阅读说明：本技术 一种硅碳复合材料及其制备方法 (Silicon-carbon composite material and preparation method thereof ) 是由 吴武 仰永军 仰韻霖 于 2021-09-07 设计创作，主要内容包括：本发明涉及锂电池负极材料领域,特别是涉及一种硅碳复合材料的制备方法,包括如下步骤：将纳米硅颗粒分散到有机溶剂中得到分散液,向分散液中加入偶联剂并调节pH值为4～5,依次进行洗涤、干燥,得改性纳米硅颗粒；分别配置的水相溶液包括比例为2：1的乳化剂和pH稳定剂,油相溶液包括比例为3：1的聚合物单体、交联剂,将步骤S1得到的改性纳米硅颗粒分散到油相溶液中后一并加入到水相溶液中,加入引发剂,依次进行离心、洗涤、干燥,得到复合材料；将步骤S2得到的复合材料进行碳化,得到硅碳复合材料。本发明提供一种聚合物包覆均匀、结构稳定、电化学性能优良的硅碳复合材料；还提供一种工艺简单、对环境友好的硅碳复合材料的制备方法。(The invention relates to the field of lithium battery cathode materials, in particular to a preparation method of a silicon-carbon composite material, which comprises the following steps: dispersing the nano silicon particles into an organic solvent to obtain a dispersion liquid, adding a coupling agent into the dispersion liquid, adjusting the pH value to 4-5, and washing and drying the dispersion liquid in sequence to obtain modified nano silicon particles; the aqueous phase solution prepared respectively comprises the following components in a ratio of 2: 1, the oil phase solution comprises an emulsifier and a pH stabilizer in a ratio of 3: 1, dispersing the modified nano silicon particles obtained in the step S1 into an oil phase solution, adding the dispersed modified nano silicon particles into a water phase solution, adding an initiator, and sequentially centrifuging, washing and drying to obtain a composite material; and carbonizing the composite material obtained in the step S2 to obtain the silicon-carbon composite material. The invention provides a silicon-carbon composite material with uniform polymer coating, stable structure and excellent electrochemical performance; also provides a preparation method of the silicon-carbon composite material, which has simple process and is environment-friendly.)

1. The preparation method of the silicon-carbon composite material is characterized by comprising the following steps:

s1, dispersing the nano silicon particles into an organic solvent to obtain a dispersion liquid, then adding a coupling agent into the dispersion liquid, adjusting the pH value to 4-5, and washing and drying the mixture in sequence to obtain modified nano silicon particles;

s2, respectively preparing an aqueous phase solution and an oil phase solution, wherein the aqueous phase solution comprises the following components in a ratio of 2: 1 and a pH stabilizer, the oil phase solution comprising a mixture of an emulsifier and a pH stabilizer in a ratio of 3: 1, dispersing the modified nano-silicon particles obtained in the step S1 into the oil phase solution, adding the dispersed modified nano-silicon particles into the water phase solution, adding an initiator, and sequentially centrifuging, washing and drying to obtain a composite material of the polymer coated on the nano-silicon particles;

and S3, carbonizing the composite material obtained in the step S2 to obtain the silicon-carbon composite material.

2. The method according to claim 1, wherein in step S1, the organic solvent is 2.3-8% by mass of the nano-silicon particles.

3. The method for preparing a silicon-carbon composite material according to claim 1, wherein in the step S1, the washing step is: the ratio of alcohol to water is 1: 2 and pure water are washed in this order.

4. The method of claim 1, wherein in the step S2, the emulsifier is one or more selected from glycerol monostearate, sucrose fatty acid triester and sorbitan monostearate.

5. The method of claim 1, wherein in step S2, the pH stabilizer is one of dimethylethanolamine, monoethanolamine, diethanolamine, and triethanolamine.

6. The method according to claim 1, wherein in step S2, the initiator is one of potassium persulfate and ammonium persulfate.

