Safer, Non-Toxic, Alternative Electrolytes

79248S The use of ultra-capacitors in hybid electric vehicles is hampered by the toxicity and flammability of acetonitrile (AN), which is used as the basic solvent for the ultra-capacitor electrolyte. For non-AN, non-aqueous, ultra-capacitor electrolytes to achieve comparable performance to the current AN-containing ultra-capacitor electrolytes, both the performance and the much lower conductivities of non-AN electrolyte must be increased. This project will develop improved performance and safer, high boiling (>205oC) non-AN aprotic ultra-capacitor electrolytes based on ethylene carbonate (EC), butyrolactone (GBL), and high quaternary ammonium salt concentrations (2.0 to 3.5 M), which include a mix of quat salt and ionic liquid. Phase I will (1) optimize the conductivity of non-acetonitrile electrolyte systems based on GBL/EC with HIGH SALT concentrations; (2) synthesize and evaluate new quaternary ammonium tetrafluoroborate salts containing carbonyl, ester, and methoxy-substituted alkyl groups for intra-molecular solvation to the quaternary ammonium cation; and (3) evaluate optimum non-acetonitrile (AN) electrolyte in the laboratory in constructed double layered capacitors and in refilled commercial ultra-capacitors. Commercial Applications and other Benefits as described by the awardee: The replacement of acetonitrile and any other toxic and/or highly flammable solvent with relatively non-flammable (high boiling) solvents in the ultra-capacitor electrolyte should accelerate the use of the ultra-capacitor in vehicles and other applications where safety is a primary concern. The elimination of the safety concern without affecting cost or performance should enable the use of ultra-capacitors in hybrid electric and fuel-cell-powered vehicles. Also, a recycling service (patent pending) for these super-capacitors could be performed, thereby eliminating any environmental concerns about the solvents used in the super-capacitors as well as the super-capacitor salts themselves.