The perfect matching between the low-cost Fe2O3 nanowire anode and the NiO nanoflake cathode significantly enhances the energy density of asymmetric supercapacitors

Abstract

The real-world applications of supercapacitors are hindered by their relatively low energy density compared with rechargeable batteries. Even with tremendous efforts in developing cathodes for aqueous asymmetric supercapacitors (AASCs), their supercapacitive performance is still severely restricted by the low specific capacitance of anodes which mostly consist of carbonaceous materials. We developed a novel low-cost anode of homogenous Fe₂O₃ nanowires grown on carbon fiber paper (CFP) that achieves a high specific capacitance of 908 F g⁻¹ at 2 A g⁻¹ and excellent rate performance (90% capacitance retention up to 10 A g⁻¹) in a wide negative potential window of 0 to −1.35 V. Such an excellent supercapacitive performance makes it a perfect anode compared with other reported ones. Matching it with the NiO nanoflake cathode (1520 F g⁻¹ at 2 A g⁻¹ in 0–0.45 V) on CFP, an extremely high energy density of 105 W h kg⁻¹ is obtained at a power density of 1400 W kg⁻¹ and still retains 72.6 W h kg⁻¹ at 12 700 W kg⁻¹ for the AASCs, which is much superior to previously reported AASCs and even exceeding those of Ni-MH batteries.