7. The method for preparing the silicon-carbon composite material according to claim 1, wherein the amount of the initiator is 1-2% by mass of the modified nano silicon particles.

8. The method of preparing a silicon-carbon composite material according to claim 1, wherein the carbonizing comprises the steps of: under the inert gas atmosphere environment, the temperature is increased from room temperature to 300-500 ℃ at the speed of 0.5-6 ℃/min, the temperature is kept for 2-5 h, then the temperature is continuously increased to 500-850 ℃, and the temperature is kept for 1-5 h.

9. A silicon-carbon composite material, characterized in that it is produced using the production method according to any one of claims 1 to.

10. The silicon-carbon composite material according to claim 9, wherein the particle size of the silicon-carbon composite material is 75 to 130 nm.

Technical Field

The invention relates to the field of lithium battery cathode materials, in particular to a silicon-carbon composite material and a preparation method thereof.

Background

In recent years, lithium ion batteries are rapidly developed, and the application of power batteries gradually shows an increasingly hot situation. The cathode material is a key factor for improving the rate capability of the lithium ion battery and is an important direction for light weight of the current power supply system.

The carbonaceous negative electrode material has small volume change in the charge and discharge process and good circulation stability, the huge volume expansion of silicon can be buffered by utilizing the mechanical elasticity of the carbonaceous material, and the rate capability of the composite material can be improved by utilizing the high electron conductivity, so the carbonaceous negative electrode material becomes a preferred matrix compounded with the silicon. In the silicon-carbon composite material, silicon serves as an active material to provide high capacity, and the carbon material can improve the volume change of the silicon material during charge and discharge. In the structure of silicon-carbon composite materials, silicon/carbon composite materials with core-shell structures have received much attention, because the core-shell structures can not only improve the contact range of carbon and silicon, increase the conduction channel of electrons, but also isolate electrolyte from silicon. However, the carbon coating method on the surface of silicon particles reported in the literature at present is easy to cause uneven carbon source coating and easy to agglomerate the particles.

Disclosure of Invention

In order to solve the technical problems, the invention provides the silicon-carbon composite material with uniform polymer coating, stable structure and excellent electrochemical performance.

The invention also provides a preparation method of the silicon-carbon composite material, which is simple in process and environment-friendly.

The invention adopts the following technical scheme:

a preparation method of a silicon-carbon composite material comprises the following steps:

s1, dispersing the nano silicon particles into an organic solvent to obtain a dispersion liquid, then adding a coupling agent into the dispersion liquid, adjusting the pH value to 4-5, and washing and drying the mixture in sequence to obtain modified nano silicon particles;

s2, respectively preparing an aqueous phase solution and an oil phase solution, wherein the aqueous phase solution comprises the following components in a ratio of 2: 1 and a pH stabilizer, the oil phase solution comprising a mixture of an emulsifier and a pH stabilizer in a ratio of 3: 1, dispersing the modified nano-silicon particles obtained in the step S1 into the oil phase solution, adding the dispersed modified nano-silicon particles into the water phase solution, adding an initiator, and sequentially centrifuging, washing and drying to obtain a composite material of the polymer coated on the nano-silicon particles;

and S3, carbonizing the composite material obtained in the step S2 to obtain the silicon-carbon composite material.

The technical scheme is further improved in that in the step S1, the mass of the organic solvent is 2.3-8% of the mass of the nano silicon particles.

In a further improvement of the above technical solution, in the step S1, the washing step includes: the ratio of alcohol to water is 1: 2 and pure water are washed in this order.

In a further improvement of the above technical solution, in the step S2, the emulsifier is any one or a mixture of more of glycerin monostearate, sucrose fatty acid triester and sorbitan monostearate.

In a further improvement of the above technical solution, in the step S2, the pH stabilizer is one of dimethylethanolamine, monoethanolamine, diethanolamine, and triethanolamine.

In a further improvement of the above technical solution, in the step S2, the initiator is one of potassium persulfate and ammonium persulfate.

The technical scheme is further improved in that the using amount of the initiator is 1-2% of the mass of the modified nano silicon particles.

