Double-layer carbon-coated silicon-based composite material, preparation method and application thereof

A silicon-based composite material and coating technology, applied in nanotechnology for materials and surface science, active material electrodes, nanotechnology, etc., can solve the problems of complex and dangerous preparation processes, incompatibility, and low Coulombic efficiency, and achieve Improve the first Coulombic efficiency, reduce irreversible loss, and small volume effect

Active Publication Date: 2022-03-29
BERZELIUS (NANJING) CO LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The silicon particle size (generally greater than 100nm) selected by the method is much larger than the nano-silicon particle (generally less than 50nm) generated by the disproportionation reaction in the silicon-oxygen compound, so the volume expansion / shrinkage effect of the silicon particle during battery charging and discharging is obvious; in addition , the dispersion of silicon particles in the method is not as good as that of nano-silicon produced by the disproportionation reaction in silicon-oxygen compounds. The uneven dispersion of silicon particles will also lead to uneven distribution of internal stress in the material during charging and discharging of the battery, thereby causing the material particles to break Furthermore, the interfacial stability of silicon particles and lithium silicate in the material is not as good as the silicon simple substance / lithium silicate complex generated after disproportionation and pre-lithiation reactions in silicon-oxygen compounds, and it is more likely to cause material damage during battery charging and discharging. Particle break
In summary, the cycle stability of the silicon-based composite material is difficult to be guaranteed
[0007] Therefore, the existing silicon-based negative electrode materials have problems such as low capacity, low coulombic efficiency, poor cycle stability, complicated and dangerous preparation process, and incompatibility with the commonly used aqueous homogenate system, making it difficult to realize commercial application in lithium-ion batteries. , is a technical problem in the field

Method used

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  • Double-layer carbon-coated silicon-based composite material, preparation method and application thereof
  • Double-layer carbon-coated silicon-based composite material, preparation method and application thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0056] Mix 1000g of silicon-oxygen compound particles with a median particle size of 5 μm (the atomic ratio of silicon to oxygen is 1:1), and 62.5g of coal tar pitch powder in the coating tank, and then heat the coating tank to 300°C and keep Stir at constant temperature for 3 hours to obtain a silicon oxide compound material coated with coal tar pitch. The above-mentioned materials were heated to 800° C. under a nitrogen atmosphere and kept for 10 hours to carbonize the coal tar pitch, and at the same time, the disproportionation reaction of the silicon oxide occurred. The material obtained after cooling is crushed and passed through a 500-mesh sieve to obtain silicon oxide powder coated with the first layer of carbon film.

[0057] In a drying room with a relative humidity lower than 30%, use a planetary ball mill to crush the lithium hydride coarse powder and pass it through a 600-mesh sieve to obtain a lithium hydride fine powder with a maximum particle size of about 23 μm...

Embodiment 2

[0064] Compared with Example 1, the silicon oxide particle-coated carbon film process in Example 2 is completed by chemical vapor deposition, using acetylene as a carbon precursor at 950° C. for 2 hours. The material obtained after cooling is crushed and passed through a 500-mesh sieve to obtain silicon oxide powder coated with the first layer of carbon film.

[0065] In a drying room with a relative humidity lower than 30%, use a planetary ball mill to crush the lithium hydride coarse powder and pass it through a 600-mesh sieve to obtain a lithium hydride fine powder with a maximum particle size of about 23 μm. Take 50 g of lithium hydride fine powder with a maximum particle size equal to about 23 μm after sieving, and mix it with 500 g of the carbon film-coated silicon oxide powder in a VC mixer at high speed for 20 minutes. Put the above mixed powder into a tube furnace, do lithium doping and doping heat treatment in an argon atmosphere, raise the temperature to 700°C and k...

Embodiment 3

[0068] Mix 1000g of silicon oxide compound particles with a median particle size of 3μm (atomic ratio of silicon to oxygen is 1:1), and 25g of petroleum asphalt powder in the coating tank, and then heat the coating tank to 300°C and keep it at a constant temperature Stir for 3 hours to obtain a silicon oxide compound material coated with coal tar pitch. The above materials were heated to 1100° C. under a nitrogen atmosphere and kept for 2 hours to carbonize the petroleum pitch, and at the same time, the disproportionation reaction of the silicon oxide occurred. The material obtained after cooling is crushed and passed through a 500-mesh sieve to obtain silicon oxide powder coated with the first layer of carbon film.

[0069] In a drying room with a relative humidity lower than 30%, use a planetary ball mill to crush the lithium hydride coarse powder and pass it through a 600-mesh sieve to obtain a lithium hydride fine powder with a maximum particle size of about 23 μm. Take 5...

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Abstract

The invention relates to a silicon-based composite material and its preparation method and application. The material is composed of silicon oxide lithium compound particles and two layers of carbon films coated on its surface. Elemental silicon nanometers are dispersed in the silicon oxide lithium compound particles. Crystal grains and lithium silicate compounds. The method is to coat the surface of silicon oxide compound particles with a first layer of carbon film, followed by crushing and sieving; the obtained material is uniformly mixed with lithium-containing compound powder; the mixed material is heated in a non-oxidizing atmosphere to make The lithium element diffuses into the silicon-oxygen compound particles to obtain the silicon-oxygen-lithium compound; the silicon-oxygen-lithium compound is coated with a second layer of carbon film at low temperature, and then crushed and sieved to obtain a silicon-based composite material. The invention is applied to the battery negative electrode, not only to the oil system but also to the water system homogenate system. Meanwhile, the prepared battery has the advantages of high first efficiency, low expansion, long cycle and high energy density, and is suitable for commercial use.

Description

technical field [0001] The invention relates to a silicon-based composite material and its preparation method and application, belonging to the technical field of battery materials. Background technique [0002] Due to the rapid development and wide application of various portable electronic devices, electric vehicles, and energy storage systems in recent years, the demand for lithium-ion batteries with high energy density and long cycle life has become increasingly urgent. At present, the negative electrode material of commercial lithium-ion batteries is mainly graphite, but due to the low theoretical capacity (372mAh / g), the further improvement of the energy density of lithium-ion batteries is limited. Since the silicon anode material has the advantage of high capacity that other anode materials cannot match, it has become a research and development hotspot in recent years, and has gradually moved from laboratory research to commercial application. There are two main type...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01M4/36H01M4/38H01M4/583H01M10/0525B82Y30/00
CPCH01M4/366H01M4/386H01M4/583H01M10/0525B82Y30/00H01M2004/027Y02E60/10
Inventor 张和宝李喆罗姝查道松汪芳王岑
Owner BERZELIUS (NANJING) CO LTD
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