Supercapacitors are increasingly used in short-distance electric transportation due to their long lifetime (≈15 years) and fast charging capability (>10 A g−1). To improve their market penetration, while minimizing onboard weight and maximizing space-efficiency, materials costs must be reduced (<10 $ kg−1) and the volumetric energy-density increased (>8 Wh L−1). Carbon nanofibers display good gravimetric capacitance, yet their marketability is hindered by their low density (0.05–0.1 g cm−3). Here, the authors increase the packing density of low-cost, free-standing carbon nanofiber mats (from 0.1 to 0.6 g cm−3) through uniaxial compression. X-ray computed tomography reveals that densification occurs by reducing the inter-fiber pore size (from 1–5 µm to 0.2–0.5 µm), which are not involved in double-layer capacitance. The improved packing density is directly proportional to the volumetric performances of the device, which reaches a volumetric capacitance of 130 F cm−3 and energy density of 6 Wh L−1 at 0.1 A g−1 using a loading of 3 mg cm−2. The results outperform most commercial and lab-scale porous carbons synthesized from bioresources (50–100 F cm−3, 1–3 Wh L−1 using 10 mg cm−2) and contribute to the scalable design of sustainable electrodes with minimal ‘dead volume’ for efficient supercapacitors.
Bibliographical noteFunding Information:
The authors would like to thank the Engineering & Physical Sciences Research Council (EPSRC EP/S018204/2, EP/R021554/2) for the Ph.D. funding of Servann Hérou and the group of Christine Roßberg at Fraunhofer Center for Chemical‐Biotechnological Processes for the extraction of highly pure organosolv lignin. Dr. Julien Roman is also acknowledged for the measurement of Raman spectroscopy. The authors would also like to thank the staff at Nanoforce Technology Ltd. at the Queen Mary University London for its help in preparing the compressed samples and the electrospun materials. The research leading to the X‐ray CT results received funding from the EPSRC via grants EP/P009050/1 and EP/M028100/1. P.R.S. acknowledges the support of the Royal Academy of Engineering (CIET 1718/59).
© 2021 The Authors. Advanced Science published by Wiley-VCH GmbH
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- carbon nanofiber supercapacitors
- volumetric capacitance
ASJC Scopus subject areas
- Medicine (miscellaneous)
- Chemical Engineering(all)
- Materials Science(all)
- Biochemistry, Genetics and Molecular Biology (miscellaneous)
- Physics and Astronomy(all)