Development of a High Temperature PEO-Based Li-O2 Battery

Li-air battery has the potential of becoming the ultimate power source among all electrochemical energy conversion and storage configurations derived from lithium chemistry. Unfortunately, current configurations, mostly based on a non-aqueous organic liquid electrolyte, suffer from numerous challenges, namely high electrolyte volatility, electrolyte decomposition, low cycle-life, low discharge rates and high discharge/charge over-potential. A very appealing Li-air configuration is obviously one which sees the use of a solid, solvent-free, electrolyte, such as those formed by combining poly(ethylene oxide), PEO, and a lithium salt. Polymer electrolytes are well known promising materials for high energy density rechargeable batteries. Polymer electrolytes poses several advantages over liquid based electrolytes systems, in terms of high chemical, thermal and electrochemical stabilities, all of those are important factors for batteries in number of applications, ranging from portable electronics to electric vehicles. However, wide use of solid polymer electrolyte is still prevented by the decay in ionic conductivity (10^-7 to 10^-5 S cm^-1 at room temperature), resulting from low ionic mobility, high degree of polymer matrix crystallinity, and low degree of charge separation in addition to ion association. We hereby offer a new Li-air battery configuration, based on the well-investigated PEO- lithium salt electrolyte system. The Li-air battery will be comprised of a lithium metal anode, a highly Li⁺ conductive, oxygen permeable PEO-based, lithium polymer electrolyte and a high surface area carbon air cathode.  As opposed to current lithium polymer electrolytes, which operate at room temperature and suffer from low ionic conductivity, the new proposed configuration will operate at a high temperature of 80°c. Above 70°c PEO predominantly exists in the amorphous state, thus a practically useful conductivity is easily achievable in the temperature range of 70-95°c. Our Li-air cell is discharged/ charged at high temperature, thus enabling better kinetics, resulting in high current densities and lower over-potential. The system is studied by electrochemical methods as well as spectroscopic ones.

The results of this work will contribute to the development of practically viable Li-air batteries.