A lithium–air battery and gas handling system demonstrator

Abstract

The lithium–air (Li–air) battery offers one of the highest practical specific energy densities of any battery system at >400 W h kg_system⁻¹. The practical cell is expected to operate in air, which is flowed into the positive porous electrode where it forms Li₂O₂ on discharge and is released as O₂ on charge. The presence of CO₂ and H₂O in the gas stream leads to the formation of oxidatively robust side products, Li₂CO₃ and LiOH, respectively. Thus, a gas handling system is needed to control the flow and remove CO₂ and H₂O from the gas supply. Here we present the first example of an integrated Li–air battery with in-line gas handling, that allows control over the flow and composition of the gas supplied to a Li–air cell and simultaneous evaluation of the cell and scrubber performance. Our findings reveal that O₂ flow can drastically impact the capacity of cells and confirm the need for redox mediators. However, we show that current air–electrode designs translated from fuel cell technology are not suitable for Li–air cells as they result in the need for higher gas flow rates than required theoretically. This puts the scrubber under a high load and increases the requirements for solvent saturation and recapture. Our results clarify the challenges that must be addressed to realise a practical Li–air system and will provide vital insight for future modelling and cell development.