Improved energy storage performance of NiS2/CoNi2S4 heterostructure with reduced graphene oxide and carbon nanofiber synergistic optimization for hybrid supercapacitor

Developing excellent electrode materials have been one of the unremitting pursuits to promote the widespread application of high-performance energy storage devices for clean and renewable energy. This work rationally designed a novel nanocomposite (NiS₂/CoNi₂S₄/RGO/CNFs, denoted as NCNS@R/C) by introducing carbon nanofibers (CNFs) and reduced graphene oxide (RGO) nanosheets to synergistically optimize NiS₂/CoNi₂S₄ heterostructure via a simple hydrothermal route. Owing to the CNFs and RGO with high conductivity and high specific surface area co-construct hierarchical porous network nanostructures, which not only helps to obtain excellent charge transport and ion diffusion kinetics, but also promotes the generated dispersion-anchored NiS₂/CoNi₂S₄ nanoparticles to present abundant exposed electroactive sites. Consequently, the NCNS@R/C electrode exhibits superior energy storage properties than the NCNS@R and NCNS@C electrodes, including high specific capacitance of 1577.7 F g⁻¹ at 0.8 A g⁻¹ and excellent rate performance (77.1 %, 0.8 → 20 A g⁻¹). Excitingly, the designed NCNS@R/C//AC hybrid supercapacitor exhibits a promising energy density of 51.4 Wh kg⁻¹ at power density of 418.3 W kg⁻¹ and an ultra-long cycle durability with 83.78 % capacitance retention after 26,000 cycles. These results demonstrate that the NCNS@R/C nanocomposite exhibits excellent electrochemical energy storage performance, and shows good application potential in low-cost, long-life and high-efficiency hybrid supercapacitors.