Synthesis of Sn-Si composite films by co-sputtering technique for high-capacity microbattery anodes

Sn-Si composite anodes with linear variation composition could be synthesized by co-sputtering method directly. Ductile Sn was used as an additive material for improving the capacity and electrical conductivity of the brittle Si since the synergetic effect. The deposited films possessed a unique phase-separated structure and is beneficial to buffer the volume expansion introduced by an alloying/dealloying process, and the distributed Sn particles improved the transportation of Li+ and remedy the inherent poor conductivity of Si. As a result, the optimal Sn-Si composite film (Sn:Si = 35.9:64.1) possessed a stable discharge capacity of 1134.0 mAh/g after two cycles and a high-capacity retention of 82.8% after 50 cycles. Si played an important role as a buffer matrix, and the increased Si content could suppress the growth of Sn grains, reduce the structural damage and enhance film adhesion. The obtained Sn-Si component film was one strong candidate for next-generation thin film anode.