Silicon oxide composite material for lithium ion battery negative electrode and preparation method thereof

Abstract

The application provides a silicon oxide composite material for a lithium ion battery negative electrode and a preparation method thereof, and comprises the following steps: (1) dissolving 1 part of a silicon source in 2-4 parts of anhydrous ethanol, adding 4-6 parts of deionized water, and then adding an acidic catalyst dropwise to obtain a first solution; dissolving an organic carbon source in anhydrous ethanol to obtain a second solution; wherein the organic carbon source is a mixture of sucrose, phenolic resin and epoxy resin with a mass ratio of 1:1.4-1.6:0.5-0.7; (2) preparing a gel; (3) preparing an aged gel, and drying under normal pressure to obtain a precursor product; (4) under a nitrogen protective atmosphere, heating the precursor product to 1100 DEG C and keeping the temperature for 3 hours, and then cooling the product to room temperature in the furnace to obtain the silicon oxide composite material for the lithium ion battery negative electrode. The silicon oxide composite material for the lithium ion battery negative electrode can improve the cycle stability and specific energy density of the battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium batteries, and particularly relates to a silicon oxide composite material for a lithium ion battery negative electrode and a preparation method thereof. BACKGROUND

[0002] The negative electrode material of a lithium ion battery plays a key role in the charging and discharging process of the battery, and it is responsible for storing and releasing lithium ions. At present, the negative electrode material of a lithium ion battery can be mainly divided into two categories: carbon-based materials and other non-carbon-based materials. Carbon-based negative electrode materials, graphite materials are the most common negative electrode materials of lithium ion batteries, including natural graphite and artificial graphite. Graphite materials have a layered structure, and lithium ions can be inserted and extracted between the layers, which is called "lithium intercalation" and "delithiation". The advantages of graphite negative electrode materials include: high coulomb efficiency: during charging and discharging, graphite can efficiently accept and release lithium ions. Stable cycle performance: graphite materials can maintain their structural stability after multiple charging and discharging. Low redox potential: conducive to improving the overall voltage and energy density of the battery. Low cost: graphite materials are widely available and relatively low in price. In addition to graphite, there are some other carbon-based materials, such as hard carbon and soft carbon, which are also used as negative electrode materials for lithium ion batteries, and are often more popular in certain special applications. Non-carbon-based negative electrode materials, silicon-based materials are widely concerned due to their high theoretical capacity. In theory, the capacity of silicon can be more than ten times that of graphite. However, silicon will have a large volume expansion during charging and discharging, which may lead to the destruction of the material structure and the degradation of the battery performance. Tin-based materials and alloy-based materials (such as silicon-based alloys, germanium-based alloys, etc.) are also studied due to their high theoretical capacity, but they also face the problem of volume expansion. Lithium metal is theoretically the most ideal negative electrode material because it has very high energy density and low electrochemical potential, but due to the formation of lithium dendrites and safety problems, lithium metal has not been widely used in commercial lithium ion batteries.

[0003] With the development of technology, some new negative electrode materials such as nanomaterials, composite materials and transition metal oxides are also being continuously researched and developed, aiming to solve the limitations of existing materials and improve the energy density, power density and cycle life of the battery. At present, graphite is still the most widely used negative electrode material on the market, but in the future, with the progress of technology, new negative electrode materials may gradually occupy a larger market share.

[0004] Silicon oxide-based materials as anode materials for lithium ion batteries are considered as one of the most promising next-generation anode materials for lithium ion batteries due to their high theoretical capacity, abundant resources, and low cost. Silicon oxide-based materials mainly include silicon dioxide, silicon suboxide, and other compounds containing silicon and oxygen. The current market capacity of silicon oxide-based anode materials is not good, which cannot meet the market demand, therefore, there is an urgent need for a silicon oxide composite material for lithium ion battery anodes and a preparation method thereof. SUMMARY

[0005] The purpose of the present application is to provide a silicon oxide composite material for lithium ion battery anodes and a preparation method thereof.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] A preparation method of a silicon oxide composite material for lithium ion battery anodes, comprising the following steps:

