WO2022000589A1

WO2022000589A1 - Method for preparing silicon-based composite negative electrode material

Info

Publication number: WO2022000589A1
Application number: PCT/CN2020/102976
Authority: WO
Inventors: 张健; 赵前进; 徐斌
Original assignee: 瑞声声学科技(深圳)有限公司; 瑞声科技（南京）有限公司
Priority date: 2020-06-29
Filing date: 2020-07-20
Publication date: 2022-01-06
Also published as: CN111816852B; CN111816852A

Abstract

Provided is a method for preparing a silicon-based composite negative electrode material. The method comprises: treating a silicon-based raw material to obtain a nano silicon-based particle; performing a conductive treatment on the nano silicon-based particle to obtain a conductive nano silicon-based particle; and taking the conductive nano silicon-based particle as an inner core and using a macromolecular material as a shell to build a core-shell structure allowing the conductive nano silicon-based particle to change in volume inside the shell. The core-shell structure is the silicon-based composite negative electrode material. The silicon-based composite negative electrode material of the present invention can achieve volume change of the conductive nano silicon-based particle in the inner space of the shell by means of nano-treatment, conductive treatment and core-shell structure building in sequence, thereby improving the circulation performance thereof, so that the silicon-based composite material has good rate performance and circulation stability.

Description

Preparation method of silicon-based composite negative electrode material

technical field

The invention relates to the technical field of lithium ion batteries, in particular to a preparation method of a silicon-based composite negative electrode material.

Background technique

At present, the popularization of 5G technology is imminent. In the future, electronic products such as smartphones will consume more and more energy. In the past two years, the market of TWS Bluetooth headsets, smart watches and smart bracelets has exploded, and the demand for batteries in the wearable device market is also increasing. Considering the entire consumer electronics market, people's requirements for batteries are miniaturization and high energy density. However, the current negative electrode material in commercial battery systems is graphite, which has a long cycle life and low cost, but its theoretical capacity is too low (372 mA h g-1), which greatly limits the energy density of such batteries and cannot meet market demand.

As an anode material for next-generation lithium-ion batteries, silicon anode has the advantages of high capacity (4200 mAh g-1), high abundance, low operating voltage platform and low price, attracting the attention of many researchers, but the volume of silicon-based anode materials Large swelling (300%) and poor electrical conductivity lead to poor cycle performance and rate performance of batteries based on it.

technical problem

The purpose of the present invention is to provide a preparation method of a silicon-based composite negative electrode material, which can improve the silicon negative electrode by using the shell structure, buffer its volume expansion, improve its electrical conductivity, and improve the cycle performance and rate performance of the silicon-based negative electrode material.

technical solutions

The technical scheme of the present invention is as follows: a preparation method of a silicon-based composite negative electrode material, comprising:

Processing silicon-based raw materials to obtain nano-silicon-based particles;

conducting conductive treatment on the nano-silicon-based particles to obtain conductive nano-silicon-based particles;

Using the conductive nano-silicon-based particles as the core and the polymer material as the outer shell, build a shell structure that enables the conductive nano-silicon-based particles to change in volume in the shell, and the shell structure is The silicon-based composite negative electrode material.

Preferably, the nano-silicon-based particles include one or more of nano-silicon particles, nano-silicon oxide particles, and nano-silicon-silicon oxide composite particles, and the particle size of the nano-silicon-based particles is less than or equal to 150 nm.

Preferably, the shell structure includes one or more of hollow nanosphere structure, nanotube structure, porous nanofiber structure, coaxial nanowire structure, and porous nanotube structure.

Preferably, the conductive nano-silicon-based particles are used as the inner core and the polymer material is used as the outer shell to build a shell structure that enables the conductive nano-silicon-based particles to change in volume in the outer shell. The method is one of electrospinning method, vapor deposition method, spray drying method, electrospray method, microfluidic method and solution method.

