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

Manganese‐based layered oxide cathodes, particularly KxMnO2 (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. Here, lithium difluoro(oxalate) borate (LiDFOB) is introduced as an electrolyte additive to improve the performance of K‐ion batteries. LiDFOB creates a uniform, thin, and robust cathode‐electrolyte interphase layer on the K0.5MnO2 cathode surface, which enhances the reaction kinetics, prevents manganese dissolution, and stabilizes the structure. In K||K0.5MnO2, the capacity retention is 78.6% at 100 mA g−1 after 300 cycles in the presence of LiDFOB.