[0008] (1) Dissolve 1 part by mass of a silicon source in 2-4 parts by mass of anhydrous ethanol, then add 4-6 parts by mass of deionized water, stir uniformly, add an acidic catalyst dropwise, adjust the pH value to 2-4, to obtain a first solution; dissolve an organic carbon source in anhydrous ethanol, stir uniformly, the concentration of the organic carbon source is 30-50 g / 100 mL, adjust the pH value to 2-4, to obtain a second solution; dissolve ammonia water in deionized water, stir uniformly, the concentration of the ammonia water is controlled to be 0.1-0.2 mol / 100 mL, to obtain a third solution; wherein the organic carbon source is a mixture of sucrose, phenolic resin and epoxy resin with a mass ratio of 1:1.4-1.6:0.5-0.7;

[0009] (2) Add the third solution dropwise to the second solution, and adjust the pH value to 8-9, stand for 6-10 h, to form a gel;

[0010] (3) Add 3-5 times the volume of anhydrous ethanol to the gel for aging, replace the anhydrous ethanol every 24 h, repeat 1-3 times, to obtain an aged gel, and dry at normal pressure to obtain a precursor product;

[0011] (4) Under a nitrogen protective atmosphere, heat the precursor product to 1100℃ and keep for 3 h, cool to room temperature with the furnace, to obtain a silicon oxide composite material for lithium ion battery anodes.

[0012] Further, the free phenol mass percentage of the phenolic resin is 10-14%. It is purchased from Hebei Zetian Chemical Co., Ltd., with a brand of 2127-1.

[0013] Further, the epoxy resin is glycidyl ether epoxy resin with an epoxy equivalent weight of 180-190 g / eq and a viscosity of 11000-15000 cps at 25℃, which is commercially available from Wancheng Chemical Technology Co., Ltd. with model number NPEL-128.

[0014] Further, the acid catalyst is hydrochloric acid, nitric acid or acetic acid.

[0015] Further, the third solution is added dropwise to the second solution to obtain a mass ratio of carbon to silicon of 2-4:1.

[0016] Further, the normal pressure drying is performed at 100-120℃ for 15-20h.

[0017] Further, the silicon source is a mixture of medium-long chain trialkoxysilane and tetraethyl orthosilicate with a mass ratio of 1:2-4.

[0018] Further, the medium-long chain trialkoxysilane is one or more of propyl triethoxysilane, butyl triethoxysilane and propyl trimethoxysilane.

[0019] Further, the medium-long chain trialkoxysilane is a mixture of propyl triethoxysilane, butyl triethoxysilane and propyl trimethoxysilane with a mass ratio of 1:0.2-0.5:1.6-1.8.

[0020] The present application provides a silicon oxide composite material for lithium ion battery anodes prepared by the preparation method.

[0021] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0022] 1. The present application uses a specific ratio of carbon source for mixing. The carbon material plays a key role in the conductive effect in the composite material, ensuring the rapid transmission of lithium ions in the material. Silicon oxide will undergo significant volume changes during lithiation and delithiation, which may lead to the destruction of the material structure. An appropriate amount of carbon source helps to alleviate this problem. The present application forms a strong structural framework to support the silicon oxide particles, preventing them from breaking or peeling off during charging and discharging. During the first charging and discharging process, a solid electrolyte interface (SEI) film is formed on the surface of the negative electrode. A suitable proportion of carbon source helps to form a stable and thin SEI film, which is crucial for improving the first charging and discharging efficiency and prolonging the cycle life of the battery. The carbon source produces a certain pore structure during the high-temperature carbonization process, which is beneficial for improving the diffusion rate of lithium ions and the power characteristics of the battery. Proper porosity can balance the capacity and power performance. Carbon material not only provides an electronic conduction path, but also serves as an additional lithium ion storage site. A specific proportion of carbon source can increase the reversible storage amount of lithium ions in the composite material, thereby improving the capacity.

