Designing ester-ether hybrid electrolytes for aldehyde-based organic anode to achieve superior K-storage

Electrolyte engineering strategy has attracted high expectations for addressing the universally existed serious dynamics and thermodynamics issues in potassium-ion batteries (PIBs), especially for the batteries adopted with organic electrode materials. Herein, a new kind of ester-ether hybrid electrolytes (EEHEs) was developed with widely manipulatable solvation structures from solvent-separated ion pair (SSIP) to aggregate (AGG)-dominated states for PIBs. The optimized EEHEs of 5 M KFSI/EC+DME enabled high Coulombic efficiency and ultra-stable K plating/stripping stability in K||Cu cells and K||K symmetric cells, respectively. When the developed novel organic anode material of 2-Bromobenzene-1,3-dialdehyde/carbon nanotube (BBD/CNT) was matched with the 5 M KFSI/EC+DME electrolyte, it delivered a reversible capacity of about 288 mAh g at 50 mA g and approximately 244 mAh g at 200 mA g with negligible capacity fade. The excellent performance should be attributed to the surface capacitive-dominated mechanism with fast K-storage kinetics guaranteed by the AGG-dominated solvation structures.