Unravelling the Solvation Structure and Interfacial Mechanism of Fluorinated Localized High Concentration Electrolytes in K-ion Batteries

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.

Automated summary

The high-concentration electrolyte has significant effects in improving the cycle life of potassium ion batteries. However, its application is challenging due to high viscosity, low conductivity, and poor electrode wettability. In this study, a fluorinated localized high concentration electrolyte (LHCE) is designed and proven to have excellent oxidation stability, low flammability, and excellent electrode wettability. The LHCE is further investigated in a half-cell and exhibits high-capacity retention upon cycling. The work provides a theoretical guidance and significant reference for electrode interphase design and engineering.