High-Microporous CNT-Composited Carbon as Electrode for Aqueous Supercapacitor with Large Energy Density

Carbon nanotubes (CNTs) exhibit superior conductivity but are hindered by a low energy density (<10 Wh/kg) when used as electrodes for supercapacitor energy storage, primarily due to their limited electrochemically active surface area. In this study, we propose a composting strategy to produce a CNT–carbon composite through a ball-milling process involving mixing, carbonizing, and activating CNT and glucose. The resulting composite, referred to as CGK, demonstrates a high microporosity (ranging from 38.1% to 98.5%), significantly increased surface area (390 m2/g compared to 181 m2/g for CNT alone), and a considerable presence of oxygen-containing functional groups such as −C–O, –C═O, and O–C═O. When utilized as an electrode in supercapacitors, the CGK samples (specifically CGK1–3) prepared with the optimal CNT-to-glucose ratio display a notable capacitance of 301 F/g at 1.0 A/g, far surpassing the 121 F/g at 1.0 A/g capacitance exhibited by pure CNTs. Additionally, the CGK samples exhibit a high energy density of 20.6 Wh/kg at 925 W/kg, compared to 14.3 Wh/kg at 1000 W/kg for CNTs alone and some recently reported carbon-based symmetric supercapacitors. Notably, the cycling stability of the CGK electrodes is exceptional, maintaining over 98% capacitance retention after 30,000 charge/discharge cycles. Overall, this work presents a straightforward and versatile approach for synthesizing highly microporous carbon materials doped with heteroatomic functionalities, offering a promising alternative for various applications.