Highly reversible electrochemical magnesium/lithium insertion performance in TiO2(B) nanosheets with Ti cationic vacancies

Multivalent ion batteries show a promising future. As one of the crucial defects, cationic vacancies can improve diffusion coefficient and electronic conductivity and provide additional metal ions storage sites. Here, we prepare 2D cation-deficient TiO2(B) nanosheets (D-TiO2(B)) through the substitute of O by F. The D-TiO2(B) exhibits excellent properties of charge transfer and electrochemical kinetics. In the Mg-ion battery, the D-TiO2(B) electrode delivers a high reversible capacity of 129.4 mAh g−1 at 100 mA g−1 after 200 cycles. Furthermore, the D-TiO2(B) electrode also displays high specific capacity, good long-cycling stability and rate capability in Li-ion battery. The improved electrochemical performance is attributed to the elevated diffusion coefficient, abundant energy storage sites and reduced interface resistance due to cation vacancies and F.