An anti-freezing and anti-drying multifunctional gel electrolyte for flexible aqueous zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) have attracted immense attention for flexible energy storage devices due to their high safety and low cost. However, conventional flexible aqueous ZIBs will undergo severe capacity loss at subzero temperature due to the inevitably freeze of electrolytes. In addition, under large bending or stretching strains, the encapsulation of devices would be damaged, which causes the evaporation of water in electrolytes and results in device failure. Herein, an anti-freezing and anti-drying gel electrolyte based on polyacrylamide (PAM) and glycerol (Gly) is developed. The strong hydrogen-bonding interactions between PAM or Gly and water molecules not only avoid the crystallization of the gel electrolyte at low temperatures, but also constrain the free water and restrict its evaporation. Therefore, such gel electrolyte displays a high ionic conductivity of 9.65 × 10−5 S cm−1 at −40°C. Furthermore, it can restrict the dehydration process when the electrolyte is exposed to ambient environment. The flexible ZIBs based on such gel electrolyte exhibit excellent electrochemical performance at −40°C and the devices without encapsulation retain 98% of their initial capacity in ambient condition after 30 days. This work provides a route to design anti-freezing and anti-drying gel electrolytes for aqueous energy storage devices.