Defective lithium titanate oxide with stable cycling over a wide voltage window

Spinel lithium titanate oxide (Li₄Ti₅O₁₂, LTO) is a promising electrode material with a maximum capacity of 295 mAh·g⁻¹ that accommodate 5Li ions at 0.01 V. However, upon accepting 2Li ions at Wyckoff site 8a at low potentials, its capacity and stability significantly decrease because of the short Li-Li distance. To address this issue, we synthesize defective LTO (D-LTO) nanoparticles via the calcination of porous LTO. Notably, the discharge capacity of D-LTO is close to the theoretical value, and does not lead to structural decomposition in the voltage range of 3.0–0.01 V. D-LTO retain 95 % of their initial capacity after 100 cycles with a coulombic efficiency of 99.8 %. In situ synchrotron PXRD analysis and the density functional theory calculations unequivocally demonstrate the high stability of D-LTO during cyclic charge/discharge. Therefore, this simple strategy will provide insight into novel Li-ion electrode materials with high capacity and long-term stability.