Degradation, Intrinsic Microstrains, and Phase Structure Engineering in Lithium-Rich Oxide Cathode Materials

Owing to anionic oxygen redox, cathode materials containing lithium-rich oxides (LROs) exhibit a large discharge capacity exceeding 300 mAh/g. This makes them viable choices for fabrication of cathode materials for future development of lithium-ion batteries with an energy density exceeding 500 Wh/kg. However, O redox is irreversible, resulting in voltage/capacity fade with precipitation of lattice oxygen during cycling. In this work, we review the mechanism of O redox, the role of intrinsic microstrains and potential defects in O redox, and strategies to achieve a reversible O redox through artificial engineering of these intrinsic microstrains and defects. We also evaluate facile and simple methods that are effective to modify these microstrains through engineering of phase distribution, phase structure, and morphology, as well as methods for modification of intrinsic defects, so that discharge capacity can also be improved. This work provides routes to achieve high-performance LROs with a long lifespan.