Preferably, the conductive nano-silicon-based particles are used as the inner core and the polymer material is used as the outer shell to build a shell structure that enables the conductive nano-silicon-based particles to change in volume in the outer shell. The method is electrospinning, including:

Dispersing the conductive nano-silicon-based particles with a mass fraction of 3-10% into the first solution, adding a pore-forming agent with a mass fraction of 6-16%, to form a uniform suspension inner core liquid;

Dissolving the polymer material with a mass fraction of 8-20% in the second organic solvent to form a shell solution;

placing the inner core suspension and the outer shell solution in an electrospinning device and spinning to obtain a spinning mixture;

The spinning mixture is cured at a high temperature to obtain a cured mixture, wherein the curing temperature is 250-500° C. and the curing time is 1-4 h;

The cured mixture is sintered at high temperature to obtain the shell structure, that is, the silicon-based composite negative electrode material, wherein the sintering temperature is 600-1500° C. and the sintering time is 1-10 h.

Preferably, the first solution includes several kinds of water, glycerol, N,N dimethylformamide, acetone, acetonitrile and ethanol; the pore-forming agent includes sodium carbonate, potassium carbonate, calcium carbonate, ammonium bicarbonate and several kinds of polymethyl methacrylate; the polymer material includes several kinds of polyacrylonitrile, polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl butyral and polyvinylidene fluoride; the second organic Solvents include several of glycerol, N,N dimethylformamide, acetone, and acetonitrile.

Preferably, the electrospinning includes one of needle spinning, drum spinning and solution spinning.

Preferably, the conductive nano-silicon-based particles are subjected to conductive treatment to obtain conductive nano-silicon-based particles, and the method used is one of a doping method, a coating method and an alloying method.

Preferably, conducting conductive treatment on the nano-silicon-based particles to obtain conductive nano-silicon-based particles, the method used is a doping method, and the doped elements include B, Al, Na, Mg, Ca, Ba, Ti , one or more of Mn, Fe, Co, Ni, Cu, Zn, Zr, Li, Mo, Ge, Sn.

Preferably, it is characterized in that the nano-silicon-based particles are subjected to conductive treatment to obtain conductive nano-silicon-based particles, and the method used is an alloying method, and the alloy includes Fe-Si alloy, Au-Si alloy, Sn- One or more of Si alloy, V-Si alloy, C-Si alloy and B-Si alloy.

Preferably, the nano-silicon-based particles are subjected to conductive treatment to obtain conductive nano-silicon-based particles, and the method used is a coating method, and the coating includes carbon coating, oxide coating, and polymer coating. One or more, the number of coating layers is one or more layers.

Preferably, the carbon-coated carbon source includes graphite, pitch, graphene, sucrose, glucose, polyacrylic acid, polyacrylonitrile, polyvinyl alcohol, polymethyl cellulose methyl ester, polymethyl methacrylate, polymethyl methacrylate One or more of vinylidene tetrafluoroethylene and various biomass carbons; the oxide-coated oxide is a metal oxide, including one or more of Al2O3, Fe2O3, Co3O4 and WO3; the The polymer-coated polymer is a structural conductive polymer, including one or more of polyacetylene, linear polyphenylene, polyketonephthalein, and surface-type high polymer.

Preferably, the silicon-based raw material is processed to obtain nano-silicon-based particles, and the method used is one of grinding method, ball milling method, gas phase synthesis method, solid phase synthesis method and sand milling method.

beneficial effect

The beneficial effect of the present invention is that: the silicon-based composite negative electrode material of the present invention is sequentially constructed by nano-processing, conductive processing and shell structure, so that the volume change of the conductive nano-silicon-based particles in the inner space of the shell can be realized, thereby improving the Its cycle performance makes the silicon-based composite material have good rate performance and cycle stability.

