Li Salt Anion Effect on O2 Solubility in an Li-O2 Battery
Journal article, 2018
For the promising Li-O 2 battery to be commercialized, further understanding of its constituents is needed. This study deals with the role of O 2 in Li-O 2 batteries, both its influence on electrochemical performance and its solubility in lithium-salt-containing dimethyl sulfoxide (DMSO) electrolytes. Experimentally, the electrochemical performance was evaluated using cylindrical ultramicroelectrodes. Two independent techniques, using a mass spectrometer and an optical sensor, were used to evaluate the O 2 solubility, expressed as Henry's constant. Furthermore, the ionic conductivity, dynamic viscosity, and density were also measured. Density functional theory calculations were made of the interaction energy between O 2 and the different species in the electrolytes. When varying O 2 partial pressure, the current was larger at high pressures confirming that the O 2 concentration is of key importance when studying the kinetics of this system. Compared with neat DMSO, the O 2 solubility increased with addition of LiTFSI and decreased with addition of LiClO 4 , indicating that the salt influences the solubility. This solubility trend is best explained in terms of apparent molar volume and interaction energy between O 2 and the salt anion. In conclusion, this study shows the importance of O 2 concentration, not just its partial pressure, and that the choice of Li salt can make this concentration increase or decrease.