In Situ Structure Modulation of Cathode-Electrolyte Interphase for High-Performance Potassium-Ion Battery

Manganese-based layered oxide cathodes, particularly K x MnO 2 (KMO), have shown great potential in potassium-ion batteries (PIBs) due to their low cost, high theoretical capacities, and excellent thermal stability. However, Jahn-Teller distortion, manganese dissolution, and interface instability of electrode/electrolyte lead to structural instability and performance decay. Here, lithium difluoro(oxalate) borate (LiDFOB) is introduced as an electrolyte additive to improve the electrochemical performance of P3-type KMO. LiDFOB creates a uniform, thin, and robust cathode-electrolyte interphase layer on the cathode surface, enhancing reaction kinetics, preventing manganese dissolution, and stabilizing the structure. The P3-KMO cathode with LiDFOB in the basic electrolyte exhibits significantly improved electrochemical performance, such as a remarkable Coulombic efficiency of ≈99.5% and high capacity retention of 78.6% after 300 cycles at 100 mA g −1 . Moreover, the full cell of P3-KMO||soft carbon demonstrates satisfactory specific capacity and energy density. This study emphasizes the importance of interface chemistry for PIBs.