ZnO-reinforced dual-network lignin hydrogel electrolyte for robust mechano-electrochemically supercapacitors

The development of hydrogels with high mechanical strength, ionic conductivity and electrochemical activity is crucial for advancing flexible supercapacitors. In this study, zinc oxide nanoparticles (ZnO NPs), recognized for their high chemical activity and conductivity, were incorporated into dual-network hydrogel based on poly (acrylic acid- co -acrylamide) (P (AA- co -AM)) matrix to improve its properties. By optimizing the ratio of AA to AM and adjusting the amounts of AlCl 3 and ZnO NPs, the -COO - groups in AA and the -CONH 2 in AM form a hydrogen bond network. This network effectively integrated the -SO 3 - groups of lignosulfonate (LS) with Zn 2+ , and Al 3+ ions, establishing a multi-pathway ion transport system that served as a dual conductive channel. Leveraging the nanoscale effect, the transport of Zn 2+ and Al 3+ connection framework enhanced the tensile strength from 140.48 kPa to 420.16 kPa by three times. The optimized flexible supercapacitor exhibited a specific capacitance of 99.63 F g −1 , accompanied by exemplary flexibility, with capacitance retention rate of 80.63 % and nearly 100 % coulomb efficiency. This strategy offers a new framework for designing hydrogel electrolytes with high mechanical strength and ionic conductivity, suitable for use in high-performance energy storage devices.