Review—Recent Advances and Remaining Challenges for Lithium Ion Battery Cathodes

Electrodes prepared from lithium-rich (Li-rich) xLi 2 MnO 3 ⋅(1-x)LiNi a Co b Mn c O 2 materials (a + b + c = 1) show extremely high discharge capacities, arising from excess Li + present in their Li 2 MnO 3 component, and the ability to reversibly store charge with O 2− anions. These electrodes suffer serious voltage and capacity fading however, due to the migration of transition metals to the Li-layer at advanced states of charging, partial structural layered-to-spinel transformation and other reasons. In this focus paper, the current understanding of the above materials is summarized, briefly concluding with attempts by our groups to mitigate the voltage and capacity fade of these electrodes.