阅读说明：本技术 一种低成本制备锂电池负极用高容量高倍率纳米硅/亚硅负极复合材料的方法及材料 (Method and material for preparing high-capacity high-rate nano silicon/sub-silicon negative electrode composite material for lithium battery negative electrode at low cost ) 是由 王有治 王力君 贺金味 罗才坤 吴旭翔 张明 黄强 于 2021-08-17 设计创作，主要内容包括：本发明公开了一种低成本制备锂电池负极用高容量、高倍率纳米硅/亚硅负极复合材料及其制备方法,选用硅太阳能电池废料或边角料、材料厂废弃氧化亚硅料,经处理得到硅原料和氧化亚硅原料,二者按比例混合,研磨破碎得到纳米颗粒浆料,在浆料中加入酸液及表面活性剂对纳米颗粒表面处理,调节溶液PH值后,加入适量特定成分偶联剂与纳米粒子表面官能团作用得到凝胶状浆料,再加入导电剂、粘结剂、锂源,经超声混合分散、干燥、热合反应、造粒,得到类球形状的前驱体,碳包覆后经高温碳化得到负极材料。该方法有助于资源的回收再生利用,降低了材料反应的苛刻程度,材料具有形貌规整、体积膨胀效应小、电导率优异、库伦效率高且导电性好等优点。(The invention discloses a high-capacity and high-magnification nano silicon/sub-silicon negative electrode composite material for preparing a lithium battery negative electrode at low cost and a preparation method thereof. The method is beneficial to recycling resources, reduces the rigor degree of material reaction, and has the advantages of regular shape, small volume expansion effect, excellent conductivity, high coulombic efficiency, good conductivity and the like.)

1. A method for preparing a high-capacity high-rate nano silicon/sub-silicon negative electrode composite material for a lithium battery negative electrode at low cost is characterized by comprising the following steps:

(1) respectively carrying out primary crushing, screening, acid washing, drying and roasting on silicon solar cell waste materials or leftover materials and silica tailings which do not reach the standard in a material factory to obtain a silicon raw material and a silica raw material;

(2) mixing a silicon raw material and a silicon monoxide raw material, adding a dispersing agent and a surfactant, and sanding to obtain nano Si/SiO slurry;

(3) adding acid into the nano Si/SiO slurry, adjusting the pH value to 4-6, adding a certain proportion of a coupling agent to carry out polymerization reaction to obtain viscous gel slurry;

(4) adding a binder, a conductive agent and a lithium source into the viscous gel-like slurry, grinding, ultrasonically dispersing, drying, carrying out thermal reaction, and granulating to obtain a spheroidal precursor;

(5) and coating the spheroidal precursor with a carbon source, and roasting to obtain the nano silicon/silicon-containing negative electrode composite material.

2. The method for preparing the high-capacity high-rate nano-silicon/silicon-idene anode composite material for the anode of the lithium battery at low cost according to claim 1, wherein the acid used in the acid washing in the step (1) is one of nitric acid, sulfuric acid, hydrochloric acid, perchloric acid and hydrobromic acid, and the pH value of the acid solution is controlled to be 1-3; in the step (1), the roasting is carried out for 1-6 h at 600-1100 ℃ under the protection of one of nitrogen, argon and hydrogen-argon mixed gas.

3. The method for preparing the high-capacity high-rate nano silicon/sub-silicon negative electrode composite material for the negative electrode of the lithium battery at low cost as claimed in claim 1, wherein the step (2) is to mix a silicon raw material and a sub-silicon oxide raw material according to a mass ratio of (10-1000): 100; the dispersing agent is one or more of deionized water, absolute ethyl alcohol, ethylene glycol, methanol, normal hexane and cyclohexane, and the volume ratio of the dispersing agent to the total mass of the silicon raw material and the silicon oxide raw material is (3-19) mL:1 g; the surfactant is one or more of stearic acid, sodium dodecyl benzene sulfonate, fatty glyceride, polysorbate, lauric acid, dodecyl trimethyl ammonium bromide, 3-aminopropyl triethyl silane, dodecyl dimethyl benzyl ammonium chloride and polydimethyl diallyl ammonium chloride, and the volume ratio of the surfactant to the dispersant is 1 (10-1000).

4. The method for preparing the high-capacity high-rate nano silicon/inferior silicon negative electrode composite material for the negative electrode of the lithium battery at low cost according to claim 1, wherein the acid in the step (3) is one or more of oxalic acid, hydrobromic acid, citric acid, hydrofluoric acid, formic acid, acetic acid, hypochlorous acid, silicic acid, stearic acid and oleic acid; the coupling agent in the step (3) is one of methacrylic acid acyloxy propyl trimethoxy silane, vinyl triethoxy silane, ethylenediamine propyl methyl dimethoxy silane, ethylenediamine propyl triethoxy silane, hydrophobic propyl trimethoxy silane, aminopropyl triethoxy silane and glycidol triethoxy propyl trimethoxy silane, and the ratio of the mass of the coupling agent to the total mass of the silicon raw material and the silicon oxide raw material is (0.001-0.1): 1.

