What is it about?

Separator is an important component of electric double-layer capacita (EDLC), an electric device, to maintain its electrochemical performance at a high level. Some properties, such as electrical insulation, electrolyte permeation and flexibility, are required for separator material. Our paper describes how we have developed self-standing polyester film by melt-polycondensation of 3 ingredients including lignin. The electrochemical performance of the assembled EDLC using the polyester film were found to be compatible to that of the EDLC using commercial cellulosic separator.

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Why is it important?

EDLC is believed to be one of the important, next generation electric storage device with power density (e.g. high-speed chrage/discharge process). The drawback of EDLC to be addressed is its poorer energy density than that of, for example, lithium ion battery. Our research group have been trying to develop components of EDLC (i.e. electrode, separator and electrolyte) to address the drawback. This paper deals with the development of separator material from lignin, aiming at better utilization of lignocellulosics as a value-added, functional material for sustainable use of woody biomass.


Adding flexibility to lignin-based polymer film is of great importance, because aromatic structure of lignin macromolecules works as a hard segment in the lignin-based polymer, only to result in molded body that is so brittle in most cases. We have successfully developed so flexible a film in this paper, using an organisolv lignin (poly[ethylene glycol] lignin) and poly(ethylene glycol) 500,000, including a lot of ethylene oxide repeating units working as a soft segment, that the film could be folded like a paper airplane without breakage. Flexibility of the separator film was considered to be a key to a good contact with other EDLC components, leading to excellent electrochemical performance (i.e. high capacity and low resistance) of the EDLC assembled with the separator film. Together with the improved EDLC components (e.g. electrode and electrolyte), the elecrochemical performance, especially energy density, of EDLC using lignin as a part of ingredients is expected to be much more improved.

Dr. Keiichi Koda
Hokkaido Daigaku

Read the Original

This page is a summary of: Development of Lignin-Based Terpolyester Film and Its Application to Separator Material for Electric Double-Layer Capacitor, Journal of Wood Chemistry and Technology, January 2019, Taylor & Francis,
DOI: 10.1080/02773813.2018.1562472.
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