Direct Growth of Binder-Free CNTs on a Nickel Foam Substrate for Highly Efficient Symmetric Supercapacitors.

In the modern civilized world, energy scarcity and associated environmental pollution are the center of focus in the search for reliable energy storage and harvesting devices. The need to develop cheaper and more competent binder-free electrodes for high-performance supercapacitors has attracted considerable research attention. In this study, two different procedures are followed to enhance the growth of carbon nanotubes (CNT-E and CNT-NF) directly coated on a Ni-foam substrate by a well-functioning chemical vapor deposition (CVD) method. Thus, directly grown optimized CNT electrodes are used as electrodes for electrochemical devices. Furthermore, solid-state symmetric supercapacitors are fabricated using CNT-NF//CNT-NF, and fruitful results are obtained with maximum specific capacitance (250.51 F/g), energy density (68.19 Wh/kg), and power density (2799.77 W/kg) at 1 A/g current density. The device exhibited good cyclic stability, with 92.42% capacitive retention and 99.68% Coulombic efficiency at 10 000 cycles, indicating the suitability of the electrodes for practical applications. This study emphasizes the importance of studying the direct growth of binder-free CNT electrodes to understand the actual behavior of electrodes and the proper storage mechanism.