Sn₄P₃/Sb Composite Electrodes as High-Performance Anodes for Li-Ion and Na-Ion Storages (Supporting Information)

Various composite electrodes were prepared using Sn₄P₃ and other active materials (Sb, Bi, Ge, TiO₂, In, and Fe) with weight ratios of 70 and 30 wt% for Na-ion battery anode to improve capacity decay of Sn₄P₃ caused by Sn aggregation. No improvement was observed in the case of composite electrodes of Sn₄P₃/Ge and Sn₄P₃/TiO₂ due to poor electronic conductivities of Ge and TiO₂. Although In and Fe have good electronic conductivities, no improvement was achieved in Sn₄P₃/In and Sn₄P₃/Fe because of their low Na⁺ diffusion abilities. In contrast, the capacity decay was improved by the Sn₄P₃/Sb and Sn₄P₃/Bi electrodes. We consider that Sb and Bi have good electronic conductivity as well as Na⁺ diffusion ability, making it easier for electrons and Na⁺ to permeate the entire active material layer. In addition, the longest cycle life of 900 cycles was attained when the Sb addition amount was 15 wt%. This improvement was also achieved in Li-ion battery evaluation. Among the composite electrodes with various Sb amount, the longest cycle life was achieved by Sn₄P₃/Sb(85 : 15 wt%) electrode.