Nanocell-structured carbon nanotube composite fibers for ultrahigh energy and power density supercapacitors

The increasing demand for efficient and sustainable energy storage emphasizes the need for enhanced supercapacitors. While supercapacitors are characterized by high power density, long lifespan, and rapid charge/discharge rates, their low energy density restricts broader applications. This study introduces a novel strategy to develop high-performance supercapacitors utilizing a fiber-type nanoscale electrochemical cell structure. Liquid crystalline wet-spinning was used to produce highly conductive carbon nanotube (CNT) composite fibers with polyaniline (PANI), active material. The PANI was grafted with CNT via Ullmann-type C–N coupling to provide enhanced chemical stability and low interfacial resistance, resulting in superior electrochemical performance. This structure ensures uniform PANI distribution across the fiber, facilitating the formation of nanoscale electrochemical cell. This allows most of the PANI, even the PANI present inside the fiber, to participate in the electrochemical reactions. Therefore, the composite fiber exhibits a specific capacitance of 1714 F g⁻¹ (at 1 A g⁻¹), an energy density of 820 mW h cm^⁻3 (418 W h kg⁻¹), and a power density of 1150 W cm^⁻3 (587 kW kg⁻¹). Moreover, the device also exhibits excellent stability, retaining nearly 100 % of its initial capacitance after 100,000 charge/discharge cycles and enduring over 10,000 mechanical deformations. This approach provides a novel approach for durable, nanocell-based high-performance supercapacitors, advancing sustainable energy storage technologies.