Efficient high-rate aqueous alkaline battery with dual-ion intercalation chemistry enabled by asymmetric electrode polarization

Aqueous batteries hold promise for grid energy storage for their intrinsic safety and cost effectiveness. Suppressing water electrolysis is a prime consideration, while the round-trip efficiency is an often-overlooked issue. Here, we report an aqueous alkaline dual-ion battery with Na+ and OH− intercalating anode and cathode. Despite the oxygen-evolving cathode, the battery exhibits high Coulombic efficiency because oxygen evolution is suppressed by asymmetric anode and cathode polarization. Together with the low voltage loss, the battery yields a high round-trip efficiency of 77.7% at 1 A g−1. Other merits of this battery include moderate energy density and the use of safe, harmless, and cheap materials, manifesting a practical choice for grid energy storage. The ultra-fast intercalation reactions also endow the battery with high-rate performances comparable to supercapacitors. Moreover, this work proposes and verifies the concept of asymmetric electrode polarization, shifting the paradigm for electrode selection in aqueous batteries.