Enhanced electrochemical performance of Ti-doped Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ for lithium-ion batteries

Lithium-rich manganese-based layer-structured oxides (xLi₂MnO₃⋅(1-x)LiNi_1/3Co_1/3Mn_1/3O₂) have attracted great attention for their potential applications as cathode materials of high energy-density lithium ion batteries. However, these oxides suffer from inferior cycling and poor rate capability due to presence of the Li₂MnO₃ phase. Herein, the Li⁺ ions in the Li-layer of the Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ (or 0.5Li₂MnO₃⋅0.5LiNi_1/3Co_1/3Mn_1/3O₂) are partially substituted with aliovalent Ti⁴⁺ ions to improve its long-term cycling stability and rate performance. The obtained oxide (Li_1.2-xTi_xMn_0.54Co_0.13Ni_0.13O₂, x = 2.5%) exhibits an initial capacity of 320 mAh g⁻¹ and a capacity retention of 71% after 300 cycles as well as good rate performance. In addition, although Ti doping cannot prevent the transformation from the layered to the spinel-like phase, it stabilizes the structure of the spinel-like phase below 3.0 V. Based on first-principles calculations and performance evaluation, these improvements are attributed to the Ti-doping induced enhancement in conductivity, diffusion, activation energy of Mn migration and [Formula presented] bonding. This novel design may furthermore open a door for the synthesis of lithium-rich materials with high rate performance.