Ionic–Electronic Conductivity in Ternary Polymer/Reduced Graphene Oxide/Polyelectrolyte Nanocomposite Coatings for Potential Application in Energy Storage

Polymeric mixed ionic–electronic conductors are desired for a range of applications. The growing interest in the shift from liquid to solid polymer electrolytes further fueled research interest in this domain. However, the predominant research in the field has been limited to binary systems where components are selected for their electronic and ionic conduction. Here, in a systematic study, we have developed ternary nanocomposites comprising an insulating polymer poly­(benzyl methacrylate-stat-n-butyl acrylate) used as a binder, reduced graphene oxide as an electronic conductor nanofiller, and different concentrations of polyelectrolytes lignosulfonate (LS) and polystyrene sulfonate as ionic conductors. The developed ternary nanocomposite can be simply coated to obtain a uniform film at ambient temperature, exhibiting mixed ionic–electronic conduction. Scanning electron microscopy–energy-dispersive spectroscopy mapping revealed the distribution of polyelectrolytes throughout the film surface. The nanocomposite coatings exhibited the highest ionic conductivity of ∼54 S m^–1 (30 wt % LS relative to monomer) and electronic conductivity of ∼40 S m^–1 (7 wt % LS relative to monomer). The obtained ionic–electronic conductivity values were some of the highest reported in the literature (compared against binary systems), despite comprising an insulating binder as a majority component. The present work provides the important fundamental understanding behind the design and fabrication of ternary polymeric mixed ionic–electronic conductive coatings and paves the way for further research in the field. The developed nanocomposite coatings are anticipated to find application in a range of fields including energy storage, biomedical engineering, and sensors.