Electrolyte is critical for the electrochemical properties of potassium‐ion batteries. The high‐concentration electrolyte has achieved significant effects in inhibiting the growth of dendrites and improving the cycle life of potassium ion batteries. However, the application remains challenging owing to the issues of high viscosity, low conductivity and poor electrode wettability. Herein, a fluorinated localized high concentration electrolyte (LHCE) based on potassium bis(fluorosulfonyl) imide/dimethoxyethane is designed for use in K‐ion batteries. The electrolyte structure, interfacial mechanism and diffusion kinetics are analyzed systematically through physical/electrochemical characterization and molecular dynamics simulations. The LHCE is proven to have excellent oxidation stability, low flammability, and excellent electrode wettability. Furthermore, the LHCE is investigated in a half‐cell assembled by using polyimide‐derived nitrogen doped carbon material as an anode, which exhibits a reversible capacity of 169 mAh g−1 and high‐capacity retention upon 200 cycles at a current rate of 100 mA g−1. Fundamental mechanism on enhanced cycling stability of the carbon anodes using optimized LHCE is also investigated. This work demonstrates an example of developing new electrolytes for high performance potassium ion batteries, and also provides theoretical guidance and significant reference for electrode interphase design and engineering.

Due to their reliability, affordability and high safety, rechargeable aqueous zinc ion batteries (ZIBs) have garnered a lot of attention. Nevertheless, undesirable long-term cycle performance and the inadequate energy density of cathode materials impede the development of ZIBs. Herein, we report a layered CaV4O9-MXene (Ti3C2Tx) composite assembled using CaV4O9 nanosheets on Ti3C2Tx and investigate its electrochemical performance as a new cathode for ZIBs, where CaV4O9 nanosheets attached on the surface of MXene and interlamination create a layered 2D structure, efficiently improving the electrical conductivity of CaV4O9 and avoiding the stacking of MXene nanosheets. The structure also enables fast ion and electron transport. Further discussion is conducted on the effects of adding MXene in various amounts on the morphology and electrochemical properties. The composite shows an improved reversible capacity of 274.3 mA h g−1 at 0.1 A g−1, superior rate capabilities at 7 A g−1, and a high specific capacity of 107.6 mA h g−1 can be delivered after 2000 cycles at a current density of 1 A g−1. The improvement of the electrochemical performance is due to its unique layered structure, high electrical conductivity, and pseudo capacitance behavior.