Li insertion/extraction characteristics of a vacuum-deposited Si-Sn two-component film

Vacuum-deposited Si-Sn two-component films were prepared by depositing Si and Sn simultaneously on a metal foil substrate. The composition of the films was estimated from the ratio of consumption of the two evaporation sources. SEM and XRD revealed the film structure consisting of two different phases, where Sn nanoparticles were dispersed homogeneously in the amorphous Si matrix. The film with higher Sn content gave unsatisfactory results, which is in contrast to the much improved results obtained with a film containing less Sn. The conductivity of the Si-Sn film was found to be higher than that of a pure Si film, which was attributed to the homogenously deposited Sn nanoparticles. This enabled us to realize a discharge capacity of 400 mAh g−1 even after 500 charge/discharge cycles at a very high rate of 20 C.