Description of drawings

Fig. 1 is the schematic flow chart of the preparation method of the silicon-based composite negative electrode material of the present invention;

Fig. 2 is the scanning electron microscope picture before and after nano-processing of silicon material;

Fig. 3 is the optical picture before and after the conductive treatment of nano-silicon powder;

Figure 4 is the half-cell charge-discharge curve of the material obtained by coaxial needle spinning;

Figure 5 is the half-cell cycle performance curve of the material obtained by coaxial needle spinning;

Figure 6 is the half-cell charge-discharge curve of the material obtained by coaxial non-needle spinning;

Figure 7 is the half-cell cycle performance curve of the material obtained by coaxial non-needle spinning;

Figure 8 is the half-cell charge-discharge curve of the material obtained by uniaxial needle spinning;

Figure 9 is the cycle performance curve of the half-cell obtained by uniaxial needle spinning;

Figure 10 shows the full battery charge-discharge curve of the special structure silicon anode material;

Figure 11 is the cycle performance curve of the full battery of the special structure silicon anode material;

FIG. 12 is a schematic structural diagram of a silicon-based composite negative electrode material.

Embodiments of the present invention

The present invention will be further described below with reference to the accompanying drawings and embodiments.

Referring to Fig. 1, a preparation method of a silicon-based composite negative electrode material of the present invention includes:

S100, nano-processing: processing silicon-based raw materials to obtain nano-silicon-based particles;

Specifically, the main purpose of nano-processing is to solve the problem of pulverization of silicon particles during charging and discharging, and the methods used are grinding, ball milling, gas phase synthesis, solid phase synthesis and sand milling. The present invention preferably adopts a grinding method and a gas phase synthesis method, wherein the grinding method is simple and practical, and has a wide range of applications, and can use low-cost raw materials such as micron silicon powder and semiconductor industry waste. The requirements are strict, but the product has high uniformity, small particle size and good performance.

The present invention is specifically described as follows by taking the grinding method as an example:

This example provides a simple nano-processing method, including:

S110. Add zirconia ball grinding beads (particle size range 0.5~3 μm) into a 500mL grinding jar, so that the total volume of the ball grinding beads is one-third of the grinding jar, and add an appropriate amount of water so that the water level does not cover the ball grinding beads;

S120. Disperse 5g of micron silicon powder into the above-mentioned grinding jar, and grind it. The grinder used is a horizontal grinder, the rotational speed is 200rpm, and the grinding time is 5h;

S130. Centrifuge the dispersion liquid obtained in S2, take the precipitate, and dry to obtain nano-treated silicon powder, that is, nano-silicon powder.

The left picture of Figure 2 shows the silicon powder before nano-treatment, with a particle size of more than 5 μm, mixed with random particles of about 200 nm; as shown in the right picture of Figure 2, the material can be optimized to a particle size of Uniform particles below 150 nm.

The nano-silicon-based particles after nano-processing are 150 nm and below, thereby improving the pulverization problem of silicon particles during the charging and discharging process. The nano-silicon-based particles are nano-silicon particles, nano-silicon monoxide particles, and nano-silicon-silica composite one or more of the particles.

S200, conductive treatment: conducting conductive treatment on the nano-silicon-based particles to obtain conductive nano-silicon-based particles;

The main purpose of conductive treatment is to improve the rate performance of silicon-based materials. Silicon is a typical semiconductor material with low intrinsic conductivity. When used as a negative electrode material for lithium-ion batteries, the rate performance is poor, and certain improvements are required to meet battery performance. magnification requirement. Modification methods include, but are not limited to, doping, cladding, and alloying.

If the doping method is used, the doping element includes one of B, Al, Na, Mg, Ca, Ba, Ti, Mn, Fe, Co, Ni, Cu, Zn, Zr, Li, Mo, Ge, Sn or more.

If an alloying method is used, the alloy includes one or more of Fe-Si alloy, Au-Si alloy, Sn-Si alloy, V-Si alloy, C-Si alloy and B-Si alloy.

