Delocalized Li@Mn6 superstructure units enable layer stability of high-performance Mn-rich cathode materials

Abstract

<h2>Summary</h2> The search for cathode materials with high energy density, long-term cycling stability, and low cost is one of the most important challenges for current lithium-ion batteries. To address the structural instability in Mn-rich layered cathodes, we demonstrate herein through thorough experimental and theoretical studies that delocalizing Li@Mn₆ superstructure units within transition-metal layers is an effective strategy to enhance the layer stability of a Li-excess Mn-rich layered oxide (LMRO) cathode. The delocalized Li@Mn₆ superstructure units can not only increase the Mn valence to inhibit the adverse Jahn-Teller effect but also harness the anionic redox activity with suppressed O–Mn₀ species. Benefited from its stable layered structure, the LMRO cathode can retain a high capacity and energy density of 251 mA h g⁻¹ and 791 W h kg⁻¹, respectively, after 100 cycles with nearly 100% retention. This work provides a feasible route to develop the high-performance layered cathodes with stable anionic redox chemistry.