Improvements in Li Air Batteries through Electrocatalysts, Electrode Structure Design and Modelling

Rechargeable Li-air batteries allow Li⁺ and e^- in the cell to react with O₂ from the air and enable an increase in storage capacities up to 10 times cf. with Li ion. The air cathode is a new challenge for the battery. New nanostructured air cathode materials were fabricated, characterised by using XRD, TEM and SEM and tested as cathodes in rechargeable Li-air batteries. Such 3D nanomaterials displayed high capacity (up to 3000 mAhg^-1). The superior performance of the nanomaterials was attributed to their structures which acted as transport pores The relationship between composition, especially ratios of catalyst to carbon, structure, properties and performance shall be discussed. Measures to tackle technical barriers in battery design and engineering will also be addressed. We have investigated the use of bifunctional MnO₂/Au catalysts. This has provided significant improvement in its stability (stable cycling > 100) as well as a great  improvement in the lithium air cell capacity (10,000mAh/g). 

Battery performance is still affected by loss in capacity after repeated cycling due to instability of certain solvents and cathode carbon supports and ingress of CO₂. A micro-macro homogeneous mathematical model was developed for the cycling operation of a porous Li-air cathode using concentrated binary electrolyte theory. The model includes mechanism for solvent degradation and production of Li carbonates. The physical and chemical property data is carefully applied in this model to predict the time dependance of electrolyte concentration, non-uniform porosity and reaction rate and loss of capacity after cycling. Alternative modes of battery operation are explored to improve power and energy density performance