Nb-doped Li₄Ti₅O₁₂-TiO₂ hierarchical microspheres as anode materials for high-performance Li-ion batteries at low temperature

Nb-doped Li₄Ti₅O₁₂-TiO₂ (Nb-LTO-TO) hierarchical microspheres are successfully synthesized by a facile hydrothermal route and subsequent annealing. The doping of Nb⁵⁺ enables partial reduction of Ti⁴⁺ to Ti³⁺, improving the conductivity of the composites and expanding the crystal lattice to increase the lithium-ion diffusion coefficient. Accordingly, Nb-LTO-TO shows a much improved low-temperature capacity compared with undoped LTO-TO when used as an anode material for Li-ion batteries. The discharge capacity of the Nb-LTO-TO composite under a current rate of 1 C reached 128.6 mAh g⁻¹ at − 20 °C (85.8% utilization of the capacity of Nb-LTO-TO at room temperature), as well as a long-term stability of 500 cycles at a utilization of 93.9%. A discharge capacity of 119.4 mAh g⁻¹ can still be reached at − 20 °C under a high current rate of 5 C. This encouraging performance sheds light on the design of advanced anodes for high-performance Li-ion batteries at low temperature.