Achieving Ultrahigh Cycling Stability of LiMnFePO Through Oxygen Vacancy with Jahn-Teller Distortion Accommodation Induced by B-Doping at P-site.

The development of lithium manganese iron phosphate (LiMnFePO) as a high-energy-density cathode material offers significant advantages over LiFePO, but its practical application is hindered by the Jahn-Teller distortion induced by Mn during charge-discharge cycles, leading to reduced cycling stability. In this study, B-doping at the P-site through a solvothermal method is introduced, which induces the formation of oxygen vacancies. These vacancies result in the partial removal of oxygen from MnO octahedra, creating structural flexibility to accommodate Jahn-Teller distortion, thereby enhancing the cycling stability of LiMnFePO. The B-doped sample, LiMnFePBO/C (LMFP-B3/C), exhibited superior electrochemical performance, retaining 98.09% of its capacity after 1000 cycles at a 1C rate, with a final capacity of 121.43 mAh g. In contrast, the undoped sample retained only 74.28% of its capacity under the same conditions, with a final capacity of 86.17 mAh g. Density functional theory (DFT) calculations confirmed that the presence of oxygen vacancies not only mitigates lattice volume changes during cycling but also reduces Li⁺ migration barriers. This work provides critical insights into the role of B-doping and oxygen vacancies in stabilizing the structure and improving the electrochemical performance of phosphate-based cathode materials, paving the way for more durable and efficient lithium-ion batteries.