WO2021233439A1 - 硅氧复合负极材料及其制备方法和锂离子电池 - Google Patents

硅氧复合负极材料及其制备方法和锂离子电池 Download PDF

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WO2021233439A1
WO2021233439A1 PCT/CN2021/095260 CN2021095260W WO2021233439A1 WO 2021233439 A1 WO2021233439 A1 WO 2021233439A1 CN 2021095260 W CN2021095260 W CN 2021095260W WO 2021233439 A1 WO2021233439 A1 WO 2021233439A1
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silicon
sio
nano
negative electrode
lithium
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PCT/CN2021/095260
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English (en)
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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Application filed by 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 filed Critical 贝特瑞新材料集团股份有限公司
Priority to US17/771,734 priority Critical patent/US20220376228A1/en
Priority to EP21809751.7A priority patent/EP4044283A4/en
Priority to KR1020217039298A priority patent/KR20220002633A/ko
Priority to JP2021571413A priority patent/JP7323140B2/ja
Publication of WO2021233439A1 publication Critical patent/WO2021233439A1/zh

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Definitions

  • the application 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, and in particular to a silicon-oxygen composite negative electrode material, 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 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 achieve industrialization.
  • the problem of poor processing performance generally exists by pre-lithium pre-lithium on the material side, which is mainly manifested as: serious gas production of water-based slurry, low viscosity, tailing during coating, and appearance after the pole piece is dried. Pinholes, stomata, etc. Therefore, poor processing performance is still a common problem in pre-lithium materials, and it is also a technical difficulty.
  • the purpose of this application is to provide a silicon-oxygen composite negative electrode material, a preparation method thereof, and a lithium ion battery.
  • the negative electrode material provided by the present application can improve the processing stability of the negative electrode material, and can improve the cycle stability and battery capacity of the lithium battery.
  • the present application provides a silicon-oxygen composite anode material.
  • the silicon-oxygen composite anode material has a core-shell structure, and the core includes nano-silicon and silicon oxide SiO x , where 0 ⁇ x ⁇ 1.2, and The shell includes Li 2 SiO 3 .
  • the silicon-oxygen composite negative electrode material provided in the present application Li 2 SiO 3 with a stable structure is coated outside the inner core. Nano silicon does not directly contact water, so it can effectively inhibit gas production, improve the processing stability of pre-lithium materials, and solve the problem of chemical reaction and gas release in the prior art when silicon contacts water in an alkaline environment.
  • the slurry for preparing the silicon-oxygen composite negative electrode material provided in the present application does not generate gas, and the coating is normally without pinholes, which solves the problem that the negative electrode material in the prior art produces strong alkaline or easily soluble by-products after pre-lithium and affects subsequent processing. The problem of improving material processing stability, and can improve the cycle stability and battery capacity of lithium batteries.
  • the shell further includes a conductive material, and the conductive material satisfies at least one of the following conditions a to f:
  • the conductive material is dispersed on the inside and/or surface of the shell;
  • the conductive material is dispersed in Li 2 SiO 3 ;
  • the conductive material includes inorganic carbon materials and/or conductive polymers
  • the conductive material includes an inorganic carbon material, and the inorganic carbon material includes at least one of cracked carbon, carbon fiber, carbon nanotube, and conductive carbon black;
  • the conductive material includes a conductive polymer, and the conductive polymer includes at least one of polyaniline, polypyrrole, polythiophene, and polyacetylene;
  • the mass ratio of the Li 2 SiO 3 to the conductive substance is 1: (0.01-0.6).
  • the nano silicon is dispersed in the silicon oxide SiO x in the form of nano silicon aggregates
  • the nano-silicon is dispersed in the silicon oxide SiO x in the form of nano-silicon aggregates, and the nano-silicon aggregates include a plurality of nano-silicon crystal grains;
  • the particle size of the nano-silicon crystal grains is 0nm-15nm, and does not include 0nm;
  • the mass ratio of the nano-silicon to the silicon oxide is (0.05-0.7):1;
  • the thickness of the shell is 50nm ⁇ 2000nm;
  • the mass fraction of Li 2 SiO 3 in the silicon-oxygen composite anode material is 20wt% to 80wt%;
  • the average particle size of the silicon-oxygen composite negative electrode material is 1 ⁇ m-50 ⁇ m.
  • this application provides a method for preparing a silicon-oxygen composite anode material, which includes the following steps:
  • the composite material containing Li 2 SiO 3 is immersed in an acid solution to obtain the silicon-oxygen composite negative electrode material;
  • the silicon-oxygen composite negative electrode material has a core-shell structure, wherein the core includes nano silicon and silicon Oxide SiO x , where 0 ⁇ x ⁇ 1.2, and the shell includes Li 2 SiO 3 .
  • the pre-lithium reaction is first performed so that only part of the silicon oxide on the surface of the silicon source is converted into Li 2 SiO 3 , while retaining the internal silicon oxide structure.
  • the nano-silicon is dispersed in the SiO x in the form of nano-silicon aggregates. Internally, a product with a special structure provided by the present application is obtained, and the preparation method is simple in operation, short in flow, and low in production cost.
  • the silicon-oxygen composite negative electrode material satisfies at least one of the following conditions a to g:
  • the nano silicon is dispersed in the silicon oxide SiO x in the form of nano silicon aggregates
  • the nano-silicon is dispersed in the silicon oxide SiO x in the form of nano-silicon aggregates, and the nano-silicon aggregates include a plurality of nano-silicon crystal grains;
  • the particle size of the nano-silicon crystal grains is 0nm-15nm, and does not include 0nm;
  • the mass ratio of the nano-silicon to the silicon oxide is (0.05-0.7):1;
  • the thickness of the shell is 50nm ⁇ 2000nm;
  • the mass fraction of Li 2 SiO 3 in the silicon-oxygen composite anode material is 20wt% to 80wt%;
  • the average particle size of the silicon-oxygen composite negative electrode material is 1 ⁇ m-50 ⁇ m.
  • the lithium source is an oxygen-free lithium compound
  • the lithium source includes at least one of lithium hydride, lithium amide, alkyl lithium, elemental lithium, and lithium borohydride;
  • the silicon source is SiO y , 0 ⁇ y ⁇ 2;
  • the molar ratio of the silicon source to the lithium source is (0.6 ⁇ 7.9):1;
  • the non-oxygen atmosphere gas 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 2h-8h.
  • the acid solution is a mixed acid formed by mixing nitric acid and hydrofluoric acid;
  • the acid solution is a mixed acid formed by mixing nitric acid and hydrofluoric acid in a mass ratio of 1:(0.5 ⁇ 3);
  • the immersion time is 20min ⁇ 90min.
  • the method further includes:
  • the heat-treated product is cooled and sieved.
  • the method further includes:
  • the impregnated solid product was washed with water to neutrality.
  • the method before mixing the silicon source with the lithium source, the method further includes:
  • the mixture of Si and SiO 2 is heated and gasified in a protective atmosphere or in a vacuum to produce silicon oxide gas, which is cooled and shaped to obtain a silicon source.
  • the general formula of the silicon source is SiO y , 0 ⁇ y ⁇ 2.
  • the heating temperature is 900°C ⁇ 1500°C;
  • the shaping includes at least one of crushing, ball milling or classification
  • the average particle size of the silicon source is 0.2 ⁇ m-50 ⁇ m;
  • the gas of the protective atmosphere includes at least one of nitrogen, helium, neon, argon, krypton, and xenon.
  • the preparation method further includes:
  • the product obtained by the immersion is fused with a conductive material to obtain a silicon-oxygen composite negative electrode material containing the conductive material.
  • the conductive material satisfies at least one of the following conditions a to e:
  • the conductive material is dispersed in Li 2 SiO 3 ;
  • the conductive material includes inorganic carbon materials and/or conductive polymers
  • the conductive material includes an inorganic carbon material, and the inorganic carbon material includes at least one of cracked carbon, carbon fiber, carbon nanotube, and conductive carbon black;
  • the conductive material includes a conductive polymer, and the conductive polymer includes at least one of polyaniline, polypyrrole, polythiophene, and polyacetylene;
  • the mass ratio of the Li 2 SiO 3 to the conductive substance is 1: (0.01-0.6).
  • the method includes the following steps:
  • the general formula of the silicon source is SiO y , 0 ⁇ y ⁇ 2;
  • the silicon source and the oxygen-free lithium compound are mixed at a mass ratio of 1: (0.02 ⁇ 0.20), and the heat treatment is carried out at 450°C ⁇ 800°C in a non-oxidizing atmosphere.