If a coating method is used, it can be one or more of carbon coating, oxide coating, and polymer coating, and the number of coating layers can be one or more layers; specifically, the carbon coating layer The carbon sources include graphite, pitch, graphene, sucrose, glucose, polyacrylic acid, polyacrylonitrile, polyvinyl alcohol, polymethyl cellulose methyl ester, polymethyl methacrylate, polyvinylidene fluoride and various raw materials. One or more of substance carbon; the oxide coating layer includes but is not limited to Al2O3, Fe2O3, Co3O4 and WO3 and other metal oxides with good rigidity and high strength; the polymer coating source includes but not limited to Polyacetylene, linear polyphenylene, polyketone phthalocyanine, surface polymer and other structural conductive polymers.

Specifically, in this embodiment, a coating method is used to conduct conductive treatment, and the coating method includes but is not limited to solution method, vapor deposition, spray drying, microfluidics, and electrospray. Taking the solution coating method and the gas phase coating method as an example, the description is as follows:

The solution coating method includes:

S211, the nano-silicon-based particles are uniformly dispersed in a mixed solution of sulfuric acid and hydrogen peroxide, wherein the volume ratio of sulfuric acid and hydrogen peroxide ranges between 3:1 and 1:2 to form a dispersion;

S212, ultrasonically stirring the dispersion at 30-70 °C, and filtering to obtain nano-silica powder with hydroxyl groups on the surface;

S213, uniformly dispersing the nano-silicon powder into water, adding ammonia water to adjust the pH to 9-10.5, adding dopamine, the mass fraction of the dopamine is 10%-40% of the nano-silicon powder, and maintaining a weak alkaline Under the condition of vigorous stirring, the stirring time is 15~30h, and the precursor is obtained after filtration;

S214 , putting the precursor into an atmosphere furnace for high-temperature sintering, the sintering temperature is 600-1200° C., and the sintering time is 2-6 h to obtain the conductive nano-silicon-based particles.

The use of vapor cladding methods includes:

S221, placing the nano-silicon-based particles in a tube furnace, feeding nitrogen gas, and ventilating time for 1h, so that the inert gas completely replaces the air in the furnace;

S222, heating the tube furnace to a temperature of 700°C for heat preservation, switching the ventilation gas source, and feeding 10% acetylene gas into the furnace, and the ventilation time is 30 minutes;

S223, switch the gas source to nitrogen, stop the heating function of the tube furnace, and obtain the conductive nano-silicon-based particles after the tube furnace is cooled to room temperature.

As shown in FIG. 3 , after the conductive treatment, the surface of the silicon particles changed from brown to black.

S300, building a shell structure: using the conductive nano-silicon-based particles as a core and a polymer material as a shell to build a shell structure that enables the conductive nano-silicon-based particles to change in volume in the shell, The shell structure is the silicon-based composite negative electrode material.

The biggest problem of silicon-based anode materials is that the volume expansion is too large during the charging and discharging process, resulting in poor cycle performance of lithium-ion batteries. Therefore, material structure design is extremely important in the development of silicon-based materials. The present invention designs hollow structures, nanowires, porous nanomaterials The silicon anode material is modified by tube and concentric circle structure, etc., in order to achieve the effect of improving the cycle stability. Among them, various special structures are not used singly, but interspersed with various structures, and a material includes at least one special structure. The realization methods of the shell structure include, but are not limited to, electrospinning, vapor deposition, spray drying, electrospray, microfluidics, and solution methods.

The present invention adopts electrospinning or microfluidic control method, wherein electrospinning includes but is not limited to needle spinning, drum spinning, solution spinning, etc. The needle spinning has high precision, uniform and stable products, but relatively low productivity. Low, drum spinning product uniformity is poor, but can greatly improve the production capacity.

Specifically, the electrospinning includes several kinds of needle spinning, drum spinning and solution spinning.