5. The method for preparing the high-capacity high-rate nano-silicon/sub-silicon negative electrode composite material for the negative electrode of the lithium battery at low cost as claimed in claim 1, wherein the lithium source in the step (4) is LiPF₆LiH, lithium borohydride,LiOH、Li₂CO₃One of inert lithium metal powder and lithium alloy, wherein the ratio of the mass of the lithium source to the total mass of the silicon raw material and the silicon monoxide raw material is (0.001-0.5): 1; the conductive agent in the step (4) is one or more of carbon black, acetylene black, graphene, carbon nano tubes and polyaniline, and the mass ratio of the conductive agent to the total mass of the silicon raw material and the silicon monoxide raw material is 1 (19-99); the binder in the step (4) is one of sucrose, glucose, starch, phenolic resin, urea-formaldehyde resin, asphalt, PVP, cellulose acetate, sodium carboxymethylcellulose, polyacrylonitrile and citric acid, and the mass ratio of the binder to the total mass of the silicon raw material and the silicon monoxide raw material is 1 (5-100).

6. The method for preparing high-capacity high-rate nano silicon/sub-silicon negative electrode composite material for the negative electrode of the lithium battery at low cost as claimed in claim 1, wherein the heat seal reaction in the step (4) is to maintain the vacuum degree of 10 in a vacuum furnace^-1～10^-5Pa, heating to 500-1300 ℃ at the speed of 2-10 ℃/min, preserving heat for 0.5-6 h, and cooling to room temperature.

7. The method for preparing the high-capacity high-rate nano silicon/silicon-idene anode composite material for the lithium battery anode at low cost as claimed in claim 1, wherein the carbon source in the step (5) is one or more of sodium carboxymethylcellulose, N-methyl pyrrolidone, sucrose, acetylene, glucose, phenolic resin, urea resin, methane, ethylene, citric acid, asphalt, PVP, acetone, formaldehyde, acetaldehyde, phenol, organic solvent containing unsaturated double bonds or compound, and the mass ratio of the carbon source to the coated material is (2-30): 100.

8. The method for preparing the high-capacity high-rate nano silicon/sub-silicon negative electrode composite material for the negative electrode of the lithium battery at low cost as claimed in claim 1, wherein the step (5) comprises the steps of coating the spherical precursor with a carbon source, heating to 400-800 ℃ at a rate of 5-15 ℃/min under the protection of inert gas, preserving heat for 0.5-8 h, naturally cooling to room temperature, and then roasting for carbonization.

9. The method for preparing the high-capacity high-rate nano-silicon/sub-silicon negative electrode composite material for the negative electrode of the lithium battery at low cost as claimed in claim 1, wherein the roasting in the step (5) is to perform high-temperature carbonization treatment on the coated material under the protection of nitrogen, argon or a hydrogen-argon mixture, the carbonization temperature is increased to 700-1100 ℃ at a heating rate of 3-10 ℃/min, the temperature is kept for 1-10 h, and then the material is naturally cooled to room temperature.

10. The nano silicon/sub-silicon anode composite material prepared by the method according to any one of claims 1 to 9.

Technical Field

The invention relates to the field of lithium ion battery cathode materials, in particular to a high-capacity and high-rate nano silicon/sub-silicon cathode composite material for a lithium battery cathode prepared at low cost, a preparation method of the high-capacity and high-rate nano silicon/sub-silicon cathode composite material, and a nano silicon/sub-silicon cathode composite material prepared by the method.

Background

The graphite carbon material commonly used for the cathode of the current commercial lithium ion battery has the excellent characteristics of low de-intercalation lithium potential, high reversible capacity, high first efficiency, good cycle stability and the like, and has rich carbon resources and low price. However, its theoretical specific capacity is not high (372 mAhg)^-1) And the endurance is poor, which restricts the application of the high-performance 3C product and the electric automobile field to a certain extent.

Silicon is used as an element in the earth crust, has abundant reserves and has high theoretical specific capacity (4200 mAhg)^-1) Thus, the graphite anode material is one of the alternative materials of the graphite anode material.

As a typical lithium ion battery cathode material, a silicon monoxide (SiO) material has good cycle performance and an insignificant volume expansion effect, but the problems of poor electrical conductivity and low first efficiency of charge and discharge always exist, and for these problems, pre-lithiation and carbon coating treatment are generally adopted at the present stage for improvement.

Aiming at the advantages and disadvantages of Si and SiO, if the performance neutralization and complementation of the Si and the SiO can be realized, the silicon and the sub-silicon raw materials are effectively utilized through resource recovery, and the development and the application of the silicon-based negative electrode material are greatly promoted.

