A theoretical framework for oxygen redox chemistry for sustainable batteries

Abstract

Lithium-rich layered oxides have emerged as a new model for designing the next generation of cathode materials for batteries to assist the transition to a greener energy system. The unique oxygen redox mechanism of such cathodes enables extra energy storage capacity beyond the contribution from merely transition metal ions; however, their practical application is hindered by the destabilizing structural changes during operation. Here we present a theoretical framework for the triptych of structural disorder, bond covalency and oxygen redox chemistry that applies to a wide range of layered oxides. It is revealed that structural disorder stabilizes the oxygen redox by promoting the formation of oxygen covalent bonds in favour of electrochemical reversibility. Oxygen dimers are found to move freely within the lattice structure and serve as a key catalyst of the poor structural resilience. Such fundamental understanding provides fresh insights that could inform strategies to mitigate the limitations of anionic redox cathodes, moving us a step closer to tapping into their enormous potential. Anionic redox has emerged as a new frontier in the design of high-energy cathode materials for next-generation batteries. This study provides a theoretical framework to understand the trilateral correlation of oxygen redox, structural disorder and bond covalency.