The further improvement of the technical scheme is that the carbonization comprises the following steps: under the inert gas atmosphere environment, the temperature is increased from room temperature to 300-500 ℃ at the speed of 0.5-6 ℃/min, the temperature is kept for 2-5 h, then the temperature is continuously increased to 500-850 ℃, and the temperature is kept for 1-5 h.

A silicon-carbon composite material is prepared by the preparation method.

The technical scheme is further improved in that the particle size of the silicon-carbon composite material is 75-130 nm.

The invention has the beneficial effects that:

the preparation method provided by the invention fully utilizes the interaction between the surface and the chemical functional groups of the carbon source, and the difference of decomposition temperatures between different carbon sources, and has simple process and environmental friendliness; the nano silicon particles are coated with the high molecular polymer by adopting emulsion polymerization and solution polymerization methods, the interaction between the modified nano silicon particles and the polymer is tighter, the polymer coating is more uniform, and after high-temperature carbonization treatment, the carbon coating layer of the composite material has a stable structure and is not easy to break; the silicon-carbon composite electrode material can improve the cycle stability and the power performance of the lithium ion battery.

Detailed Description

The present invention will be further described with reference to the following examples for better understanding of the present invention, but the embodiments of the present invention are not limited thereto.

A preparation method of a silicon-carbon composite material comprises the following steps:

s1, dispersing the nano silicon particles into an organic solvent to obtain a dispersion liquid, then adding a coupling agent into the dispersion liquid, adjusting the pH value to 4-5, and washing and drying the mixture in sequence to obtain modified nano silicon particles;

s2, respectively preparing an aqueous phase solution and an oil phase solution, wherein the aqueous phase solution comprises the following components in a ratio of 2: 1 and a pH stabilizer, the oil phase solution comprising a mixture of an emulsifier and a pH stabilizer in a ratio of 3: 1, dispersing the modified nano-silicon particles obtained in the step S1 into the oil phase solution, adding the dispersed modified nano-silicon particles into the water phase solution, adding an initiator, and sequentially centrifuging, washing and drying to obtain a composite material of the polymer coated on the nano-silicon particles;

and S3, carbonizing the composite material obtained in the step S2 to obtain the silicon-carbon composite material.

Further, in the step S1, the mass of the organic solvent is 2.3 to 8% of the mass of the nano silicon particles.

Further, in the step S1, the washing step is: the ratio of alcohol to water is 1: 2 and pure water are washed in this order.

Further, in the step S2, the emulsifier is any one or a mixture of more of glycerin monostearate, sucrose fatty acid triester and sorbitan monostearate.

Further, in the step S2, the pH stabilizer is one of dimethylethanolamine, monoethanolamine, diethanolamine, and triethanolamine.

Further, in the step S2, the initiator is one of potassium persulfate and ammonium persulfate.

Further, the using amount of the initiator is 1-2% of the mass of the modified nano silicon particles.

Further, the carbonization comprises the following steps: under the inert gas atmosphere environment, the temperature is increased from room temperature to 300-500 ℃ at the speed of 0.5-6 ℃/min, the temperature is kept for 2-5 h, then the temperature is continuously increased to 500-850 ℃, and the temperature is kept for 1-5 h.

A silicon-carbon composite material is prepared by the preparation method.

Furthermore, the particle size of the silicon-carbon composite material is 75-130 nm.

Example 1

A preparation method of a silicon-carbon composite material comprises the following steps:

s1, dispersing the nano silicon particles into an organic solvent to obtain a dispersion liquid, then adding a coupling agent into the dispersion liquid, adjusting the pH value to 4, and washing and drying the mixture in sequence to obtain modified nano silicon particles;

s2, respectively preparing an aqueous phase solution and an oil phase solution, wherein the aqueous phase solution comprises the following components in a ratio of 2: 1 and a pH stabilizer, the oil phase solution comprising a mixture of an emulsifier and a pH stabilizer in a ratio of 3: 1, dispersing the modified nano-silicon particles obtained in the step S1 into the oil phase solution, adding the dispersed modified nano-silicon particles into the water phase solution, adding an initiator, and sequentially centrifuging, washing and drying to obtain a composite material of the polymer coated on the nano-silicon particles;

and S3, carbonizing the composite material obtained in the step S2 to obtain the silicon-carbon composite material.

