Regeneration of Degraded Li-rich Layered Oxide Materials Through Heat Treatment-Induced Transition Metal Reordering

Abstract Lithium-rich layered oxides (LRLO) have drawn great attention recently as a high energy density cathode material. However, the practical deployment of this materials is hindered by voltage and capacity decay during electrochemical cycling. Applying mild thermal energy to cycled LRLO materials allows to recover the decayed voltage. In this work, a detailed mechanism study of the voltage and structure recovery is conducted through various analytical tools. Heat treatment provides the necessary energy for the transition metal to overcome the kinetic barrier to move from honeycomb center to honeycomb vertex and recover the honeycomb ordering in the transition metal layer. An ambient-air relithiation using Li+ molten salt was also conducted along with the heat treatment to the cycled LRLO cathode and lead to a material regeneration in both the voltage and capacity. This work identifies the transition metal reordering as the key factor under the structure recovery of degraded LRLO materials. It opens a door for the promising strategies to mitigate the voltage and capacity degradation problem in LRLO and provides the potential routes to recycle degraded LRLO materials.