A flexible Zn-ion capacitor based on wood derived porous carbon and polyacrylamide/cellulose nanofiber hydrogel

Abstract

To achieve the sustainable development of portable electronic device, there arises an urgent need for exploiting the safe and wearable energy storage device from natural resources. Herein, a flexible Zn-ion hybrid capacitor (ZIHC) is developed using the oil palm wood derived hierarchical porous carbon (PC) and cellulose nanofiber (CNF)-based hydrogel as cathode and electrolyte, respectively. The PC is synthesized via the KOH-assisted carbonization approach, which exhibits high surface area of 1210.05 m2·g-1 and hierarchical porous structure that can offer abundant active sites to accumulate electrolyte ions and accelerate the diffusion of electrolyte ions. Through in-situ polymerization and impregnation strategies, the polyacrylamide/cellulose nanofiber (PAM/CNF) hydrogel electrolyte with high ionic conductivity (17.7 mS·cm-1) is successfully produced. Consequently, a flexible ZIHC based on the as-prepared PC and PAM/CNF hydrogel electrolyte delivers a favorable specific capacity of 67.4 mAh·g-1 at 0.2 A·g-1, a large energy density of 53.7 Wh·kg-1 at 152.9 W·kg-1, and remarkable cycling stability. Furthermore, the ZIHC possesses a stable capacitive behavior in different bending states. This work provides guidance for the sustainable development of portable energy storage device from the abundant, renewable, inexpensive woody biomass.