Rational design of spherical NiCoB@rGO nanocomposites for efficient electrochemical energy storage

Research on the synthesis of electrode materials for the fabrication of efficient supercapacitors has attracted considerable attention over the past few decades. Although numerous materials with excellent electrochemical characteristics have been reported, key challenges such as high cost, complex synthesis, low electrochemical activity, and absence of long-term cycling stability remain inadequately addressed. In this study, six distinct types of NiCoB@rGO nanocomposites with varying rGO loadings were synthesized, systematically characterized using various spectral techniques and used for the fabrication of six different electrodes. These electrodes were studied extensively using CV, GCD and EIS techniques, and the obtained data were used for the calculation of specific capacitance (C_s), energy density (E_D) and power density (P_D) individually. Among them, NiCoB@rGO (0.75%) exhibits a high specific capacitance of 1791.66 F g^-1 at 1 A g^-1 with a retention rate of 30% at 15 A g^-1 in a three-electrode configuration. Galvanostatic charge-discharge studies reveal 91% capacitance retention with a coulombic efficiency of 99.98% after 5000 cycles. A symmetric supercapacitor fabricated using NiCoB@rGO (0.75%) delivers a specific capacitance of 262.5 F g^-1 at 1 A g^-1, an energy density of 23.33 Wh kg^-1, and a power density of 399.94 W kg^-1 while retaining 92% of its initial capacitance after 2000 cycles. Furthermore, the asymmetric supercapacitor exhibits a specific capacitance of 131.8 F g^-1 with an energy density of 46.86 Wh kg^-1 and a power density of 800 W kg^-1, maintaining 93% capacitance retention over 2000 cycles. The successful illumination of red, green, and blue LEDs connected in series using the NiCoB@rGO (0.75%)//AC asymmetric supercapacitor demonstrates its practical applicability for high-energy commercial supercapacitor systems.