Development of NiO-BCN nanocomposite electrodes through in-situ polymerization for flexible supercapacitors capable of powering temperature sensors

The integration of two-dimensional materials with transition metal oxides offers synergistic electrochemical properties for supercapacitors. A nickel oxide/boron carbonitride (NiO/BCN) nanocomposite is synthesized via in-situ polymerization. X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR) confirm the cubic crystalline NiO framework strongly interfaced with aromatic BCN via van der Waals forces. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution TEM (HR-TEM) reveal uniform nanostructures. Electrochemical performance is assessed by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) within 0–0.55 V in 3 M potassium hydroxide (KOH). The NiO/BCN electrode delivers 813 F g⁻¹at 0.9 A g⁻¹, outperforming individual components. Density functional theory (DFT) analysis indicates improved electronic conductivity from interfacial metallicity and charge transfer. A flexible symmetric supercapacitor (SSC) using a gel polymer electrolyte (GPE) achieves 789 F g⁻¹at 1 A g⁻¹, with an energy density of 26.4 Wh kg⁻¹and a power density of 245 W kg⁻¹. It retains 81.96 % capacitance after 350 cycles and maintains performance under bending at 45°, 90°, and 180°. It powers a 1.5 V digital sensor for ∼120 s after direct current (DC) charging. These results highlight NiO/BCN nanocomposites as promising for flexible, wearable energy storage.