Strengthening the Hydrogen-Bond Network for Practical Aqueous Aluminum–Air Battery

Abstract

The aqueous aluminum–air (Al–air) battery demonstrates promising applications in energy storage and conversion due to its high energy density and cost effectiveness. Nevertheless, it suffers from the grievous corrosion of the Al anode and parasitic hydrogen evolution reaction (HER). Herein, a strategy that manipulates the H-bond network of the electrolyte is applied to alleviate the parasitic reactions. It is verified that the introduced low-cost urea (CO(NH2)2) molecules with abundant N and O atoms can significantly strengthen the H-bond in the electrolyte and reduce the water activity, thereby effectively inhibiting the HER at the Al metal anode. The hydrogen evolution tests demonstrate that the HER rate decreases by 82% in the optimized electrolyte. Moreover, the performances of Al–air full cells are greatly improved, and the specific capacities based on Al anodes can reach 2330 mAh g–1 at 35 mA cm–2, far higher than that of a pristine electrolyte (4 M KOH, 1052 mAh g–1). Furthermore, in the on–off cycle discharge tests that simulate real applications, the operating life of the cell is extended by about 3 times. This approach of strengthening the H-bond network should shed some light on improving aqueous Al–air batteries as well as other aqueous batteries.