A gel polymer electrolyte based on ternary deep eutectic solvent for flexible, wide-temperature tolerant zinc-ion hybrid supercapacitors

Abstract

Aqueous zinc ion hybrid supercapacitor (ZIHS) is attracting considerable interest due to its noticeable safety, low cost, and high theoretical energy density. However, the widely used hydrogel electrolytes suffer from freeze and evaporation issues, which hinder the practical applications of ZIHS over a wide temperature range. Herein, we develop a gel polymer electrolyte (GPE) based on a ternary deep eutectic solvent (DES) with a low eutectic point (<-90 °C). The optimal GPE not only shows excellent flexibility and satisfactory mechanical properties in the temperature from −40 °C to room temperature, but also exhibits high ionic conductivity of 7.3 mS cm−1 at −40 °C. When it is served as the electrolyte in a ZIHS, it endows the ZIHS with an energy density of 66.83 Wh kg−1 at a power density of 187.96 W kg−1 and outstanding cycling stability with ∼95.5% capacitance retention after 20000 cycles. Furthermore, the assembled flexible device indicates favorable bendability and outstanding wide-temperature adaptability from −40 to 60 °C. More importantly, the flexible device still works well under various harsh conditions, such as pressing, bending, puncturing, and cutting. The obtained results can provide new guidance and insight for exploring wide-temperature tolerant GPEs for ZIHS.