Fabrication of Nanoneedle and Nanograss Array of Ni-Mixed CuCo2S4@Ni-Foam as Binder-Free Electrode Materials for High-Performance Supercapacitor Applications

Abstract

The surface morphologies of the active electrode materials have a significant impact on the electrochemical performance of supercapacitors. The Ni-mixed CuCo₂S₄ materials were successfully prepared on Ni-Foam using the hydrothermal method followed by the sulfidation process. CuCo_1.5Ni_0.5S₄ has a nanoneedle structure, whereas CuCo_1.0Ni_1.0S₄ has a vertically aligned nanograss structure. Due to the high theoretical capacity and redox behavior of Ni, Co, and Cu elements, the low electronegativity of S atoms, favorable structural behavior, and low hydration sphere radius with high ionic mobility character of OH^– ions, the resulting CuCo_1.0Ni_1.0S₄ nanograss was used as a binder-free electrode for supercapacitor application. It has delivered outstanding specific capacity, rate capability, and cycle performance characteristics. The CuCo_1.0Ni_1.0S₄ electrode produced a maximum specific capacity of 325.5 mA h/g at a current density of 1 A/g, while maintaining good rate capability. After 5000 cycles at 20 A/g, the CuCo_1.0Ni_1.0S₄ electrode retains 86% of its initial capacity. Furthermore, the asymmetric supercapacitor device is made with CuCo_1.0Ni_1.0S₄ as the positive electrode material and activated carbon as the negative electrode material. The fabricated ASC has a maximum energy density of 38.5 W h/kg at a power density of 356 W/kg. In summary, the CuCo_1.0Ni_1.0S₄ electrode is a promising material for electrochemical energy storage and conversion applications.