Improve the low-temperature electrochemical performance of Li₄Ti₅O₁₂ anode materials by ion doping

We adopt the strategy of doping ions of Mg²⁺, Cr³⁺, and F⁻ into Li₄Ti₅O₁₂ (LTO) to substitute Li, Ti, and O, respectively (called the corresponding sample Mg-LTO, Cr-LTO, and F-LTO, respectively), and investigated its influences on the low-temperature electrochemical performance of LTO. After doping, the electrical conductivity of Mg-LTO, Cr-LTO, and F-LTO increased from less than < 10^− 13 S cm^− 1 to 3.07 × 10^− 7 S cm^− 1, 5.57 × 10^− 7 S cm^− 1, and 7.04 × 10^− 7 S cm^− 1, respectively. Structural refinement shows that doping has little effect on the radius of the crystal diffusion sites. Further research shows that the main reason for the improvement of low-temperature electrochemical performance is that doping affects the electrical conductivity, micromorphology, and phase composition of LTO. At −20 °C/10 C (1C corresponding to 175 mAh g^− 1), the discharge capacities of Mg-LTO, Cr-LTO and, F-LTO are 113 mAh g^− 1, 123 mAh g^− 1, and 128 mAh g^− 1, respectively. As a contrast, there is no discharge capacity for Pure LTO at the same conditions. After 600 cycles at −20 °C/5C, the discharge capacities of the sample of Pure LTO, Mg-LTO, Cr-LTO, and F-LTO are 69.7 mAh g^− 1, 107.5 mAh g^− 1, 142.3 mAh g^− 1, and 133.2 mAh g^− 1, respectively. Mg-LTO, Cr-LTO, and F-LTO exhibit excellent low-temperature rate performance and cycling stability. The related electrochemical factors and materials structure mechanisms involved were discussed in detail.