Patent CN111883760A discloses a nano-silicon cathode for a nano-silicon composite conductor and a polymer, and the prepared material has poor shape controllability; CN111653746A, CN112467114A, CN111969196A and CN112259708A disclose a mode of briefly coating and granulating silicon oxide particles to prepare a core-shell structure silicon oxide lithium battery cathode material, and the prepared material has the problems of low capacity and low first efficiency; CN112421018A discloses a silicon oxide/carbon negative electrode material with an internal porous structure prepared by taking silicon-magnesium alloy particles as a framework, wherein the obtained material is low in efficiency for the first time and fast in capacity attenuation; CN111900368A discloses a method for preparing a metal oxide-coated silicon oxide/carbon composite material by vapor deposition and metal oxide coating, wherein the prelithiation process of the material is complicated; CN112086630A discloses a method for preparing a sandwich interlayer, a composite negative electrode material of silicon monoxide, by using a simple substance of silicon and silicon dioxide as raw materials and performing reaction and chemical vapor deposition, and the preparation process is harsh and tedious.

Analyzing the prior art, aiming at the silicon material, the method is improved by mainly focusing on the pre-lithiation of the silicon oxide raw material and coating a conductive layer; for silicon materials, a doped conductive material, or a carbon layer coated by nano silicon particles, or a vapor deposition carbon layer is mostly adopted to improve the material performance, the first efficiency, reversible capacity, particle morphology and the like of the obtained silicon/silicon-based negative electrode material are not ideal, and the large-scale application difficulty is large. Therefore, the development of a silicon-based composite material with low cost, excellent appearance, high capacity and high conductivity is urgent.

Disclosure of Invention

The invention overcomes the defects of the prior art, and provides a high-capacity and high-rate nano silicon/sub-silicon negative electrode composite material for preparing a lithium battery negative electrode at low cost and a preparation method thereof, so that the conductivity of the silicon-based composite negative electrode material in the prior art is improved, the volume expansion effect of the material is relieved, and the first efficiency and rate performance of the material are improved.

In order to solve the technical problem, the embodiment of the invention adopts the following technical scheme:

selecting silicon solar cell waste materials or leftover materials and silica tailings which do not reach the standard in a material factory, weighing silicon and silica in a specific proportion through primary crushing, flotation, acid washing and high-temperature roasting, grinding and crushing to obtain primary nano particles (namely nano Si/SiO slurry), adding a surfactant and an acid solution to treat the surface of the nano particles, adjusting the pH value of the solution, adding a certain proportion and variety of surfactants and coupling agents, polymerizing with the functional groups on the surface of the nano particles to obtain gel slurry, adding a proper proportion of conductive agent, adhesive and lithium source, performing ultrasonic mixing dispersion, drying, heat seal reaction and granulation to obtain secondary particles (namely a spheroidal precursor), then coating the composite material by using a carbon source in coating equipment, and carbonizing the composite material at high temperature to obtain the high-capacity and high-rate nano silicon/silicon-containing cathode composite material, wherein the preparation steps are as follows:

(1) selecting silicon solar cell waste materials or leftover materials and silica tailings which do not reach the standard in a material factory, respectively carrying out primary crushing and flotation to remove foreign matters, removing impurities in the raw materials through acid washing reaction, drying, and then carrying out high-temperature roasting to remove surface functional groups and other impurities of the materials to obtain silicon raw materials and silica raw materials;

(2) weighing the silicon raw material and the silicon monoxide raw material which are processed in the step (1) and have corresponding mass, adding a certain amount of dispersant and surfactant, and preparing uniformly dispersed nano Si/SiO slurry through sanding by a sand mill;

(3) adding a proper amount of acid into the slurry obtained in the step (2) to adjust the pH value to 4-6, adding a coupling agent with a certain component and proportion, and carrying out polymerization reaction to obtain viscous gel-like slurry;

(4) adding a proper amount of binder, conductive agent and lithium source into the gel-like slurry obtained in the step (3), grinding, performing ultrasonic dispersion treatment, drying, performing heat seal reaction, and granulating to obtain spheroidal precursor particles;

(5) coating the spheroidal precursor particles obtained in the step (4) with a proper amount of carbon source, and then carrying out high-temperature carbonization, sieving, demagnetizing and sieving to finally obtain a target product, namely the nano silicon/silicon-containing negative electrode composite material;

(6) and (3) collecting the materials which do not reach the standard in the step (5) or are screened, and then treating the materials in the step (1) to be reused in the step (2).

The further improvement of the invention is that the selected silicon solar cell waste material or leftover material is one of monocrystalline silicon, polycrystalline silicon and amorphous silicon, and the selected silicon monoxide tailing material is the waste silicon monoxide material of a material factory.

The further improvement of the invention is that the particle size of the silicon raw material and the silicon monoxide raw material is 0.5-70 um after the step (1) is subjected to primary crushing.

In a further improvement of the invention, when the material in the step (1) is subjected to acid washing treatment, the acid is one of nitric acid, sulfuric acid, hydrochloric acid, perchloric acid and hydrobromic acid, and the pH value of the acid solution is controlled to be 1-3.

The further improvement of the invention is that the material roasting in the step (1) is carried out under the protection of one gas of nitrogen, argon and hydrogen-argon mixed gas at 600-1100 ℃ for 1-6 h, and preferably the temperature of the roasted material is raised to 600-1100 ℃ at the speed of 1-10 ℃/min.

