C/N/Br co-doped Li4Ti5O12/Ti3C2Tx/TiO2 nanosheet heterojunction lithium-ion battery cathode material

Abstract

Exploring high-rate and large-capacity electrode materials with superior electrical conductivity and rapid Li⁺ diffusion properties remains crucial for improving the performance of Li₄Ti₅O₁₂ (LTO) anodes. In this study, a C/N/Br co-doped Li₄Ti₅O₁₂/Ti₃C₂T_x/TiO₂ nanosheet heterojunction was synthesized through a one-step hydrothermal method. Ti₃C₂T_x MXene nanosheets with relatively low electronegativity function as conductive enhancers and substrates for LTO anchoring, whereas cetyltrimethylammonium bromide (CTAB) acts as a structural directing agent, surfactant, and dopant in the composite material. Theoretical modeling and experimental findings confirm that heterostructures and elemental doping effectively modulate the electronic structure at material interfaces, improving both the diffusion and adsorption characteristics of Li⁺. Additionally, the incorporation of flexible and conductive Ti₃C₂T_x enhances the electrical conductivity of the material and mitigates volumetric changes in the composite. The high capacity (336 mAh/g) of partially oxidized TiO₂ on the surface of Ti₃C₂T_x further contributes to the material’s electrochemical performance. The modified CNBr-Li₄Ti₅O₁₂/Ti₃C₂T_x/TiO₂ material demonstrated notable improvements in rate capability and cycling stability, achieving a capacity of 169.6 mAh/g at 20C (1C = 201.9 mAh/g) after 3000 cycles, with 100 % capacity retention. At 50C, the capacity retention is 83.82 % after 3000 cycles, with a final capacity of 124.9 mAh/g. The integration of heterostructure engineering, elemental doping, and two-dimensional nanoscale architectures offers a promising strategy for designing advanced lithium-ion anode materials with enhanced high-rate performance.