In this work, we will discuss a detailed electrochemical model describing the discharge process of the growth of Li2O2 on terraces, steps and kinks. The different kinds of growth mode along the different kinds of sites have vastly different thermodynamic overpotential. This leads to an explanation of the high Tafel slope observed in Li-air batteries. We will also discuss the effect of deep discharge and the origin of ‘sudden death’ in these lithium-air batteries and we will show that the origin of this ‘sudden death’ in flat electrode cells is due to the limitation imposed by electron transport to support the required electrochemistry. Using a simple metal-insulator-metal model, we show that discharge products beyond > 10 nm, have serious transport limitations and this leads to a bias rise across the film. In addition, we also discuss the effects of the presence of a carbonate layer which has been recently identified experimentally. We will also discuss the development of a model incorporating details from some of the recent experiments that show the presence of a carbonate layer. We conclusively show that the origin of potential rise during recharge of the lithium-air batteries is due to a rising concentration of carbonate impurities at the Li2O2-electrolyte interface. This rise in the overpotential leads ultimately to the decomposition of the electrolyte and limits the rechargability of lithium-air batteries.
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