A modified carbothermal reduction method for preparation of high-performance nano-scale core/shell Cu₆Sn₅ alloy anodes in Li-ion batteries

Core-shell structured, carbon-coated, nano-scale Cu₆Sn ₅ has been prepared by a modified carbothermal reduction method using polymer coated mixed oxides of CuO and SnO₂ as precursors. On heat treatment, the mixture oxides were converted into Cu₆Sn₅ alloy by carbothermal reduction. Simultaneously, the remnants carbon was coated on the surface of the Cu₆Sn₅ particles to form a core-shell structure. Transmission electron microscope (TEM) images demonstrate that the well-coated carbon layer effectively prevents the encapsulated, low melting point alloy from out flowing in a high-temperature treatment process. Core-shell structured, carbon coated Cu₆Sn₅ delivers a reversible capacity of 420 mAh g^-1 with capacity retention of 80% after 50 cycles. The improvement in the cycling ability can be attributed to the fact that the carbon-shell prevents aggregation and pulverization of nano-sized tin-based alloy particles during charge/discharge cycling.