Redox Couple Strategy for Improving the Oxygen Redox Activity and Reversibility of Li- and Mn-Rich Cathode Materials.

Abstract

The specific capacity of Li- and Mn-rich layered oxide (LMROs) cathodes can be enhanced by the oxidation of lattice oxygen at high voltages. Nevertheless, an irreversible oxygen loss emerges with cycling, which triggers interlocking surface/interface issues and results in the fast deterioration of cycling performance. Herein, we prepare a surface modified LMRO electrode by one step doctor-blade casting and introducing a benzoquinone species DBBQ redox couple. The electrochemical test shows that the DBBQ-modified electrode has a high reversible capacity (>320 mAh g-1) and excellent rate performance, while the cyclic stability has been significantly improved as well. The capacity retention reaches as high as 93.3% after 500 cycles at 1 C. Mechanism analysis shows that DBBQ can not only play a redox couple in LMROs which achieves the adsorption and reduction of surface oxygen gas but also significantly enhance anionic redox in the bulk, thus realizing extraordinary capacity.