Scaling up pullulan-based supercapacitors: A sustainable approach to binder and separator integration in EDLCs

Electrochemical double-layer capacitors (EDLCs) play a critical role in high-power energy storage, offering exceptional durability and longevity for diverse applications. EDLCs typically utilize activated carbon electrodes combined with organic electrolytes, produced through cost-effective roll-to-roll manufacturing, and achieving operating voltages of approximately 2.7 V. Replacing toxic materials in electrode fabrication is critical for transitioning towards sustainable manufacturing practices. A key component in their production is the binder, which must ensure uniform coating, thermal and mechanical stability, optimal microstructural properties, electrochemical inertness, and environmentally friendly processing. Pullulan (PUL), a water-soluble polysaccharide, emerges as a promising alternative, offering reduced environmental impact and cost benefits. Our recent studies demonstrated the feasibility of PUL as a binder for aqueous processed EDLCs at the laboratory-scale. However, scaling up this process and validating it for large-scale EDLC electrodes remain open challenges. Here, we present a comprehensive investigation into the optimization of low-binder-content, high-mass-loading electrode manufacturing at both laboratory and pre-industrial scales. Moreover, a PUL electrospun membrane has been also investigated as separator. The optimized electrode formulations are validated in pouch cells with 20 cm2 electrodes, providing critical insights into the feasibility and scalability of the proposed supercapacitor configuration.