Lignocellulosic Materials for the Next-Generation of Eco-Friendly Polymeric Energy Storage Devices

In the last 20 years, the Li-ion battery (LiB) market has rapidly grown thanks to the extensive diffusion of mobile electronics devices. In order to lower the cost and reduce the environmental impact of 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 also 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 paper-making 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 produce high performing, safe and extremely flexible electrolytes for LiBs. No organic solvents or synthetic polymer binders are used during the entire electrode/electrolyte/cell preparation process. Materials and procedures are also extended to other “beyond-LiB” technologies, such as Na-ion and Li-S, thus demonstrating the possibility of obtaining “truly green” energy storage devices in the near future. Noteworthy, the all-paper-cell can be easily re-dispersed in water by simple mechanical stirring, as well as common paper handsheets and battery materials can be recovered using well-known water-based recycling process.