Electrolyte matching design for carboxylic Acid-Based organic K-Storage anode

Carboxylic acid-based organic anodes are emerging as sustainable alternatives to traditional inorganic materials for potassium-ion batteries (PIBs), owing to their potential to improve both sustainability and K-storage performance. Herein, a readily available 4-fluorobenzoic acid (4FA) supported on ordered mesoporous carbon (4FA/CMK3) is proposed as a novel K-storage anode material. Importantly, we extensively investigated the compatibility of various electrolytes with the 4FA/CMK3 anode, focusing on electrolytes with tunable solvation structures to optimize electrode/electrolyte interfacial electrochemistry. A significantly decreased amount of free solvent in the optimized ether-based electrolytes compared to conventional ester-based electrolytes provides excellent compatibility with the modified 4FA/CMK3 anode, which promotes the formation of salt anion-derived interfacial phases, thereby improving K-storage performance. As a result, the optimized 4FA/CMK3||KFSI/DME storage system delivered a reversible capacity of 164 mAh/g with Coulombic efficiency above 99.8 % after 500 cycles at high current density of 200 mA/g. These excellent electrochemical properties are attributed to the synergistic effects of 4FA modification and electrolyte solvation structure modulation, which collectively mitigate the dissolution issues of organic actives and improve the cycling life of PIBs. This work presents a novel vision for designing PIBs with high energy density and long cycle life based on carboxylic acid-based organic electrodes.