Long-Term Anti-freezing Active Organohydrogel Based Superior Flexible Supercapacitor and Strain Sensor

Multifunctional conductive hydrogels attract booming attention with the prosperity of flexible and wearable soft devices such as energy storage systems and sensors. However, conventional water-based conductive hydrogels inevitably lose ionic conductivity and mechanical flexibility at subzero temperature, thus restricting their practical utilizations in extremely cold environments. On the other hand, simultaneous realization of high freezing tolerance, toughness, ionic conductivity, and electrochemical property through a simple approach is still a challenge. Herein, a novel long-term anti-freezing and mechanically tough conductive active organohydrogel is designed and prepared by simultaneously introducing poly(vinyl alcohol) (PVA), alizarin red S (ARS), and H2SO4 into a H2O/ethylene glycol (EG) binary solvent. Benefiting from the exceptionally low temperature tolerance capability of H2O/EG and extra pseudocapacitance contribution of ARS active molecules, even at the temperature as low as −37 °C, the as-fabricated flexible supercapacitor still demonstrates a large electrode specific capacitance (240 F g–1), high energy density (21 Wh kg–1), excellent cycling stability (only 9% capacitance decay over 5000 cycles), and superior durability (97% capacitance retention after stored for 50 days). More impressively, owing to the excellent strain sensitivity (GF = 2.18) and significant repeatability, the active organohydrogel based anti-freezing strain sensor can not only precisely monitor the large-scale and subtle human movements but also efficiently distinguish the directions of the movements under RT or −37 °C. Overall, our investigation of long-term low temperature tolerant active organohydrogels provides a versatile strategy to exploit superior flexible energy storage devices and strain sensors applied in extremely cold environments.