[0023] 2、In the process of preparing the silicon oxide composite material for lithium ion battery negative electrode, the selection and proportion of silicon source have significant influence on the electrochemical performance of the final composite material, especially the electric capacity, the silicon source of the present application is a mixture of medium-long chain trialkoxy silane and tetraethyl orthosilicate with a mass ratio of 1:2-4, and different proportions of trialkoxy silane and tetraethyl orthosilicate can affect the microstructure of the final composite material. Trialkoxy silane contains longer organic side chains, which helps to form a more open pore structure, while TEOS tends to form a more dense network structure. Different structures of materials have different influences on the diffusion capacity of lithium ions, electronic conductivity and mechanical stability, which further affect the electric capacity. The proportion of silicon source determines the size and aggregation state of the generated silicon oxide particles. Smaller particle size helps to improve the diffusion rate of lithium ions, and moderate aggregation can enhance the mechanical strength of the material. Suitable particle size and aggregation state are crucial to improve the electric capacity and cycle stability; the amount of silicon source directly affects the content of silicon oxide in the composite material. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0025] Embodiment 1

[0026] The present embodiment provides a preparation method of a silicon oxide composite material for lithium ion battery negative electrode, comprising the following steps:

[0027] (1) Dissolve 1 part by mass of silicon source in 3 parts by mass of anhydrous ethanol, then add 5 parts by mass of deionized water, stir uniformly, add an acidic catalyst dropwise, and adjust the pH value to 3 to obtain a first solution; dissolve an organic carbon source in anhydrous ethanol, stir uniformly, and adjust the pH value to 3, so that the concentration of the organic carbon source is 40 g / 100 mL to obtain a second solution; dissolve ammonia water in deionized water, stir uniformly, and control the concentration of the ammonia water to be 0.15 mol / 100 mL to obtain a third solution; wherein the organic carbon source is a mixture of sucrose, phenolic resin and epoxy resin with a mass ratio of 1:1.5:0.6;

[0028] (2) Add the third solution dropwise to the second solution, and adjust the pH value to 8.5, and stand for 8 h to form a gel;

[0029] (3) Add 4 times the volume of anhydrous ethanol to the gel for aging, replace the anhydrous ethanol every 24 h, and repeat for 2 times to obtain an aged gel, and then dry under normal pressure to obtain a precursor product;

[0030] (4) under the protection of nitrogen atmosphere, the precursor product is heated to 1100℃ and kept for 3h, and then the furnace is cooled to room temperature, thereby obtaining the silicon oxide composite material for the negative electrode of lithium ion battery.

[0031] The free phenol mass percentage of the phenolic resin is 10-14%. It is purchased from Hebei Zetian Chemical Co., Ltd., and the brand is 2127-1.

[0032] The epoxy resin is a glycidyl ether type epoxy resin, and the epoxy equivalent weight is 180-190 g / eq, and the viscosity at 25℃ is 11000-15000 cps. It is purchased from Wanqing Chemical Technology Co., Ltd., and the model is NPEL-128.

[0033] The acidic catalyst is 0.1 mol / L hydrochloric acid.

[0034] The third solution is added dropwise into the second solution, and the mass ratio of carbon and silicon is 3:1.

[0035] The normal pressure drying is dried at 110℃ for 17h.

[0036] The silicon source is a mixture of medium-long chain trialkoxy silane and tetraethyl orthosilicate with a mass ratio of 1:3.

[0037] The medium-long chain trialkoxy silane is a mixture of propyl triethoxy silane, butyl triethoxy silane and propyl trimethoxy silane with a mass ratio of 1:0.3:1.7.

[0038] Comparative Example 1

[0039] The difference between this comparative example and Example 1 is that the phenolic resin is different.

[0040] A preparation method of a silicon oxide composite material for the negative electrode of lithium ion battery, comprising the following steps:

[0041] (1) 1 part by mass of silicon source is dissolved in 3 parts by mass of anhydrous ethanol, and then 5 parts by mass of deionized water is added, stirred uniformly, and an acidic catalyst is added dropwise to adjust the pH value to 3, thereby obtaining a first solution; an organic carbon source is dissolved in anhydrous ethanol and stirred uniformly, and the concentration of the organic carbon source is 40 g / 100 mL, and the pH value is adjusted to 3, thereby obtaining a second solution; ammonia water is dissolved in deionized water and stirred uniformly, and the concentration of the ammonia water is controlled to be 0.15 mol / 100 mL, thereby obtaining a third solution; wherein the organic carbon source is a mixture of sucrose, phenolic resin and epoxy resin with a mass ratio of 1:1.5:0.6;