  • the heat treatment time is 2h ⁇ 8h, and then it is cooled and sieved. To obtain a composite material containing Li 2 SiO 3;
  • the composite material containing Li 2 SiO 3 is immersed in an acid solution formed by mixing nitric acid and hydrofluoric acid with a mass ratio of 1: (0.5-3) for 20 min to 90 min, and then washed with water to neutrality after immersion to obtain Impregnated product
  • the impregnated product and the conductive material are fused to obtain the silicon-oxygen composite negative electrode material.
  • the present application provides a lithium ion battery comprising the silicon-oxygen composite anode material described in the first aspect above or the silicon-oxygen composite anode material prepared according to the preparation method described in the second aspect above .
  • Li 2 SiO 3 with a stable structure is coated outside the inner core. Nano-silicon will not come into physical contact with substances other than SiO x . Although Li 2 SiO 3 has a certain alkalinity, nano-silicon is dispersed in the silicon oxide SiO x in the form of aggregates and cannot be directly contacted with water, so it can It can effectively inhibit gas production, improve the processing stability of the pre-lithium material, and solve the problem of chemical reaction and gas release in the prior art that silicon contacts with water in an alkaline environment.
  • the slurry for preparing the silicon-oxygen composite negative electrode material provided in the present application does not generate gas, and the coating is normally without pinholes, which solves the problem that the negative electrode material in the prior art produces strong alkaline or easily soluble by-products after pre-lithium and affects subsequent processing.
  • Preparation method of the present application provided by controlling suitable pre lithium extent, only the silicon source surface layer portion of the silicon oxide is Li 2 SiO 3, while retaining the silicon oxide structure within the formed nano-silicon in the form of aggregates dispersed in The internal structure of the silicon oxide SiO x obtains the product with a special structure provided by the present application.
  • the preparation method is simple in operation, short in flow, and low in production cost.
  • FIG. 1 is a process flow diagram of a method for preparing a silicon-oxygen composite anode material provided by an embodiment of the application;
  • Figure 4 is a gas production test photo of the negative electrode material prepared in Comparative Example 1;
  • FIG. 5 is a photo of the coating test of the negative electrode material prepared in Comparative Example 1.
  • the present application provides a silicon-oxygen composite anode material.
  • the silicon-oxygen composite anode material has a core-shell structure, and the core includes nano-silicon and silicon oxide SiO x , where 0 ⁇ x ⁇ 1.2, and The shell includes Li 2 SiO 3 .
  • Li 2 SiO 3 with a stable structure is coated outside the inner core.
  • Nano-silicon is not in direct contact with water, so it can effectively inhibit gas production, improve the processing stability of pre-lithium materials, and solve the problem of chemical reaction and gas release in the prior art when silicon contacts water in an alkaline environment.
  • lithium silicate can improve the first effect, buffer volume expansion, and increase the lithium ion conductivity of the material.
  • the negative electrode material can improve the cycle stability and battery capacity of the lithium battery.
  • the chemical formula of the silicon oxide is SiO x , where 0 ⁇ x ⁇ 1.2, and SiO x can be SiO 0.1 , SiO 0.2 , SiO 0.3 , SiO 0.4 , SiO 0.5 , SiO 0.6 , At least one of SiO 0.7 , SiO 0.8 , SiO 0.9 , SiO and SiO 1.1.
  • SiO x can be understood to be formed by uniformly dispersing at least one of amorphous silicon or crystalline Si in SiO 2 .
  • the surface of the negative electrode material provided in the present application is covered with Li 2 SiO 3 with a stable structure, so that the nano-silicon will not come into physical contact with substances other than amorphous silicon oxide.
  • Nano-silicon is dispersed in the SiO x in the form of nano-silicon aggregates.
  • Nano-silicon aggregates include multiple nano-silicon crystal grains; because nano-silicon is dispersed in SiO x in the form of aggregates, and the surface of SiO x is wrapped with a stable structure of Li 2 SiO 3 , it is difficult for nano-silicon to interact with other than SiO x .
  • Li 2 SiO 3 is in physical contact. Although Li 2 SiO 3 has a certain alkalinity, nano-silicon is distributed in the SiO x in the form of nano-silicon aggregates and cannot be directly contacted with water. Therefore, it can effectively inhibit gas production and improve the processing of pre-lithium materials. stability.
  • the nano-silicon aggregate is composed of a plurality of nano-silicon crystal grains, and the nano-silicon aggregate refers to an aggregate composed of several or even thousands of nano-silicon crystal grains through physical or chemical bonding.
  • the average particle size of the nano silicon crystal grains is 0-15 nm, and does not include 0 nm, such as 1 nm, 3 nm, 5 nm, 8 nm, 10 nm, 12 nm, or 15 nm. Understandably, when the silicon content is the same, compared with large-sized crystalline silicon grains, due to the isotropic expansion of silicon, when small-sized silicon grains form aggregates, the interaction force can be used to offset part of the expansion, so The expansion of the nano-silicon aggregate is smaller and the cycle life is longer, which can help improve the cycle performance and rate performance of the negative electrode material.
  • the mass ratio of the nano-silicon to the silicon oxide is (0.05-0.7):1, specifically may be 0.05:1, 0.08:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, or 0.7:1, etc., but not limited to the listed values, and other unlisted values within this range of values are also applicable.
  • the mass ratio of the nano-silicon to the silicon oxide is controlled within the range of (0.05-0.7):1, and the final negative electrode material can obtain higher capacity and cycle.
  • the proportion of nano-silicon is too high, the negative electrode The cycle and expansion performance of the material is poor; when the proportion of silicon oxide is too high, the capacity of the negative electrode material is low.
  • the average particle size of the silicon-oxygen composite negative electrode material is 1 ⁇ m-50 ⁇ m; more specifically, it can be 1 ⁇ m, 10 ⁇ m, 15 ⁇ m, 20 ⁇ m, 25 ⁇ m, 30 ⁇ m, 35 ⁇ m, 40 ⁇ m, 50 ⁇ m, etc., but It is not limited to the listed values, and other unlisted values within this 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 thickness of the shell is 50nm-2000nm, specifically, it can be 50nm, 100nm, 300nm, 500nm, 800nm, 1000nm, 1500nm, 1800nm or 2000nm, but it is not limited to the listed values. Other unlisted values within the numerical range also apply. If the shell layer is too thick, the lithium ion transmission efficiency is reduced, which is not conducive to the large-rate charge and discharge of the material, and the overall performance of the negative electrode material is reduced. Lead to long cycle performance price difference.
  • the shell further includes a conductive material, and the conductive material is dispersed in the inside and/or surface of the shell.
  • the inside of the shell refers to the part between the inner surface and the outer surface of the shell, that is, it penetrates into the shell without being on the surface of the shell.
  • the conductive material is dispersed in Li 2 SiO 3 ;
  • the conductive substance includes an inorganic carbon material and/or a conductive polymer.
  • the inorganic carbon material includes at least one of cracked carbon, carbon fiber, carbon nanotube, and conductive carbon black;
  • the conductive polymer includes at least one of polyaniline, polypyrrole, polythiophene, and polyacetylene.
  • the mass ratio of Li 2 SiO 3 and the conductive substance is 1: (0.01-0.6), and specifically can be 1:0.01, 1:0.05, 1:0.1, 1:0.2, 1:0.3 , 1:0.4, 1:0.5 or 1:0.6, etc., but not limited to the listed values, other unlisted values within this range of values are also applicable.
  • Controlling the mass ratio of Li 2 SiO 3 and conductive material within the range of 1:(0.01 ⁇ 0.6) can improve the conductivity of lithium silicate.
  • the conductive material can be uniformly dispersed in the lithium silicate. If the conductive material is too small, The improvement of conductivity is not obvious, and there are too many conductive materials, which is not conducive to uniform dispersion in lithium silicate.
  • the present application provides a method for preparing a silicon-oxygen composite anode material, as shown in FIG. 1, including the following steps:
  • the preparation method provided in this application obtains the silicon-oxygen composite negative electrode material by impregnating a composite material containing Li 2 SiO 3.
  • the heat treatment of the silicon source and the lithium source performs the pre-lithiation reaction, and the impregnation is to remove the exposed silicon; during the pre-lithiation, the silicon oxide will be consumed, making Li 2 SiO 3 Aggregates on the surface, while Si has a tendency to agglomerate, tending to migrate to the inside of the silicon source to agglomerate with other Si.
  • the composite material containing Li 2 SiO 3 includes SiO x , Si, and Li 2 SiO 3 .
  • the chemical formula of the silicon source is SiO y , where 0 ⁇ y ⁇ 2, and SiO y can specifically be SiO 0.1 , SiO 0.2 , SiO 0.5 , SiO 0.7 , SiO, SiO 1.2 , SiO 1.4 , SiO 1.6 , SiO 1.8 or SiO 1.9, etc.
