High‐Performance Aqueous Rechargeable K/Zn Hybrid Batteries Based on Berlin Green Cathode Materials

Abstract Abstract : Aqueous rechargeable zinc‐based batteries with the advantages of sustainability, safety, and low cost, are suitable for large‐scale electrochemical energy storage applications. In this work, aqueous zinc‐based batteries with low defect Berlin green (FeHCF) cathode, a hybrid zinc triflate and potassium triflate electrolyte, and zinc anodes are developed. In the hybrid electrolyte, the K + ions with the weak solvation effect and small electrostatic interaction are the dominant intercalation species in the FeHCF, resulting in the fast charge transfer process and rapid diffusion kinetics. The Zn 2+ ions stay at the surface rather than penetrate into the bulk phase. Thus, the hybrid batteries deliver a high specific capacity of 169.2 mAh g −1 at 100 mA g −1 , excellent rate performance with 45.7 mAh g −1 at 6 A g −1 , and good long‐term cyclability with a capacity retention of 57 % over 1000 cycles at 1 A g −1 . The results suggest using aqueous K/Zn hybrid electrolytes can improve the electrochemical performance of FeHCF.