Doping the Li₄Ti₅O₁₂ lattice with extra-large anions

Doping is always serving as an effective way to improve the performance of electrode materials of lithium ion batteries (LIBs). This study reports the synthesis of a well-defined Li₄Ti₅O₁₂−xBrx anode (x = 0–0.4) using a conventional solid-state reaction method. Atomic resolution scanning transmission electron microscopy revealed that the large-radius Br dopant was uniformly distributed and occupied the specific locations of oxygen ions in spinel Li₄Ti₅O₁₂ leading to slight lattice expansion. A density functional theory calculation (DFT) further confirmed the obtained experimental results and demonstrated the change of the local fine structure due to the large radius of the dopant Br. The electrochemical performance of the Br-doped Li₄Ti₅O₁₂ was improved, as confirmed by both theoretical calculations and experimental results. These results provide new insights into improving the electrochemical performance of electrode materials for lithium ion batteries by introducing large-radius anions.