In the step (2), the mass ratio of the Si and the SiO raw material treated in the step (1) is (10-1000): 100, and the mass ratio of the ball material of the sand mill is (5-20): 1. Any ratio can be selected within the mass ratio range of (10-1000): 100, such as 300:100, 400:100, 500:100, 600:100, 700:100, 800:100, 900:100, and the like, and other ratios not listed within these ratio ranges.

The invention is further improved in that the used dispersing agent is one or more of deionized water, absolute ethyl alcohol, ethylene glycol, methanol, normal hexane and cyclohexane, and the volume ratio of the used dispersing agent to the total mass of the silicon raw material and the silicon monoxide raw material is (3-19) mL:1 g. The dispersant is preferably one or more of absolute ethanol, ethylene glycol, methanol, n-hexane, and cyclohexane. When the other steps in the method adopt more preferable process parameters, deionized water can be used as the dispersing agent, but the performance of the product is slightly reduced due to insufficient dispersibility of raw materials.

The invention is further improved in that the used surfactant is one or more of stearic acid, sodium dodecyl benzene sulfonate, fatty glyceride, polysorbate, lauric acid, dodecyl trimethyl ammonium bromide, 3-aminopropyl triethyl silane, dodecyl dimethyl benzyl ammonium chloride or polydimethyl diallyl ammonium chloride, and the volume ratio of the surfactant to the dispersant is 1 (10-1000).

The invention has the further improvement that the mixed particle size of Si and SiO after grinding by the sand mill in the step (2) is 10-500 nm.

In a further improvement of the invention, the acid in the step (3) is one or more of oxalic acid, hydrobromic acid, citric acid, hydrofluoric acid, formic acid, acetic acid, hypochlorous acid, silicic acid, stearic acid and oleic acid.

The invention is further improved in that the coupling agent used in the step (3) is one of methacrylic acid acyloxy propyl trimethoxy silane, vinyl triethoxy silane, ethylenediamine propyl methyl dimethoxy silane, ethylenediamine propyl triethoxy silane, hydrophobic propyl trimethoxy silane, aminopropyl triethoxy silane and glycidol triethoxy propyl trimethoxy silane, and the ratio of the mass of the coupling agent to the total mass of the silicon raw material and the silicon oxide raw material is (0.001-0.1): 1.

In a further improvement of the invention, the lithium source selected in step (4) is LiPF₆LiH, lithium borohydride, LiOH, Li₂CO₃One of the inert lithium metal powder and the lithium alloy, wherein the ratio of the mass of the lithium source to the total mass of the silicon raw material and the silicon monoxide raw material is (0.001-0.5): 1.

The further improvement of the invention is that the conductive agent selected in the step (4) is one or more of carbon black, acetylene black, graphene, carbon nano tube and polyaniline, and the ratio of the mass of the conductive agent to the total mass of the silicon raw material and the silicon monoxide raw material is 1 (19-99).

The further improvement of the invention is that the binder selected in the step (4) is one of sucrose, glucose, starch, phenolic resin, urea-formaldehyde resin, asphalt, polyvinylpyrrolidone (PVP), cellulose acetate, sodium carboxymethylcellulose, polyacrylonitrile and citric acid, and the ratio of the mass of the selected binder to the total mass of the silicon raw material and the silicon monoxide raw material is 1 (5-100).

The further improvement of the invention is that the conductive agent, the binder and the lithium source in the step (4) are added after the grinding of the sand mill is finished, and the grinding is continued for 0.1-4 h.

The invention has the further improvement that when the ultrasonic dispersion is carried out in the step (4), the selected ultrasonic frequency is 40kHz, and the ultrasonic time is 1-5 h.

The further improvement of the invention is that the drying mode in the step (4) is one or more of a spray drying method, a flash evaporation method, a freeze drying method and a standing evaporation method.

The further improvement of the invention is that the heat seal reaction in the step (4) means that the vacuum degree of the dried material is maintained at 10 in a vacuum furnace^-1～10^-5Pa, heating to 500-1300 ℃ at the speed of 2-10 ℃/min, preserving the heat for 0.5-6 h, and then cooling to room temperature.

The invention has the further improvement that the material after the thermal synthesis reaction in the step (4) is subjected to airflow crushing and classification, and the particle size of the spheroidal precursor is controlled to be 0.5-50 um.

The further improvement of the invention is that the carbon source for coating the precursor in the step (5) is one or more of sodium carboxymethylcellulose, N-methylpyrrolidone (NMP), sucrose, acetylene, glucose, phenolic resin, urea resin, methane, ethylene, citric acid, asphalt, PVP, acetone, formaldehyde, acetaldehyde, phenol, organic solvent containing unsaturated double bonds or compound, and the mass ratio of the carbon source to the coated material is (2-30): 100.

The further improvement of the invention is that the coating equipment/coating mode in the step (5) is one of a tube furnace, a box furnace, a push plate kiln, a roller kiln, a coating kettle, a high-temperature high-pressure reaction kettle and a kiln with a shovel plate.

The further improvement of the invention is that after the carbon source is used for coating the spheroidal precursor in the step (5) and before roasting, under the protection of inert gas, the temperature is raised to 400-800 ℃ at the speed of 5-15 ℃/min, the temperature is kept for 0.5-8 h, and then the spherical precursor is naturally cooled to the room temperature.

