Extreme properties of double networked ionogel electrolytes for flexible and durable energy storage devices

Achieving both performances and functionalities of energy storage devices at extreme conditions remains a critical challenge due to the property trade-offs of materials. Here, we demonstrate highly ion-conducting, stretchable, and ultradurable double network (DN) ionogel films, where ionic liquids are confined in chemically-coupled DNs consisting of hard and soft polymers, for high-temperature flexible supercapacitors (hfSCs). Both mechanical and electrochemical integrities at high temperatures are attributed to the unique DN structure and thermally activated ionic transport of the ionogels. Even at 100 °C, the DN ionogel film demonstrates remarkable properties, such as the ionic conductivity of 36.8 mS cm⁻¹, the tensile strength of 1.4 MPa, stretchability of 500%, and dissipation energy of 216 kJ m⁻³. Thus, the hfSCs achieve the highest energy density of 51.0 Wh kg⁻¹ at 180 °C among previous solid-state SCs, showing extreme durability of 91% over 100,000 cycles and functional hybrid system at both elevated temperatures and bent states.