Mathematical Modelling of the Discharge Process of Lithium-Air Batteries with Redox Mediators

The main objective of this work is to develop a mathematical model for a non-aqueous Li-Air battery, capable to simulate the discharge process in presence of a Redox Mediator based on experimental evidence, and to define how the design of the cathode should be modified to enhance the discharge process in this condition. After thorough analysis of experimental evidence, and based on an existing mathematical framework, a mathematical model was developed for a Li-Air battery. The mathematical model comprehends original additions to be able to take into account for the morphology evolution during the discharge process. This model was validated against experimental data, before being used to perform the design optimisation simulations. The dynamic behaviour of cathode porosity was determined by numerical solution of the governing, transport and reaction equations. The microscopic behaviour included the local mass transfer and the change in morphology related to the growth of Li2O2 particles driven by the mediator mechanism. The effect of the deformation given from the current collector was also included in the model. Simulations were performed first in 1D to calibrate the model parameters, which were used for the validation of the 2D model against experimental data. Then, 2D simulations were performed to achieve the design optimisation of the cathode geometry with embedded micro-channels to enhance oxygen supply