CoSn5 Phase: Crystal Structure Resolving and Stable High Capacity as Anodes for Li Ion Batteries

Tin alloys form a class of interesting high-energy-density anode materials for Li ion batteries, but the improvement of their cycling stability is elusive. Here, we provide new insight on this fatal issue by synthesizing novel CoSn5-phase nanospheres via a conversion chemistry route and directly comparing their cell behavior with that of recently found FeSn5-phase nanospheres. The CoSn5 phase is absent in previous Co-Sn phase diagrams. Co0.83Sn5 nanospheres show a much longer cycle life, which partially is related to milder evolution of their cycling profiles over time.