Highly compressible and superior low temperature tolerant supercapacitors based on dual chemically crosslinked PVA hydrogel electrolytes

It remains a challenge for flexible supercapacitors to maintain high electrochemical performance under high compressive stress and subzero temperature conditions simultaneously. Here, a highly compressible and superior low temperature tolerant supercapacitor is fabricated comprising a designed dual chemically crosslinked PVA hydrogel electrolyte (DN + EG hydrogel) by incorporating an EG/H2O binary solvent. The synthesized DN + EG hydrogel displays a significant improvement of compressive stress compared to a single chemically crosslinked PVA hydrogel (25-fold) and a DN - EG hydrogel (5.3fold), and also exhibits a high compressive stress (15.5 MPa), excellent shape recovery properties and a high ionic conductivity (0.48 S m(-1)) even at -40 degrees C. These impressive compressibility and anti-freezing properties benefit from the increased hydrogen bonding interactions between the first and second networks, and the solvent molecules and polymer chains. Remarkably, the fabricated supercapacitors show a high capacitance retention under strong compressive stress (nearly 100% retention) or after four thousand cycles of 180 degrees bending (86.5% retention) at -30 degrees C, displaying prominent compression-resistant properties at subzero temperature. It is believed that this work paves a new way for developing high performance compression-resistant energy storage devices which are compatible with extremely cold environments.