Wide-temperature and high-ionic conductivity nanocellulose-based gel electrolyte prepared by a facile freeze-thaw method for supercapacitors

The rational and effective combination of different electrochemical substances to prepare high ionic conductivity supercapacitor gel polymer electrolytes (GPEs) has been widely studied by researchers. Currently, most work focuses on adding many crosslinker or initiator agents into polymers to prepare the GPE of supercapacitor. This method is efficient, but the steps are tedious. In this study, a GPE exhibiting high ionic conductivity across a wide temperature range is developed by integrating TEMPO-oxidized cellulose nanofiber (TOCNF) through a facile freeze-thaw method. The findings revealed that the gel polymer electrolyte of PTC-7 showed a high ionic conductivity of 6.0 S m −1 at a temperature of 25 °C, a tensile strength of 403.81 kPa, and a compressive strength of 624.17 kPa. The fabricated symmetric supercapacitor demonstrates stable charge-discharge characteristics under harsh environmental conditions ranging from − 25 °C to 75 °C. Even after bending 90° or 180° at room temperature, it retains its original electrochemical properties, thereby demonstrating exceptional practical applicability. This work offers an effective strategy to design gel electrolytes for the supercapacitors, solid-state batteries, and other fields.