ZIF-derived carbon-coated Co9S8 for a silicon anode with superior performance in lithium-ion batteries

Abstract

During the charge and discharge process, silicon reacts with lithium ions, and the volume of the product Li_xSi after the reaction is much larger than that of silicon before the reaction (∼300%). Many researchers have attempted to tackle this tough problem. If the volume expansion effect of silicon were solved, it would represent a breakthrough in a bottleneck of battery material research at this stage. Herein, we report a multilayer cladding structure, Si@void@C@Co₉S₈@C, prepared using simple methods at room temperature. The silicon–carbon yolk–shell structure was wrapped in the zeolitic imidazole frameworks (ZIFs), and the composite material was then obtained by vulcanization and carbon coating. Finally, it was assembled into batteries to test its electrochemical performance. In an effort to ameliorate the volume expansion effect of silicon, the principle described in this paper is to use a multi-layer carbon layer as a support structure to prevent the internal silicon from expanding too much and causing structural rupture. Additionally, the external coated carbon layer has excellent electrical conductivity, which is instrumental to boost the electrochemical properties of the material. The structure presented in this paper shows satisfactory electrochemical performance when applied in a lithium-ion battery as an anode material. After 500 cycles at a current density of 1 A g⁻¹, the material maintains a specific discharge capacity of 658.1 mA h g⁻¹. In this study, an extraordinary method for the preparation of silicon anode materials with a unique structure for lithium-ion batteries is provided.