Bismuth oxyformate microspheres assembled by ultrathin nanosheets as an efficient negative material for aqueous alkali battery.

A negative electrode with high capacity and rate capability is essential to match the capacity of a positive electrode and maximize the overall charge storage performance of an aqueous alkali battery (AAB). Due to the 3-electron redox reactions within a wide negative potential range, bismuth (Bi)-based compounds are recognized as efficient negative electrode materials. Herein, hierarchically structured bismuth oxyformate (BiOCOOH) assembled by ultrathin nanosheets was prepared by a solvothermal reaction for application as negative material for AAB. Given the efficient ion diffusion channels and sufficient exposure of the inner surface area, as well as the pronounced 3-electron redox activity of Bi species, the BiOCOOH electrode offered a high specific capacity (C, 229 ± 4 mAh g at 1 A g) and superior rate capability (198 ± 6 mAh g at 10 A g) within 0 ∼ -1 V. When pairing with the NiS-MoS battery electrode, the AAB delivered a high energy density (E, 217 mWh cm at a power density (P) of 661 mW cm), showing the potential of such a novel BiOCOOH negative material in battery-type charge storage.