Biosourced Polymers and Lignocellulosic Materials for the Next-Generation of Eco-Friendly Electrochemical Energy Storage and Conversion Devices

In order to lower the cost and reduce the environmental impact of Li-ion batteries (LiBs), efforts must be devoted to reduce the amount of inactive components in the cell, to substitute synthetic polymer binders / separators and organic solvents with low-cost and biosourced materials and to develop new eco-friendly processes for the manufacture of cell components. Natural nanoscale-microfibrillated cellulose (NMFC) fibers are readily available; they show stiffness, impressive mechanical robustness, low weight and, furthermore, their preparation process is easy and does not involve chemical reactions. They can significantly reinforce polymer electrolytes already at low filler loadings and replace the commonly used PVdF as binder for self-standing and flexible electrodes, thus serving as a promising candidate for bio-composite production. Here we review the use of papermaking technique for manufacturing low cost bio-inspired all-paper Li-ion polymer cells, constituted by NMFC-binded paper-electrodes, and NMFC reinforced polymer electrolytes. The use of NMFC as filler/binder leads to high performing, safe, highly flexible electrolytes for LiBs. No organic solvents or synthetic binders are used during the electrode/electrolyte/cell preparation process. Materials and procedures are extended to other “beyond-LiB” technologies (Na-ion, Li-S), and paper-based dye-sensitised solar cells (DSSC), thus demonstrating the possibility of obtaining “truly green” energy storage/conversion devices. Noteworthy, the all-paper-cells can be easily re-dispersed in water by simple mechanical stirring, as common paper handsheets and materials can be recovered using well-known water-based recycling process.