[0042] (2) the third solution is added dropwise into the second solution, and the pH value is adjusted to 8.5, and then it is left to stand for 8h to form a gel;

[0043] (3) adding 4 times the volume of anhydrous ethanol to the gel for aging, replacing the anhydrous ethanol every 24 hours, repeating twice to obtain an aged gel, and drying at normal pressure to obtain a precursor product;

[0044] (4) Under a nitrogen protective atmosphere, the precursor product was heated to 1100°C and kept at this temperature for 3 hours, and then cooled to room temperature in the furnace to obtain a silicon oxide composite material for lithium-ion battery negative electrode.

[0045] Phenolic resin, free phenol content ≤4.5% by mass. Hebei Zetian Chemical Co., Ltd., brand 4123B.

[0046] The epoxy resin is a glycidyl ether epoxy resin with an epoxy equivalent weight of 180-190 g / eq and a viscosity of 11,000-15,000 cps at 25° C. It was purchased from Wanqing Chemical Technology Co., Ltd. under the model number NPEL-128.

[0047] The acidic catalyst is 0.1 mol / L hydrochloric acid.

[0048] The third solution was added dropwise to the second solution so that the mass ratio of carbon to silicon was 3:1.

[0049] Normal pressure drying is drying at 110°C for 17 hours.

[0050] The silicon source is a mixture of medium- and long-chain trialkoxysilane and ethyl orthosilicate in a mass ratio of 1:3.

[0051] The medium- and long-chain trialkoxysilane is a mixture of propyltriethoxysilane, butyltriethoxysilane, and propyltrimethoxysilane in a mass ratio of 1:0.3:1.7.

[0052] Comparative Example 2

[0053] The difference between this comparative example and Example 1 is that the epoxy resin is different.

[0054] A method for preparing a silicon oxide composite material for a lithium ion battery negative electrode comprises the following steps:

[0055] (1) dissolving 1 part by mass of silicon source in 3 parts by mass of anhydrous ethanol, adding 5 parts by mass of deionized water, stirring evenly, adding an acidic catalyst dropwise, and adjusting the pH value to 3 to obtain a first solution; dissolving an organic carbon source in anhydrous ethanol, stirring evenly, the organic carbon source concentration is 40 g / 100 mL, and adjusting the pH value to 3 to obtain a second solution; dissolving ammonia water in deionized water, stirring evenly, and controlling the ammonia water concentration to 0.15 mol / 100 mL to obtain a third solution; wherein the organic carbon source is a mixture of sucrose, phenolic resin, and epoxy resin in a mass ratio of 1:1.5:0.6;

[0056] (2) The third solution is added dropwise into the second solution, and the pH value is adjusted to 8.5, and the gel is formed after standing for 8 hours;

[0057] (3) The aged gel is obtained by adding 4 times of volume of anhydrous ethanol into the gel, and the anhydrous ethanol is replaced every 24 hours for 2 times, and the precursor product is obtained by drying under normal pressure.

[0058] (4) The precursor product is heated to 1100℃ under nitrogen atmosphere for 3 hours, and the furnace is cooled to room temperature to obtain the silicon oxide composite material for lithium ion battery negative electrode.

[0059] The free phenol mass percentage of the phenolic resin is 10-14%, which is purchased from Hebei Zetian Chemical Co., Ltd., and the brand is 2127-1.

[0060] The epoxy resin is different. The epoxy resin is a glycidyl ether type epoxy resin, and the epoxy equivalent weight is 120-150 g / eq, and the viscosity at 25℃ is 7000-10000 cps. It is purchased from South Asia Epoxy Resin 901.

[0061] The acidic catalyst is 0.1 mol / L hydrochloric acid.

[0062] The third solution is added dropwise into the second solution, and the mass ratio of carbon and silicon is 3:1.

[0063] The normal pressure drying is dried at 110℃ for 17 hours.