In an embodiment of the present invention, a method for preparing a silicon anode material by a coaxial needle electrospinning method is provided, which includes the following steps:

S311. Add nano-silica powder into N,N dimethylformamide, the mass fraction of silicon is 5%, stir and ultrasonically disperse uniformly, and the ultrasonic time is more than 1h;

S312. Dissolve the pore-forming agent polymethyl methacrylate in the above-mentioned dispersion liquid, and its mass fraction is 10%, and stir until it is completely dissolved at 60 ° C to form a core solution;

S313. Dissolving polyacrylonitrile in N,N dimethylformamide, its mass fraction is 15%, to form a shell solution;

S314. Add the inner core solution and the outer shell solution into the peristaltic pump of the electrospinning device, and perform coaxial electrospinning. Adjust the advancing speed of the inner core solution to 0.5 mL/h, the advancing speed of the outer shell solution to 1 mL/h, and the electrostatic voltage to be set to 15kV, the acceptance distance is 10cm, and the corresponding nanofiber precursor is obtained;

S315. Put the obtained nanofiber precursor into an air furnace for curing treatment, the curing temperature is 280°C, and the time is 1 h to obtain a cured body;

S316. Put the solidified body into a vacuum furnace for sintering treatment, the sintering temperature is 1000° C. and the sintering time is 5 hours, and the corresponding silicon-based negative electrode material can be obtained.

A non-aqueous electrolyte lithium ion half-cell can be prepared from the above-mentioned silicon-based negative electrode material.

Specifically, a non-aqueous electrolyte lithium ion half-cell prepared by using the above-mentioned silicon-based negative electrode material as the positive electrode active material, the lithium sheet as the negative electrode, the polyethylene separator, and the lithium hexafluorophosphate as the electrolyte salt; it should be noted that the material is characterized in the half-cell Therefore, the silicon-based anode material is the cathode active material in the half-cell. The above-mentioned non-aqueous electrolyte lithium-ion half-cell was charged and discharged in the voltage range of 0.01~1V, the first discharge capacity could reach 1200mAh/g, and the first Coulomb efficiency was 60%, as shown in Figure 4; the reversible capacity at 0.1 C rate Reaching 800mAh/g, the stable cycle is 2800 cycles, while other untreated Si/C materials have poor cycle performance. As shown in Figure 5, the cycle number of the non-aqueous electrolyte lithium-ion half-cell based on the black thick line is the same as The schematic curve of specific capacity, the other curves are the schematic curves of cycle number and specific capacity of untreated Si powder material, Si/Graph blended material and commercial SiO/C material, it is obvious that the non-water The electrolyte lithium-ion half-cell has strong cyclability and good stability.

The above-mentioned silicon-based negative electrode material can also be used as the negative electrode active material, 4.35V high-voltage lithium cobalt oxide, polyethylene separator, and lithium hexafluorophosphate as the non-aqueous electrolyte lithium ion half-cell prepared by the electrolyte salt; The charge-discharge test was carried out in the voltage range of 2.75~4.35V. The first charge capacity of the anode material in the full battery can reach 1200 mAh/g (calculated based on silicon), as shown in Figure 10, the reversible capacity at 0.1 C rate It reaches 1000mAh/g and is stable for 50 cycles, as shown in Figure 11.

In another embodiment of the present invention, a method for preparing a silicon anode material by a coaxial needle electrospinning method is provided, which includes the following steps:

S321. Add nano-silica powder into N,N dimethylformamide, the mass fraction of silicon is 5%, stir and ultrasonically disperse uniformly, and the ultrasonic time is more than 1h;

S322. Dissolve the pore-forming agent polymethyl methacrylate in the above-mentioned dispersion liquid, and its mass fraction is 10%, and stir until it is completely dissolved at 60 ° C to form a core solution;

S323. Dissolve polyvinylpyrrolidone in ethanol, and its mass fraction is 10% to form a shell solution;