Further, in the step S1, the mass of the organic solvent is 2.3% of the mass of the nano silicon particles.

Further, in the step S1, the washing step is: the ratio of alcohol to water is 1: 2 and pure water are washed in this order.

Further, in the step S2, the emulsifier is any one or a mixture of more of glycerin monostearate, sucrose fatty acid triester and sorbitan monostearate.

Further, in the step S2, the pH stabilizer is one of dimethylethanolamine, monoethanolamine, diethanolamine, and triethanolamine.

Further, in the step S2, the initiator is one of potassium persulfate and ammonium persulfate.

Further, the amount of the initiator is 1% of the mass of the modified nano silicon particles.

Further, the carbonization comprises the following steps: under the inert gas atmosphere environment, the temperature is raised to 300 ℃ from the room temperature at the speed of 1 ℃/min, the temperature is kept for 2h, then the temperature is raised to 550 ℃, and the temperature is kept for 2 h.

A silicon-carbon composite material is prepared by the preparation method; the particle size of the silicon-carbon composite material is 80 nm.

Example 2

A preparation method of a silicon-carbon composite material comprises the following steps:

s1, dispersing the nano silicon particles into an organic solvent to obtain a dispersion liquid, then adding a coupling agent into the dispersion liquid, adjusting the pH value to 4, and washing and drying the mixture in sequence to obtain modified nano silicon particles;

s2, respectively preparing an aqueous phase solution and an oil phase solution, wherein the aqueous phase solution comprises the following components in a ratio of 2: 1 and a pH stabilizer, the oil phase solution comprising a mixture of an emulsifier and a pH stabilizer in a ratio of 3: 1, dispersing the modified nano-silicon particles obtained in the step S1 into the oil phase solution, adding the dispersed modified nano-silicon particles into the water phase solution, adding an initiator, and sequentially centrifuging, washing and drying to obtain a composite material of the polymer coated on the nano-silicon particles;

and S3, carbonizing the composite material obtained in the step S2 to obtain the silicon-carbon composite material.

Further, in the step S1, the mass of the organic solvent is 2.3 to 8% of the mass of the nano silicon particles.

Further, in the step S1, the washing step is: the ratio of alcohol to water is 1: 2 and pure water are washed in this order.

Further, in the step S2, the emulsifier is any one or a mixture of more of glycerin monostearate, sucrose fatty acid triester and sorbitan monostearate.

Further, in the step S2, the pH stabilizer is one of dimethylethanolamine, monoethanolamine, diethanolamine, and triethanolamine.

Further, in the step S2, the initiator is one of potassium persulfate and ammonium persulfate.

Further, the amount of the initiator is 2% of the mass of the modified nano silicon particles.

Further, the carbonization comprises the following steps: under the inert gas atmosphere environment, the temperature is increased from room temperature to 500 ℃ at the speed of 6 ℃/min, the temperature is kept for 5h, then the temperature is continuously increased to 850 ℃, and the temperature is kept for 5 h.

A silicon-carbon composite material is prepared by the preparation method; the particle size of the silicon-carbon composite material is 130 nm.

