Construction of PVA-lignosulfonate hydrogels for improved mechanical performances and all-in-one flexible supercapacitors.

All-in-one supercapacitors are one of the best candidates for realizing flexible supercapacitors because of their outstanding flexibility and stability. The pursuit of improved electrochemical performance while meeting the requirements of flexible functionalization has always been a long-term goal. To this aim, lignosulfonate (LS) can be used in the field of all-in-one supercapacitors and contribute to its unique three-dimensional structure and abundant functional groups. By doping a small amount of LS, a simple approach is developed to achieve a one-step improvement in electrochemical performance and flexible functional design in this study. PVA-lignosulfonate hydrogel (PLH) obtains a compact and regular three-dimensional porous structure, higher ionic conductivity (0.17 S/cm), bending flexibility, and compression resistance. Polyaniline (PANI) based solid-state supercapacitors PANI-PVA and PANI-PLH show specific capacitance values of 505 and 558 mF/cm, respectively, at a current density of 0.5 mA/cm. After 5000 charge-discharge cycles, the capacitance retention rate increases from 53 % to 73 %, and the PANI-PLH can maintain the stability of electrochemical performance under bending, folding, puncturing, and squeezing. After 1600 times folding, the capacity remains almost 100 %. This study presents a one-step optimization for the construction of functional and high-performance all-in-one supercapacitors in a simple way and a novel idea for the potential application of the high-value lignin.