  • the composition of SiO y is relatively complicated, and can be understood to be formed by uniformly dispersing at least one of amorphous silicon and crystalline silicon in SiO 2 . At high temperatures, its thermodynamic properties are very unstable and easily undergo a reduction reaction with the lithium source to form Li 2 SiO 3 .
  • the average particle size of the silicon source is 0.2 ⁇ m-50 ⁇ m, more specifically, it may be 0.2 ⁇ m, 10 ⁇ m, 15 ⁇ m, 20 ⁇ m, 25 ⁇ m, 30 ⁇ m, 35 ⁇ m, 40 ⁇ m, or 50 ⁇ m, etc., controlling the silicon oxide material within the above range can improve the cycle performance and rate performance of the negative electrode material.
  • the lithium source includes at least one of lithium hydride, lithium amide, alkyl lithium, elemental lithium, and lithium borohydride.
  • the above-mentioned lithium source can all react with the silicon source SiO y to prepare a composite material containing Li 2 SiO 3.
  • the composite material also includes nano silicon and silicon oxide SiO x , 0 ⁇ x ⁇ 1.2.
  • the molar ratio of silicon source to lithium source is (0.6 ⁇ 7.9):1, specifically 0.6:1, 1:1, 2:1, 3:1, 4:1, 5 : 1, 6:1 or 7.9:1, etc.
  • the heat treatment is performed in a non-oxygen atmosphere
  • the gas in the non-oxygen atmosphere includes at least one of hydrogen, nitrogen, helium, neon, argon, krypton, and xenon.
  • the temperature of the heat treatment is 300°C to 1000°C, specifically 300°C, 400°C, 450°C, 500°C, 600°C, 700°C, 800°C, 900°C, or 1000°C, etc., but is not limited to all. The listed values and other unlisted values within the range of values are also applicable.
  • the temperature of the heat treatment is 450°C to 800°C. After many experiments, it is found that the temperature of heat treatment is too high, the growth rate of single crystal silicon grains is accelerated, and the particle size gradually increases, which makes the cycle performance of the negative electrode material decrease. If the heat treatment temperature is too low, the pre-lithiation reaction rate will decrease or fail to proceed, which will affect the battery's first effect or fail to achieve the expected first effect.
  • the heat treatment time is 2h to 8h, specifically may be 2h, 3h, 4h, 5h, 6h, 7h or 8h, etc., but it is not limited to the listed values, and other unlisted values within the range of values The same applies.
  • the heat treatment time is too short, the pre-lithium reaction will be low and the pre-lithium effect will be poor; if the heat treatment time is too long, the silicon crystal grains will increase and the cycle performance will be reduced.
  • Si tends to agglomerate, tending to migrate to the inside of the silicon source to agglomerate with other Si to form nano-silicon aggregates, which are dispersed in the SiO x and exposed to the silicon oxide SiO
  • the part of nano silicon outside x can be removed by post-treatment.
  • the method further includes:
  • the heat-treated product is cooled and sieved.
  • the method further includes:
  • the mixture of Si and SiO 2 is heated and gasified in a protective atmosphere or in a vacuum to generate silicon oxide gas, which is cooled and shaped to obtain silicon source SiO y particles, where 0 ⁇ y ⁇ 2.
  • the shaping includes at least one of crushing, ball milling or classification.
  • the heating temperature ranges from 900°C to 1500°C, such as 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, or 1500°C, etc., but is not limited to the listed values. The listed values also apply.
  • the silicon source 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, 20 ⁇ m, etc. It should be noted that Dmax refers to the particle size of the largest particle.
  • the gas of the protective atmosphere includes at least one of nitrogen, helium, neon, argon, krypton, and xenon.
  • the acid solution is a mixed acid formed by mixing nitric acid and hydrofluoric acid.
  • the use of mixed acid can speed up the reaction speed to the silicon on the surface of the particles without losing the internal silicon.
  • the mass ratio of nitric acid and hydrofluoric acid in the acid solution is 1:(0.5-3), for example, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5 or 1: 3 and so on.
  • the time of the immersion treatment is 20 min to 90 min, for example, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, or 90 min. It is understandable that through sufficient immersion treatment, part of the nano silicon that is not covered by the silicon oxide SiO x can react with the acid solution, so that the silicon oxide SiO x can completely cover the nano silicon.
  • preparation method further includes the steps:
  • the impregnated solid product was washed with water to neutrality.
  • the solid product after washing is the silicon-oxygen composite anode material.
  • step S200 the method further includes:
  • the product obtained by the immersion is fused with a conductive material to obtain a silicon-oxygen composite negative electrode material containing the conductive material.
  • the fusion processing can be performed in the fusion machine.
  • the conductive substance includes an inorganic carbon material and/or a conductive polymer.
  • the inorganic carbon material includes at least one of cracked carbon, carbon fiber, carbon nanotube, and conductive carbon black;
  • the conductive polymer includes at least one of polyaniline, polypyrrole, polythiophene, and polyacetylene.
  • 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 produced by the preparation method described in the second aspect.
  • the silicon-oxygen composite negative electrode material was prepared according to the following method:
  • the composite material containing Li 2 SiO 3 is placed in a mixed acid solution, the composition of the mixed acid solution is nitric acid: hydrofluoric acid with a mass ratio of 1:0.8, and the pH value of the mixed acid solution is 6.8, and it is immersed at room temperature 20min, take out, filter, and dry.
  • step (3) Take 700 g of the sample of step (3), 14 g of carbon fiber, put it into a fusion machine and mix for 1 hour, and take out the silicon-oxygen composite negative electrode material.
  • the silicon-oxygen composite negative electrode material prepared in this embodiment has a core-shell structure, and the shell is coated on the surface of the core.
  • the shell includes Li 2 SiO 3 and is distributed on the surface of the shell And the conductive substance carbon fiber inside, and the mass ratio of Li 2 SiO 3 to carbon fiber is 1:0.58, and the thickness of the shell is 2000 nm.
  • the silicon-oxygen composite negative electrode material was prepared according to the following method:
  • the composite material containing Li 2 SiO 3 is placed in a mixed acid solution, the composition of the mixed acid solution is nitric acid: hydrofluoric acid with a mass ratio of 1:0.5, and the pH value of the mixed acid solution is 6.8. It is immersed at room temperature 50min, take out, filter, and dry.
  • step (3) Take 700 g of the sample of step (3), 16 g of carbon nanotubes, put them into a fusion machine and mix for 1.5 hours, and then take out the silicon-oxygen composite negative electrode material.
  • the silicon-oxygen composite negative electrode material prepared in this embodiment has a core-shell structure, and the shell is coated on the surface of the core.
  • the shell includes Li 2 SiO 3 and conductive carbon nanotubes distributed on the surface and inside of the shell . The mass ratio of Li 2 SiO 3 and the carbon nanotubes is 1:0.2, and the thickness of the shell is 800 nm.
  • the silicon-oxygen composite negative electrode material was prepared according to the following method:
  • the composition of the mixed acid solution is nitric acid: hydrofluoric acid with a mass ratio of 1:3, the pH value of the mixed acid solution is 6.8, and it is immersed at room temperature 90min, take out, filter, and dry.
  • step (3) Take 700 g of the sample of step (3), 12 g of conductive carbon black, put them into a fusion machine and mix for 1.5 hours, and take out the silicon-oxygen composite negative electrode material.
  • the silicon-oxygen composite negative electrode material prepared in this embodiment has a core-shell structure, and the shell is coated on the surface of the core.
  • the shell includes Li 2 SiO 3 and conductive carbon black distributed on the surface and inside of the shell. The mass ratio of Li 2 SiO 3 to conductive carbon black is 1:0.4, and the thickness of the shell is 1200 nm.
  • the silicon-oxygen composite negative electrode material was prepared according to the following method:
  • the composite material containing Li 2 SiO 3 is placed in a mixed acid solution, the composition of the mixed acid solution is nitric acid: hydrofluoric acid with a mass ratio of 1:1, the pH value of the mixed acid solution is 6.8, and it is immersed at room temperature 90min, take out, filter, and dry.
  • step (3) Take 700 g of the sample of step (3) and 14 g of polyaniline, put them into a fusion machine and mix for 1.5 hours, and take out the silicon-oxygen composite negative electrode material.
  • the silicon-oxygen composite negative electrode material prepared in this embodiment has a core-shell structure, and the shell is coated on the surface of the core.