Example 3

A preparation method of a silicon-carbon composite material comprises the following steps:

s1, dispersing the nano silicon particles into an organic solvent to obtain a dispersion liquid, then adding a coupling agent into the dispersion liquid, adjusting the pH value to 5, and washing and drying the mixture in sequence to obtain modified nano silicon particles;

s2, respectively preparing an aqueous phase solution and an oil phase solution, wherein the aqueous phase solution comprises the following components in a ratio of 2: 1 and a pH stabilizer, the oil phase solution comprising a mixture of an emulsifier and a pH stabilizer in a ratio of 3: 1, dispersing the modified nano-silicon particles obtained in the step S1 into the oil phase solution, adding the dispersed modified nano-silicon particles into the water phase solution, adding an initiator, and sequentially centrifuging, washing and drying to obtain a composite material of the polymer coated on the nano-silicon particles;

and S3, carbonizing the composite material obtained in the step S2 to obtain the silicon-carbon composite material.

Further, in the step S1, the mass of the organic solvent is 2.3 to 8% of the mass of the nano silicon particles.

Further, in the step S1, the washing step is: the ratio of alcohol to water is 1: 2 and pure water are washed in this order.

Further, in the step S2, the emulsifier is any one or a mixture of more of glycerin monostearate, sucrose fatty acid triester and sorbitan monostearate.

Further, in the step S2, the pH stabilizer is one of dimethylethanolamine, monoethanolamine, diethanolamine, and triethanolamine.

Further, in the step S2, the initiator is one of potassium persulfate and ammonium persulfate.

Further, the amount of the initiator is 1.5% of the mass of the modified nano silicon particles.

Further, the carbonization comprises the following steps: under the inert gas atmosphere environment, the temperature is raised to 450 ℃ from the room temperature at the speed of 4 ℃/min, the temperature is kept for 4h, then the temperature is raised to 800 ℃ continuously, and the temperature is kept for 4 h.

A silicon-carbon composite material is prepared by the preparation method; the particle size of the silicon-carbon composite material is 100 nm.

Comparative example 1

A preparation method of a silicon-carbon composite material comprises the following steps:

s1, dispersing the nano silicon particles into an organic solvent to obtain a dispersion liquid, then adding a coupling agent into the dispersion liquid, adjusting the pH value to 4, and washing and drying the mixture in sequence to obtain modified nano silicon particles;

s2, respectively preparing a water phase solution and an oil phase solution, dispersing the modified nano-silicon particles obtained in the step S1 into the oil phase solution, then adding the modified nano-silicon particles into the water phase solution, adding an initiator, and sequentially performing centrifugation, washing and drying to obtain a composite material of the polymer coated on the nano-silicon particles;

and S3, carbonizing the composite material obtained in the step S2 to obtain the silicon-carbon composite material.

Further, in the step S1, the mass of the organic solvent is 3% of the mass of the nano silicon particles.

Further, in the step S1, the washing step is: the ratio of alcohol to water is 1: 2 and pure water are washed in this order.

Further, in the step S2, the emulsifier is any one or a mixture of more of glycerin monostearate, sucrose fatty acid triester and sorbitan monostearate.

Further, in the step S2, the pH stabilizer is one of dimethylethanolamine, monoethanolamine, diethanolamine, and triethanolamine.

Further, in the step S2, the initiator is one of potassium persulfate and ammonium persulfate.

Further, the amount of the initiator is 1% of the mass of the modified nano silicon particles.

Further, the carbonization comprises the following steps: under the inert gas atmosphere environment, the temperature is raised to 300 ℃ from the room temperature at the speed of 1 ℃/min, the temperature is kept for 2h, then the temperature is raised to 550 ℃, and the temperature is kept for 2 h.

A silicon-carbon composite material is prepared by the preparation method; the particle size of the silicon-carbon composite material is 80 nm.

The preparation method provided by the invention fully utilizes the interaction between the surface and the chemical functional groups of the carbon source, and the difference of decomposition temperatures between different carbon sources, and has simple process and environmental friendliness; the nano silicon particles are coated with the high molecular polymer by adopting emulsion polymerization and solution polymerization methods, the interaction between the modified nano silicon particles and the polymer is tighter, the polymer coating is more uniform, and after high-temperature carbonization treatment, the carbon coating layer of the composite material has a stable structure and is not easy to break; the silicon-carbon composite electrode material can improve the cycle stability and the power performance of the lithium ion battery.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.