Low‐Strain and High‐Energy KVPO 4 F Cathode with Multifunctional Stabilizer for Advanced Potassium‐Ion Batteries

KVPO 4 F with excellent structural stability and high operating voltage has been identified as a promising cathode for potassium‐ion batteries (PIBs), but limits in sluggish ion transport and severe volume change cause insufficient potassium storage capability. Here, a high‐energy and low‐strain KVPO 4 F composite cathode assisted by multifunctional K 2 C 4 O 4 electrode stabilizer is exquisitely designed. Systematical electrochemical investigations demonstrate that this composite cathode can deliver a remarkable energy density up to 530 Wh kg −1 with 142.7 mAh g −1 of reversible capacity at 25 mA g −1 , outstanding rate capability of 70.6 mAh g −1 at 1000 mA g −1 , and decent cycling stability. Furthermore, slight volume change (~5%) and increased interfacial stability with thin and even cathode–electrolyte interphase can be observed through in situ and ex situ characterizations, which are attributed to the synergistic effect from in situ potassium compensation and carbon deposition through self‐sacrificing K 2 C 4 O 4 additive. Moreover, potassium‐ion full cells manifest significant improvement in energy density and cycling stability. This work demonstrates a positive impact of K 2 C 4 O 4 additive on the comprehensive electrochemical enhancement, especially the activation of high‐voltage plateau capacity and provides an efficient strategy to enlighten the design of other high‐voltage cathodes for advanced high‐energy batteries.