Changes of electro-deposited Sn-Ni alloy thin film for lithium ion battery anodes during charge discharge cycling

We have reported in our past work that electrodeposited Sn-Ni alloy with different composition show considerably different performance as anode materials for Li-ion batteries, and the performance was remarkably well (ca. 650 mAh g−1 at 70th cycle) when the composition was controlled to Sn62Ni38. In this work, structural changes during charge discharge cycling of Sn-Ni alloy with different composition were investigated to evaluate their differences in the cycle performance. From the XRD result, Ni3Sn4 phase was the main phase seen in Sn62Ni38, and its reversible reactivity with Li was confirmed. We suggest that this is the key phase for its high capacity and lengthened cycle life. From Sn54Ni46, which showed low capacity, only a metastable phase close to the structure of SnNi was confirmed. The results from Sn84Ni16 indicated the presence of pure Sn and Sn rich metastable phase would lead to relatively fast electrode degradation.