Enhanced Electrochemical Performance of Nanocellulose/PPy·CuCl2 Electrodes for All-Cellulose-Based Supercapacitors

Abstract

Supercapacitive devices using a bacterial nanocellulose (BNC)-based separator and electrodes, providing mechanical support with high surface area while allowing the permeability of ions and avoiding short circuits, have been assembled and characterized. For the electrodes, BNC membranes were incorporated with polypyrrole (PPy) at different concentrations using copper chloride as oxidizing agent. As the separator, pure nanocellulose membranes were used. Scanning electron microscopy analysis revealed that increasing the pyrrole concentration from 0.04 mol/L to 0.08 mol/L and the molar ratio of oxidizing agent to monomer (CuCl2:Py) from 2:1 to 4:1 resulted in a uniform BNC coating. Symmetrical supercapacitor devices were assembled and subjected to cyclic voltammetry, charge–discharge measurements, and cycle stability testing. A maximum specific capacitance value of 1789 mF/cm2 was extracted from the voltammetry curves for the device constructed using the membrane with the highest Py concentration and oxidizing agent-to-monomer ratio. The best power density and energy density values obtained during discharge testing at 1 mA/cm2 were 5.47 mW/cm2 and 187 μWh/cm2, respectively. These promising results confirm the feasibility of using BNC as both the separator and electrodes when building supercapacitors.