Achieving a High-Rate and Stable Li4Ti5O12 Anode via a “Three-in-One” Strategy

Improving the electronic conductivity and lithium-ion diffusion ability is quite essential for Li4Ti5O12 (LTO) anode materials. Herein, we propose a synergistic strategy to facilitate Li+ insertion/extraction and conductivity by integrating Na2TiO3 coating, Na+ doping, and oxygen vacancy engineering. The rate capability (115 mAh/g vs 70 mAh/g at 5 C) and cyclic performance (91% retention vs 58% at 10 C after 500 cycles) have all been enhanced greatly, and the underlying modulation mechanism has been revealed. First, the Na2TiO3 coating layer mitigates the corrosion of the electrolyte and inhibits the side reactions between the electrode and electrolyte. Second, Na+ doping optimizes the crystal structure, expanding the lattice parameter as well as the unit cell volume and decreasing the bond length of Li1–O, which effectively facilitates Li+ diffusion. In addition, the introduction of oxygen vacancies promotes more Ti4+ to be reduced to Ti3+ and narrows the band gap of LTO material, thus improving the electronic conductivity. This “three-in-one” synergistic strategy sheds some new light on tuning crystal structure and electronic structure for designing high-performance electrode materials.