Performance Comparison of Three Polymer Electrolytes for Zinc Ion Batteries

Abstract

With the increasing demand for zinc ion batteries working over a wider temperature range, several electrolyte strategies have been proposed, including organic additives, water-in-salt solutions, and polymers. However, organic additives typically decrease the ionic conductivity of the aqueous electrolyte, while highly concentrated salts (water-in-salt) decrease electrolytes’ wettability and raise the cost. In contrast, polymer electrolytes are an appealing option. They are resistant to zinc dendrite attack and side reactions and maintain a good electrode-electrolyte interface. They are also flexible, making them suitable for soft electronics applications. In this presentation, we compare the properties of three polymer membranes as electrolytes: polysaccharides carboxymethyl chitosan-based hydrogel, polybenzimidazole, and polyvinyl alcohol-based hydrogels. We also show their interactions with zinc perchloride (Zn(ClO4)2), a high-conductive zinc salt, to enable low-temperature performance. The chaotropic activity of ClO4 - anion, as well as the formation of ternary and weak hydrogen bonds (HB) with water and polymer chains, are described to aid in the reduction of free water and anti-freezing performance at subzero temperatures.