Morphological Tailoring of Transition Metal Tungstate Nanoreinforced Composite: A Key to Unlock High-Performance Supercapacitors

Nickel tungstate (NW) is a favorable probe material for supercapacitors (SCs), but optimizing its material properties and morphology for better activity and stability remains challenging. The annealing temperature crucially affects metal tungstate’s material properties, phase formation, and morphology. This study employs solvothermal synthesis and calcination at 550 °C (NW-1), 650 °C (NW-2), and 750 °C (NW-3) to produce NW nanoparticles for SC electrodes, with graphene oxide (GO) incorporated to enhance electrochemical performance. The synthesized materials were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy-energy dispersive X-ray (SEM-EDX), Raman spectroscopy, and high-resolution transmission electron microscopy (HR-TEM). Higher calcination temperatures altered the NW morphology from spherical to spindle-like structures. Notably, NW-3 exhibited significant improvements in morphology and electrochemical properties while maintaining the NW phase structure. These enhancements, including improved conductivity, increased redox activity, and reduced internal resistance, are attributed to the mutual enhancement of GO’s carbon-based material and NW’s pseudocapacitive properties. Among the samples, the NW-3/GO composite demonstrated the maximum specific capacitance of 794 F g–1 at 1 A g–1. In a 1 M KOH electrolyte, a solid-state symmetric SC (NW-3@GO//NW-3@GO, SSC) attained a supreme energy density of 132.8 Wh kg–1 and a power density of 2863 W kg–1. The SSC retained 85% of its capacitance after 5000 cycles at 10 A g–1. These results highlight the potential of NW-3@GO as an optimized electrode for SCs.