Hydrogen-bond network manipulation of aqueous electrolytes with high-donor solvent additives for Al-air batteries

Aqueous electrolyte is one of the most favored choices for various high-energy, low-cost and safe batteries. However, the undesired parasitic hydrogen evolution reaction (HER), especially on high reactive metal anodes, brought by aqueous electrolyte remains the development bottleneck of these batteries. Here, introducing solvents to manipulate the hydrogen-bond network of aqueous electrolyte is proposed to suppress the parasitic HER. Significantly, theoretical simulations and experimental characterizations demonstrate that donor number of the solvents could serve as a descriptor to ability of confining the free water and reducing the water activity. The solvent additive with high donor number exhibits remarkable suppression on the self-discharge and hydrogen evolution of Al anodes in alkaline electrolyte, which endows a flow-based Al-air battery with an outstanding energy density of 3106.04 Wh kg−1. The findings not only provide a guidance on the rational design of aqueous electrolyte but also expand the application of high-donor solvents.