Preparation method of silicon-carbon composite material

A technology for silicon carbon composite materials and coating materials, which is applied in the preparation of silicon carbon composite materials and the preparation field of carbon silicon composite materials, can solve the problems of poor conductivity, deterioration of negative electrode material performance, unstable SEI film, etc., and achieves high ratio The effect of capacity

Pending Publication Date: 2022-03-11
BEIJING TU CREATIVE CO LTD +1
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Problems solved by technology

Nano-silicon material has become the most promising anode material for the next generation because of its higher specific capacity than graphite. However, due to the instability of the SEI film and poor conductivity of the silicon material itself, the charge-discharge cycle life of the battery is short.
For this reason, it is necessary to use a silicon-carbon composite method to improve the instability and poor conductivity of the SEI film of silicon materials.
[0003] In the preparation process of silicon-carbon composite materials in the prior art, during the high-temperature carbonization process of the silicon-carbon composite material, silicon is prone to oxidation reaction, resulting in the failure of the high specific capacity of the silicon-carbon composite material to be exerted.
Moreover, the presence of impurities such as H, O and other elements introduced from carbon sources will also degrade the performance of negative electrode materials.

Method used

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  • Preparation method of silicon-carbon composite material
  • Preparation method of silicon-carbon composite material
  • Preparation method of silicon-carbon composite material

Examples

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preparation example Construction

[0031] According to one embodiment of the present disclosure, it provides a method for preparing a silicon-carbon composite material, characterized in that the method includes:

[0032] The first step: mixing nano-silicon with pyrolytic carbon source or its aqueous solution, so as to coat the carbon source on the surface of nano-silicon to obtain the first pre-coating material;

[0033] The second step: heating the first cladding material to 500-650° C. for pre-carbonization to obtain the first cladding material;

[0034] The third step: repeating the first step and the second step to form a second cladding material;

[0035] The fourth step: Put the second cladding material into the middle of the high-temperature furnace for carbonization, add metallurgical silicon powder with a particle size of 1 μm to 1 mm at the inlet and outlet ends of the furnace as a reducing and protecting agent, and put the mixture in an inert Heating to 950-1000° C. under atmosphere for high-tempera...

Embodiment 1

[0043] Embodiment 1: Preparation of carbon-silicon composite material

[0044] A) Mix self-made nano-silicon and low-temperature pitch at a ratio of 2:3, heat to 120°C and stir in a high-speed disperser for 4 hours to obtain the first pre-coating material;

[0045] B) Then, heating the first cladding material to 500-650° C. under nitrogen to perform pre-carbonization;

[0046] C) Then mix the pre-carbonized product with pitch again at a ratio of 9:1, heat to 120°C and stir in a high-speed disperser for 2 hours to obtain the second coating material;

[0047] D) Put the second coating material into the middle of the high-temperature furnace for carbonization, add metallurgical silicon with a particle size of 500 μm as a reducing protective agent at the inlet and outlet ends of the furnace, and heat the mixture to 950 °C under an inert atmosphere To 1000 ℃ for high temperature carbonization for 4-8h, so as to obtain silicon carbon composite material.

Embodiment 2

[0048] Embodiment 2: Changes before and after high-temperature carbonization of reducing protective agent

[0049] The properties of metallurgical silicon powder in embodiment 1 before and after test are tested, figure 1 with figure 2 It shows the color and quality changes of metallurgical silicon powder before and after the test (a is before the test, b is after the test). Depend on figure 1 It can be seen that the color of metallurgical silicon changed from light black to dark black after the carbonization heating test. At the same time, by figure 2 It can be seen that the mass of metallurgical silicon increased from 9.426g to 12.417g after the carbonization heating test, and the increase of 2.91g was caused by the oxidation of part of silicon to silicon oxide.

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Abstract

The invention relates to a preparation method of a silicon-carbon composite material, which comprises the following steps: 1, mixing nano silicon with a pyrolysis carbon source or an aqueous solution thereof to coat the surface of the nano silicon with the carbon source to obtain a first pre-coated material; 2, the first coating material is heated to 500 DEG C to 650 DEG C to be pre-carbonized, and the first coating material is obtained; 3, repeating the first step and the second step to form a second coating material; 4, the second coating material is placed in the middle of a high-temperature furnace to be carbonized, metallurgical silicon with the particle size ranging from 1 micrometer to 1 mm is added to the gas inlet end and the gas outlet end in the furnace to serve as a reduction protective agent, the mixture is heated to 950-1000 DEG C in the inert atmosphere, high-temperature carbonization is conducted for 4-8 h, and therefore the silicon-carbon composite material is obtained. The metallurgical silicon powder disclosed by the invention can prevent the silicon-carbon composite material from being oxidized during carbonization, is low in cost, can be used for multiple times, and is suitable for large-scale production.

Description

technical field [0001] The present disclosure relates to a preparation method of a composite material. Specifically, the present disclosure relates to a method for preparing a carbon-silicon composite material, in particular to a method for preparing a silicon-carbon composite material used for a negative electrode of a lithium-ion battery. Background technique [0002] In the field of lithium-ion batteries, in order to increase energy density, it is necessary to develop electrode materials with high specific capacity. Nano-silicon material has become the most promising anode material for the next generation because of its higher specific capacity than graphite. However, due to the instability of SEI film and poor conductivity of silicon material itself, the battery charge-discharge cycle life is short. For this reason, it is necessary to use a silicon-carbon composite method to improve the instability and poor conductivity of the SEI film of silicon materials. [0003] In...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M4/36H01M4/38H01M4/62H01M10/0525B82Y40/00
CPCH01M4/366H01M4/386H01M4/62H01M4/625H01M4/628H01M10/0525B82Y40/00Y02E60/10
Inventor 邱新平张文广郑曦李慧玉
Owner BEIJING TU CREATIVE CO LTD
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