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

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).