Stabilization of VOPO4·2H2O voltage and capacity retention in aqueous zinc batteries with a hydrogen bond regulator

Abstract

The transformation of polyanion cathodes into oxides in aqueous Zn batteries results in voltage decay. Herein, we uncover a polyanion dissolution and oxide re-electrodeposition process for this transformation. Accordingly, the dissolution is inhibited by reducing the water activity in the electrolyte with the hydrogen bond regulator of glucose (Glu). In the 4 m Zn(OTf)₂/5.5 m Glu electrolyte, the VOPO₄·2H₂O cathode maintains the redox reactions at a high voltage of 1.6 V/1.5 V with stable capacity retention during cycling at different rates. It also shows promising electrochemical activity and stability at temperatures down to −20 °C.