(296g) Novel Graphene Supported Bifunctional Catalysts Combined with Ionic Liquid Electrolyte in Rechargeable Lithium-Air Batteries for Prolong Cyclic Stability

Li-air battery is widely considered to be the next generation battery chemistry with extremely high energy density comparable to gasoline. They are very promising technology to prolong the driving ranges of electric vehicles.  Compare to their high theoretical value, the practical energy density of Li-air battery is much lower due to the slow kinetics of both discharge and charge reactions and hence, high overpotential at air cathode. To address this technical barrier, Pt catalyst has been used to overcome the activation energy and consequently reduce the overpotential. However, the high cost of Pt still restricts the wide application of Pt in air-cathode. In this presentation, low cost, bi-functional catalyst has been developed to replace Pt catalyst. A Li-Air system capable of 100 cycles with an average capacity of 2000 mAh/g and total energy efficiency of 75% has been achieved compared to 30 cycles with 1800 mAh/g average energy density and 85% energy efficiency as a control.

 Another important factor that hinders the cycle life of Li-air battery is the increasing solution resistance due to the consumption of carbonate based electrolyte, especially during the high charge voltages.  Electrolyte oxidation, evaporation and side reactions with active electrode materials are believed to be the main reason of the electrolyte lost. In this presentation, the conductivity, voltage window, viscosity and other electrochemical related properties of several ionic liquids as well as their mixture at different mass ration have been also investigated. by employing the optimized ionic liquid electrolyte, the high resistance after cycling is expected to be addressed and the cycle life of Li-air batteries are expected to be prolonged to 300 cycles.