材料中的Li 2Si 2O 5含量增加，负极材料循环性能明显提升；当Li 2SiO 3全部转化为Li 2Si 2O 5之后，材料的循环保持率稳定在88％以上。
实施例9-10没有使用成核转化剂P 2O 5，而使用了其他种类的成核转化剂。相比于实施例4，实施例9和10制备出来的材料容量、循环均比添加P 2O 5的较差，可能是转化剂的种类不同所致。因为P 2O 5对于Li 2SiO 3转换为Li 2Si 2O 5的效果更显著，加入P 2O 5后材料中的Li 2Si 2O 5含量也更多，对循环过程带来的膨胀抑制作用更强。
实施例11-12中添加吸热剂，吸热剂促进高温相的Li 2SiO 3向低温相的Li 2Si 2O 5转变，也能使最终产物只有Li 2Si 2O 5，且表现出良好的首次库伦效率以及循环性能。
对比例1在实施例1的基础上没有加入成核转化剂，导致Li 2SiO 3含量较高，加工性能变差，产气多，涂布后出现明显针孔，首效和循环性能均明显劣于实施例1。对比例2的情况与对比例1相同，也是没有加入成核转化剂，导致产品加工性能变差，产气多，涂布后出现明显针孔，首效和循环性能不及实施例4。
对比例3、对比例4分别在实施例2的基础上，改变了成核转化剂的添加量，硅氧化物与成核转化剂的质量比分别为100：0.5和100:1，对比例3～4中的成核转化剂不足，不能将Li 2SiO 3完全转换为Li 2Si 2O 5，导致材料加工性能变差，放置后也会出现产气现象，涂布时出现针孔。
申请人声明，本申请通过上述实施例来说明本申请的详细方法，但本申请并不局限于上述详细方法，即不意味着本申请必须依赖上述详细方法才能实施。所属技术领域的技术人员应该明了，对本申请的任何改进，对本申请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，均落在本申请的保护范围和公开范围之内。

Claims (14)