[0064] The silicon source is a mixture of medium-long chain trialkoxysilane and tetraethyl orthosilicate with a mass ratio of 1:3.

[0065] The medium-long chain trialkoxysilane is a mixture of propyl triethoxysilane, butyl triethoxysilane and propyl trimethoxysilane with a mass ratio of 1:0.3:1.7.

[0066] Comparative Example 3

[0067] The difference between this comparative example and Example 1 is that the organic carbon source is a mixture of sucrose, phenolic resin and epoxy resin with a mass ratio of 1:1:1.

[0068] A preparation method of a silicon oxide composite material for lithium ion battery negative electrode, comprising the following steps:

[0069] (1) 1 part by mass of a silicon source was dissolved in 3 parts by mass of anhydrous ethanol, 5 parts by mass of deionized water was added, and stirred uniformly, an acidic catalyst was added dropwise, and the pH value was adjusted to 3 to obtain a first solution; an organic carbon source was dissolved in anhydrous ethanol, stirred uniformly, the concentration of the organic carbon source was 40 g / 100 mL, and the pH value was adjusted to 3 to obtain a second solution; ammonia water was dissolved in deionized water, stirred uniformly, and the concentration of the ammonia water was controlled to 0.15 mol / 100 mL to obtain a third solution; wherein the organic carbon source is a mixture of sucrose, phenolic resin and epoxy resin in a mass ratio of 1:1:1;

[0070] (2) The third solution was added dropwise to the second solution, and the pH value was adjusted to 8.5, and left to stand for 8 h to form a gel;

[0071] (3) 4 times the volume of anhydrous ethanol was added to the gel for aging, and the anhydrous ethanol was replaced every 24 h, and the operation was repeated twice to obtain an aged gel, which was dried at normal pressure to obtain a precursor product;

[0072] (4) The precursor product was heated to 1100℃ under a nitrogen protective atmosphere for 3 h, and the furnace was cooled to room temperature to obtain a silicon oxide composite material for lithium ion battery negative electrodes.

[0073] The free phenol mass percentage of the phenolic resin is 10-14%. It is purchased from Hebei Zetian Chemical Co., Ltd., and the brand is 2127-1.

[0074] The epoxy resin is a glycidyl ether type epoxy resin, the epoxy equivalent weight is 180-190 g / eq, and the viscosity at 25℃ is 11000-15000 cps. It is purchased from Wanqing Chemical Technology Co., Ltd., and the model is NPEL-128.

[0075] The acidic catalyst is 0.1 mol / L hydrochloric acid.

[0076] The third solution was added dropwise to the second solution to make the mass ratio of carbon to silicon 3:1.

[0077] Normal pressure drying is drying at 110℃ for 17 h.

[0078] The silicon source is a mixture of medium and long chain trialkoxysilane and tetraethyl orthosilicate in a mass ratio of 1:3.

[0079] The medium and long chain trialkoxysilane is a mixture of propyl triethoxysilane, butyl triethoxysilane and propyl trimethoxysilane in a mass ratio of 1:0.3:1.7.

[0080] Comparative Example 4

[0081] The difference between this comparative example and Example 1 is that the silicon source is a mixture of medium and long chain trialkoxysilane and tetraethyl orthosilicate in a mass ratio of 1:1.

[0082] A preparation method of a silicon oxide composite material for a lithium ion battery negative electrode, comprising the following steps:

[0083] (1) Dissolve 1 part by mass of a silicon source in 3 parts by mass of anhydrous ethanol, then add 5 parts by mass of deionized water, stir uniformly, drop in an acidic catalyst, and adjust the pH value to 3 to obtain a first solution; dissolve an organic carbon source in anhydrous ethanol, stir uniformly, and adjust the pH value to 3, with the concentration of the organic carbon source being 40 g / 100 mL, to obtain a second solution; dissolve ammonia water in deionized water, stir uniformly, and control the concentration of the ammonia water to be 0.15 mol / 100 mL to obtain a third solution; wherein the organic carbon source is a mixture of sucrose, phenolic resin and epoxy resin in a mass ratio of 1:1.5:0.6;

[0084] (2) Drop the third solution into the second solution, and adjust the pH value to 8.5, and stand for 8 h to form a gel;

[0085] (3) Add 4 times the volume of anhydrous ethanol to the gel for aging, replace the anhydrous ethanol every 24 h, repeat 2 times, obtain an aged gel, and dry at normal pressure to obtain a precursor product;

[0086] (4) Under a nitrogen protective atmosphere, heat the precursor product to 1100℃ and keep for 3 h, cool to room temperature with the furnace, and prepare a silicon oxide composite material for a lithium ion battery negative electrode.

