A New Polyvinyl Alcohol Lithium Chloride Hydrogel Electrolyte: High Ionic Conductivity and Wide Working Temperature Range

Abstract Polyvinyl alcohol/lithium chloride hydrogel (PVA/LiCl) is one of the most used electrolyte in supercapacitors. Increasing the ionic conductivity and operating temperature range of PVA/LiCl would greatly boost the electrochemical performance of supercapacitors and enhance the devices’ environmental adaptability. This is of great significance yet rarely concerned about in energy communities. In this work, SiO2 functionalized PVA/LiCl (PVA‐SiO2/LiCl) is experimentally realized with high ionic conductivity and wide operating temperature range. The spectroscopic and theoretical experiments prove that SiO2 significantly regulates cation solvation structure to promote cation‐anion pair dissociation and diminish coagulation of PVA chains, increasing ionic conductivity from 19.01 mS cm−1 of PVA/LiCl to 56.17 mS cm−1 of the new electrolyte. SiO2 can also prevent cation‐anion association as temperature decreases, and the abundant hydroxyl groups on the SiO2 and the stretched PVA chains tune hydrogen bonds among dipolar water molecules. They effectively expand the operating temperature range of PVA‐SiO2/LiCl. PVA‐SiO2/LiCl greatly boosts the electrochemical performance of MnO2‐based supercapacitor. The design concept developed here opens up a way toward high‐performance hydrogel electrolyte development.