Polybenzoxazine-Based Nitrogen-Containing Porous Carbon and Their Composites with NiCo Bimetallic Oxides for Supercapacitor Applications

Supercapacitors (SCs) are considered as emerging energy storage devices that bridge the gap between electrolytic capacitors and rechargeable batteries. However, due to their low energy density, their real-time usage is restricted. Hence, to enhance the energy density of SCs, we prepared hetero-atom-doped carbon along with bimetallic oxides at different calcination temperatures, viz., HC/NiCo@600, HC/NiCo@700, HC/NiCo@800 and HC/NiCo@900. The material produced at 800 °C (HC/NiCo@800) exhibits a hierarchical 3D flower-like morphology. The electrochemical measurement of the prepared materials was performed in a three-electrode system showing an enhanced specific capacitance for HC/NiCo@600 (Cs = 1515 F g⁻¹) in 1 M KOH, at a current density of 1 A g⁻¹, among others. An asymmetric SC device was also fabricated using HC/NiCo@800 as anode and HC as cathode (HC/NiCo@600//HC). The fabricated device had the ability to operate at a high voltage window (~1.6 V), exhibiting a specific capacitance of 142 F g⁻¹ at a current density of 1 A g⁻¹; power density of 743.11 W kg⁻¹ and energy density of 49.93 Wh kg⁻¹. Altogether, a simple strategy of hetero-atom doping and bimetallic inclusion into the carbon framework enhances the energy density of SCs.