Abstract

Rechargeable aqueous Zn batteries are promising energy storage devices owing to the high capacity of Zn anode, high safety and cost-effectiveness1, but they all suffer from severe hydrogen evolution at the anode2. Here, we explore the use of highly alkaline electrolytes to reduce the activity of water and suppress the hydrogen evolution. In a near-saturation 15 M KOH electrolyte, spectroscopic characterizations reveal distinct the solvation structure associated with the low water activity. Despite the high viscosity, the highly alkaline electrolyte retains high ionic conductivity due to the unique hydroxide transfer mechanism, which enables a high-power Zn-air battery that is stable for over 110 hours. Reference 1. Wang, F.; Borodin, O.; Gao, T.; Fan, X.; Sun, W.; Han, F.; Faraone, A.; Dura, J. A.; Xu, K.; Wang, C. Nature Materials, 2018, 17, 543–549. 2. Fu, J.; Cano, Z. P.; Park, M. G.; Yu, A.; Fowler, M.; Chen, Z. Advanced Materials, 2017, 29, 1604685.