Work

Recycled carbon fibers as viable anode materials for sodium-ion capacitors

Year: 2026

Type: article

Abstract: In the context of a circular economy, recycling advanced composite materials has become a major challenge. Carbon fibers (CF), primarily sourced from polyacrylonitrile (PAN) and pitch, offer a great potential for end-of-life valorization. Despite improvements in recycling processes targeted at preserving the fibers' original mechanical properties, most recovered fibers remain unsuitable for reuse due to diminished tensile strength, reduced fiber length, and possible structural degradation. These limitations emphasize the need to identify new applications for recycled carbon fibers (rCF). This study proposes a change of paradigm, aiming to evaluate the suitability of recycled PAN-based (rCF-PAN) and pitch-based (rCF-Pitch) carbon fibers - recovered via vapothermolysis (vapo), pyrolysis (pyro), or solvolysis (solvo) - as electrode materials for sodium-ion capacitors (SIC). The physical and structural properties of these recycled fibers were characterized and compared with those of conventional hard carbon (HC). Fibers produced by vapothermolysis and pyrolysis, exhibiting favorable structural and surface characteristics for sodium-ion storage, were selected for further analysis. These fibers were milled to increase their specific surface area. Electrochemical performance was assessed through cyclic voltammetry to identify redox processes, followed by galvanostatic charge-discharge measurements at various current rates to determine practical capacity and rate capability. Cycling behavior and energy density were benchmarked against hard carbon electrodes. The results show that recycled carbon fibers are viable materials for sodium-ion storage and outperform hard carbon at high rates, indicating strong potential for power-oriented applications.

Source: Electrochimica Acta

DOI: 10.1016/j.electacta.2026.149406