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Improvement of the electrochemical performance of electrochemicalcapacitors
usingnanocarbonmaterials/
Study on carbon fibers and its composites
Izuru SHIMABUKURO
Assistant Professor, Dr. Sci. and Tech.
Email : i-shimabukuro@gifu-nct.ac.jp
Research Fields
Keywords

Carbon materials (nanocarbon, carbon fiber), ElectrochemistryElectrochemical capacitors, carbon fiber and its composite● Research Outline
Electrochemical capacitor using GIC

Carbon fiber and its composite

Compared to rechargeable batteries such as Li-ion
batteries, electric double layer capacitors (EDLCs) aregarnering attention as storage devices due to theirsuperior high-speed charge/discharge capabilities andlong cycle life. However, a challenge lies in their low
energy density. To address this issue, hybrid capacitors(HCs) combining EDLC-type electrode and batterytype electrode with high energy density have beendeveloped. In a HC, one electrode stores electric energy
through a non-Faradaic process, while the otherelectrode stores energy through a Faradaic process.

Carbon fiber-reinforced plastics (CFRPs) areutilized in a multitude of fields, including aerospace,automotive, sports and leisure goods, due to their
exceptional specific strength, specific modulus, andchemical stability, among other qualities. In particular,
the incorporation of CFRP in automotive components isanticipated to increase in the future, driven byanticipated benefits such as enhanced fuel efficiency
through vehicle weight reduction and reduced
greenhouse gas emissions.

In our previous studies, we demonstrated the ability
to regenerate used Li primary batteries into novel
electrochemical capacitors (ECs). The positiveelectrode of Li primary batteries employs a covalenttype graphite intercalation compounds (GICs), which
undergoes electrochemical reduction during the firstlydischarge process. The electrochemically reduced GICs
exhibit conductivity, enabling it to behave as an EDLCtype electrode. These novel HCs derived from Li
primary batteries possess remarkably high energy
densities. Particularly, the GO/Li capacitor utilizing
graphite-oxide (GO) showed a very high energy densityof 80 Wh/L. however, at high power densities, theenergy density significantly decreases, indicating
challenges related to high internal resistance.
Currently, we address the reduction of the internalresistance and further improvement of theelectrochemical properties of these ECs.

Currently, carbon fibers are primarily manufactured
from either polyacrylonitrile (PAN) or pitch-based
precursors. Prior to the high-temperature carbonization
process, which is typically conducted at temperatures
between 200–300 °C, a stabilization process is essential.
This stabilization process requires significant time andenergy, contributing to the high cost of carbon fibers.
Consequently, current research is focused on
developing novel carbon fibers with low cost and highmechanical properties by reconstructing raw materials
and exploring novel manufacturing approaches.
Furthermore, carbon fiber-reinforced plastics (CFRP)
are utilized in aircraft components and wind turbine
blades, among other applications. As the anticipatedusage of CFRPs is expected to increase in the future,
there is a growing concern about the disposal of CFRP
waste as it reaches the end of its service life. While themajority of CFRP waste is currently disposed of in
landfills, landfill disposal is already prohibited in EU.
Additionally, carbon fibers are expensive to produce
and require high energy consumption, which highlights
the necessity for CFRP waste recycling in order toachieve a sustainable society. Currently, the focus is on
recovering recycled carbon fibers from CFRP waste,with various recycling technologies proposed, including
pyrolysis, chemical dissolution, and physical methods.
The pyrolysis method is anticipated to be a promising
approach in terms of the processing volume of CFRP
waste. However, the recycled carbon fibers recovered
through the pyrolysis method exhibit a notablereduction in tensile strength. Consequently, efforts arebeing made to address this issue by subjecting therecycled carbon fibers to a simple and mild surface
treatment with the objective of restoring strength andimproving adhesion to the matrix resin.