Functionalized methyl cellulose/LiClO4 composite as an environmentally friendly quasi-solid polymer electrolyte for solid-state electrochromic devices and cellulose-based supercapacitors

Electrochemical devices, including energy storages and modulators, are expected to play key roles in creating a sustainable future. However, to achieve the technological break-through in electrochemical technologies, the development of solid electrolytes applicable in various electrochemical devices seem necessary. In this study, an environmentally friendly fluorine-free quasi-solid polymer electrolyte derived from a functionalized cellulose composited with LiClO4 is synthesized. The synthesized quasi -solid polymer electrolyte, LiClO4-sulfonated methyl cellulose incorporating lithium ion (LiSMC), ex-hibits a high conductivity exceeding 1 mS/cm with negligible electron leakage. The LiClO4-LiSMC electrolyte also exhibits high optical transparency and mechanical flexibility, thus it can be applied in various solid-state electrochemical systems including electrochromic devices and energy storages. The applicability of the LiClO4-LiSMC electrolyte in quasi-solid-state electrochromic devices and cellulose -based supercapacitor is demonstrated, from which reduction of the operating voltage and enhance-ment in performances compared with the similar devices with conventional polymer electrolytes are demonstrated. The cellulose-based supercapacitor demonstrates an excellent stability against mechan-ical bending and charge-discharge cycling (up to 30,000 cycles) as well. Considering the natural abundance and low environmental impacts of cellulose and its derivatives, this work may open a path to the truly sustainable future through the development of an environmentally friendly material for environmentally friendly applications.(c) 2023 Elsevier Ltd. All rights reserved.