Sr-dopant microstructure engineering enables strong pseudocapacitive effects of TiNb2O7 anode for fast-charging lithium-ion batteries

Abstract

TiNb₂O₇ (TNO) is a potential high-power type of anode owing to its extremely fast charging speed, but its actual application is limited by the inherent low electron/ion conductivity. Herein, TNO doped with the alkaline earth metal strontium (Sr) is designed to overcome these drawbacks. The ion conductivity is enhanced due to the expansion of the ion transport path caused by the large ion radius of doped Sr. Meanwhile, more oxygen vacancies change the electronic structure of the TNO anode, thereby improving the electronic conductivities. Therefore, the electrochemical performance of Sr-TNO is significantly improved, where the Sr_0.01-TNO electrode shows an excellent discharge capacity of 237.0 mAh g⁻¹ at 1C after 150 cycles and outstanding rate capability, especially at 40C (196 mAh g⁻¹). Furthermore, the LiFePO₄|Sr_0.01-TNO full cell demonstrates excellent cycling stability, maintaining a stable structure and morphology after cycling. This work offers insights for developing fast-charging TNO-based lithium-ion batteries with long cycle life and high rate capability.