PENLiB

Due to the needs to drastically decrease greenhouse gas emission and to the end of oil scheduled for the middle of the 21th century, there is currently a worldwide effort to move from cars powered by thermal combustion engines to cars partly (HEV, PHEV) or fully electrified (EV). Among the solutions to power electric cars they are roughly two approaches. The first one, which deals with Fuel Cells as energy sources, is indisputably attractive but exhibits severe restrictions related to their cost, their lifespan, and to the lack of a Fuel (hydrogen, alcohols, etc.) distribution network. The second one deals with the use of high performance batteries exhibiting high power and energy density (in weight & volume) batteries. NiMH (Nickel Metal Hydride) batteries, while having been used in HEV Toyota Prius, face severe issues related to (i) a fairly high self-discharge (ii) a limited specific energy and (iii) the use of rare-earth elements which are mainly produced in China. Lithium batteries have much higher energy and power density and lower self-discharge (very low in LPB) than NiMH ones. Although Lithium-ion batteries are extensively used as power sources for nomad electronic devices, namely the 4C (computer, camcorder, cellular phone, cordless tool) market, the technology adaptation from the small batteries required from electronic devices to battery packs of several hundred kg of batteries face severe issues related to (i) the safety (ii) the lifespan (iii) the cost and (iiii) the indispensable recycling. The safety improvement is absolutely required to address the electric transportation mass market. The unsafe nature of the existing batteries lies partly in the electrolyte and partly on the positive electrodes. A neat improvement of the mechanical strength of the polymer electrolyte will allow avoiding short-circuits but this improvement must not increase its resistivity. As for the security issues induced by the positive electrode, it results in particular from the oxygen release (lithium metal oxides). Lithium Iron Phosphate does not release oxygen but it presents several drawbacks (i) the lack of electronic conductivity (ii) a limited capacity and (iii) a fairly low potential. PENLiB addresses simultaneously the two main mature technologies that currently compete: the lithium polymer battery and the lithium-ion one. PENLiB motivation: PENLiB project aims at developing through new environmentally friendly battery components i.e. nanocomposite polymer electrolytes NPE and new positive electrodes based on redox polymers, advanced lithium batteries. The use of these components will result in safer and less costly batteries exhibiting enhanced energy and power density. • Indeed thanks to a huge reinforcement of the polymer electrolyte by non-toxic, non-costly, and recyclable cellulosic nanofibers, the polymer electrolyte thickness can be strongly decreased while keeping a very high mechanical strength. This allows first strongly decreasing the resistivity and therefore improving the battery efficiency. As the battery electrolyte is an inactive but costly, any decrease in thickness decreases the battery cost. • The new redox polymers can be substituted to current metal oxide positives and can improve the battery specific energy & power. The redox potential of these polymeric positives can be modulated to be adapted both to lithium polymer batteries (limited oxidation potential ~3.9 V vs Li/Li+) and to lithium-ion batteries (> 4.1 V vs Li/Li+ ). They will markedly increase the safety as, despite their high redox potential, they cannot undergo any oxygen release.