Lithium-ion batteries and supercapacitors with ionic liquid based electrolytes for hybrid electric vehicle application

We report and compare the performance of a graphite/LiFePO4 battery and of a double-layer carbon supercapacitor which were assembled with innovative and safe ionic liquid based electrolytes, N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl) imide and N-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide, respectively. The devices were characterized in terms of specific energy and power after the USABC-DOE protocol for hybrid electric vehicle (HEV) application. This study demonstrates that the use of ILs as electrolyte components of batteries and supercapacitors is a powerful strategy to develop systems for power assist in full-HEVs, thanks to the inherent safety of a barely-igniting electrolyte, beneficial to evolve large-size battery market, and to the wide electrochemical stability, favorable for carbon supercapacitors of high voltage and specific energies.