Modeling of hierarchical cathode for lithium air batteries with aqueous electrolyte

Lithium air batteries show a great promise as energy storage devices due to their high energy densities. Meanwhile, the exploiting of renewable energy sources stimulates the development of the batteries. However, currently, there are numerous scientific and technical challenges that must be addressed before commercialization. Recently, our lab has demonstrated a new hierarchical and nanostructured air cathode which shows high activity. In this work, a new mathematical model for a hierarchical and nanostructured air cathode has been established. The model is implemented in the commercial software COMSOL and verified with the existing experimental data. Furthermore, the effects of different air cathode structure parameters have been investigated. The gas diffusion pore width plays a dual role on the cell performance and an optimal pore width has been found. The backing paper thickness has minor influence on the cell performance. Finally, the cell performance increases with the increase of the length and density of carbon nanotube assays (CNTAs) under sufficient oxygen circumstance. However, when the oxygen transport is limited, the increase of the length and density of CNTAs has no significant effect. The model developed in this work can be used as a tool to predict and optimize the structure of Li-air cathode