Polymer/reduced graphene oxide/lignosulfonate nanocomposite films as pseudocapacitor cathodes

Abstract

Robust and electrochemically stable electrodes are critical for emerging energy storage devices. In this work, we describe the synthesis and characterization of an asymmetric pseudocapacitor with a P(nBA-stat-BzMA)/reduced graphene oxide (rGO, 5 wt %) nanocomposite cathode incorporating a low content of lignosulfonate (LS, 5 wt %) and a P(nBA-stat-BzMA)/rGO anode. Besides the advantageous green source and low cost of LS, its properties as a binder and its redox groups contribute to the electrochemical performance improvement of the pseudocapacitor. First, the electrochemical optimization and characterization of an asymmetric unit cell is performed. Subsequently, a series of 10 unit cells are arranged in a “stack of cells”; electrochemical tests show this assembly to have a capacitance of 4.90 F cm–3 (8.60 F g–1), maximum power of 610 W kg–1, energy of 4.32 W h kg–1, loss of electroactivity of 1.8%, capacitance retention of 98%, and Coulombic efficiency of 108% after 1000 charge–discharge cycles at a constant current of 0.12 A cm–3. Morphological analysis revealed an increase in surface roughness after LS incorporation within the cathode. Electrode–electrolyte resistances were calculated via electrochemical impedance spectroscopy, which allowed us to propose a model of electrode–electrolyte interaction for this system.