W6+ & Br− codoped Li4Ti5O12 anode with super rate performance for Li-ion batteries

Abstract

We report a novel Li₄Ti_5−xW_xO_12−xBr_x (x = 0.025, 0.050 and 0.100) anode material simultaneously doped with W⁶⁺ and Br⁻ ions prepared by a simple solid-state reaction in air, aiming to significantly improve electrical conductivity of Li₄Ti₅O₁₂. Our theoretical calculation predicts that codoping with W⁶⁺ on the Ti⁴⁺ site and Br⁻ on the O²⁻ site can remarkably narrow down the band gap, and thus facilitate the electron transport in the lattice of LTO. The comparative experiments prove that W & Br-codoped LTO exhibits higher electrical conductivity compared with undoped LTO as expected, thus leading to improved rate capability and specific capacity. Particularly, Li₄Ti_5−xW_xO_12−xBr_x (x = 0.05) exhibits the best rate capability and cycling stability with an outstanding capacity retention of 88.7% even at 10 C rate after 1000 cycles. This codoping strategy with high valence transition metal and halide ions holds promise to be applied to other insulating cathode materials suffering from inferior electrical conductivity.