Conductive hydrogels have shown great promise in flexible electronics, but their practical applications may be impeded by the time-consuming and energy-consuming polymerization process. We proposed a sodium lignosulfonate−Fe (SLS−Fe) strategy to address this challenge and took advantage of carboxymethyl cellulose (CMC) and poly(acrylic acid) to prepare the CMC/PAA/Fe 3+ /LiCl interpenetrating conductive hydrogels with good self-healing properties, antifreezing properties, and a 6fold increase in conductivity in this study. The hydrogel-based flexible strain sensors demonstrated a broad detection range (400%), high sensitivity (GF = 6.19 at 200−400%), and human motion detection capability. The hydrogel-based supercapacitor exhibited a single-electrode specific capacitance of 122.36 F g −1 which successfully powered LEDs. Furthermore, the supercapacitor showed a single-electrode specific capacitance of 83.16 F g −1 at −23 °C (68% of the one exhibited at 25 °C). Therefore, the multifunctional performance of the CMC/PAA/Fe 3+ /LiCl hydrogel is anticipated to play an exemplary role in a new generation of flexible electronics.

Functional materials for solar energy collection, conversion, and storage need to be developed to address the global energy crisis. In this study, phase-change nanofiber films [PCNFs, sodium lignosulfonate (SLS)/polyvinyl alcohol (PVA)/polyethylene glycol (PEG)], which maintain their shape, were developed for solar-to-thermal energy conversion and storage. The films were constructed by electrospinning with PEG as the phase-change material, SLS/PVA mixture as the supporting matrix, and SLS as the photothermal material. SLS effectively improved the supporting property of the PCNFs owing to sturdy hydrogen bonds and electrostatic entanglement between its macromolecule chains and PVA/PEG, which prevented the leakage and transfer issue for PEG. Moreover, the PCNFs showed excellent solar-to-thermal energy conversion and storage ability, attributed to the π–π stacking of SLS molecules and the phase-change process, respectively. The SLS/PVA/PEG film with a PEG content of 32.43% exhibited a diameter of 465 ± 109 nm and a latent heat of fusion of 42.16 J·g–1, with a phase-change temperature of 45.20 °C. The film showed favorable stability over 50 heating–cooling cycles, thermal stability below 220 °C, good shape stability, and a solar-thermal energy conversion and storage efficiency of 18.03%. This study demonstrates a potential route to improve the utilization of lignin and solar energy and promotes the development of sustainable energy.