High-throughput processing of nanographite–nanocellulose-based electrodes for flexible energy devices

The current work aims at understanding factors that influence the processability of nanographite–nanocellulose suspensions onto flexible substrates for production of conductive electrodes. A custom-built slot-die was used in a continuous roll-to-roll process to coat the nanomaterial suspension onto substrates with varying surface smoothness, thickness, pore structure, and wet strength. The influence of a carboxymethyl cellulose (CMC) additive on suspension rheology, water release properties, and coating quality was probed. CMC addition reduced the suspension yield stress by 2 orders of magnitude and the average pore diameter of the coated electrodes by 70%. Sheet resistances of 5–9 Ω sq^–1 were obtained for the conductive coatings with a coat weight of 12–24 g m^–2. Calendering reduced the sheet resistance to 1–3 Ω sq^–1 and resistivity to as low as 12 μΩ m. The coated electrodes were used to demonstrate a metal-free aqueous-electrolyte supercapacitor with a specific capacitance of 63 F g^–1. The results increase our understanding of continuous processing of nanographite–nanocellulose suspensions into electrodes, with potential uses in flexible, lightweight, and environmentally friendly energy devices.