Bulk Modification of Porous TiNb 2 O 7 Microsphere to Achieve Superior Lithium‐Storage Properties at Low Temperature

Abstract TiNb 2 O 7 , as a promising alternative of Li 4 Ti 5 O 12 , exhibits giant potential as low‐temperature anode due to its higher theoretical capacity and comparable structural stability. However, the sluggish electronic conductivity still remains a challenge. Herein, bulk modification of Cu + doping in porous TiNb 2 O 7 microsphere is proposed via a simple one‐step solvothermal method with subsequent calcination treatment. The results show that the electronic conductivity is improved effectively due to the reduced band gap after doping, while enhanced lithium‐ion diffusion is achieved benefiting from the increased interplanar spacing. Therefore, the optimal sample of Cu 0.06 Ti 0.94 Nb 2 O 7 exhibits a high reversible capacity of 244.4 mA h g −1 at 100 mA g −1 after 100 cycles, superior rate capability, and long‐term cycling stability at 1000 mA g −1 at room temperature. Particularly, it can also display good performance in a wide temperature range from 25 to –30 °C, including a reversible capacity of 76.6 mA h g −1 at –20 °C after 200 cycles at 200 mA g −1 . Moreover, Cu 0.06 Ti 0.94 Nb 2 O 7 //LiFePO 4 full cell can deliver a high reversible capacity of 177.5 mA h g −1 at 100 mA g −1 . The excellent electrochemical properties at both ambient and low‐temperatures demonstrate the great potential of Cu + ‐doped TiNb 2 O 7 in energy‐storage applications.