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 x 10(- 7) S cm(- 1), 5.57 x 10(- 7) S cm(- 1), and 7.04 x 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 degrees 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 degrees 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.