Janus POSS‐based hydrogel electrolytes with highly stretchable and low‐temperature resistant performances for all‐in‐one supercapacitors

Abstract Conductive hydrogels can be utilized in the field of flexible supercapacitors due to their stretchable properties and high ionic conductivity. However, many of the conductive hydrogels lose their stretchability and conductivity at subzero temperatures. Herein, a novel Janus POSS‐based hydrogel electrolyte that shows excellent flexibility and ionic conductivity at low temperatures is designed and prepared by the copolymerization of acrylamide and a water‐soluble Janus‐type polyhedral oligomeric silsesquioxane (AS‐POSS) containing sodium sulfonate groups and double bonding groups. The sodium sulfonate groups of AS‐POSS and LiCl endow the hydrogel electrolyte with excellent anti‐freezing ability. Simultaneously, the double bonding groups of AS‐POSS enable a successful POSS crosslinking in the polymer network, resulting in a highly stretchable hydrogel electrolyte (1445%) with high ionic conductivity (0.067 S cm −1 ) at −20°C. Thereafter, the all‐in‐one flexible supercapacitor is prepared by in‐situ polymerization of aniline. Based on the exceptional anti‐freezing properties of the Janus POSS‐based hydrogel electrolyte, the all‐in‐one supercapacitor exhibits stable electrochemical performance (>90% capacitance retained under deformation at −20°C) and excellent cycling stability (only 19.7% capacitance decay over 2000 charge/discharge cycles at −20°C) at low temperatures. The Janus POSS‐based hydrogel electrolyte is expected to be a promising gel electrolyte for an all‐in‐one supercapacitor that resists freezing.