  • the shell includes Li 2 SiO 3 and is distributed on the surface of the shell
  • the mass ratio of the Li 2 SiO 3 conductive material to the inner conductive material polyaniline is 1:0.018, and the thickness of the shell is 600 nm.
  • step (2) except that the heat treatment temperature in step (2) is 1100° C., other operating conditions and raw materials are the same as in embodiment 1.
  • the silicon-oxygen composite negative electrode material prepared in this embodiment has a core-shell structure, and the shell is coated on the surface of the core.
  • the shell includes Li 2 SiO 3 and is distributed on the surface of the shell The mass ratio of Li 2 SiO 3 and carbon fiber to the internal conductive material carbon fiber is 1:0.58, and the thickness of the shell is 2000 nm.
  • the silicon-oxygen composite negative electrode material prepared in this embodiment has a core-shell structure, and the shell is coated on the surface of the core.
  • the shell layer includes Li 2 SiO 3 and is distributed on the surface of the shell layer
  • the mass ratio of Li 2 SiO 3 and carbon fiber to the internal conductive material carbon fiber is 1:0.008, and the thickness of the shell is 20 nm.
  • the silicon-oxygen composite negative electrode material was prepared in the same manner as in Example 1, except that the step (3) of Example 1 was not performed in this comparative example.
  • the composite material containing Li 4 SiO 4 is placed in a mixed acid solution, the composition of the mixed acid solution is nitric acid: hydrofluoric acid with a mass ratio of 1:0.8, and the pH value of the mixed acid solution is 6.8, immersed at room temperature 20min, take out, filter, and dry.
  • step (3) Take 700 g of the sample of step (3), 14 g of carbon fiber, put it into a fusion machine and mix for 1 hour, and take out the silicon-oxygen composite negative electrode material.
  • the silicon-oxygen composite negative electrode material prepared in this comparative example has a core-shell structure, and the shell is coated on the surface of the core.
  • the shell includes Li 4 SiO 4 and is distributed on the surface of the shell and The internal conductive material carbon fiber, the mass ratio of Li 4 SiO 4 and carbon fiber is 1:0.12, and the thickness of the shell is 800 nm.
  • Lithium metal sheet as the counter electrode polypropylene (PP)/polyethylene (PE) as the separator, LiPF6/ethylene carbonate (EC) + diethyl carbonate (DEC) + dimethyl carbonate (DMC) (EC, DEC)
  • EC, DEC dimethyl carbonate
  • the volume ratio with DMC is 1:1:1) as the electrolyte, a simulated battery (case model is 2016) is assembled in a glove box filled with argon.
  • the electrochemical performance of the button cell was tested with the blue power 5V/10mA battery tester. The charging voltage was 1.5V, the discharge was 0.01V, and the charge and discharge rate was 0.1C.
  • Cyclic test mix the silicon-oxygen composite anode material provided by the example or comparative example with graphite at a mass ratio of 1:9 and use it as the active material, using lithium metal sheet as the counter electrode, PP/PE as the separator, and LiPF6/EC +DEC+DMC (the volume ratio of EC, DEC and DMC is 1:1:1) is used as the electrolyte, and the button cell is assembled in a glove box filled with argon (the case model is 2016), using blue power 5V/10mA
  • the type battery tester tests the electrochemical performance of the battery after 50 cycles, the charging voltage is 1.5V, the discharge to 0.01V, the charge and discharge rate is 0.1C.
  • Figure 2 is a gas production test photo of the negative electrode material prepared in this embodiment. It can be seen from this figure that the aluminum-plastic film bag has no bulges or protrusions, and the surface is flat, indicating that the material has no gas production phenomenon.
  • Figure 3 is the preparation of this embodiment The photo of the coating test of the negative electrode material, it can be seen that the pole piece is smooth and flat;
  • Figure 4 is the gas production test photo of the negative electrode material prepared in the comparative example, and it can be seen that the sealed aluminum-plastic film bag is bulging , It shows that gas is generated inside;
  • Figure 5 is a photo of the coating test of the negative electrode material prepared in the comparative example. It can be seen from this figure that the pole piece is full of pinholes.
  • Li 2 SiO 3 has a certain alkalinity
  • silicon is wrapped by SiO x and cannot be directly contacted with water, so it can effectively inhibit gas production and improve the pre-lithium material
