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 (ZnCl2) 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. [Display omitted] •A universal adhesion strategy for the electrolyte/electrode interface with robust adhesion and anti-freezing properties is developed.•Adhesive hydrogel electrolyte is achieved by introducing a bio-inspired polymer coating into the tough hydrogel matrix.•The assembled devices using this interfacial strategy exhibit excellent capacitive performance and mechanical stability at 25 to –60 °C.•This work marks a milestone in the design and development of solid-state energy storage devices that meet both the stable electrolyte/electrode interface and low-temperature adaptability.