Electrolyte engineering for a highly stable, rechargeable hybrid aqueous battery

Abstract

Abstract The zinc electrode in secondary zinc batteries suffers from many side reactions, namely corrosion, hydrogen evolution, passivation, and dendrite formation. This electrode also suffers from changes in surface textures, mechanical properties, and volume increases due to the formation and growth of porous space inside the zinc electrode. Keeping the zinc electrode from deterioration is a major challenge because one must address multiple problems at a time. In this study, we introduce a three-functional electrolyte based on ethylene glycol oligomers and aqueous components. When in contact with this electrolyte, the corrosion current density decreases by 37%, which means that corrosion and hydrogen evolution are partially mitigated. The chronoamperometry current density decreases by 77.5%, complemented by a nearly flat and layered zinc deposit (confirmed by SEM and ex situ XRD). Applying this concept to a typical Zn/LiMn2O4 battery with 2 M Li2SO4 and 1 M ZnSO4 mixed electrolyte, the capacity retention is up to 80.2% after 1000 charge-discharge cycles at 4 C rate. This is approximately 12% higher than that of the reference battery using an aqueous electrolyte. Furthermore, the float charge current under constant voltage (2.1 V) dramatically decreases by approximately 36% versus the float charge current of the reference battery, and the rate capability is nearly maintained.