Silicon oxide-based silicon-oxygen-carbon composite material and preparation method and application thereof

Abstract

The invention discloses a silicon oxide-based silicon-oxygen-carbon composite material, which is of a three-layer structure comprising an inner layer, an intermediate layer and an outer layer, wherein the inner layer is an SiOx substrate; the intermediate layer is a carbon coating layer; the outer layer is graphite; the SiOx substrate has the characteristics consistent with SiO or a compound of Si and SiOx in the crystal structure characteristic; the value range of x is greater than 0 and smaller than 2; the SiOx substrate is of a powdery structure; the average grain diameter of the SiOx substrate is 2.0-5.0 microns; and the SiOx substrate is prepared through technical details of Si and SiO2 high-temperature reaction, sublimation and condensation. The silicon oxide-based silicon-oxygen-carbon composite material has the most obvious characteristics that added polyethylene powder is decomposed to form small pores in a high-temperature pyrolysis carbon coating process; and meanwhile, the decomposed product and introduced carbon source gas can be cracked to form a carbon coating layer, so that the carbon coating efficiency and thickness are improved. Active material particles obtained by the method are controllable in size, good in conductivity and stable in structure; and the silicon-oxygen-carbon composite material has high reversible capacity and excellent cycling stability when used as a negative electrode of a lithium-ion battery.

Description

technical field [0001] The invention belongs to the field of electrode material preparation / energy storage devices, and in particular relates to a silicon oxide-based silicon-oxygen-carbon composite material and its preparation method and application. Background technique [0002] At present, the negative electrode materials of lithium-ion secondary batteries in commercial application are basically negative electrode materials based on graphite carbon. After years of development, their specific capacity is close to the theoretical value (372mAh / g), which cannot meet the current requirements for high-energy-density lithium-ion batteries. growing demand. At the same time, because the lithium intercalation potential of graphite is relatively close to the deposition potential of metal lithium, metal lithium is easy to precipitate during the charging process, especially during low-temperature charging or fast charging, which affects the safety of lithium-ion batteries. In additi...

AI Technical Summary

Problems solved by technology

[0003] Although silicon materials can solve many problems of current commercial carbon anode materials, they also face two serious problems: first, as a semiconductor material, silicon has low electrical conductivity, which leads to a large degree of irreversibility in the process of lithium ion deintercalation. The Coulombic efficiency is low; second, the volume change of silicon can reach 400% during the intercalation and deintercalation of lithium ions (Li 22 Si 5 ), which leads to the destruction of the electrode structure, it is difficult to form a stable SEI (solid electrolyte interface) film, and the pole pieces appear to be powdered and peeled off, which seriously affects the cycle performance of the prepared battery

However, these carbon coating methods have shortcomings such as insufficient carbon coating, low efficiency, and poor controllability. Moreover, although the cycle performance of the prepared SiO-C material is improved compared with SiO materials, it cannot meet the needs of commercialization.

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