[0087] The free phenol mass percentage of the phenolic resin is 10-14%. It is purchased from Hebei Zetian Chemical Co., Ltd., and the brand is 2127-1.

[0088] The epoxy resin is a glycidyl ether type epoxy resin, with an epoxy equivalent weight of 180-190 g / eq and a viscosity of 11000-15000 cps at 25℃. It is purchased from Wanqing Chemical Technology Co., Ltd., and the model is NPEL-128.

[0089] The acidic catalyst is 0.1 mol / L hydrochloric acid.

[0090] The third solution is dropped into the second solution to make the mass ratio of carbon to silicon be 3:1.

[0091] Normal pressure drying is drying at 110℃ for 17 h.

[0092] The silicon source is a mixture of medium and long chain trialkoxy silane and tetraethyl orthosilicate in a mass ratio of 1:1.

[0093] The medium and long chain trialkoxy silane is a mixture of propyl triethoxy silane, butyl triethoxy silane and propyl trimethoxy silane in a mass ratio of 1:0.3:1.7.

[0094] Comparative Example 5

[0095] The difference between the present comparative example and Example 1 is that the medium-long chain trialkoxy silane is a mixture of propyl triethoxy silane, butyl triethoxy silane and propyl trimethoxy silane in a mass ratio of 1:1:1.

[0096] A preparation method of a silicon oxide composite material for a lithium ion battery negative electrode, comprising the following steps:

[0097] (1) 1 part by mass of a silicon source is dissolved in 3 parts by mass of anhydrous ethanol, 5 parts by mass of deionized water is added, and stirring is performed until uniform, an acidic catalyst is added dropwise, and the pH value is adjusted to 3 to obtain a first solution; an organic carbon source is dissolved in anhydrous ethanol, stirring is performed until uniform, the concentration of the organic carbon source is 40 g / 100 mL, and the pH value is adjusted to 3 to obtain a second solution; ammonia water is dissolved in deionized water, stirring is performed until uniform, and the concentration of the ammonia water is controlled to be 0.15 mol / 100 mL to obtain a third solution; wherein the organic carbon source is a mixture of sucrose, phenolic resin and epoxy resin in a mass ratio of 1:1.5:0.6;

[0098] (2) the third solution is added dropwise into the second solution, the pH value is adjusted to 8.5, and standing is performed for 8 h to form a gel;

[0099] (3) 4 times the volume of anhydrous ethanol is added to the gel for aging, the anhydrous ethanol is replaced every 24 h, and the operation is repeated twice to obtain an aged gel, and normal pressure drying is performed to obtain a precursor product;

[0100] (4) under a nitrogen protective atmosphere, the precursor product is heated to 1100°C and kept for 3 h, the furnace is cooled to room temperature, and a silicon oxide composite material for a lithium ion battery negative electrode is prepared.

[0101] The free phenol mass percentage of the phenolic resin is 10-14%, which is purchased from Hebei Zetian Chemical Co., Ltd., and the model number is 2127-1.

[0102] The epoxy resin is a glycidyl ether type epoxy resin, the epoxy equivalent weight is 180-190 g / eq, and the viscosity at 25°C is 11000-15000 cps. It is purchased from Wanqing Chemical Technology Co., Ltd., and the model number is NPEL-128.

[0103] The acidic catalyst is 0.1 mol / L hydrochloric acid.

[0104] The third solution is added dropwise into the second solution to make the mass ratio of carbon to silicon be 3:1.

[0105] Normal pressure drying is drying at 110°C for 17 h.

[0106] The silicon source is a mixture of medium-long chain trialkoxy silane and tetraethyl orthosilicate in a mass ratio of 1:3.

