Robust α-Fe2O3@TiO2 Core-Shell Structures With Tunable Buffer Chambers for High-Performance Lithium Storage

alpha-Fe2O3 has high potential energy storage capacity and can serve as a green and low-cost anode material for lithium-ion batteries. However, alpha-Fe2O3 suffers large volume expansion and pulverization. Based on DFT calculations, TiO2 can effectively maintain the integrity of the crystal structure during the discharge/charge process. Well-defined cubic alpha-Fe2O3 is coated with a TiO2 layer using the hydrothermal method with the assistance of oxalic acid surface treatment, and then alpha-Fe2O3@TiO2 with tunable buffer chambers is obtained by altering the hydrochloric acid etching time. With the joint efforts of the buffer chamber and the robust structure of the TiO2 layer, alpha-Fe2O3@TiO2 alleviates the expansion of alpha-Fe2O3 during the discharge/charge process. The optimized sample (FT-1h) achieves good cycling performance. The reversible specific capacity remains at 893.7 mA h g(-1), and the Coulombic efficiency still reaches up to 98.47% after 150 cycles at a current density of 100 mA g(-1). Furthermore, the reversible specific capacity can return to 555.5 mA h g(-1) at 100 mA g(-1) after cycling at a high current density. Hence, the buffer chamber and the robust TiO2 layer can effectively improve the cycling stability and rate performance of alpha-Fe2O3.