Energy Storage Breakthrough: CNT Fibers Meet Polyaniline

By Muhammad OsamaReviewed by Laura ThomsonMay 13 2025

In a recent article published in the Composites Part B: Engineering, researchers introduced a high-performance supercapacitor based on nanocell-structured carbon nanotube (CNT) composite fibers grafted with polyaniline (PANI). This novel nanoscale electrochemical design enhances energy density while maintaining rapid charge-discharge capabilities, addressing the demand for efficient, sustainable energy storage and supporting advancements in next-generation clean technologies.

Advancements in Fiber-Based Energy Storage

Supercapacitors, also known as electrochemical capacitors, are key components in modern energy storage due to their high power density, rapid charge-discharge capabilities, and long lifespan. These features make them ideal for applications needing quick energy bursts, such as electric vehicles, robotics, and renewable energy systems. However, their low energy density limits broader use, especially in scenarios demanding sustained energy output.

Traditional designs often involve layered structures where active materials are coated onto conductive substrates, facing challenges related to electrical conductivity, durability, and efficiency at larger scales. In context, CNT fibers present a promising alternative due to their excellent conductivity, mechanical strength, and flexibility. Despite these advantages, their chemical inertness and hydrophobicity hinder effective bonding with active materials. While methods like oxidative functionalization have improved CNT hydrophilicity, they often degrade electrical performance. These challenges highlight the need for novel approaches to enhance energy density without compromising power or longevity.

Novel Integration Method: CNT-PANI Composite Fiber

In this paper, the authors introduce a fiber-type nanoscale electrochemical cell structure to enhance supercapacitor performance. They develop composite fibers by integrating PANI, a highly pseudocapacitive material, with CNTs using a liquid crystalline wet-spinning process. Crucially, PANI is covalently grafted onto CNTs via Ullmann-type C-N coupling, improving chemical stability and reducing interfacial resistance.

This technique enabled a uniform distribution of PANI throughout the fiber, allowing surface and embedded PANI to contribute to electrochemical reactions, addressing limitations in conventional coating-based designs. Using chlorosulfonic acid (CSA) as a solvent ensured effective dispersion of CNTs and PANI during fabrication. The resulting CNT-PANI composite fibers demonstrated high specific capacitance, energy, power density, and excellent mechanical stability. Electrochemical performance was evaluated using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS), confirming the effectiveness of this nanoscale architecture.

Key Findings and Electrochemical Performance

The outcomes showed that the unique fiber structure of the CNT-PANI composites enabled the formation of nanoscale electrochemical cells, significantly enhancing supercapacitor performance. Covalent grafting of PANI onto CNTs ensured a uniform distribution of active material, maximizing contact with the current collector and improving specific capacitance. The fibers retained a high weight percentage of sulfuric acid from the spinning process, serving as an internal electrolyte that boosted electrochemical efficiency.

Electrochemical evaluations indicated a specific capacitance of 1714 Fg^-1 at 1 Ag^-1, with corresponding energy and power densities of 820 mWhcm^-3 (418 Wh kg^-1) and 1150 Wcm^-3 (587 kW kg^-1), respectively (values that surpass those of conventional supercapacitors). The supercapacitors maintained 55% and 34% of their capacitance at current densities of 10 and 100 Ag^-1, respectively, showcasing impressive rate capability.

They exhibited exceptional long-term stability, retaining nearly 100% of their initial capacitance after 100,000 charge/discharge cycles and sustaining performance after 10,000 mechanical deformations, highlighting their durability and potential for flexible electronics.

The redox activity of PANI supported electric double-layer capacitance (EDLC) and pseudocapacitive behavior. The study emphasized optimizing the molecular weight of PANI and the fiber composition to achieve near-theoretical performance, making CNT-PANI composites a promising solution for high-performance, long-lasting energy storage.

Applications in Clean and Sustainable Energy Storage

This research has significant implications for developing flexible and durable energy storage systems. The CNT-PANI composite fibers' high electrochemical performance and mechanical resilience make them well-suited for various clean technology applications, including portable electronics, wearable devices, electric vehicles, and robotics. Their ability to maintain performance supports integration into flexible electronics and smart textiles.

The innovative design featuring nanoscale electrochemical cells within the fibers and the liquid crystalline wet-spinning process's scalability highlights these materials' commercial potential. With exceptional energy and power densities, rapid charge-discharge capabilities, and long-term stability, these composite fibers offer a promising solution for applications requiring efficient, reliable, and sustainable energy storage.

Conclusion and Future Directions

The CNT-PANI composite fibers significantly advance energy storage technology. Their nanocell-based design ensures uniform active material distribution and high energy efficiency, making them ideal for various applications. The findings highlight the key role of advanced nanomaterials in addressing the demand for efficient energy solutions.

These fiber-type supercapacitors show excellent charge-discharge stability and mechanical resilience, supporting their integration into dynamic, real-world environments.

As the world shifts toward cleaner energy systems, this technology offers a promising pathway to more reliable, high-performance storage solutions. Future work should optimize the fiber fabrication process, explore alternative active materials or conductive polymers, and enhance long-term stability under practical conditions. Overall, this research lays a foundation for next-generation energy storage devices and emphasizes the critical role of innovative materials in the clean technology revolution.

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