Preparation of High-Performance VN/C Supercapacitor Electrode Materials by PAM-Based Interpenetrating Network Gel Precursors

Vanadium nitride (VN) is of substantial interest for supercapacitors, owing to its high specific capacitance and high conductivity. Nevertheless, it is hindered by inherent limitations of particle agglomeration, dissolution, and oxidation during the charge/discharge process. To address these challenges, a carbon framework was constructed through thermal treatment of cross-linked polymers between polyacrylamide (PAM) and poly(p-phenylenediamine) (PPPD). Subsequently, a VN/C composite was prepared by in-situ pyrolysis of the polymer gel precursor containing adsorbed V3+ ions under a N2 protective atmosphere. This treatment enabled the in-situ formation of VN anchored to the terminal amino groups along the polymer chains. Furthermore, the effects of VCl3 mass loading (0.15–0.35 g) and temperature (700–900 °C) were studied in the synthetic process. The optimized VN/C composite with a vanadium loading of 0.25 g (denoted VN/C-0.25) sintered at 800 °C delivered a specific capacitance of 251.1 F g–1 at a current density of 0.5 A g–1. Additionally, an asymmetric supercapacitor was assembled using Ni(OH)2 as the positive electrode and VN/C-0.25 as the negative electrode. This device showed a maximum energy density of 26.0 Wh kg–1 at a power density of 511.4 W kg–1, accompanied by outstanding cycling stability over repeated charge–discharge cycles.