Revealing the alkali ions effects in potential shift and Zn dendrites suppression via electrolyte concentration regulation in aqueous zinc ion batteries

Abstract

The energy density of aqueous reachable batteries (ARBs) is limited by the output voltage in the aqueous electrolyte. Herein, low-cost aqueous hybrid electrolytes composed of ZnSO4 and K2SO4 dual salts effectively improve the output voltage and suppress the zinc dendrites. The aqueous full cells assembled with potassium zinc hexacyanoferrate (KZnHCF) cathodes and zinc foil anodes reach an output voltage of 1.92 V and an energy density of 107.6 Wh kg−1. It is demonstrated the reversible insertion/extraction of K+ at the cathodes and uniform zinc deposition/striping at the anode in hybrid electrolyte via a series in-situ and ex-situ investigation. The dual salt electrolyte can not only satisfy the reversible capacitive dominated process at the cathodes but also suppress the zinc dendrite. Density functional theory (DFT) calculation demonstrates the K+ preferential intercalation mechanism of KZnHCF in hybrid electrolyte and the inhibition effect of K+ insertion on Zn2+ insertion. This strategy presents a promising approach for development of high performance and low-cost aqueous electrolyte.