Paper-supported skeleton for ultrahigh strength and thinness conductive gel polymer electrolytes towards zinc-air batteries

The dense cellulose fiber network, enriched with hydroxyl groups and hydrogen bonds, endows paper with exceptional mechanical strength and dimensional stability even under alkaline conditions. In this study, paper derived from hardwood pulp was explored as a robust skeleton for constructing advanced alkaline gel polymer electrolytes (AGPEs). The cellulose fiber-based network offers a highly interconnected and durable 3D scaffold. By performing in-situ free-radical polymerization of acrylamide (AM) within the paper matrix, followed by freeze-thaw cycling of a PAM/PVA (polyacrylamide/poly vinyl alcohol) hybrid gel and subsequent KOH (potassium hydroxide) immersion, a novel paper-supported alkaline gel polymer electrolyte (PS-AGPE) was fabricated. ​​The paper skeleton effectively restrained structural retraction and thickening caused by entropic elasticity during polymerization, resulting in an ultrathin membrane of only 200 μm.​​ The resultant PS-AGPE exhibited ultrahigh tensile strength (8.20 MPa), outstanding flexibility, exceptional resistance to alkaline swelling, and achieved a high ionic conductivity of 177.43 mS·cm-1 in 10 M KOH. When applied in flexible zinc-air batteries, the PS-AGPE delivered an open-circuit voltage of 1.51 V, an energy efficiency of 67.2%, and a remarkable stable discharge duration of 841.4 minutes. This work provides a strategy for designing ultrathin, mechanically strong, and flexible energy storage devices using readily available paper.