High-performance and dendrite-free Zn/KZnHCF batteries boosted by aqueous electrolyte mixed with ethanol

Abstract

Aqueous Zn-based batteries (AZBs) have attracted great attention due to their high safety, low cost, and environmental friendliness. However, the Zn anode suffers from problems such as the formation of Zn dendrites. And there are only few active cathode materials which can allow the insertion/extraction of Zn 2+ ions. Thereinto, Prussian blue analogs (PBAs) are promising active cathode materials for AZBs, having high operation voltage but poor electrochemical stability. Herein, K 2 Zn 3 [Fe(CN) 6 ] 2 (KZnHCF) particles with cubic morphology are prepared for AZBs, and the electrochemical stability is improved by simply adjusting the composition of the electrolyte solvent in the battery system. Electrochemical tests indicate that the electrolyte with ethanol (EA) as solvent can promote the uniform deposition of zinc, thereby inhibiting the growth of Zn dendrites. Furthermore, ex-situ XRD results prove that the structural damage of KZnHCF during charging-discharge process is greatly alleviated when EA is used as the electrolyte solvent. Nonetheless, using pure EA as electrolyte solvent exposes the batteries to potential safety hazards, and compared with the Zn/KZnHCF batteries with H 2 O as solvent, the specific capacities of the batteries with EA as solvent are lower. Hence, the mixed electrolytes with different volume ratios (H 2 O/EA-1:1, H 2 O/EA-1:2, H 2 O/EA-2:1) are applied. It’s obvious that not only the growth of zinc dendrites is suppressed, but also the electrochemical performances of the batteries are further improved. Overall, a dendrite-free and high-performance Zn/KZnHCF battery is obtained by using a mixed electrolyte solvent (H 2 O/EA-1:1), presenting average specific capacities of 50.0, 49.0, 46.3, and 43.2 mAh g −1 at current densities of 50, 100, 150, and 200 mA g −1 , and remaining a specific capacity of 29.1 mAh g −1 at a current density of 200 mA g −1 after 500 cycles. • A dendrite-free and high-performance Zn/KZnHCF battery is created. • The inhibition effect of ethanol on the growth of Zn dendrites is clarified. • The effect of different electrolyte solvents is investigated by ex-situ XRD tests. • As-prepared Zn/KZnHCF batteries are superior to the reported aqueous zinc batteries.