Interface-Mediated Jahn-Teller Effect in a Structure-Reinforced LiMnO₂ Cathode

Lithium manganese-rich oxides are promising cobalt-free cathodes, but their viability is plagued by cooperative Jahn-Teller (CJT) distortions of Mn³⁺ ions. Conventional strategies only partially mitigate this instability without addressing its electronic origin. Herein, we demonstrate a paradigm of interfacial orbital ordering to suppress CJT distortions at its root. We construct a spinel-layered LiMnO₂ heterostructure with noncollinear JT ordering (SLNC-LMO) and benchmark it against a collinear analog. Atomic-resolution imaging confirms the near-orthogonal arrangement of MnO₆ octahedra across the interfaces. Combined with density functional theory calculations, we reveal that this noncollinear ordering introduces orbital geometric frustration, which drastically reduces the e_g orbital splitting energy to 0.24 eV from 1.12 eV of the collinear structure. This near restoration of orbital degeneracy suppresses long-range distortion propagation and enhances interfacial cohesion. Consequently, the SLNC-LMO cathode delivers exceptional cycling stability, retaining 100% of its capacity after 500 cycles, far outperforming the collinear counterpart. This work establishes interfacial orbital engineering as a general design principle for stabilizing manganese-rich and other Jahn-Teller-active electrode materials.