The further improvement of the invention is that the roasting in the step (5) is to carry out high-temperature carbonization on the coated material under the protection of nitrogen, argon or a hydrogen-argon mixed gas, the carbonization temperature is increased to 700-1100 ℃ at 3-10 ℃/min, the temperature is kept for 1-10 h, and then the material is naturally cooled to the room temperature;

the further improvement of the invention is that in the step (5), the high-temperature carbonized product is filtered by a 325-mesh screen and demagnetized by a demagnetizer to obtain the target product.

By the method, the nano silicon/sub-silicon cathode composite material is prepared, and has the advantages of high capacity and high multiplying power.

The invention introduces the coupling agent with specific components by adjusting the acid environment suitable for the hydrolysis of the coupling agent, reacts and couples functional groups on the surface of the nano particles to form stable sol-gel, and then dynamically or/and statically coats a conductive carbon layer on the granulated particle material to obtain the nano particle agglomerated balls, wherein the formed particles are spherical particles which are formed by uniformly distributing nano particles, embedding the nano particles into a core of a carbon source and coating the nano particles with the conductive carbon layer.

What used respectively to nanoparticle dispersion, coupling connection, preliminary cladding is surfactant active, coupling agent, binder, restrict the controllability of every step reaction, particle distribution is even in the obtained kernel of granule reunion, the ball nuclear appearance is excellent, the binder plays preliminary cladding and the inflation effect of constraint nanoparticle when charging and discharging as preliminary cladding to solitary nanoparticle, and final cladding is outer carbon-layer, plays electrically conductive, alleviates the volume expansion and reduces the gain effect of inside granule and electrolyte contact reaction.

The dispersing, coupling and connecting of the nano particles and the primary coating respectively use a surfactant, a coupling agent and a binder, so that the nano particles are uniformly distributed, the controllability of the reaction in each step is limited, and finally the spherical core particles with excellent morphology formed by the polymerization of the nano particles are obtained. The binder serves as a primary coating layer to perform primary coating on single nano-particles, simultaneously performs buffering and reduces the volume expansion effect of the nano-particles in the charging and discharging process, and the final coating layer is an outer carbon layer and performs the gain effects of conducting electricity, inhibiting volume expansion and reducing contact reaction of internal particles and electrolyte.

Lithium salt with specific proportion and components is doped and dispersed among the nano-sized silicon/silicon monoxide nano-particles, and the disproportionation reaction condition of the lithium salt and the silicon/silicon monoxide particles is achieved through heat treatment, so that the lithium salt can be more easily diffused and has disproportionation reaction with the silicon/silicon monoxide particles, the lithium salt enters the crystal lattices of the nano-particles/prelithiates the material, the added lithium salt is stable and effective in the synthetic material, and the first charge-discharge efficiency of the composite material is remarkably improved. And finally, the material is firmly wrapped after the lithium salt and the nano particles react by coating the carbon layer, so that the effective gain effect of improving the first efficiency and the rate discharge performance of the material is achieved.

Compared with the prior art, the invention has at least the following beneficial effects:

the invention adopts a grinding treatment process, uses Si and SiO raw materials with low cost, can repeatedly use the Si and SiO raw materials, can improve the utilization rate of the raw materials and greatly reduce the production and preparation cost; crushing Si and SiO particles to a nanometer scale, adding a proper amount of conductive agent, surfactant and binder, reacting and connecting with the crushed Si and SiO in the nanometer scale through surface functional groups under the action of a specific coupling agent to obtain uniformly dispersed silicon and silicon dioxide gel slurry, performing series treatment to obtain Si/SiO precursor particles, and uniformly distributing a conductive network formed by the conductive agent, so that the material is uniformly dispersed and compounded on the nanometer scale, the volume expansion of the material caused by charging and discharging is buffered, the reversible capacity and the first efficiency of the material are improved, the volume expansion effect of the material is reduced, and the charge-discharge cycle performance of the composite material is improved; after heat treatment granulation, a uniform carbon layer is coated on the surface of the precursor in a modifying way, so that the morphology of the particles is improved, and the conductivity rate performance is improved.

Drawings

FIG. 1 is a scanning electron micrograph of a material prepared in example 3.

FIG. 2 is a sectional electron micrograph of a material prepared in example 3.

FIG. 3 is an XRD pattern of the materials prepared, where A-example 3, B-comparative example 1, C-comparative example 2.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

Preparing 20L of nitric acid solution with the pH value of 1, weighing 2000g of polycrystalline silicon solar cell waste and 2000g of silicon monoxide tailing powder respectively, crushing by using a mechanical crusher, sieving by using a 120-mesh sieve, adding the materials into the prepared nitric acid solution respectively, stirring in a dispersion machine for 30min, filtering, washing with water, drying, carrying out heat preservation treatment at 800 ℃ for 1h under the protection of nitrogen, and cooling to room temperature to obtain impurity-removed Si and SiO granular materials.

