Manipulating the Electronic Structure of Li-Rich Manganese-Based Oxide Using Polyanions: Towards Better Electrochemical Performance

摘要

Lithium-rich manganese-based layered oxides show great potential as high-capacity cathode materials for lithium ion batteries, but usually exhibit a poor cycle life, gradual voltage drop during cycling, and low thermal stability in the highly delithiated state. Herein, a strategy to promote the electrochemical performance of this material by manipulating the electronic structure through incorporation of boracic polyanions is developed. As-prepared Li[Li_(0.2)Ni_(0.13)Co_(0.13)Mn_(0.54)](BO_4)_(0.015)(BO_3)_(0.005)O_(1.925) shows a decreased M-O covalency and a lowered O 2p band top compared with pristine Li[Li_(0.2)Ni_(0.13) Co_(0.13)Mn_(0.54)]O_2. As a result, the modified cathode exhibits a superior reversible capacity of 300 mA h g~(-1) after 80 cycles, excellent cycling stability with a capacity retention of 89% within 300 cycles, higher thermal stability, and enhanced redox couple potentials. The improvements are correlated to the enhanced oxygen stability that originates from the tuned electronic structure. This facile strategy may further be extended to other high capacity electrode systems.