The lithium ions storage property of a novel polyhedral SnFe2O4 and Core-shell composite SnFe2O4@carbon or carbon@SnFe2O4 for lithium ion batteries

A novel inverse spinel SnFe 2 O 4 , with a polyhedral morphology and a mixed core–shell SnFe 2 O 4 @Carbon or Carbon@SnFe 2 O 4 composite are prepared by a facile solvothermal method, and evaluated as anode material for lithium ion batteries (LIBs). The SnFe 2 O 4 exhibits a higher initial discharge/charge capacities of 1212/858 mAh g −1 with an initial coulombic efficiency (ICE) of 70.8% and maintains 812/799 mAh g −1 at the 200th cycle at 0.5 A g −1 and 540/535 mAh g −1 at the 400th cycle even at 4.0 A g −1 . An interesting phenomenon that the capacity of pure SnFe 2 O 4 at each current density decreases rapidly first and then increases gradually and remains stable, which is attributed to the polyhedral morphology and the inverse spinel structure. It can be relieved by compositing with carbon forming core–shell SnFe 2 O 4 @Carbon or Carbon@SnFe 2 O 4 . The composite shows an initial discharge/charge capacities of 1238/820 mAh g −1 with an ICE of 66.2% and maintains much larger capacities of 1223/1200 mAh g −1 at the 200th cycle at 0.5 A g −1 and 608/603 mAh g −1 at the 400th cycle at 4.0 A g −1 . The lithium ions storage mechanism is first elucidated as a diffusion control of pure SnFe 2 O 4 and a combination of capacitive and diffusion control of SnFe 2 O 4 @C composite, respectively.