Silicon-hard carbon composite material and preparation method thereof

Abstract

The invention provides a silicon-hard carbon composite material and a preparation method thereof, and belongs to the technical field of lithium-ion battery material preparation. The preparation methodcomprises the steps of stably combining sulfonated polystyrene microspheres and a piezoelectric material to form a core material; mixing the core material with nano-silicon and phenolic resin, and enabling phenolic resin and nano-silicon to uniformly wrap the surfaces of the polystyrene microspheres; removing polystyrene through elution so as to form a piezoelectric material core with a porous structure; carbonizing phenolic resin into a carbon material through carbonization treatment to coat the surface of the core material, and thus forming the shell-core silicon-hard carbon composite material with the core being the porous piezoelectric material and the shell being hard carbon. The porous structure of the silicon-hard carbon composite material is conducive to absorbing and holding a liquid, the expansion of the silicon material is reduced, the G capacity development and cycle performance of the silicon-hard carbon composite material, the characteristics of large interlayer spacingand high lithium ion de-intercalation rate of hard carbon are given into full play, and the rate performance is improved. Meanwhile, the addition of the piezoelectric material improves the safety of the silicon-hard carbon composite material.

Description

technical field [0001] The invention relates to the technical field of preparation of lithium ion battery materials, in particular to a silicon-hard carbon composite material and a preparation method thereof. Background technique [0002] With the increasing demand for high specific energy measurement in the market, lithium-ion batteries are required to have high specific energy density, while the fast charging performance and safety performance of the battery can also be guaranteed, and hard carbon materials have a large layer spacing, stable structure, Due to its excellent low temperature performance, low expansion rate and high safety performance, it is used in the fields of start-stop power supply, hybrid electric vehicle and other high-temperature performance requirements, but its low specific capacity and low compaction density limit its application. [0003] Silicon carbon materials have become the preferred materials for high specific energy density batteries due to ...

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Problems solved by technology

[0002] With the increasing demand for high specific energy measurement in the market, lithium-ion batteries are required to have high specific energy density, while the fast charging performance and safety performance of the battery can also be guaranteed, and hard carbon materials have a large layer spacing, stable structure, Excellent low-temperature performance, low expansion rate and high safety performance are used in the field of start-stop power supply, hybrid electric vehicle and high-temperature performance, but its low specific capacity and low compaction density limit its application.

[0003] Silicon carbon materials have become the preferred materials for high specific energy density batteries due to their advantages such as high specific capacity, wide range of material sources, and low voltage platform, but their high expansion rate and poor cycle performance limit their popularization and application.

Although researchers have improved the cycle performance by coating hard carbon on the surface of silicon-carbon materials, the effect is not obvious, and even the rate performance of the material is deviated.

For example, patent CN107863512A discloses a silicon-carbon negative electrode material with a core-shell structure and a preparation method thereof. The silicon-carbon negative electrode material is composed of a core, a buffer layer and a shell in turn from the inside to the outside; the core material is composed of SiO, Si , SiO 2 and silicate; the buffer layer material is carbon dots or graphene quantum dots; the shell material is hard carbon material, which improves the specific capacity and cycle performance of the material, but its safety performance does not improve

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