[0107] The medium-long chain trialkoxysilane is a mixture of propyl triethoxysilane, butyl triethoxysilane and propyl trimethoxysilane with a mass ratio of 1:1:1.

[0108] Performance test

[0109] The silicon oxide composite materials of the examples and the comparative examples are used as negative materials of lithium ion batteries, and the mass ratio of the composite material, acetylene black and PVDF is 85:7:8, which is mixed into a uniform paste with N-methyl pyrrolidone (NMP) solvent. The paste is coated on a copper foil, and a doctor blade is used to uniformly coat it into a film sheet and adhere to the surface of the copper foil. The prepared coating is placed in an oven and dried at 110°C for 12 hours. After drying, it is moved into a vacuum drying oven and dried at 120°C for 10 hours. The dried composite material coating is then pressed by a roll mill or a tablet press. The electrode sheet is cut by a mechanical cutting machine, lithium sheet is used as a counter electrode, and a commercially available 1 mol / L LiPF6 / EC+DMC solution is used as an electrolyte. The charge-discharge performance is tested by a battery tester under a current density of 100 mA / g for 100 cycles. The results are shown in Table 1.

[0110] Table 1 Performance test results

[0111]

[0112] From the above performance test results, it can be seen that the specific capacity of Example 1 is high and the cycle stability is good, while the comparative examples do not use the necessary technical solutions, resulting in a significant difference in the corresponding performance test compared with the examples. The above experimental results further prove the importance of the technical solutions defined in the present application to its technical effects.

[0113] The above is a preferred embodiment of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a silicon oxide composite material for a lithium ion battery negative electrode, characterized in that: The following steps are involved: (1) dissolving 1 part by mass of silicon source in 2-4 parts by mass of anhydrous ethanol, adding 4-6 parts by mass of deionized water, stirring evenly, adding an acidic catalyst dropwise, and adjusting the pH value to 2-4 to obtain a first solution; dissolving an organic carbon source in anhydrous ethanol, stirring evenly, the organic carbon source concentration is 30-50 g / 100 mL, and adjusting the pH value to 2-4 to obtain a second solution; dissolving ammonia water in deionized water, stirring evenly, and controlling the ammonia water concentration to 0.1-0.2 mol / 100 mL to obtain a third solution; wherein the organic carbon source is a mixture of sucrose, phenolic resin and epoxy resin in a mass ratio of 1:1.4-1.6:0.5-0.7; the free phenol mass percentage of the phenolic resin is 10-14%; the epoxy resin is a glycidyl ether epoxy resin with an epoxy equivalent of 180-190 g / eq and a viscosity of 11000-15000 cps at 25°C; (2) adding the second solution dropwise to the first solution to make the mass ratio of carbon to silicon be 2-4:1, adjusting the pH value to 8-9, and standing for 6-10 hours to form a gel; (3) adding 3-5 times the volume of anhydrous ethanol to the gel for aging, replacing the anhydrous ethanol every 24 hours, repeating 1-3 times to obtain an aged gel, and drying at normal pressure to obtain a precursor product; (4) Under a nitrogen protective atmosphere, the precursor product was heated to 1100° C. and kept at this temperature for 3 h, and then cooled to room temperature in the furnace to obtain a silicon oxide composite material for lithium-ion battery negative electrode; The silicon source is a mixture of medium-chain trialkoxysilane and ethyl orthosilicate in a mass ratio of 1:2-4; the medium-chain trialkoxysilane is a mixture of propyltriethoxysilane, butyltriethoxysilane and propyltrimethoxysilane in a mass ratio of 1:0.2-0.5:1.6-1.

8.

2. The method for preparing the silicon oxide composite material for lithium ion battery negative electrode according to claim 1, characterized in that: The acidic catalyst is hydrochloric acid, nitric acid or acetic acid.

3. The method for preparing the silicon oxide composite material for lithium ion battery negative electrode according to claim 1, characterized in that: Normal pressure drying is drying at 100-120°C for 15-20 hours.

4. A silicon oxide composite material for lithium ion battery negative electrode prepared according to the preparation method according to any one of claims 1 to 3.

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