Synergistic Effect of Co-Mo Pinning in Lay-Structured Oxide Cathode for Enhancing Stability toward Potassium-Ion Batteries.

Owing to the high economic efficiency and energy density potential, manganese-based layer-structured oxides have attracted great interests as cathode materials for potassium ion batteries. In order to alleviate the continuous phase transition and K re-embedding from Jahn-Teller distortion, the [Mn-Co-Mo]O octahedra are introduced into P3-KMnO herein to optimize the local electron structure. Based on the experimental and computational results, the octahedral center metal molybdenum in [MoO] octahedra proposes a smaller ionic radius and higher oxidation state to induce second-order JTE (pseudo-JTE) distortion in the adjacent [MnO] octahedra. This distortion compresses the [MnO] octahedra along the c-axis, leading to an increased interlayer spacing in the K layer. Meanwhile, the Mn/Mn is balanced by [CoO] octahedra and the K diffusion pathway is optimized as well. The proposed P3-KMnCoMoO cathode material shows an enhanced cycling stability and rate performance. It demonstrates a high capacity of 80.2 mAh g at 100 mAh g and 77.3 mAh g at 500 mAh g. Furthermore, it showcases a 2000 cycles stability with a 59.6% capacity retention. This work presents a promising solution to the challenges faced by manganese-based layered oxide cathodes and offers a deep mechanism understanding and improved electrochemical performance.