Achieving Ultra-High-Energy-Density Lithium Batteries: Elimination of Irreversible Anionic Redox through Controlled Cationic Disordering.

Lithium-rich layered oxides (LLOs) capable of supporting both cationic and anionic redox chemistry are promising cathode materials. Yet, their initial charge to high voltages often trigger significant oxygen evolution, resulting in substantial capacity loss and structural instability. In this study, we applied a straightforward low-potential activation (LOWPA) method alongside a relatively stable electrolyte to address this issue. This approach enables precise control over the order-to-disorder transformation of the transition metal layers in LLOs, producing an in-plane cation-disordered LiMnCoNiO that averts irreversible oxygen evolution at 4.8 V by stabilizing Mn-O or Mn-O species within the Li/Mn-disordered nanopores. Consequently, an ultrahigh reversible capacity of 322 mAh g (equating to 1141 Wh kg), 91.5% initial Coulombic efficiency, and enhanced durability and rate capability are simultaneously achieved. As LOWPA does not alter any chemical composition of LLOs, it also offers a simple model for untangling the complex phenomena associated with oxygen-redox chemistry.