Weighing 200g of silicon powder subjected to high-temperature treatment and 1800g of silicon monoxide powder, adding 10000mL of ethanol into a ball material dispersion machine for rough mixing for 20min, transferring the material into a sand mill circulating liquid storage tank, filling 10kg of zirconium beads in a grinding cavity, detecting that the particle size D50 of Si and SiO particles is 95.3nm after grinding is finished, adding 30g of acetylene black and 10g of stearic acid for continuous grinding for 1h, adding an appropriate amount of oxalic acid to adjust the pH to be 5 before discharging, transferring liquid to the dispersion machine for dispersion, adding 50g of sparse propyl trimethoxy silane for dispersion for 30min, adding an appropriate amount of ammonia water to adjust the pH to be 7, then adding 80g of urea-formaldehyde resin powder and 20g of inert metal lithium powder, externally arranging ultrasonic equipment, performing ultrasonic dispersion at an ultrasonic frequency of 40kHz, performing ultrasonic dispersion treatment for 1h, and performing flash evaporation drying to obtain a blocky material.

The material was placed in a vacuum oven with a vacuum dimension maintained at 1 x 10^-5Pa, heating to 1000 ℃ at the heating rate of 5 ℃/min, preserving the heat for 2h, cooling to room temperature, and crushing the obtained blocky material airflow to obtain particles with the particle size of D50 being 6.53 mu m; adding the crushed material 900g into a VC coating machine, adjusting the stirring linear speed to 20m/s, heating to 800 ℃ at the speed of 5 ℃/min, slowly adding NMP 225g, keeping the temperature for 1h, and naturally cooling to room temperature.

Heating the coated material to 900 ℃ at a speed of 10 ℃/min under the protection of nitrogen, preserving heat for 2h, naturally cooling to room temperature, discharging, sieving with a 325-mesh sieve, and then carrying out demagnetization treatment by a demagnetizing machine to obtain the target product.

Example 2

Preparing 20L of nitric acid solution with the pH value of 1, weighing 2000g of polycrystalline silicon solar cell waste and 2000g of silicon monoxide tailing powder respectively, crushing by using a mechanical crusher, sieving by using a 120-mesh sieve, adding the materials into the prepared nitric acid solution respectively, stirring in a dispersion machine for 30min, filtering, washing with water, drying, carrying out heat preservation treatment at 600 ℃ for 4h under the protection of nitrogen, and cooling to room temperature to obtain impurity-removed Si and SiO granular materials.

Weighing 500g of silicon powder and 1500g of silicon monoxide powder after high-temperature treatment, adding 9000mL of n-hexane into a ball material dispersion machine for coarse mixing for 10min, transferring the materials into a sand mill circulating liquid storage tank, filling 10kg of zirconium beads in a grinding cavity, detecting that the particle sizes of Si and SiO particles D50 are 88.5nm after grinding, adding 10g of carbon nano tube and 20g of sodium dodecyl benzene sulfonate for continuous grinding for 0.5h, adding a proper amount of hydrofluoric acid to adjust the pH value to be 5 before discharging, transferring liquid to the dispersion machine for dispersion, adding 50g of ethylenediamine propyl methyldimethoxysilane for dispersion for 30min, adding ammonia water to adjust the pH value to be 7, then adding 60g of asphalt and 30g of LiOH, externally arranging ultrasonic equipment, ultrasonically dispersing at the ultrasonic frequency of 40kHz, and carrying out ultrasonic dispersion treatment for 2h and then carrying out flash evaporation and drying on the materials.

Placing the dried material in a vacuum furnace, and maintaining the vacuum degree at 1 x 10^-3Pa, heating to 800 ℃ at the heating rate of 5 ℃/min, preserving heat for 1h, then cooling to room temperature, crushing the obtained massive material airflow to obtain a material with the particle size of D50 being 5.8um, weighing 900g of the material, adding the material into a roller kiln, heating to 800 ℃ at the heating rate of 5 ℃/min, slowly adding 225g of NMP, preserving heat for 2h, and naturally cooling to room temperature.

Heating the coated material to 900 ℃ at a speed of 10 ℃/min under the protection of nitrogen, preserving heat for 2h, naturally cooling to room temperature, discharging, sieving with a 325-mesh sieve, and then carrying out demagnetization treatment by a demagnetizing machine to obtain the target product.

Example 3

Preparing 20L of sulfuric acid solution with the pH value of 1, weighing 2000g of polycrystalline silicon solar cell waste and 2000g of silicon monoxide tailing powder respectively, crushing by using a mechanical crusher, sieving by using a 300-mesh sieve, adding the materials into the prepared nitric acid solution respectively, stirring in a dispersion machine for 30min, filtering, washing with water, drying, carrying out heat preservation treatment at 800 ℃ for 1h under the protection of nitrogen, and cooling to room temperature to obtain impurity-removed Si and SiO granular materials.