  • the processing stability of the silicon dioxide solves the problem of chemical reaction and gas release when silicon contacts with water in an alkaline environment in the prior art.
  • the negative electrode material prepared in Example 5 has stable processing performance and does not generate gas; however, during the manufacturing process, the pre-lithiation temperature is relatively high, and the silicon crystal grains rapidly grow during the pre-lithiation process, which reduces the cycle performance of the material.
  • the negative electrode material prepared in Example 6 has stable processing performance and does not produce gas; however, during the production process, the pre-lithiation temperature is low, which causes the pre-lithium reaction to fail to proceed, and the expected first effect improvement cannot be obtained.
  • Comparative Example 1 did not perform the acid solution immersion treatment, and the nano-silicon exposed outside the silicon oxide SiO x could not be removed, resulting in the reaction of the nano-silicon with the solvent, electrolyte, etc. during the material processing, resulting in serious gas production. , which in turn makes the battery's first coulombic efficiency and cycle capacity retention rate drop significantly;
  • Comparative example 2 uses Li 4 SiO 4 , the water solubility of this kind of lithium silicate is higher than Li 2 SiO 3 , so the solubility in water is stronger, the slurry stability is worse, that is, it is prone to slurry instability problems such as gas production. .

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Abstract

本申请提供了硅氧复合负极材料及其制备方法和锂离子电池。所述硅氧复合负极材料为核壳结构，所述核包括纳米硅及硅氧化物SiOx，所述壳包括Li2SiO3。所述制备方法包括：将硅源与锂源混合，在非氧气氛下进行热处理，得到含有Li2SiO3的复合材料；将所述含有Li2SiO3的复合材料置于酸溶液中浸渍处理，得到所述硅氧复合负极材料。本申请提供的负极材料中的纳米硅被SiOx包裹，在SiOx的表面再包裹着结构稳定的Li2SiO3，纳米硅便难以与除SiOx以外的物质发生物理接触，不能直接与水接触，能够有效抑制电池产气。

Description

硅氧复合负极材料及其制备方法和锂离子电池
本申请要求于2020年5月22日提交中国专利局，申请号为2020104421221、申请名称为“硅氧复合负极材料、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，尤其涉及一种硅氧复合负极材料、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。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。
申请内容
针对现有技术存在的上述问题，本申请的目的在于提供一种硅氧复合负极材料及其制备方法和锂离子电池。本申请提供的负极材料，能够提高负极材料加工稳定性，并且能够提高锂电池的循环稳定性及电池容量。
为达此目的，本申请采用以下技术方案：
第一方面，本申请提供一种硅氧复合负极材料，所述硅氧复合负极材料为核壳结构，所述核包括纳米硅及硅氧化物SiO x，其中，0＜x＜1.2，所述壳包括Li 2SiO 3。
本申请提供的硅氧复合负极材料中，结构稳定的Li 2SiO 3包覆在内核外。纳米硅不直接与水接触，故能有效抑制产气，改善预锂材料的加工稳定性，解决了现有技术中硅在碱性环境下与水接触，发生化学反应、释放气体的问题。本申请提供的硅氧复合负极材料制备浆料不产气，涂布正常无针孔，解决了现有技术中负极材料在预锂后 产生强碱性或者易溶于水的副产物影响后续加工的问题，提高材料加工稳定性，并且能够提高锂电池的循环稳定性及电池容量。
结合第一方面，在一种可行的实施方式中，所述壳还包括导电物质，所述导电物质满足以下条件a～f的至少一者：
a.所述导电物质分散在壳的内部和/或表面；
b.所述导电物质分散于Li 2SiO 3中；
c.所述导电物质包括无机碳材料和/或导电聚合物；
d.所述导电物质包括无机碳材料，所述无机碳材料包括裂解碳、碳纤维、碳纳米管及导电炭黑中的至少一种；
e.所述导电物质包括导电聚合物，所述导电聚合物包括聚苯胺、聚吡咯、聚噻吩及聚乙炔中的至少一种；
f.所述Li 2SiO 3与所述导电物质的质量比为1：(0.01～0.6)。
结合第一方面，在一种可行的实施方式中，其满足以下条件a～g的至少一者：
a.所述纳米硅是以纳米硅聚集体的形式分散在所述硅氧化物SiO x内部；
b.所述纳米硅是以纳米硅聚集体的形式分散在所述硅氧化物SiO x内部，所述纳米硅聚集体包括多个纳米硅晶粒；
c.所述纳米硅晶粒的粒径为0nm～15nm，且不包含0nm；
d.所述纳米硅与所述硅氧化物的质量比为(0.05～0.7)：1；
e.所述壳的厚度为50nm～2000nm；
f.所述硅氧复合负极材料中的Li 2SiO 3的质量分数为20wt％～80wt％；
g.所述硅氧复合负极材料的平均粒径为1μm～50μm。
第二方面，本申请提供一种硅氧复合负极材料的制备方法，包括以下步骤：
将硅源与锂源混合，在非氧气氛下进行热处理，得到含有Li 2SiO 3的复合材料；
将所述含有Li 2SiO 3的复合材料置于酸溶液中浸渍处理，得到所述硅氧复合负极材料；所述硅氧复合负极材料为核壳结构，其中，所述核包括纳米硅及硅氧化物SiO x，其中，0＜x＜1.2，所述壳包括Li 2SiO 3。
在上述方案中，首先进行预锂反应使得只将硅源表层部分硅氧化物转化为Li 2SiO 3，同时保留内部的硅氧化物结构，纳米硅是以纳米硅聚集体的形式分散在SiO x内部，得到了本申请提供的具有特殊结构的产品，该制备方法操作简单，流程短，生产成本低。
结合第二方面，在一种可行的实施方式中，所述硅氧复合负极材料满足以下条件a～g的至少一者：
a.所述纳米硅是以纳米硅聚集体的形式分散在所述硅氧化物SiO x内部；
b.所述纳米硅是以纳米硅聚集体的形式分散在所述硅氧化物SiO x内部，所述纳米硅聚集体包括多个纳米硅晶粒；
c.所述纳米硅晶粒的粒径为0nm～15nm，且不包含0nm；
d.所述纳米硅与所述硅氧化物的质量比为(0.05～0.7)：1；
e.所述壳的厚度为50nm～2000nm；
f.所述硅氧复合负极材料中的Li 2SiO 3的质量分数为20wt％～80wt％；
g.所述硅氧复合负极材料的平均粒径为1μm～50μm。
结合第一方面，在一种可行的实施方式中，其满足以下条件a～g的至少一者：
a.所述锂源为不含氧的锂化合物；
b.所述锂源包括氢化锂、氨基锂、烷基锂、锂单质及硼氢化锂中的至少一种；
c.所述硅源为SiO y，0＜y＜2；
d.所述硅源与所述锂源的摩尔比为(0.6～7.9):1；
e.所述非氧气氛的气体包括氢气、氮气、氦气、氖气、氩气、氪气及氙气中的至少一种；
f.所述热处理的温度为300℃～1000℃；
g.所述热处理的时间为2h～8h。
结合第二方面，在一种可行的实施方式中，其满足以下条件a～c的至少一者：
a.所述酸溶液为硝酸和氢氟酸混合形成的混酸；
b.所述酸溶液为硝酸和氢氟酸按照质量比为1:(0.5～3)混合形成的混酸；
c.所述浸渍的时间为20min～90min。
结合第二方面，在一种可行的实施方式中，在所述热处理之后，并在所述浸渍处理之前，所述方法还包括：
将热处理得到的产物进行冷却和筛分。
结合第二方面，在一种可行的实施方式中，在所述浸渍之后，所述方法还包括：
将浸渍后的固体产物用水洗涤至中性。
结合第二方面，在一种可行的实施方式中，在将硅源与锂源混合之前，所述方法还包括：
在保护性气氛下或真空下对Si和SiO 2的混合物进行加热气化，产生硅氧化物气体，并进行冷却、整形得到硅源，所述硅源的通式为SiO y，0＜y＜2。
结合第二方面，在一种可行的实施方式中，其满足以下条件a～d的至少一者：
a.所述加热的温度为900℃～1500℃；
b.所述整形包括破碎、球磨或分级中的至少一种；
c.所述硅源的平均粒径为0.2μm～50μm；
d.所述保护性气氛的气体包括氮气、氦气、氖气、氩气、氪气及氙气中的至少一种。
结合第二方面，在一种可行的实施方式中，所述制备方法还包括：
将所述浸渍得到的产品与导电物质融合，得到含有导电物质的硅氧复合负极材料。
结合第二方面，在一种可行的实施方式中，所述导电物质满足以下条件a～e的至少一者：
a.所述导电物质分散于Li 2SiO 3中；
b.所述导电物质包括无机碳材料和/或导电聚合物；
c.所述导电物质包括无机碳材料，所述无机碳材料包括裂解碳、碳纤维、碳纳米管及导电炭黑中的至少一种；
