Synergistic integration of cobalt phosphide and jute carbon in a high-performance asymmetric supercapacitor for enhanced energy storage and long-term stability

The growing demand for efficient and sustainable energy storage systems drives increasing interest in high-performance supercapacitors. In this work, cobalt phosphide (CoP₃) is synthesized via a vapor-phase phosphorization process and used as a positive electrode, while biomass-derived jute carbon (JC) serves as the negative electrode in an asymmetric supercapacitor using a 3 M NaOH electrolyte. Structural characterization confirms the formation of a highly crystalline orthorhombic CoP₃ phase with a grain-like, porous morphology that enhances electrolyte accessibility and charge transport. Electrochemical analysis reveals a predominantly pseudocapacitive charge storage mechanism with mixed capacitive–diffusive behavior, supported by cyclic voltammetry, impedance spectroscopy and kinetic estimation. In the assembled CoP₃//JC device, an energy density of 29.7 Wh kg⁻¹ is achieved at a current density of 0.1 A g⁻¹, corresponding to a power density of 327 W kg⁻¹, indicating a favorable balance between energy and power output. At higher current density (5 A g⁻¹), the energy density decreases to 13 Wh kg⁻¹, while the power density increases to 2301.9 W kg⁻¹. The device exhibits excellent long-term stability, retaining 95% of its capacitance after 10,000 cycles with a Coulombic efficiency of 99.8%. These results highlight the synergistic integration of CoP₃ and sustainable jute carbon as an effective strategy for developing durable and high-performance supercapacitor systems.