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

α-FeO has high potential energy storage capacity and can serve as a green and low-cost anode material for lithium-ion batteries. However, α-FeO suffers large volume expansion and pulverization. Based on DFT calculations, TiO can effectively maintain the integrity of the crystal structure during the discharge/charge process. Well-defined cubic α-FeO is coated with a TiO layer using the hydrothermal method with the assistance of oxalic acid surface treatment, and then α-FeO@TiO 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 TiO layer, α-FeO@TiO alleviates the expansion of α-FeO 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, and the Coulombic efficiency still reaches up to 98.47% after 150 cycles at a current density of 100 mA g. Furthermore, the reversible specific capacity can return to 555.5 mA h g at 100 mA g after cycling at a high current density. Hence, the buffer chamber and the robust TiO layer can effectively improve the cycling stability and rate performance of α-FeO.