Weighing 1000g of silicon powder and 1000g of silicon monoxide powder after high-temperature treatment, adding 9000mL of ethanol, roughly mixing for 10min in a ball material dispersion machine, transferring the material to a circulating liquid storage tank of a sand mill, filling 14kg of zirconium beads in a grinding cavity, measuring the particle size D50 of Si and SiO particles to be 58.8nm after grinding, adding 30g of carbon black and 10g of fatty glyceride, continuously grinding for 2h, adding an appropriate amount of oxalic acid to adjust the pH to be 5 before discharging, transferring liquid to the dispersion machine for dispersion, adding 80g of aminopropyl triethoxysilane, adding ammonia water to adjust the pH to be 7 after dispersing for 30min, then adding 80g of urea-formaldehyde resin and 50g of lithium carbonate, externally arranging ultrasonic equipment, performing ultrasonic dispersion treatment at an ultrasonic frequency of 40kHz for 2h, and performing spray drying granulation to obtain a material with the particle size D50 of 8.6 um.

The material was placed in a vacuum oven with a vacuum dimension maintained at 5 x 10^-5Pa, heating to 1200 ℃ at the speed of 8 ℃/min, preserving heat for 0.5h, and cooling to room temperature. Weighing 900g of materials, adding the materials into a high-temperature high-pressure reaction kettle, heating to 800 ℃ at the heating rate of 5 ℃/min, filling 120g of acetone, keeping the temperature for 2h, and naturally cooling to room temperature.

Heating the coated material to 1000 ℃ at a speed of 10 ℃/min under the protection of nitrogen, preserving heat for 5h, naturally cooling to room temperature, discharging, sieving with a 325-mesh sieve, and then carrying out demagnetization treatment by a demagnetizing machine to obtain the target product.

Example 4

Preparing 20L of nitric acid solution with the pH value of 1, weighing 2000g of polycrystalline silicon solar cell waste and 2000g of silicon monoxide tailing powder respectively, crushing by using a mechanical crusher, sieving by using a 300-mesh sieve, adding the materials into the prepared nitric acid solution respectively, stirring in a dispersion machine for 30min, filtering, washing with water, drying, carrying out heat preservation treatment at 900 ℃ for 3h under the protection of nitrogen, and cooling to room temperature to obtain impurity-removed Si and SiO granular materials.

1400g of silicon powder and 600g of silicon monoxide after high-temperature treatment are weighed, 9000mL of dispersing agent (ethanol: 4500mL) is added into a ball material dispersion machine for rough mixing for 10min, then the material is transferred into a circulating liquid storage tank of a sand mill, the filling amount of zirconium beads in a grinding cavity is set to be 15kg, the particle size D50 of Si and SiO particles is measured to be 74.6nm after grinding is finished, 10g of carbon nano tube and 10g of dodecyl trimethyl ammonium bromide are added for continuous grinding for 1h, a proper amount of hydrofluoric acid is added before discharging to adjust the pH to be 5, liquid is transferred into the dispersion machine to add 50g of propyl trimethoxy silane, ammonia water is added after dispersion for 30min to adjust the pH to be 7, then 100g of PVP powder and 30g of LiH are added, external ultrasonic equipment is used, ultrasonic dispersion treatment is carried out at an ultrasonic frequency of 40kHz for 2h, and then the material is stood and dried.

The material was placed in a vacuum oven with a vacuum dimension maintained at 5 x 10^-3Pa, heating to 900 ℃ at the speed of 6 ℃/min, keeping the temperature for 1h, cooling to room temperature, carrying out jet milling on the blocky material to obtain particles with the particle size of D50 being 4.83um, weighing 900g of the material and 180g of asphalt, adding the materials and the 180g of asphalt into a VC covering machine, heating to 600 ℃ at the speed of 5 ℃/min, keeping the temperature for 2h, and then naturally cooling to the room temperature.

Heating the coated material to 1000 ℃ at a speed of 10 ℃/min under the protection of nitrogen, preserving heat for 6 hours, naturally cooling to room temperature, discharging, sieving with a 325-mesh sieve, and then carrying out demagnetization treatment by a demagnetizing machine to obtain the target product.

Comparative example 1

Weighing 1000g of commercially available silicon powder and 1000g of commercially available silicon monoxide powder, adding 9000mL of absolute ethyl alcohol, roughly mixing for 10min in a ball material dispersion machine, transferring the material to a circulating liquid storage tank of a sand mill, wherein the filling amount of zirconium beads in a grinding cavity is 14kg, measuring the particle diameter D50 of Si particles to be 63.9nm after grinding, adding 30g of carbon black and 10mL of fatty glyceride, continuously grinding for 2h, adding a proper amount of oxalic acid to adjust the pH to be 5 before discharging, transferring liquid to the dispersion machine for dispersion, adding 80g of aminopropyltriethoxysilane, adding ammonia water to adjust the pH to be 7 after dispersing for 30min, adding 80g of urea-formaldehyde resin and 50g of lithium carbonate, externally arranging ultrasonic equipment, performing ultrasonic dispersion treatment for 2h under the ultrasonic frequency of 40kHz, and standing and drying the slurry.

The material was placed in a vacuum oven with a vacuum dimension maintained at 5 x 10^-5Pa, heating to 1200 ℃ at the heating rate of 8 ℃/min, keeping the temperature for 0.5h, cooling to room temperature, and crushing the obtained blocky material airflow to obtain particles with the particle size of D50 being 5.53 um; weighing 900g of materials, adding the materials into a high-temperature high-pressure reaction kettle, heating to 800 ℃ at the heating rate of 5 ℃/min, filling 120g of acetone, keeping the temperature for 2h, and naturally cooling to room temperature.

