Negative electrode active material and secondary battery

Abstract

The invention provides a negative electrode active material and a secondary battery. The negative electrode active material comprises a core material and a polymer modified coating layer on at least part of the surface of the core material, wherein the core material is one or more of a silicon-based negative electrode material and a tin-based negative electrode material, the polymer modified coating layer comprises a sulfur element and a carbon element, the mass ratio of the sulfur element in the negative electrode active material is 0.2%-4%, the mass ratio of the carbon element in the negative electrode active material is 0.5%-4%, and the polymer modified coating layer comprises -S-C- bonds. According to the invention, damage to the surface structure of the negative electrode active material in the charging and discharging process of the battery can be reduced, active ion loss is reduced, and the capacity loss of the battery is reduced. Meanwhile, the Coulombic efficiency of the battery can be well improved, and the cycle performance of the battery is improved.

Description

technical field [0001] The invention relates to the field of batteries, in particular to a negative electrode active material and a secondary battery. Background technique [0002] In recent years, due to the higher energy density requirements of the electric vehicle industry, a lot of research has been carried out around high-capacity negative electrode active materials. Among them, silicon-based materials and tin-based materials have been paid attention to because of their high theoretical gram capacity, but silicon-based and tin-based materials have serious volume effects, which will cause huge volume expansion during charging, and thus in the charging and discharging process Among them, the negative electrode active material is easily broken and pulverized, and it is difficult to form a stable SEI film on the surface, which leads to too fast capacity decay of the battery and poor cycle performance. In addition, as a semiconductor material, silicon has the defect of low ...

AI Technical Summary

Problems solved by technology

Among them, silicon-based materials and tin-based materials have been paid attention to because of their high theoretical gram capacity, but silicon-based and tin-based materials have serious volume effects, which will cause huge volume expansion during charging, and thus in the charging and discharging process Among them, the negative electrode active material is easily broken and pulverized, and it is difficult to form a stable SEI film on the surface, resulting in too fast capacity decay of the battery and poor cycle performance.

In addition, as a semiconductor material, silicon has the defect of low conductivity, and the irreversibility of active ions in the process of charging and discharging is relatively large, which will also affect the cycle performance of the battery.

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