S324. Add the inner core solution and the outer shell solution to the peristaltic pump of the electrospinning device, and perform coaxial electrospinning. Adjust the advancing speed of the inner core solution to 0.5 mL/h, the advancing speed of the outer shell solution to 1.5 mL/h, and set the electrostatic voltage. is 15kV, the acceptance distance is 10cm, and the corresponding nanofiber precursor is obtained;

S325. Put the obtained nanofiber precursor into an air furnace for curing treatment, the curing temperature is 300 °C, and the time is 2 h to obtain a cured body;

S326. Put the solidified body into an argon furnace for sintering treatment, the sintering temperature is 800° C., and the sintering time is 4 hours, and the corresponding coaxial nanowire silicon-based negative electrode material can be obtained.

The non-aqueous electrolyte lithium ion half-cell can be prepared by the above-mentioned silicon-based negative electrode material. Specifically, the above-mentioned silicon-based negative electrode material is used as a positive electrode active material, a lithium sheet is used as a negative electrode, a polyethylene separator is used, and lithium hexafluorophosphate is used as a non-aqueous electrolyte lithium phosphate prepared as an electrolyte salt. Ion half-cell; the above-mentioned non-aqueous electrolyte lithium-ion half-cell was charged and discharged in the voltage range of 0.01~2V, the first discharge capacity could reach 1300mAh/g, and the first Coulomb efficiency was 77%, as shown in Figure 6; at 0.1 C The reversible capacity reached 1050 mAh/g at the rate, and the stable cycle was 100 cycles, as shown in Figure 7.

In another embodiment of the present invention, a method for preparing a silicon anode material by a coaxial drum electrospinning method is provided, which includes the following steps:

S331. Add nano-silica powder into N,N dimethylformamide, the mass fraction of silicon is 5%, stir and ultrasonically disperse uniformly, and the ultrasonic time is more than 1h;

S332. Dissolve the pore-forming agent polymethyl methacrylate in the above-mentioned dispersion liquid, and its mass fraction is 10%, and stir until it is completely dissolved at 60 ° C to form a core solution;

S333. Dissolve polyvinylpyrrolidone in ethanol, and its mass fraction is 10% to form a shell solution;

S334. Add the inner core solution and the outer shell solution into the roller groove of the drum electrospinning, so that the steel wire on the drum first passes through the inner core solution and then the outer shell solution, so that the drum spinning is carried out in a cycle, the electrostatic voltage is set to 20kV, and the receiving distance is 15cm , to obtain nanofiber precursors;

S335. Put the obtained nanofiber precursor into an air furnace for curing treatment, the curing temperature is 300°C, and the time is 2 h to obtain a cured body;

S336. Put the solidified body into a nitrogen furnace for sintering treatment, the sintering temperature is 900°C, and the sintering time is 4 hours, and then the silicon-based negative electrode material with the corresponding coaxial nanofiber structure can be obtained.

The non-aqueous electrolyte lithium ion half-cell can be prepared by the above-mentioned silicon-based negative electrode material. Specifically, the silicon-based material obtained by the above-mentioned coaxial needle spinning is used as the negative electrode active material, 4.45V high-voltage lithium cobalt oxide, polyethylene diaphragm, and lithium hexafluorophosphate are The non-aqueous electrolyte lithium-ion half-cell prepared from the electrolyte salt; the above-mentioned non-aqueous electrolyte lithium-ion half-cell is charged and discharged in the voltage range of 2.75~4.45V, and the negative electrode material can reach 1000 mAh in the first charging capacity /g at 0.1 The reversible capacity reaches 950mAh/g at C rate, and the stable cycle is 80 cycles.

