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

Abstract

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]O₆ octahedra are introduced into P3-K_0.45 MnO₂ herein to optimize the local electron structure. Based on the experimental and computational results, the octahedral center metal molybdenum in [MoO₆ ] octahedra proposes a smaller ionic radius and higher oxidation state to induce second-order JTE (pseudo-JTE) distortion in the adjacent [MnO₆ ] octahedra. This distortion compresses the [MnO₆ ] octahedra along the c-axis, leading to an increased interlayer spacing in the K⁺ layer. Meanwhile, the Mn³⁺ /Mn⁴⁺ is balanced by [CoO₆ ] octahedra and the K⁺ diffusion pathway is optimized as well. The proposed P3-K_0.45 Mn_0.9 Co_0.05 Mo_0.05 O₂ cathode material shows an enhanced cycling stability and rate performance. It demonstrates a high capacity of 80.2 mAh g^-1 at 100 mAh g^-1 and 77.3 mAh g^-1 at 500 mAh g^-1 . 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.

Keywords: elements doping; layer-structured oxide; potassium-ion batteries; synergistic effect; transition metal oxide.