Multi-element gradient composite high-first-effect lithium battery negative electrode material and preparation method thereof

Abstract

The invention relates to a multi-element gradient composite high-first-effect lithium battery negative electrode material and a preparation method thereof. The negative electrode material is of a multi-layer core-shell structure, and comprises an inner core, a buffer layer and an outer layer. The inner core and the buffer layer of the negative electrode material are silicon-oxygen compounds, and the outer layer is a carbon coating layer. The inner core and the buffer layer further contain lithium salt and magnesium salt, and the concentration of the magnesium salt is increased progressively from the inner core to the buffer layer to form gradient distribution. There is more lithium salt in the core of the negative electrode material, so that a large amount of active oxygen can be consumed,the initial coulombic efficiency of the material is effectively improved, and meanwhile, the ion conductivity of the material is improved. There is more magnesium silicate in the buffer layer, so that the initial charge-discharge efficiency of the material is further improved, meanwhile, the magnesium silicate forms a high-strength protective layer, the structural stability of the material is enhanced, and the cycle performance of the material is improved.

Description

technical field [0001] The invention relates to the technical field of lithium battery materials, in particular to a multi-element gradient composite high-first-efficiency lithium battery negative electrode material and a preparation method thereof. Background technique [0002] Silicon materials have been widely studied because of their piezoelectric properties similar to graphite and high specific lithium storage capacity. At present, the main research and application forms of silicon-based materials include pure Si, silicon oxide, silicon carbon and silicon alloys. Relatively speaking, silicon oxide and silicon carbon are more mature and widely used. However, silicon oxide will generate irreversible products such as lithium oxide and lithium silicate during the first lithium intercalation process, resulting in low initial Coulombic efficiency. [0003] In order to solve the above problems, researchers pre-lithiated silicon oxide materials by thermal doping, which greatl...

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Problems solved by technology

However, silicon oxide will generate irreversible products such as lithium oxide and lithium silicate during the first lithium intercalation process, resulting in low initial Coulombic efficiency.

[0003] In order to solve the above problems, researchers pre-lithiated silicon oxide materials by thermal doping, which greatly improved the first Coulombic efficiency, but the conditions for lithium-doped modification were harsh and the production cost was high, and the slurry after lithium doping There are problems such as instability

Some people also synthesized Mg-doped modified silicon oxide materials by homogeneous gas phase reaction, which improved the first Coulombic efficiency to a certain extent, but the reaction between Mg and silicon oxide was fast, resulting in the rapid disproportionation of silicon oxide into Si and SiO 2 , the Si crystal grows rapidly, resulting in a decrease in cycle life, and the first Coulombic efficiency does not meet the use requirements

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