S341. Add nano-silica powder into N,N dimethylformamide, the mass fraction of silicon is 5%, stir and ultrasonically disperse uniformly, and the ultrasonic time is more than 1h;

S342. Dissolve the pore-forming agent polymethyl methacrylate in the above-mentioned dispersion liquid, and its mass fraction is 10%, and stir until it is completely dissolved at 60 ° C to form a core solution;

S343. Dissolving polyvinylidene fluoride in N-methylpyrrolidone, its mass fraction is 10%, to form a shell solution;

S344. Add the inner core solution and the outer shell solution into the roller groove of the drum electrospinning, so that the steel wire on the drum first passes through the inner core solution and then the outer shell solution, so that the drum spinning is carried out in a cycle, the electrostatic voltage is set to 20kV, and the receiving distance is 15cm , to obtain nanofiber precursors;

S345. Put the obtained nanofiber precursor into an air furnace for curing treatment, the curing temperature is 300°C, and the time is 2 h to obtain a cured body;

S346. Put the solidified body into a nitrogen furnace for sintering treatment, the sintering temperature is 900° C., and the sintering time is 4 hours, and the corresponding coaxial nanowire silicon-based negative electrode material can be obtained.

In another embodiment of the present invention, a method for preparing a silicon anode material by a uniaxial needle electrospinning method is provided, which comprises the following steps:

S351. Add nano-silica powder into N,N dimethylformamide, the mass fraction of silicon is 5%, stir and ultrasonically disperse uniformly, and the ultrasonic time is more than 1h;

S352. Dissolve polymethyl methacrylate in the above dispersion liquid, and its mass fraction is 10%, and the solution is heated to 60 ° C and stirred until completely dissolved;

S353. Dissolve polyacrylonitrile in the dispersion obtained from S2, with a mass fraction of 10%, heat to 60°C, stir until completely dissolved, and form a spinning solution;

S354. add the spinning solution obtained in S3 to the peristaltic pump of the needle spinning equipment, carry out needle classic spinning, the voltage is set to 15kV, the receiving distance is 15cm, the advancing speed is 2mL/h, and the nanofiber precursor is obtained ;

S355. Put the obtained nanofiber precursor into an air furnace for curing treatment, the curing temperature is 300°C, and the time is 2 h to obtain a cured body;

S356. Put the solidified body into a nitrogen furnace for sintering treatment, the sintering temperature is 900°C, and the sintering time is 4 hours, and the corresponding porous nanofiber silicon-based negative electrode material can be obtained.

The non-aqueous electrolyte lithium ion half-cell can be prepared by the above-mentioned silicon-based negative electrode material. Specifically, the silicon-based material obtained by the above-mentioned uniaxial needle spinning is used as the positive electrode active material, the lithium sheet is the negative electrode, the polyethylene separator is used, and the lithium hexafluorophosphate is used as the electrolyte salt. The prepared non-aqueous electrolyte lithium-ion half-cell; the above-mentioned non-aqueous electrolyte lithium-ion half-cell is charged and discharged in the voltage range of 0.01~2V, the first discharge capacity can reach 1200 mAh/g, and the first Coulomb efficiency is 73%, such as As shown in Figure 8; the reversible capacity reaches 970mAh/g at a rate of 0.1 C, and the stable cycle is 80 cycles, as shown in Figure 9.

It can be seen from the detection effect of the above embodiment that, compared with the existing production technology, the above electrospinning method can solve the problem of poor cycle stability of the silicon-based negative electrode material, and the solution spinning and drum spinning greatly improve the spinning efficiency. , solves the problem of low production capacity of traditional spinning, and this solution is beneficial to subsequent industrial production.

On the other hand, please further refer to FIG. 12 , the present invention also discloses a silicon-based composite negative electrode material, prepared by the above-mentioned method, comprising an inner core of conductive nano-silicon-based particles and an outer shell of a polymer material, the inner core and all The shell is built to form a shell structure, and a, b, and c in FIG. 12 are respectively exemplary structural forms of different shell structures. The silicon-based composite negative electrode material prepared by the present invention includes, but is not limited to, one or more of a core-shell structure, a concentric circle structure, a hollow structure, a nanowire structure and a nanotube structure. In the formed negative electrode material, the content of conductive nano-silicon-based particles is 5~50%, and the capacity of the negative electrode material for lithium ion batteries is 500~1500mAh/g, and the cycle performance meets the needs of commercial batteries.

