Crystal Modulation of Mn‐Based Layered Oxide toward Long‐Enduring Anionic Redox with Fast Kinetics for Sodium‐Ion Batteries

Abstract

Mn‐based layered oxide cathodes for sodium‐ion batteries with anionic redox reactions hold great potential for energy storage applications due to their ultra‐high capacity and cost effectiveness. However, achieving high capacity requires overcoming challenges such as oxygen‐redox failure, sluggish kinetics, and structural degradation. Herein, we employ an innovative crystal modulation strategy, using Mn‐based Na0.72Li0.24Mn0.76O2 as a representative cathode material, which shows that the highly exposed {010} active facets enable an enhanced rate capability (119.6 mAh g−1 at 10C) with fast kinetics. Meanwhile, the reinforced Mn–O bond inhibits excessive oxidation of lattice oxygen and O–O cohesion loss, stabilizing and maintaining a long‐enduring reversible oxygen‐redox activity (100% high capacity retention after 100 cycles at 0.5C and 84.28% retention after 300 cycles at 5C). Time‐resolved operando two‐dimensional X‐ray diffraction reveals the robust structural stability, zero‐strain behavior, and suppressed phase transition with ultra‐low volume variation during cycling at different rates (0.1C: 1.75%, 1C: 0.31%, 5C: 0.04%). Additionally, the full cell coupled with hard carbon achieves a high energy density of approximately 211 Wh kg−1 with superior performance. This work highlights the significance of crystal modulation and presents a universal approach in developing Mn‐based oxide cathodes with stable anionic redox for high‐performance sodium‐ion batteries.