Chemical reduction-induced defect-rich bismuth oxide-reduced graphene oxide anode for high-performance supercapacitors.

We prepare bismuth oxide-reduced graphene oxide (BiO-rGO) composite anode using a one-step chemical precipitation/reduction method. Under a reducing atmosphere, oxygen atoms on the surface of BiO are gradually removed and neighboring oxygen atoms migrate to the surface, leaving oxygen vacancies. Defective BiO enhances the number of active sites, providing additional pseudocapacitive performance. The transition metal oxide-based BiO acts as an anode, providing capacitive performance that far exceeds that of conventional carbon materials. Moreover, the introduction of rGO forms a conductive network for BiO, improving capacitive contribution and ion diffusion capabilities for the electrode. The BiO-rGO-100 (GO added at 100 mg) exhibits a high specific capacitance of 1053F/g at 1 A/g, significantly higher than that of BiO (866F/g). The BiO-rGO-100 anode and NiCo-rGO cathode are assembled into a battery-type supercapacitor. The coin-cell device achieves an energy density of 88.2 Wh kg at a power density of 850 W kg. The NiCo-rGO//BiO-rGO-100 pouch-cell device demonstrates an extremely low R of 0.77 Ω. At a power density of 850 W kg, the energy density reaches 118.5 Wh kg, and remains 67.4 Wh kg at 8500 W kg.