The above are only the embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, improvements can be made without departing from the inventive concept of the present invention, but these belong to the protection of the present invention. Scope.

Claims

A method for preparing a silicon-based composite negative electrode material, comprising:

Processing silicon-based raw materials to obtain nano-silicon-based particles;

conducting conductive treatment on the nano-silicon-based particles to obtain conductive nano-silicon-based particles;

Using the conductive nano-silicon-based particles as the core and the polymer material as the outer shell, build a shell structure that enables the conductive nano-silicon-based particles to change in volume in the shell, and the shell structure is The silicon-based composite negative electrode material.
The method for preparing a silicon-based composite negative electrode material according to claim 1, wherein the nano-silicon-based particles comprise one or more of nano-silicon particles, nano-silicon monoxide particles, and nano-silicon-silicon oxide composite particles species, and the particle size of the nano-silicon-based particles is less than or equal to 150 nm.
The method for preparing a silicon-based composite negative electrode material according to claim 1, wherein the shell structure comprises a nano hollow sphere structure, a nanotube structure, a porous nanofiber structure, a coaxial nanowire structure, and a porous nanotube structure one or more of.
The method for preparing a silicon-based composite negative electrode material according to claim 1, wherein the conductive nano-silicon-based particles are used as a core and a polymer material is used as a shell to build the conductive nano-silicon-based The particles can have a volume-changing shell structure in the shell, and the method used is one of electrospinning, vapor deposition, spray drying, electrospray, microfluidic and solution methods.
The method for preparing a silicon-based composite negative electrode material according to claim 4, wherein the electrospinning comprises one of needle spinning, drum spinning and solution spinning.
The method for preparing a silicon-based composite negative electrode material according to claim 1, wherein the nano-silicon-based particles are subjected to conductive treatment to obtain conductive nano-silicon-based particles, and the method used is a doping method. The miscellaneous elements include one or more of B, Al, Na, Mg, Ca, Ba, Ti, Mn, Fe, Co, Ni, Cu, Zn, Zr, Li, Mo, Ge, and Sn.
The method for preparing a silicon-based composite negative electrode material according to claim 1, wherein the nano-silicon-based particles are subjected to conductive treatment to obtain conductive nano-silicon-based particles, and the method used is alloying The alloy includes one or more of Fe-Si alloy, Au-Si alloy, Sn-Si alloy, V-Si alloy, C-Si alloy and B-Si alloy.
The method for preparing a silicon-based composite negative electrode material according to claim 1, wherein the nano-silicon-based particles are subjected to conductive treatment to obtain conductive nano-silicon-based particles, and the method used is a coating method, The coating includes one or more of carbon coating, oxide coating, and polymer coating, and the number of coating layers is one or more layers.
The method for preparing a silicon-based composite negative electrode material according to claim 8, wherein the carbon-coated carbon source comprises graphite, pitch, graphene, sucrose, glucose, polyacrylic acid, polyacrylonitrile, polyvinyl alcohol , one or more of polymethyl cellulose methyl ester, polymethyl methacrylate, polyvinylidene fluoride and various types of biomass carbon; the oxide-coated oxide is a metal oxide, including One or more of Al2O3, Fe2O3, Co3O4, and WO3; the polymer-coated polymer is a structural conductive polymer, including polyacetylene, linear polyphenylene, polyketone phthalocyanine, and surface-type polymers. one or more of.
The method for preparing a silicon-based composite negative electrode material according to claim 1, wherein the silicon-based raw materials are processed to obtain nano-silicon-based particles, and the methods used are grinding, ball milling, gas phase synthesis, solid One of the synthetic method and the sand grinding method.