d.所述导电物质包括导电聚合物，所述导电聚合物包括聚苯胺、聚吡咯、聚噻吩 及聚乙炔中的至少一种；
e.所述Li 2SiO 3与所述导电物质的质量比为1：(0.01～0.6)。
结合第二方面，在一种可行的实施方式中，所述方法包括以下步骤：
在保护性气氛下将Si和SiO 2的混合物加热至900℃～1500℃，产生硅氧化物气体后冷却、整形得到硅源，所述硅源的通式为SiO y，0＜y＜2；
将所述硅源与不含氧的锂化合物以质量比1：(0.02～0.20)混合，在非氧化性气氛下以450℃～800℃进行热处理，热处理时间为2h～8h，之后冷却、筛分，得到含有Li 2SiO 3的复合材料；
将所述含有Li 2SiO 3的复合材料置于质量比为1：(0.5～3)的硝酸和氢氟酸混合形成的酸溶液中浸渍处理20min～90min，浸渍后用水洗涤至中性，得到浸渍产物；
将所述浸渍产物与导电物质进行融合，得到所述硅氧复合负极材料。
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根据上述第二方面所述的制备方法制得的硅氧复合负极材料。
与现有技术相比，本申请具有以下有益效果：
(1)本申请提供的硅氧复合负极材料中，结构稳定的Li 2SiO 3包覆在内核外。纳米硅便不会与除SiO x以外的物质发生物理接触，Li 2SiO 3虽然具有一定碱性，但是纳米硅以聚集体形式分散在硅氧化物SiO x内部，不能直接与水接触，故能有效抑制产气，改善预锂材料的加工稳定性，解决了现有技术中硅在碱性环境下与水接触，发生化学反应、释放气体的问题。本申请提供的硅氧复合负极材料制备浆料不产气，涂布正常无针孔，解决了现有技术中负极材料在预锂后产生强碱性或者易溶于水的副产物影响后续加工的问题，提高材料加工稳定性，并且能够提高锂电池的循环稳定性及电池容量。
(2)本申请提供的制备方法通过控制合适的预锂程度，只将硅源表层部分 硅氧 化物为Li 2SiO 3，同时保留内部的硅氧化物结构，形成纳米硅以聚集体形式分散在硅氧化物SiO x内部的结构，得到本申请提供的具有特殊结构的产品，该制备方法操作简单，流程短，生产成本低。
附图说明
图1为本申请实施例提供的一种硅氧复合负极材料的制备方法的工艺流程图；
图2为本申请实施例1制备的负极材料的产气测试照片；
图3为本申请实施例1制备的负极材料的涂布测试照片；
图4为对比例1制备的负极材料的产气测试照片；
图5为对比例1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：
第一方面，本申请提供一种硅氧复合负极材料，所述硅氧复合负极材料为核壳结构，所述核包括纳米硅及硅氧化物SiO x，其中，0＜x＜1.2，所述壳包括Li 2SiO 3。
本申请提供的硅氧复合负极材料中，结构稳定的Li 2SiO 3包覆在内核外。纳米硅便不直接与水接触，故能有效抑制产气，改善预锂材料的加工稳定性，解决了现有技术中硅在碱性环境下与水接触，发生化学反应、释放气体的问题，且硅酸锂具有提升首效、缓冲体积膨胀、增加材料的导锂离子能力，该负极材料能够提高锂电池的循环稳定性及电池容量。
以下作为本申请可选的技术方案，但不作为对本申请提供的技术方案的限制，通过以下可选的技术方案，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，所述硅氧化物的化学式为SiO x，其中，0＜x＜1.2，SiO x可以是SiO 0.1、SiO 0.2、SiO 0.3、SiO 0.4、SiO 0.5、SiO 0.6、SiO 0.7、SiO 0.8、SiO 0.9、SiO及SiO 1.1中的至少一种。SiO x可以理解为由无定型硅单质或结晶态Si中的至少一种均匀分散在SiO 2中形成。
本申请提供的负极材料表面包裹着结构稳定的Li 2SiO 3，使得纳米硅不会与除无定型硅氧化物以外的物质发生物理接触。
作为本申请可选的技术方案，纳米硅是以纳米硅聚集体的形式分散在SiO x内部。纳米硅聚集体包括多个纳米硅晶粒；由于纳米硅以聚集体形式分散在SiO x内部，在表面SiO x表面再包裹着结构稳定的Li 2SiO 3，则纳米硅难以与除SiO x以外的物质发生物理接触，Li 2SiO 3虽然具有一定碱性，但是纳米硅以纳米硅聚集体形式分布在SiO x内部，不能直接与水接触，故能有效抑制产气，改善预锂材料的加工稳定性。
作为本申请可选的技术方案，纳米硅聚集体由多个纳米硅晶粒组成，纳米硅聚集体是指由几个乃至上千个纳米硅晶粒通过物理或化学结合力组成的聚集体。
作为本申请可选的技术方案，所述纳米硅晶粒的平均粒径为0～15nm，且不包含0nm，例如1nm、3nm、5nm、8nm、10nm、12nm或15nm等。可以理解地，在硅含量相同的情况下，相比大尺寸晶体硅晶粒，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。
作为本申请可选的技术方案，所述纳米硅与所述硅氧化物的质量比为(0.05～0.7)：1，具体可以是0.05:1、0.08:1、0.1:1、0.2:1、0.3:1、0.4:1、0.5:1或0.7:1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。将所述纳米硅与所述硅氧化物的质量比控制在(0.05～0.7)：1范围内，最终的负极材料可以获得较高的容量和循环，当纳米硅的占比太高时，负极材料的循环、膨胀性能较差；当硅氧化物的占比太高，负极材料的容量较低。
作为本申请可选的技术方案，所述硅氧复合负极材料的平均粒径1μm～50μm；更具体地，可以是1μm、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，壳的厚度为50nm～2000nm，具体地，可以是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。壳层过厚，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。
作为本申请可选的技术方案，所述壳还包括导电物质，所述导电物质分散在壳的内部和/或表面。所述壳的内部，是指壳的内表面和外表面之间的部分，即深入到壳中而没有处于壳的表面。
可以理解，导电物质分散在于Li 2SiO 3中；
可选地，所述导电物质包括无机碳材料和/或导电聚合物。
具体地，所述无机碳材料包括裂解碳、碳纤维、碳纳米管及导电炭黑中的至少一种；所述导电聚合物包括聚苯胺、聚吡咯、聚噻吩及聚乙炔中的至少一种。
作为本申请可选的技术方案，Li 2SiO 3和导电物质的质量比为1：(0.01～0.6)，具体可以是1:0.01、1:0.05、1:0.1、1:0.2、1:0.3、1:0.4、1:0.5或1:0.6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。将Li 2SiO 3和导电物质的质量比控制在1：(0.01～0.6)范围内，可以提高硅酸锂的导电性，导电物质可以均匀分散在硅酸锂中，如果导电物质太少，对导电性的改善不明显，导电物质过多，不利于均匀分散在硅酸锂中。
第二方面，本申请提供一种硅氧复合负极材料的制备方法，如图1所示，包括以下步骤：
S100，将硅源与锂源混合，在非氧气氛下进行热处理，得到含有Li 2SiO 3的复合材料；
S200，将所述含有Li 2SiO 3的复合材料置于酸溶液中浸渍处理，得到所述硅氧复合负极材料。
本申请提供的制备方法通过对含有Li 2SiO 3的复合材料进行浸渍，得到所述硅氧复合负极材料。
在本申请提供的制备方法中，硅源与锂源热处理进行的是预锂化反应，浸渍则是去除裸露的硅；在进行预锂化时，会导致硅氧化物被消耗，使得Li 2SiO 3在表面聚集，而Si有团聚的趋势，倾向于迁移至硅源内部与其他Si团聚。
以下详细介绍本方案提供的制备方法：
S100，将硅源与锂源混合，在非氧气氛下进行热处理，得到含有Li 2SiO 3的复合材料。
其中，含有Li 2SiO 3的复合材料包括SiO x、Si、Li 2SiO 3。
作为本申请可选的技术方案，所述硅源的化学式为SiO y，其中，0＜y＜2，SiO y具体可以是SiO 0.1、SiO 0.2、SiO 0.5、SiO 0.7、SiO、SiO 1.2、SiO 1.4、SiO 1.6、SiO 1.8或SiO 1.9等。需要说明的是，SiO y的组成比较复杂，可以理解为由无定型硅单质及结晶态硅单质中的至少一种均匀分散在SiO 2中形成。在高温下，其热力学性质非常不稳定，容易与锂源发生还原反应，生成Li 2SiO 3。
作为本申请可选的技术方案，所述硅源的平均粒径为0.2μm～50μm，更具体地， 更具体地，可以是0.2μm、10μm、15μm、20μm、25μm、30μm、35μm、40μm或50μm等，将硅氧材料控制在上述范围内，可以提高负极材料的循环性能与倍率性能。
作为本申请可选的技术方案，所述锂源包括氢化锂、氨基锂、烷基锂、锂单质和硼氢化锂中的至少一种。上述锂源均能与硅源SiO y反应，制备得到含有Li 2SiO 3的复合材料，复合材料还包括纳米硅及硅氧化物SiO x，0＜x＜1.2。
作为本申请可选的技术方案，硅源与锂源的摩尔比为(0.6～7.9):1，具体可以是0.6:1、1:1、2:1、3:1、4:1、5:1、6:1或7.9:1等，经过多次试验发现，当硅源和锂源的摩尔比过高(即硅源过多)，硅源不能充分转化成Li 2SiO 3，从而影响负极材料的加工性能，导致负极材料的首效较低；当硅源和锂源的摩尔比过低(即锂源过多)，形成锂硅合金等物质，得不到Li 2SiO 3，则得不到理想的负极材料。
作为本申请可选的技术方案，所述热处理在非氧气氛下进行，非氧气氛的气体包括氢气、氮气、氦气、氖气、氩气、氪气及氙气中的至少一种。
可选地，热处理的温度为300℃～1000℃，具体可以是300℃、400℃、450℃、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，可选地，热处理的温度为450℃～800℃。经过多次试验发现，热处理的温度过高，单晶硅晶粒的生长速率加快，颗粒尺寸也逐渐增大，使得负极材料的循环性能下降。热处理温度过低，预锂化反应速率下降或无法进行，降低影响电池首效，或无法达到预期的首效。
可选地，所述热处理的时间为2h～8h，具体可以是2h、3h、4h、5h、6h、7h或8h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。经过多次试验发现，如果热处理时间过短，会导致预锂反应程度低，预锂效果差；如果热处理时间过长，会导致硅晶粒增大，降低循环性能。在上述时间范围内，随着热处理时间增加，Si有团聚的趋势，倾向于迁移至硅源内部与其他Si团聚，形成纳米硅聚集体，并分散在SiO x内部，而裸露在硅氧化物SiO x外的部分纳米硅即可通过后处理去除。
