Intrinsic Distortion against Jahn‐Teller Distortion: A New Paradigm for High‐Stability Na‐Ion Layered Mn‐Rich Oxide Cathodes

Abstract Layered manganese‐rich oxides (LMROs) are widely recognized as the leading cathode candidates for grid‐scale sodium‐ion batteries (SIBs) owing to their high specific capacities and cost benefits, but the notorious Jahn‐Teller (J‐T) distortion of Mn 3+ always induces severe structural degradation and consequent rapid cathode failure, impeding the practical implementation of such materials. Herein, we unveil the “intrinsic distortion against J‐T distortion” mechanism to effectively stabilize the layered frameworks of LMRO cathodes. The intrinsic distortion simply constructed by introducing bulk oxygen vacancies is systematically confirmed by advanced synchrotron X‐ray techniques, atomic‐scale imaging characterizations, and theoretical computations, which can counteract the J‐T distortion during cycling due to their opposite deformation orientations. This greatly decreases and uniformizes the lattice strain within the ab plane and along the c axis of the material, thereby alleviating the P2‐P′2 phase transition as well as suppressing the edge dislocation and intragranular crack formation upon repeated cycles. As a result, the tailored P2‐Na 0.72 Mg 0.1 Mn 0.9 O 2 cathode featuring intrinsic distortion delivers a considerably enhanced cycling durability (91.9 % capacity retention after 500 cycles) without sacrificing the Mn 3+ /Mn 4+ redox capacity (186.5 mAh g −1 at 0.3 C). This intrinsic distortion engineering paves a brand‐new and prospective avenue toward achieving high‐performance LMRO cathodes for SIBs.