Effect of Operating Temperature in Li-Air Cells
Recent works demonstrated that the best results in terms of Li/O2 battery stability and cycling may be obtained with the use of long chain, ether-based glymes, such as tetraethylene glycol dimethyl ether (TEGDME) electrolyte solutions. In a previous paper we have reported a detailed transmission electron microscopy (TEM) study showing that Li/O2 batteries based on the TEGDME-LiCF3SO3 electrolyte indeed show a very promising behavior at room temperature. In this paper we report an electrochemical and morphological study of the response of lithium−oxygen cells cycled at various temperatures, that is, ranging from -10 to 70 ℃. The results show that the electrochemical process of the cells is thermally influenced in an opposite way, that is, by a rate decrease, due to a reduced diffusion of the lithium ions from the electrolyte to the electrode interface, at low temperature and a rate enhancement, due to the decreased electrolyte viscosity and consequent increased oxygen mobility, at high temperature. In addition, we show that the temperature also influences the crystallinity of lithium peroxide, namely of the product formed during cell discharge by measuring the TEM.
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