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

Abstract 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.