本申请通过控制热处理温度、时间以及硅源的含量，使得只将硅源表层部分硅氧化物转化为Li 2SiO 3，同时保留内部的硅氧化物结构，Si有团聚的趋势，倾向于迁移至硅源内部与其他Si团聚，形成纳米硅聚集体，并分散在SiO x内部。
进一步地，在S100之后，并在S200之前，所述方法还包括：
将热处理得到的产物进行冷却和筛分。
在步骤S100之前，所述方法还包括：
在保护性气氛下或真空下对Si和SiO 2的混合物进行加热气化，产生硅氧化物气体，并进行冷却、整形得到硅源SiO y颗粒，其中，0＜y＜2。
可选地，所述整形包括破碎、球磨或分级中的至少一种。
所述加热的温度为900℃～1500℃，例如900℃、1000℃、1100℃、1200℃、1300℃、1400℃或1500℃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，硅源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。
所述保护性气氛的气体包括氮气、氦气、氖气、氩气、氪气和氙气中的至少一种。
S200，将所述含有Li 2SiO 3的复合材料置于酸溶液中浸渍处理，得到所述硅氧复合负极材料。
作为本申请可选的技术方案，所述酸溶液为硝酸和氢氟酸混合形成的混酸。采用混酸可以加快对颗粒表面硅的反应速度，同时不损失内部硅。
可选地，所述酸溶液中，硝酸和氢氟酸的质量比为1:(0.5～3)，例如1:0.5、1:1、1:1.5、1:2、1:2.5或1:3等。
可选地，所述浸渍处理的时间为20min～90min，例如20min、30min、40min、50min、60min、70min、80min或90min等。可以理解地，通过充分的浸渍处理，可以使得未被硅氧化物SiO x包裹的部分纳米硅与酸溶液反应，从而使得硅氧化物SiO x能够完全包裹纳米硅。
进一步地，所述制备方法还包括步骤：
将浸渍后的固体产物用水洗涤至中性。
洗涤后的固体产物即为硅氧复合负极材料。
更进一步地，在步骤S200之后，所述方法还包括：
将所述浸渍得到的产品与导电物质融合，得到含有导电物质的硅氧复合负极材料。
作为本申请可选的技术方案，可以在融合机内进行融合处理。
所述导电物质包括无机碳材料和/或导电聚合物。具体地，所述无机碳材料包括裂解碳、碳纤维、碳纳米管及导电炭黑中的至少一种；所述导电聚合物包括聚苯胺、聚吡咯、聚噻吩及聚乙炔中的至少一种。
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左右，得到SiO y粉体材料，y＝1.0；
(2)取SiO y 1kg放入球磨罐中，加入150g氢化锂球磨20min取出，置于气氛保护炉中热处理，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、除磁得到含有Li 2SiO 3的复合材料。
(3)将含有Li 2SiO 3的复合材料置于混合酸液中，混合酸液的组成是硝酸：氢 氟酸的质量比为1:0.8，混合酸液的pH值是6.8，室温下浸渍20min，取出、过滤、干燥。
(4)取步骤(3)样品700g，14g碳纤维，投入融合机中混合1h，取出得所述硅氧复合负极材料。
本实施例制备得到的硅氧复合负极材料为核壳结构，壳包覆在核的表面。其中，核包括纳米硅和SiO x，x＝0.6，纳米硅以聚集体形式分散在SiO x内部，纳米硅和SiO x的质量比为0.7:1；壳包括Li 2SiO 3以及分布在壳表面和内部的导电物质碳纤维，且Li 2SiO 3与碳纤维的质量比为1:0.58，壳的厚度为2000nm。
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，600gkg 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900℃并保温20h，在炉内生成SiO蒸汽经过迅速凝结生成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左右，得到SiO y粉体材料，y＝0.5；
(2)取SiO y 1kg放入球磨罐中，加入80g氢化锂球磨20min取出，置于气氛保护炉中热处理，热处理温度450℃，热处理时间8h，自然降温至室温取出物料、经筛分、除磁得到含有Li 2SiO 3的复合材料。
(3)将含有Li 2SiO 3的复合材料置于混合酸液中，混合酸液的组成是硝酸：氢氟酸的质量比为1:0.5，混合酸液的pH值是6.8，室温下浸渍50min，取出、过滤、干燥。
(4)取步骤(3)样品700g，16g碳纳米管，投入融合机中混合1.5h，取出得所述硅氧复合负极材料。
本实施例制备得到的硅氧复合负极材料为核壳结构，壳包覆在核的表面。其中，核包括纳米硅和SiO x，x＝0.2，纳米硅以聚集体形式分布在SiO x内部，纳米硅和SiO x的质量比为0.2:1。壳包括Li 2SiO 3以及分布在壳表面和内部的导电物质碳纳米管，Li 2SiO 3和碳纳米管的质量比为1:0.2，壳的厚度为800nm。
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，3.2kg 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1500℃并保温16h，在炉内生成SiO蒸汽经过迅速凝结生成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左右，得到SiO y粉体材料，y＝1.5；
(2)取SiO y 1kg放入球磨罐中，加入120g硼氢化锂球磨20min取出，置于气氛保护炉中热处理，热处理温度300℃，热处理时间6h，自然降温至室温取出物料、经筛分、除磁得到含有Li 2SiO 3的复合材料。
(3)将含有Li 2SiO 3的复合材料置于混合酸液中，混合酸液的组成是硝酸：氢氟酸的质量比为1:3，混合酸液的pH值是6.8，室温下浸渍90min，取出、过滤、干 燥。
(4)取步骤(3)样品700g，12g导电炭黑，投入融合机中混合1.5h，取出得所述硅氧复合负极材料。
本实施例制备得到的硅氧复合负极材料为核壳结构，壳包覆在核的表面。其中，核包括纳米硅和SiO x，x＝0.8，纳米硅以聚集体形式分散在SiOx内部，纳米硅和SiO x的质量比为0.5:1。壳包括Li 2SiO 3以及分布在壳表面和内部的导电物质导电碳黑。Li 2SiO 3与导电碳黑的质量比为1:0.4，壳的厚度为1200nm。
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，3.9kg 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16h，在炉内生成SiO蒸汽经过迅速凝结生成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左右，得到SiO y粉体材料，y＝1.8；
(2)取SiO y 1kg放入球磨罐中，加入20g金属锂球磨20min取出，置于气氛保护炉中热处理，热处理温度1000℃，热处理时间2h，自然降温至室温取出物料、经筛分、除磁得到含有Li 2SiO 3的复合材料。
(3)将含有Li 2SiO 3的复合材料置于混合酸液中，混合酸液的组成是硝酸：氢氟酸的质量比为1:1，混合酸液的pH值是6.8，室温下浸渍90min，取出、过滤、干燥。
(4)取步骤(3)样品700g，14g聚苯胺，投入融合机中混合1.5h，取出得所述硅氧复合负极材料。
本实施例制备得到的硅氧复合负极材料为核壳结构，壳包覆在核的表面。其中，核包括纳米硅和SiO x，x＝1.2，纳米硅以聚集体形式分散在SiO x内部，纳米硅和SiO x的质量比为0.05:1；壳包括Li 2SiO 3以及分布在壳表面和内部的导电物质聚苯胺，Li 2SiO 3导电物质的质量比为1:0.018，壳的厚度为600nm。
实施例5
本实施例除了步骤(2)中的热处理温度为1100℃，其他操作条件和原料均与实施例1相同。
本实施例制备得到的硅氧复合负极材料为核壳结构，壳包覆在核的表面。其中，核包括纳米硅和SiO x，x＝0.6，纳米硅以聚集体形式分布在SiO x内部，纳米硅和SiO x的质量比为0.72:1；壳包括Li 2SiO 3以及分布在壳表面和内部的导电物质碳纤维，Li 2SiO 3和碳纤维的质量比为1:0.58，壳的厚度为2000nm。
实施例6
本实施例除了步骤(2)中的热处理温度为200℃，其他操作条件和原料均与实施例1相同。
本实施例制备得到的的硅氧复合负极材料为核壳结构，壳包覆在核的表面。核包 括纳米硅和SiO x，x＝0.92，纳米硅以聚集体形式分散在SiO x内部，纳米硅和SiO x的质量比为0.9:1；壳层包括Li 2SiO 3以及分布在壳层表面和内部的导电物质碳纤维，Li 2SiO 3和碳纤维的质量比为1:0.008，壳的厚度为20nm。
对比例1
按照与实施例1基本相同的方法制备硅氧复合负极材料，区别在于：本对比例不进行实施例1步骤(3)的工序。
对比例2
(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左右，得到SiO y粉体材料，y＝1.0；
(2)取SiO y 1kg放入球磨罐中，加入350g氢化锂球磨20min取出，置于气氛保护炉中热处理，热处理温度320℃，热处理时间5h，自然降温至室温取出物料、经筛分、除磁得到含有Li 4SiO 4的复合材料。
(3)将含有Li 4SiO 4的复合材料置于混合酸液中，混合酸液的组成是硝酸：氢氟酸的质量比为1:0.8，混合酸液的pH值是6.8，室温下浸渍20min，取出、过滤、干燥。
(4)取步骤(3)样品700g，14g碳纤维，投入融合机中混合1h，取出得所述硅氧复合负极材料。
本对比例制备得到的硅氧复合负极材料为核壳结构，壳包覆在核的表面。其中，核包括纳米硅和SiO x，x＝0.6，纳米硅以聚集体形式分散在SiO x内部，纳米硅和SiOx的质量比为0.72:1；壳包括Li 4SiO 4以及分布在壳表面和内部的导电物质碳纤维，Li 4SiO 4和碳纤维的质量比为1:0.12，壳的厚度为800nm。
测试方法
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、加工性能测试
