Polystyrene (PS) dissolved in a mixture of N, N-dimethylformamide (DMF) and/or tetrahydrofuran (THF) was electrospun to prepare fibers with sub-micron diameters. The effects of electrospinning parameters, including solvent combinations, polymer concentrations, applied voltage on fiber morphology, as well as tensile and hydrophobic properties of the fiber mats were investigated. Scanning electron microscope (SEM) images of electrospun fibers (23% w/v PS solution with applied voltage of 15 kV) showed that a new type of fiber with double-strand morphology was formed when the mass ratio of DMF and THF was 50/50 and 25/75. The tensile strength of the PS fiber film was 1.5 MPa, indicating strong reinforcement from double-strand fibers. Bead-free fibers were obtained by electrospinning 40% (w/v) PS/DMF solution at an applied voltage of 15 kV. Notably, when the ratio of DMF and THF was 100/0, the maximum contact angle (CA) value of the electrospun PS films produced at 15 kV was 148°.

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 (5.3-fold), 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 °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° bending (86.5% retention) at −30 °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.