  1. 一种负极材料，其特征在于，所述负极材料包括SiO x及Li 2Si 2O 5，所述SiO x分散在Li 2Si 2O 5中，其中，0≤x≤1.2。
  2. 根据权利要求1所述的负极材料，其特征在于，其满足以下条件a～d的至少一者：
    a.所述负极材料的的PH值为7＜PH＜10.7；
    b.所述负极材料的平均粒径为5μm～50μm；
    c.所述负极材料中的SiO x与Li 2Si 2O 5的质量比为1：(0.74～6.6)；
    d.所述SiO x均匀分散在Li 2Si 2O 5中。
  3. 根据权利要求1或2所述的负极材料，其特征在于，其满足以下条件a～c的至少一者：
    a.所述负极材料的表面形成有碳包覆层；
    b.所述负极材料的表面形成有碳包覆层，所述碳包覆层的厚度为10nm～2000nm；
    c.所述负极材料的表面形成有碳包覆层，所述负极材料中的碳元素的质量分数为4％～6％。
  4. 一种负极材料的制备方法，其特征在于，包括以下步骤：
    将硅氧化物SiO y、还原性含锂化合物和助剂进行混合，热处理，得到所述负极材料，其中，所述助剂包括成核转化剂或吸热剂，0＜y＜2。
  5. 根据权利要求4所述的制备方法，其特征在于，其满足以下条件a～f的至少一者：
    a.所述负极材料的的PH值为7＜PH＜10.7；
    b.所述负极材料的平均粒径为5μm～50μm；
    c.所述负极材料中的SiO x与Li 2Si 2O 5的质量比为1：(0.74～6.6)。
    d.所述负极材料的表面形成有碳包覆层；
    e.所述负极材料的表面形成有碳包覆层，所述碳包覆层的厚度为10nm～2000nm；
    f.所述负极材料的表面形成有碳包覆层，所述负极材料中的碳元素的质量分数为4％～6％。
  6. 根据权利要求4或5所述的制备方法，其特征在于，其满足以下条件a～d的至少一者：
    a.所述硅氧化物和还原性含锂化合物的质量比为10：(0.08～1.2)；
    b.所述硅氧化物为一氧化硅；
    c.所述硅氧化物的D10＞1.0μm且Dmax＜50μm；
    d.所述还原性锂化合物包括氢化锂、烷基锂、金属锂、氢化铝锂、氨基锂和硼氢化锂中的至少一种。
  7. 根据权利要求4～6任一项所述的制备方法，其特征在于，其满足以下条件a～h的至少一者：
    a.所述成核转化剂包括磷的氧化物和磷酸盐中的至少一种；
    b.所述磷的氧化物包括五氧化二磷和三氧化二磷中的至少一种；
    c.所述磷酸盐包括磷酸锂、磷酸镁和磷酸钠中的至少一种；
    d.所述成核转化剂为五氧化二磷；
    e.所述吸热剂的熔点小于700℃；
    f.所述吸热剂包括LiCl、NaCl、NaNO 3、KNO 3、KOH、BaCl、KCl和LiF中的至少一种；
    g.所述硅氧化物和所述成核转化剂的质量比为100：(2～10)；
    h.所述硅氧化物和所述吸热剂的质量比为100：(8～30)。
  8. 根据权利要求4～7任一项所述的制备方法，其特征在于，其满足以下条件a～d的至少一者：
    a.所述热处理在非氧化性气氛下进行；
    b.所述热处理在非氧化性气氛下进行；所述非氧化性气氛包括氢气、氮气、氦气、氖气、氩气、氪气和氙气中的至少一种；
    c.所述热处理的温度为300℃～1000℃；
    d.所述热处理的时间为1.5h～2.5h。
  9. 根据权利要求4～8任一项所述的制备方法，其特征在于，在将硅氧化物SiO y、还原性含锂化合物和成核转化剂或吸热剂进行混合之前，所述方法还包括：
    将硅氧化物的原料进行加热气化，产生硅氧化物气体，并进行冷凝、整形得到硅氧化物SiO y，其中，0＜y＜2。
  10. 根据权利要求9所述的制备方法，其特征在于，其满足以下条件a～g的至少一者：
    a.所述硅氧化物的原料包括硅和二氧化硅；
    b.所述硅和所述二氧化硅的质量比为1:(1.8～2.2)；
    c.所述加热气化的温度为1200℃～1400℃；
    d.所述加热气化的时间为16h～20h；
    e.所述冷凝的温度为930℃～970℃；
    f.所述加热气化在保护性气氛或真空中进行；
    g.所述整形包括破碎、球磨和分级中的至少一种。
  11. 根据权利要求4～10任一项所述的制备方法，其特征在于，所述方法还包括：
    对待包碳材料进行碳包覆，所述待包碳材料包括所述硅氧化物和所述负极材料中的至少一种。
  12. 根据权利要求11所述的制备方法，其特征在于，其满足以下条件a～c的至少一者：
    a.所述碳包覆包括气相包碳和固相包碳中的至少一种；
    b.所述碳包覆包括气相包碳和固相包碳中的至少一种，所述气相包碳的条件为：将所述硅氧化物在保护性气氛下升温至600℃～1000℃，通入有机碳源气体，保温0.5h～10h后冷却；其中，所述有机碳源气体包括烃类，所述烃类包括甲烷、乙烯、乙炔和苯中的至少一种；
    c.所述碳包覆包括气相包碳和固相包碳中的至少一种，所述固相包碳的条件为：将所述硅氧化物与碳源融合0.5h～2h后，将得到的碳混合物在600℃～1000℃下碳化2h～6h，冷却；其中，所述碳源包括聚合物、糖类、有机酸和沥青中的至少一种。
  13. 根据权利要求3～12任一项所述的制备方法，其特征在于，所述方法包括以下步骤：
    按照质量比为1：(1.8～2.2)将硅和二氧化硅在真空中1200℃～1400℃加热气化16h～20h，再在930℃～970℃下冷凝，整形，得到一氧化硅；
    对所述一氧化硅进行碳包覆，得到包碳的一氧化硅；
    按照质量比为100：(2～10)将所述包碳的一氧化硅和五氧化二磷混合后，再加入还原性含锂化合物混合，在非氧化气氛下450℃～800℃下焙烧1.5h～2.5h，得到负极材料；其中，所述包碳的一氧化硅和所述还原性含锂化合物的质量比为10：(0.08～1.2)。
  14. 一种锂离子电池，其特征在于，所述锂离子电池包含如权利要求1～3任一项所述的负极材料或根据权利要求4～13任一项所述的制备方法制得的负极材料。
PCT/CN2020/124347 2019-10-30 2020-10-28 负极材料及其制备方法和锂离子电池 WO2021083199A1 (zh)

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