A kind of siox-sic-c/g silicon-carbon composite material and its preparation and application

Abstract

The invention belongs to the field of lithium ion batteries, and specifically discloses a SiO x ‑SiC‑C / G silicon-carbon composite material, consisting of a graphite core and SiO coated layer by layer on the surface of the graphite core x layer, SiC layer and amorphous carbon layer; preferably, the particle size of the graphite core is 5-15 μm; coated in SiO x The total thickness of SiC layer, SiC layer and amorphous carbon layer is 1-5 μm. The invention also discloses the preparation and application of the material. The present invention provides a silicon-carbon composite material with a new structure, which uses graphite as the core, and the core is coated with SiO in situ x layer, on SiO x A SiC layer is in-situ coated on the layer, and an amorphous carbon layer is further in-situ coated on the surface of the SiC layer. The research of the present invention finds that the material with the special structure and morphology has better structural stability, better capacity and cycle stability.

Description

technical field [0001] The invention belongs to the technical field of negative electrode materials for lithium ion batteries, and in particular relates to a preparation method for negative electrode materials, in particular using waste carbon slag as a raw material. Background technique [0002] Fossil energy based on coal and oil can no longer meet the needs of sustainable development of human beings. It is imperative to improve the energy consumption structure and reduce dependence on fossil energy. As a green energy storage device at the forefront of technology, lithium-ion batteries have been widely used in portable electronic devices and electric vehicles. At the same time, these fields have also put forward higher and higher requirements for the energy density of energy storage devices. However, the current negative electrode materials for lithium-ion batteries are mainly graphite, which has the defect of low specific capacity, making it difficult to further increase ...

AI Technical Summary

Problems solved by technology

However, when the silicon negative electrode is applied to the lithium-ion battery system, there are the following problems: during the lithium intercalation process of the silicon negative electrode, a volume expansion of up to 300% will occur, and the material will be broken and pulverized during the repeated expansion and contraction process. , lose electrical contact with the collector liquid, and eventually lead to material failure; at the same time, the solid electrolyte film (SEI) formed during the first lithium intercalation process will rupture due to the volume change effect of silicon, and repeatedly form new ones on the exposed fresh silicon surface. The continuous thickening and increase of the SEI film will eventually lead to structural damage and performance failure of the silicon material; in addition, the low electronic conductivity and ionic conductivity of silicon itself also limit the capacity of the electrode and seriously reduce the rate performance.

However, for silicon oxide-based anodes with better cycle stability, there is still the problem of low reactivity due to poor conductivity during charge and discharge, and there is still a high volume expansion during electric cycles. , leading to side reactions between the material and the electrolyte, and rapid material failure, which seriously limits the practical application of the material.

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