Heating the coated material to 1000 ℃ at a speed of 10 ℃/min under the protection of nitrogen, preserving heat for 5h, naturally cooling to room temperature, discharging, sieving with a 325-mesh sieve, and carrying out demagnetization treatment by a demagnetizer to obtain the target product.

Comparative example 2

Preparing 20L of nitric acid solution with the pH value of 1, weighing 2000g of polycrystalline silicon solar cell waste and 2000g of silicon monoxide tailing powder respectively, crushing by using a mechanical crusher, sieving by using a 300-mesh sieve, adding the materials into the prepared nitric acid solution respectively, stirring in a dispersion machine for 30min, filtering, washing with water, drying, carrying out heat preservation treatment at 800 ℃ for 1h under the protection of nitrogen, and cooling to room temperature to obtain impurity-removed Si and SiO granular materials.

Weighing 1000g of silicon powder and 1000g of silicon monoxide powder after high-temperature treatment, adding 9000mL of deionized water, roughly mixing for 20min in a ball material dispersion machine, transferring the materials to a sand mill circulating liquid storage tank, setting the zirconium bead filling amount in a grinding cavity to be 14kg, measuring the particle diameter D50 of SiO particles to be 73.6nm after grinding, adding 30g of carbon black and 10g of fatty glyceride, continuously grinding for 2h, adding an appropriate amount of oxalic acid to adjust the pH to be 5 before discharging, transferring liquid to the dispersion machine, adding 80g of aminopropyltriethoxysilane, adding ammonia water to adjust the pH to be 7 after dispersing for 30min, adding 80g and 50g of urea-formaldehyde resin lithium carbonate, externally arranging ultrasonic equipment, performing ultrasonic dispersion treatment for 2h at an ultrasonic frequency of 40kHz, and performing flash evaporation and drying on the slurry.

Placing the material in an atmosphere furnace, introducing nitrogen for protection, heating to 1200 ℃ at the heating rate of 10 ℃/min, preserving heat for 0.5h, cooling to room temperature, and crushing the obtained blocky material airflow to obtain particles with the particle size of D50 being 8.47 um; weighing 900g of materials, adding the materials into a high-temperature high-pressure reaction kettle, heating to 800 ℃ at the heating rate of 5 ℃/min, filling 120g of acetone, keeping the temperature for 2h, and naturally cooling to room temperature.

Heating the coated material to 1000 ℃ at a speed of 8 ℃/min under the protection of nitrogen, preserving heat for 5h, naturally cooling to room temperature, discharging, sieving with a 325-mesh sieve, and then carrying out demagnetization treatment by a demagnetizing machine to obtain the target product.

The electrochemical performance of the materials obtained in the above examples and comparative examples was studied by button cell testing, wherein the positive electrode was an elemental lithium sheet, and the negative electrode was an active material in mass ratio: conductive carbon black: CMC: the slurry-coated electrode sheet was prepared at a ratio of 80:10:5:5 SBR.

The production of button cell a CR2016 button cell was assembled in a glove box filled with argon, and the test was carried out under the conditions of 0.1C discharge and 3C charge, respectively, to test the material rate performance, with a charge-discharge cutoff voltage of 2V/0.005V. The test results are shown in table 1.

TABLE 1 test results of button cell performance made of negative electrode materials of each example and comparative example

As can be seen from the attached table, compared with the preparation methods of comparative examples 1 and 2, in the specific examples, the composite material after composite granulation, polymerization connection, thermal sealing reaction and coating modification is obtained, the electron microscope picture of the attached drawing also can visually show that the Si and SiO nano primary particles are uniformly dispersed in the quasi-spherical core, and the secondary particles with good morphology are formed after surface coating modification, so that the material can show better first coulombic efficiency in the charge and discharge test process, and table 1 is the comparison of the electrochemical performance and rate performance of the material obtained in the specific examples and comparative examples of the present invention. The expansion rate of the material is measured after the material is subjected to lithium intercalation (discharging) and is disassembled in a glove box filled with argon, and the expansion rate of the pole piece is measured and calculated, wherein the expansion rate of the pole piece is (the thickness of the active material in a discharge state after circulation-the thickness of the original active material)/the thickness of the original active material is 100%. As seen from the data in Table 1, the comparative example 1 only uses the commercially available raw materials and does not undergo acid washing and corresponding subsequent treatment, so that the dispersing and granulating effects of the nano-sized particles are not ideal, and finally, the 50 th capacity retention rate is low, the first-week expansion rate is high, and the 50 th-week expansion rate is high; since deionized water is used in the grinding dispersion medium adopted in the comparative example 2 and the subsequent heat treatment does not reach the heat seal disproportionation reaction condition, the material is seriously oxidized and lithium salt does not participate in the reaction or the reaction degree is limited, so that the material has low first charge capacity, low first coulombic efficiency and low 50 th capacity retention rate.

Although the invention has been described herein with reference to illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure.