Preparation of PVA based multifunctional hydrogel electrolyte reinforced by phosphoric acid-dissolved-cellulose and its application in quasi-solid supercapacitors.

The PVA hydrogel electrolyte holds significant promise in flexible supercapacitors owing to its high conductivity and foldability. However, the poor mechanical properties and low capacitance of pure PVA hydrogel electrolytes need to be further solved. Herein, phosphoric acid was employed to dissolve cellulose, which solution was used to directly mix with PVA, and formed physical crosslinking point in composite hydrogel through a freeze-thawing cycle. The interaction between PVA and cellulose molecules plays a critical role in forming the PVA-Cellulose composite hydrogel. When the cellulose content in the hydrogel is 5%, the prepared composite hydrogel (P-CE 5%) exhibited impressive tensile strength of 306 kPa and elongation at break of 1106%. After adding 8 mol/L LiCl, the assembled supercapacitor with composite hydrogel (P-CE-L8) electrolyte exhibited a high area capacitance of 217 mF cm⁻². Moreover, the incorporation of phosphoric acid and LiCl also conferred excellent frost resistance to the hydrogel electrolyte, as indicated by a capacitance retention rate of 92% after returning to room temperature from low temperature. Notably, the hydrogel exhibited remarkable self-healing capabilities, with its specific capacitance reaching 95% after wound healing. Therefore, this PVA-cellulose hydrogel electrolyte emerges as a promising candidate for the application in the energy storage device assembly. [ABSTRACT FROM AUTHOR]