(1)产气测试。采用实施例或对比例提供的硅氧复合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，将所述浆料装入铝塑膜袋中密封、静止，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(1)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、扣电首周性能测试：将实施例或对比例提供的硅氧复合负极材料作为活性物质，丁苯橡胶(SBR)和羧甲基纤维素钠(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，其中，活性物质、导电剂、粘结 剂的质量比为85:15:10。以金属锂片作为对电极，聚丙烯(PP)/聚乙烯(PE)作为隔膜，LiPF6/碳酸乙烯酯(EC)+碳酸二乙酯(DEC)+碳酸二甲酯(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(壳体型号为2016)。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：将实施例或对比例提供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，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(壳体型号为2016)，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。
实施例1～6及对比例1～2的测试结果如下表所示：
表1
Figure PCTCN2021095260-appb-000001
图2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3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；图4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5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。
综合上述实施例和对比例可知，实施例1～4通过控制合适的预锂程度，只将硅源表层部分转化为Li 2SiO 3，同时保留内部的硅氧化物结构，纳米硅以聚集体的形式分散在SiO x的内部，使得具有高活性的纳米硅被SiO x严密包裹，在SiO x的表面再包裹着结构稳定的Li 2SiO 3。纳米硅便不会与除SiO x以外的物质发生物理接触，Li 2SiO 3虽然具有一定碱性，但是硅被SiO x包裹，不能直接与水接触，故能有效抑制产气，改善预锂材料的加工稳定性，解决了现有技术中硅在碱性环境下与水接触，发生化学反应、释放气体的问题。
实施例5制得的负极材料加工性能稳定，不产气；但是在制作过程中，预锂化温度偏高，预锂化过程中硅晶粒迅速长大，使材料的循环性能下降。
实施例6制得的负极材料加工性能稳定，不产气；但是在制作过程中，预锂化温度偏低，导致预锂反应无法进行，不能获得预期的首效提升。
对比例1相比于实施例1，没有进行酸溶液浸渍处理，裸露在硅氧化物SiO x外的纳米硅不能去除，导致材料加工过程中，纳米硅与溶剂、电解液等反应，产气严重，进而使得电池的首次库伦效率及循环容量保持率均大幅下降；
对比例2采用Li 4SiO 4，该种硅酸锂的水溶特性高于Li 2SiO 3，因此水中的溶解性更强，浆料稳定性更差，即容易出现产气等浆料不稳定问题。
申请人声明，本发明通过上述实施例来说明本发明的详细工艺设备和工艺流程，但本发明并不局限于上述详细工艺设备和工艺流程，即不意味着本发明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，对本发明的任何改进，对本发明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，均落在本发明的保护范围和公开范围之内。

Claims (15)

  1. 一种硅氧复合负极材料，其特征在于，所述硅氧复合负极材料为核壳结构，所述核包括纳米硅及硅氧化物SiO x，其中，0＜x＜1.2，所述壳包括Li 2SiO 3。
  2. 根据权利要求1所述的负极材料，其特征在于，所述壳还包括导电物质，所述导电物质满足以下条件a～f的至少一者：
    a.所述导电物质分散在壳的内部和/或表面；
    b.所述导电物质分散于Li 2SiO 3中；
    c.所述导电物质包括无机碳材料和/或导电聚合物；
    d.所述导电物质包括无机碳材料，所述无机碳材料包括裂解碳、碳纤维、碳纳米管及导电炭黑中的至少一种；
    e.所述导电物质包括导电聚合物，所述导电聚合物包括聚苯胺、聚吡咯、聚噻吩及聚乙炔中的至少一种；
    f.所述Li 2SiO 3与所述导电物质的质量比为1：(0.01～0.6)。
  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～g的至少一者：
    a.所述纳米硅是以纳米硅聚集体的形式分散在所述硅氧化物SiO x内部；
    b.所述纳米硅是以纳米硅聚集体的形式分散在所述硅氧化物SiO x内部，所述纳米硅聚集体包括多个纳米硅晶粒；
    c.所述纳米硅晶粒的粒径为0nm～15nm，且不包含0nm；
    d.所述纳米硅与所述硅氧化物SiO x的质量比为(0.05～0.7)：1；
    e.所述壳的厚度为50nm～2000nm；
    f.所述硅氧复合负极材料中的Li 2SiO 3的质量分数为20wt％～80wt％；
    g.所述硅氧复合负极材料的平均粒径为1μm～50μm。
  4. 一种硅氧复合负极材料的制备方法，其特征在于，包括以下步骤：
    将硅源与锂源混合，在非氧气氛下进行热处理，得到含有Li 2SiO 3的复合材料；
    将所述含有Li 2SiO 3的复合材料置于酸溶液中浸渍处理，得到所述硅氧复合负极材料；所述硅氧复合负极材料为核壳结构，其中，所述核包括纳米硅及硅氧化物SiO x，其中，0＜x＜1.2，所述壳包括Li 2SiO 3。
  5. 根据权利要求4所述的制备方法，其特征在于，所述硅氧复合负极材料满足以下条件a～g的至少一者：
    a.所述纳米硅是以纳米硅聚集体的形式分散在所述硅氧化物SiO x内部；
    b.所述纳米硅是以纳米硅聚集体的形式分散在所述硅氧化物SiO x内部，所述纳米硅聚集体包括多个纳米硅晶粒；
    c.所述纳米硅晶粒的粒径为0nm～15nm，且不包含0nm；
    d.所述纳米硅与所述硅氧化物的质量比为(0.05～0.7)：1；
    e.所述壳的厚度为50nm～2000nm；
    f.所述硅氧复合负极材料中的Li 2SiO 3的质量分数为20wt％～80wt％；
    g.所述硅氧复合负极材料的平均粒径为1μm～50μm。
  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～g的 至少一者：
    a.所述锂源为不含氧的锂化合物；
    b.所述锂源包括氢化锂、氨基锂、烷基锂、锂单质及硼氢化锂中的至少一种；
    c.所述硅源为SiO y，0＜y＜2；
    d.所述硅源与所述锂源的摩尔比为(0.6～7.9):1；
    e.所述非氧气氛的气体包括氢气、氮气、氦气、氖气、氩气、氪气和氙气中的至少一种；
    f.所述热处理的温度为300℃～1000℃；
    g.所述热处理的时间为2h～8h。
  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～c的至少一者：
    a.所述酸溶液为硝酸和氢氟酸混合形成的混酸；
    b.所述酸溶液为硝酸和氢氟酸按照质量比为1:(0.5～3)混合形成的混酸；
    c.所述浸渍的时间为20min～90min。
  8. 根据权利要求4～7任一项所述的制备方法，其特征在于，在所述热处理之后，并在所述浸渍处理之前，所述方法还包括：
    将热处理得到的产物进行冷却和筛分。
  9. 根据权利要求4～8任一项所述的制备方法，其特征在于，在所述浸渍之后，所述方法还包括：
    将浸渍后的固体产物用水洗涤至中性。
  10. 根据权利要求4所述的制备方法，其特征在于，在将硅源与锂源混合之前，所述方法还包括：
    在保护性气氛下或真空下对Si和SiO 2的混合物进行加热气化，产生硅氧化物气体，并进行冷却、整形得到硅源，所述硅源的通式为SiO y，0＜y＜2。
  11. 根据权利要求10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.所述加热的温度为900℃～1500℃；
    b.所述整形包括破碎、球磨或分级中的至少一种；
    c.所述硅源的平均粒径为0.2μm～50μm；
    d.所述保护性气氛的气体包括氮气、氦气、氖气、氩气、氪气和氙气中的至少一种。
  12. 根据权利要求4～11任一项所述的制备方法，其特征在于，所述制备方法还包括：
    将所述浸渍得到的产品与导电物质融合，得到含有导电物质的硅氧复合负极材料。
  13. 根据权利要求12所述的制备方法，其特征在于，所述导电物质满足以下条件a～e的至少一者：
    a.所述导电物质分散于Li 2SiO 3中；
    b.所述导电物质包括无机碳材料和/或导电聚合物；
    c.所述导电物质包括无机碳材料，所述无机碳材料包括裂解碳、碳纤维、碳纳米管及导电炭黑中的至少一种；
    d.所述导电物质包括导电聚合物，所述导电聚合物包括聚苯胺、聚吡咯、聚噻吩及聚乙炔中的至少一种；
    e.所述Li 2SiO 3与所述导电物质的质量比为1：(0.01～0.6)。
  14. 根据权利要求4～13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：
    在保护性气氛下将Si和SiO 2的混合物加热至900℃～1500℃，产生硅氧化物气体后冷却、整形得到硅源，所述硅源的通式为SiO y，0＜y＜2；
    将所述硅源与不含氧的锂化合物以质量比1：(0.02～0.20)混合，在非氧化性气氛下以450℃～800℃进行热处理，热处理时间为2h～8h，之后冷却、筛分，得到含有Li 2SiO 3的复合材料；
    将所述含有Li 2SiO 3的复合材料置于质量比为1：(0.5～3)的硝酸和氢氟酸混合形成的酸溶液中浸渍处理20min～90min，浸渍后用水洗涤至中性，得到浸渍产物；
    将所述浸渍产物与导电物质进行融合，得到所述硅氧复合负极材料。
  15. 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任一项所述的硅氧复合负极材料或根据权利要求4～14任一项所述的制备方法制得的硅氧复合负极材料。
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