Patterned anodes with an activated carbon nanotube protective layer for zinc-ion hybrid capacitors

Zinc-ion hybrid supercapacitors (ZIHCs) have appeared as an encouraging type of electrochemical energy storage system due to their high-power density, lifespan, and sustainability. Nevertheless, ZIHCs suffer from poor cycling stability owing to their limited active sites, low wettability, and irreversible Zn dendrite formation and corrosion at the anode, which results in a low specific capacity. To address this issue, research has been conducted to introduce protective layers such as carbon, ceramics, and polymers onto zinc anodes, which have improved their safety. However, achieving excellent rate-performance remains insufficient. Thus, this study fabricated a patterned anode with an activated carbon nanotube (CNT) coating. Surface activation of CNT is achieved using plasma treatment. The fabricated ZIHC exhibited a specific capacity of 136.1 mA h g⁻¹ and 83.6 mA h g⁻¹ at 0.5 A g⁻¹ and 40 A g⁻¹, respectively. It also showed enhanced energy densities of 217 W h kg⁻¹ and 167 W h kg⁻¹ at 800 W kg⁻¹ and 8000 W kg⁻¹, respectively. Additionally, the ZIHC demonstrated long-term stability with a capacity retention of 99% after 7000 cycles at 10.0 A g⁻¹, which can be attributed to its improved ion diffusion capability, reduced interfacial resistance, and superior electrochemical stability of the anode.