Wood-inspired High Ionic Conductivity Hydrogel Electrolytes for Flexible Supercapacitors

Abstract

Hydrogel is a promising electrolyte substrate, but its ionic conductivity needs further improvement. In this paper, we propose a strategy to improve the ionic conductivity of hydrogels with flexible wood and fabricate a flexible wood-based poly(acrylic acid-acrylamide) composite hydrogel electrolyte (WHE) by delignification and in-situ polymerization. The flexible wood as a porous backbone for hydrogels can regulate ion transport pathways to improve the ionic conductivity of hydrogels. The straight pores of wood confine the transport of electrolyte ions along the shortest path, resulting in a high ionic conductivity of 3.0×10⁻² S cm⁻¹, which is great in composite polymer electrolytes. We have systematically investigated the effect of the degree of delignification and the polymerization process on the overall performance of the 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. The WHE is applied to flexible supercapacitor, which 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.