Electrochemical Properties of Self‐Supporting Ultra‐Flexible HCNT/PANI Aerogel Electrodes With Different Thicknesses for Supercapacitors

Abstract

The development of electrode materials that combine high capacitance with flexibility is crucial for wearable electronics. This work enables in situ growth of polyaniline (PANI) in the form of nanowires, nanosheets, and oriented nanoparticles within an acidified carbon nanotube (HCNT) network, followed by construction of a double‐cross‐linked three‐dimensional porous structure comprising polyvinyl alcohol (PVA) and PANI through repeated freeze–thaw cycles. Notably, contrary to the conventional understanding that area capacitance hardly scales linearly with electrode thickness, both single‐electrode capacitance and device capacitance of assembled coin‐type supercapacitors (SCs) show a nearly proportional relationship with electrode thickness from 0.2 to 1.05 mm, demonstrating full utilization of internal active materials. The electrode is ultra‐flexible and can be bent by 180º. At 8 mA/cm 2 , the 1.05 mm thick buckypaper electrode achieves an energy density of 2.511 mWh/cm 2 , a power density of 4 mW/cm 2 , and a capacitance of 18.08 F/cm 2 . The assembled SC delivers an energy density of 0.7347 mWh/cm 2 at a power density of 4.225 mW/cm 2 , with a capacitance of 3.52 F/cm 2 and a retention of 66.7% after 5000 cycles at 8 mA/cm 2 . This electrode features a stable structure, excellent performance, and a simple preparation process, showing potential for flexible wearable energy storage devices.