Biomimetic Wood-Confined Hydrogel Ion Channel for Flexible Supercapacitors

Abstract

Hydrogel is a promising electrolyte substrate; however, the dimensional stability and ionic conductivity need to be further improved. To tackle this issue, a flexible poly (acrylic acid-co-acrylamide) [P(AA-co-AM)]-filled wood hydrogel composite electrolyte (WHE) is rationally designed and fabricated. This is the first demonstration that flexible wood as a porous backbone for hydrogels can regulate ion transport pathways to improve ionic conductivity and enhance dimensional stability of hydrogels. Firstly, the wood is delignified. Then the P(AA-co-AM) is uniformly distributed in the low tortuosity pores of wood by an in-situ polymerization reaction. The straight pores of wood confine the transport of electrolyte ions along the shortest path. The regulation effect of wood on ion transport paths makes the ionic conductivity (3.0 × 10 -2 S cm -1 ) of the electrolyte standing among the best of composite polymer electrolyte. The optimized supercapacitor exhibits a specific capacitance of 155.64 F g -1 and an energy density of 7.45 W h kg -1 . It also exhibits good flexibility under bending conditions and can maintain similar electrochemical performance at a wide range of bending angles. This work provides an effective strategy for the efficient use of wood resources and the development of low-cost, environmentally friendly and high-performance hydrogel electrolyte materials.

Keywords: wood hydrogel, composite polymer electrolyte, flexible supercapacitor, high ionic conductivity