The transport equations in Li-air batteries are revisited andmodified to account for different poremicrostructures, pore size distribution effects and electron transport through the discharge product. Different material microstructures are analyzed including structures made of spherical and cylindrical pores, nanoparticles, carbon nanotubes and nanofibers, and a new hybrid model is proposed to describe the deposition of discharge product in the cathode. It is shown that although the different microstructures result in different dynamics in which the pores are being filled, they lead to relatively similar values of the energy and power densities. Microstructures based on carbon nanotubes, nanofibers, and spherical particles tend to increase the effective size of the fibers and particles during the first part of the discharge process and result in a slight increase of the cell voltage at the beginning of the discharge. The power density of Li-air batteries decreases with the variance of the pore size distribution function, while the capacity shows a slight increase with the variance of this distribution. In general, the resistivity of the deposit layer (e.g. Li2O2, Li2O, etc.) has a negative effect on the performance of Li-air batteries. However, it is shown that, as long as this resistivity is not too large, the deposit layer tends to increase the capacity of the battery by approximately 10%. This rather unexpected phenomenon is attributed to the fact that the voltage drop across the deposit layer reduces the reaction rate at the air side of the cathode and, in this way, delays the formation of the deposit product in this region. (C) The Author(s) 2014. Published by ECS. All rights reserved.