Short-Process Multiscale Core–Shell Structure Buffer Control of a Ni/N Codoped Si@C Composite Using Waste Silicon Powder for Lithium-Ion Batteries

A huge amount of waste silicon powder produced in the solar energy silicon wafer production process causes resource wastage and environmental pollution. As a lithium-ion battery anode, silicon has received widespread attention because of its extremely high theoretical specific capacity, abundance in nature, and low discharge potential. However, the large volume expansion and huge internal stresses lead to instability of the solid-state interphase layer upon lithiation/delithiation; it is the problem that needs to be solved for actual application of silicon-based anodes. Here, based on the waste silicon powder from a photovoltaic silicon production process as the raw material, we propose a concept of short-process multiscale structure buffer control and prepare Ni-N codoped Si@C core–shell composites to solve the abovementioned problems. The preparation method is simple and nonpolluting and has positive significance for realizing industrialization. For structure, the Si particles are completely encapsulated by the nanoscale carbon shell, and the suitable elastic buffer carbon shell can accommodate Si expansion and the introduction of metallic nickel and N can improve the electrode material conductivity and utilize the metal ductility to buffer the silicon volume expansion during the process of charge/discharge. As a result, the Ni-N codoped Si@C electrode shows a stable reversible specific capacity of 1001.5 mAh g–1 at 0.5 A g–1 after 450 cycles.