Ligno-Cellulosic Materials for the Next-Generation of Eco-Friendly Polymeric Energy Power Sources
Authors: Destro Matteo , Zolin Lorenzo , Chiappone Annalisa , Nair Jijeesh Ravi , Gerbaldi Claudio , Bodoardo Silvia , Bongiovanni Roberta , Penazzi Nerino , Beneventi Davide 
Published: February 2020

In the last 20 years, the Li-ion battery (LIB) market has rapidly grown thanks to the extensive diffusion of mobile electronics devices. The optimisation of existing chemistries by the introduction of environmentally friendly materials and the simplification of the production process are intriguing challenges to promote the future widespread diffusion of LIBs. In order to lower the cost and reduce the environmental impact of LIBs, which is crucial in the perspective of their large-scale diffusion, an effort must be made to reduce the amount of inactive components in the cell, to substitute high cost materials, such as synthetic polymer binders / separators and organic solvents, with low-cost and bio-based/bio-inspired materials and to develop new eco-friendly processes for the manufacture of cell components [1].
Nanoscale-microfibrillated cellulose particles (NMFC), first studied by Herrick and Tubark, are easily available and biodegradable; they show stiffness, impressive mechanical properties and reinforcing capability, low weight and, furthermore, their preparation process is easy, low cost 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 [2-4].
In the present work paper-making technique was used for manufacturing low cost bio-inspired all-paper Li-ion cells, constituted by two paper-electrodes, prepared using micrometric size graphite (anode) and LiFePO4 (cathode) as active materials, and paper hand-sheets reinforced polymers as electrolyte. Considering the interesting properties of NMFC and the potentials of free radical photo-polymerisation, a UV cured NMFC-polymer composite membrane could surely result highly promising. Thus, NMFC particles as reinforcement for composite methacrylic/ethylene-oxide based solid or quasi solid polymer electrolyte membranes were also prepared by UV curing. The use of such a filler/binder results extremely interesting, giving the possibility to produce high performing, safe and extremely flexible electrolytes for Li-ion batteries. No organic solvents or synthetic polymer binders are used during the entire electrode/electrolyte/cell preparation process. The all-paper-cell can be easily re-dispersed in water by simple mechanical stirring, as well as common paper hand sheets and paper-battery materials can be recovered using well-known water-based recycling process. Finally, the results of an all-solid paper-cell, comprising methacrylic and/or PEO-based membranes as polymer electrolytes are presented, which demonstrate the possibility of obtaining in the next future “truly green” Li-based energy storage devices.
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