Sn-based alloy materials are considered as a promising anode candidate for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs),whereas they suffer from severe volume change during the discharge/charge process.To address the issue,double core-shell structured Sn-Cu@SnO2@C nanocomposites have been prepared by a simple co-precipitation method combined with carbon coating approach.The double core-shell structure consists of Sn-Cu multi phase alloy nanoparticles as the inner core,intermediate SnO2 layer anchored on the surface of Sn-Cu nanoparticle and outer carbon layer.The Sn-Cu@SnO2@C electrode exhibits outstanding electrochemical performances,delivering a reversible capacity of 396 mA· h· g-1 at 100 mA· g-1 after 100 cycles for LIBs and a high initial reversible capacity of 463 mA· h· g-1 at 50 mA· g-1 and a capacity retention of 86％ after 100 cycles,along with a remarkable rate capability (193 mA· h· g-1 at 5000 mA· g-1) for SIBs.This work provides a viable strategy to fabricate double core-shell structured Sn-based alloy anodes for high energy density LIBs and SIBs.