Preparation of PVA/cellulose composite hydrogel electrolytes based on zinc chloride-dissolved cellulose for flexible solid-state capacitors

Abstract

The PVA-based hydrogel electrolyte, characterized by its high ionic conductivity and degradability, holds significant promise for applications in flexible supercapacitors. However, pure PVA hydrogel electrolytes have suffered from deficiencies in flexibility, self-healing properties, and anti-freezing performance. In this study, a novel approach was employed by in situ blending polyvinyl alcohol (PVA) with zinc chloride (ZnCl₂) dissolved cellulose. When the mass ratio of PVA to cellulose was 2 : 1, the resulting PVA/cellulose composite hydrogel electrolyte exhibited a commendable tensile strength (198 kPa) and remarkably high elongation at break (2415%); the assembled zinc/carbon asymmetric supercapacitor demonstrated an area-specific capacitance of 636 mF cm⁻² (2 mA cm⁻²). Moreover, at −30 °C, the capacitance retention exceeded 94%, indicating excellent anti-freezing properties. Subsequent electrical performance tests on the self-healed hydrogel electrolyte capacitors yielded a capacitance retention rate exceeding 94%, demonstrating outstanding self-healing properties. This novel class of hydrogel electrolytes provides a viable research perspective for addressing the aforementioned issues. Additionally, this study also involved straightforward treatment of used hydrogels, allowing for the recovery of high-value zinc salts such as zinc carbonate and zinc chloride, with a recycling efficiency as high as 55%. The entirety of the experiment exhibited an environmentally friendly and sustainable engineering process.