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Silicon-carbon composite material and its preparation method and lithium-ion battery

A technology of silicon-carbon composite materials and lithium-ion batteries, which is applied in battery electrodes, secondary batteries, circuits, etc., can solve the problem that it is difficult to realize the uniform distribution and effective contact of silicon and carbon, and limit the practical application of high-performance silicon-carbon composite materials. Effectively suppress problems such as the agglomeration of nano-silicon particles, and achieve the effects of alleviating the destructive effect of the internal stress of the electrode, high strength, and high specific capacity

Active Publication Date: 2022-03-01
CHINA ACADEMY OF SPACE TECHNOLOGY
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  • Abstract
  • Description
  • Claims
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AI Technical Summary

Problems solved by technology

However, the simple wet chemical synthesis technology cannot effectively inhibit the agglomeration of nano-silicon particles, and it is difficult to achieve uniform distribution and effective contact between the components of silicon and carbon, and it is also impossible to avoid electrode crack damage and capacity fading during previous cycles.
The main reason is that the nano-silicon is not uniformly distributed during the preparation process, so that the silicon is not sufficiently constrained by the carbon material in the nano-space, which limits the practical application of high-performance silicon-carbon composite materials in lithium-ion batteries.
[0005] At present, in the prior art, simple chemical oxidants are used to modify silicon materials and carbon materials, and then recombine them, and the effect is not good.

Method used

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  • Silicon-carbon composite material and its preparation method and lithium-ion battery
  • Silicon-carbon composite material and its preparation method and lithium-ion battery
  • Silicon-carbon composite material and its preparation method and lithium-ion battery

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preparation example Construction

[0042] The preparation method of a silicon-carbon composite material provided by the present invention comprises: mixing a silicon material modified by ultraviolet-ozone or an oxidant with a carbon material modified by ultraviolet-ozone to obtain the silicon-carbon composite material. The functional groups with opposite electrical properties are uniformly introduced into the surface of carbon and / or silicon materials, and the electrostatic attraction between carbon and silicon surfaces solves the problem of uneven distribution and effective contact between the components of carbon and silicon materials, thereby improving the performance of silicon-carbon materials. Electrochemical cycling performance of composites.

[0043] In some preferred embodiments of the present invention, the mass ratio of the carbon material to the silicon material is 8-2:2-8 (such as 8:2, 7:3, 5:5, etc.), more preferably The ratio is 8~5:2~5.

[0044] In some preferred embodiments of the present inve...

Embodiment 1

[0063] The materials used in this embodiment are:

[0064] Silicon material: nano-silicon (Si) particles, (average particle size 50nm);

[0065] Carbon material: choose carbon fiber (CNFs);

[0066] The mass ratio of nano silicon and carbon fiber is 70.05:29.95.

[0067] The synthetic method of described composite material specifically comprises the following steps:

[0068] (1) UV-ozone joint modified carbon material:

[0069] At a temperature of 150°C and a wavelength of 253.7nm, use a UVO-Cleaner (ultraviolet ozone cleaning machine) to carry out ultraviolet-ozone treatment. After irradiating 200mg of CNFs for 20 minutes, the surface of the CNFs has carboxyl functional groups, which are labeled as o-CNFs ;

[0070] (2) Surface chemically modified silicon material:

[0071] 500mg Si nanoparticles in piranha solution (3:1, V / V H 2 SO4:H 2 o 2 , the mass concentration of hydrogen peroxide is 75%), keep the solution at 80°C, stir for 1h, then use ultrapure water to filte...

Embodiment 2

[0074] The materials used in this embodiment are:

[0075] Silicon material: nano-silicon (Si) particles (average particle size 50nm);

[0076] Carbon material: choose carbon fiber (CNFs);

[0077] The mass ratio of nano silicon and carbon fiber is 1:1.

[0078] For the modification of carbon material, step (1) is identical with embodiment 1;

[0079] (2) UV-ozone joint modified silicon material:

[0080] Use UVO-Cleaner for UV-ozone treatment at a temperature of 150°C and a wavelength of 253.7nm. After irradiating 300mg of Si nanoparticles for 20 minutes, the silicon surface has hydroxyl functional groups, which are marked as SiO x ;

[0081] (3) Ball milling and mixing to make silicon-carbon composite powder:

[0082] Mix 130mg o-CNFs with 130mg SiO x Mix 1.5mL in absolute ethanol, wet mill at a ball milling speed of 500rpm for 1h, and vacuum dry at 50°C for 12h to obtain a silicon-carbon composite powder with a uniform interwoven structure, labeled as Si-o-o-CNFs, It...

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Abstract

The invention provides a silicon-carbon composite material and a preparation method thereof and a lithium ion battery, comprising the following steps: mixing a silicon material modified by ultraviolet-ozone or an oxidant with a carbon material modified by ultraviolet-ozone to obtain The silicon-carbon composite material. Furthermore, close and effective contact occurs between the carbon material and the silicon material, and the two materials are evenly and interlacedly distributed. This method has low cost, high efficiency, and simple process, and can realize large-scale industrial production. In the silicon-carbon composite material, the two materials are interlaced and have a uniform interweaving structure. The material not only has the high specific capacity and high electrochemical activity of the silicon material, but also has the dual advantages of high strength and excellent conductivity of the carbon material. It can effectively alleviate the destructive effect of the internal stress of the electrode caused by the large volume change of silicon during the battery cycle, thereby improving the cycle life of the lithium-ion battery electrode.

Description

technical field [0001] The invention relates to the technical field of energy storage and conversion, in particular to a silicon-carbon composite material, a preparation method thereof, and a lithium-ion battery. Background technique [0002] At present, the composite material obtained by combining silicon material with high theoretical capacity and conductive carbon material has become the material of choice for high energy density lithium ion battery electrodes. However, due to the complex preparation process and high cost of silicon-carbon composite materials, especially for silicon-carbon composite materials with higher silicon content (≥20%), it is difficult to solve the problem of excessive volume change (300%-400% ), leading to the cracking of lithium-ion battery electrodes, hindering the practical application of silicon-carbon composites. Therefore, the preparation technology of silicon-carbon composite electrode materials has technical problems such as unfriendly e...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01M4/36H01M4/38H01M4/62H01M10/0525
CPCH01M4/364H01M4/386H01M4/625H01M4/628H01M10/0525H01M2004/021Y02E60/10
Inventor 张辉柏晓
Owner CHINA ACADEMY OF SPACE TECHNOLOGY
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