An adhesive interface between hydrogel electrolyte and electrode for low-temperature solid-state capacitive devices

Compared to conventional liquid systems, solid-state energy storage systems show more attractive application prospects due to improved safety, higher energy density and thermal/electrochemical stability. However, the commercial development of solid-state energy storage devices is hindered by the chemo-mechanically unstable interface between solid-state electrolyte and electrode. The hydrogel electrolytes have attracted extensive attention for this issue owing to their certain adhesion, intrinsic flexibility, and eco-friendliness. Here, we report a universal strategy for adhesive hydrogel electrolyte that simultaneously achieves robust adhesion and anti-freezing properties. The robust adhesion of hydrogel electrolyte is achieved by combining the tough hydrogel matrix with strong interface interactions. Meanwhile, the hydrogel electrolyte equipped with zinc chloride (ZnCl 2 ) and lithium chloride (LiCl) ensures high ionic conductivity and stable mechanical elasticity at 25 ~ −60 °C, thus leading to the anti-freezing electrolyte/electrode interface. More encouragingly, the assembled carbon nanotubes (CNTs)||CNTs supercapacitors and Zn||CNTs hybrid capacitors possess excellent capacitive performance at low temperatures, delivering high energy densities of 3.5 Wh kg −1 for CNTs||CNTs supercapacitors and 51.3 Wh kg ‐ −1 for Zn||CNTs hybrid capacitors at −60 °C, and extraordinary cycling durability with stable capacity retention over 10,000 cycles for CNTs||CNTs supercapacitors and Zn||CNTs hybrid capacitors. We expect this strategy to simplify and guide the development of solid-state energy storage devices operating under extreme conditions.