Breaking the diffusion coefficient limitation of bismuth oxide anodes for aqueous alkaline batteries with ultra-high rate capability†

Owing to the limitation of the diffusion rate of electrolyte ions, the two key parameters of energy density and power density of energy storage devices seem contradictory, and the construction of “double-high” electrode materials is the key challenge in the electrochemical energy storage field. To achieve outstanding capacity retention at high charging/discharging current density, a hierarchical porous amorphous bismuth oxide anode (A-Bi₂O₃) was constructed via an ion-exchange strategy using a Bi-based metal–organic framework as the precursor. Under a suitable alkaline solution, organic anions will be gradually substituted by OH⁻ anions to form rich mesoporous channels, and the residual ligand can fix or functionalize the as-formed BiO_x crystallites to form amorphous configuration, which provides tree vein-like channels for fast and deep electrolyte ion feeding. Therefore, the optimized A-Bi₂O₃ cathode presents a high capacity of 319.6 mA h g⁻¹ at 1 A g⁻¹ and excellent retention rate of 83.7% when the current density was increased to 30 A g⁻¹. Furthermore, the fabricated H-Ni(OH)₂//A-Bi₂O₃ aqueous alkaline battery (AAB) shows a high energy density of 104.58 W h kg⁻¹ at 0.24 kW kg⁻¹ and can make an electronic thermometer work for 30 min with a charging of several seconds.