Hybrid-Solvent Electrolytes for Enhanced Potassium–Oxygen Battery Performance

Rechargeable potassium-oxygen batteries (KOB) are promising next-generation energy storage devices because of the highly reversible O2/O2- redox reactions during battery charge and discharge. However, the complicated cathode reaction processes seriously jeopardize the battery reaction kinetics and discharge capacity. Herein, we propose a hybrid-solvent strategy to effectively tune the K+ solvation structure, which demonstrates a critical influence on the charge-transfer kinetics and cathode reaction mechanism. The cosolvation of K+ by 1,2-dimethoxyethane (DME) and dimethyl sulfoxide (DMSO) could greatly decrease overpotentials for the cathode processes and increase the cathode discharge capacity. Furthermore, the Coulombic efficiency for the cathode could be significantly improved with the enhanced solution-mediated KO2 growth and stripping during cycling. This work provides a promising electrolyte design approach to improve the electrochemical performance of the KOB.