(Invited) Reaction Mechanism of Lithium-Rich Layered Cathode Materials in Thin-Film Solid-State Battery

Abstract

Lithium excess layered cathode materials are a promising cathode candidate because the higher discharge capacity. Among them, Li2MnO3 has the highest Li content and understanding the reaction mechanism during cycling is critical for using the material. We fabricated the cathode films and studied the reaction mechanisms by in-situ and methods using surface X-ray diffraction and operando HAXPES analyses. Experiments revealed a structural change to a high-capacity phase that proceeded gradually with cycling. First-principles calculations suggested that the activated phase has O1 stacking. We propose a mechanism: charging to a high voltage at a low Li concentration induces an irreversible transition to a phase detrimental to cycling that could, but not necessarily, be accompanied by the dissolution of Mn and/or the release of O into the electrolyte.