Modulating the Cation Ordering in Layered Battery Electrode for Enhancing the Reversibility of Lattice Oxygen Redox

Abstract

Utilizing reversible lattice oxygen redox (OR) in battery electrodes is an essential strategy to overcome the capacity limitation set by conventional transition metal redox. However, these OR reactions frequently result in irreversible oxygen oxidation, causing local structural changes and a decline in voltage and capacity. In this work, we propose that enhancing the reversibility of lattice OR can be achieved not only by adjusting the covalency between transition metals and oxygen, but also by inducing cation-disorder in layered structures. By developing two polymorphs of Li2Ir0.75Fe0.25O3 with different levels of cation ordering, we demonstrate that the cation-disordered structure could enhance the M-O hybridization and strengthen the rigidity of the oxygen framework. This effectively reduces the structural distortion in the local oxygen environment during charging, thereby improving the reversibility of lattice OR. Our findings underscore the pivotal role of transition metal-oxygen covalency and cation ordering in enhancing the reversibility of lattice OR, which is vital for the development of high-capacity electrodes that leverage OR chemistry.

Keywords: Lattice oxygen redox, Metal-oxygen covalency, Cation ordering, Structural distortion, Layered transition metal oxides