Aqueous supercapacitors possess high power density, long cycle life, and rapid charging and discharging capabilities, while their practical application is significantly limited by low energy density. The development of high-performance electrode materials, especially anodes, is crucial for enhancing the energy density of supercapacitor devices. In this work, Bi–Bi2O3 nanoparticles were anchored onto carbon fibers (Bi–Bi2O3@C) via a combined solvothermal and calcination process, using natural cotton to derive the biomass-derived carbon framework. The resulting Bi–Bi2O3@C composite was utilized as an anode material for aqueous supercapacitors, demonstrating excellent electrochemical performance with a specific capacity of 253.5 mAh g–1 (912.6 F g–1) at 1 A g–1. Furthermore, a high-performance cathode material composed of NiS2 nanoparticle-decorated Ni(OH)2 nanosheets (NiS2@Ni(OH)2) was prepared by a simple hydrothermal method to achieve optimal matching with the anode. The obtained NiS2@Ni(OH)2 nanosheets cathode composite displays high specific capacitance of 1984 F g–1 at 1 A g–1 and remarkable rate capability, retaining 57% of its original capacity even at a high current density of 10 A g–1. The constructed NiS2@Ni(OH)2//Bi–Bi2O3@C aqueous asymmetric supercapacitor (ASC) delivers a high energy density of 64.4 Wh kg–1 at a power density of 798.2 W kg–1, and maintains a high energy density of 43.1 Wh kg–1 even at a power density of 15.9 kW kg–1.
Li et al. (2026) studied this question.