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 s , 229 ± 4 mAh g −1 at 1 A g −1 ) and superior rate capability (198 ± 6 mAh g −1 at 10 A g −1 ) within 0 ∼ −1 V. When pairing with the Ni 3 S 2 -MoS 2 battery electrode, the AAB delivered a high energy density ( E cell , 217 mWh cm −2 at a power density ( P cell ) of 661 mW cm −2 ), showing the potential of such a novel BiOCOOH negative material in battery-type charge storage.