A rational design to buffer volume expansion of CoSn intermetallic in lithium and sodium storage: Multicore-shell versus monocore-shell

Carbon coated core-shell structured anode has been reported with advantages to enhance conductivity and partly buffer the volume expansion. However, huge mechanical stress and long lithium/sodium transmission distance also hinder the lithium/sodium storage performances. For maximum buffer effect, we herein design a multicore-shell CoSn@C nanocages with decreased particle size and enhanced extra space in comparison with the monocore-shell sample. This unique structure can effectively buffer the volume expansion in the deintercalation process, alleviate electrode pulverization and improve cyclic stability. Electrochemical tests show that multicore-shell CoSn@C nanocubes have excellent discharge capacities of 1010.9 mAh g−1 at 0.5 A g−1 after 160 cycles and 818 mAh g−1 at 1 A g−1 after 300 cycles for lithium ion battery anode, much higher than that of the monocore-shell sample. The sodium storage performance of the multicore-shell CoSn@C is also far more than the monocore-shell one. Above results suggests that fabrication of multicore-shell structure is an excellent design to buffer volume expansion and enhance performance for lithium and sodium storage.