Core/shell and multi-scale structures enhance the anode performance of a Sn–C–Ni composite thin film in a lithium ion battery

Abstract

A Sn–C–Ni composite thin film has been prepared by electron beam evaporation using a TiNi alloy as a reaction medium. The thin film with a multi-scale structure is composed of lots of micro-sized core/shell particles. The cores are Sn single crystals and the shells are amorphous carbon with nano-sized Sn and Ni particles dispersed inside. Both the Sn core and the sp² amorphous carbonaceous shells react with lithium and give substantial contributions to its total high capacities of 1200 mA h g⁻¹ at C/3. The multi-scale structure of the Sn phases and the coating of nanocomposite carbonaceous shells on the Sn cores, as well as the dispersion of nano-sized Sn and Ni particles in the amorphous carbon matrix enhance the Li⁺ diffusion kinetics and the stability of the structure of the active materials, and thus the thin film electrode has good capacity retention and a high-rate capability (472 mA h g⁻¹ at 12C).