The Effects of Electrolyte Variations on the Oxygen Efficiency in Lithium Air Batteries

Abstract

While the existing lithium-ion batteries have been extensively used in electric vehicles (EVs), their limited specific energy restricts the driving range. In this context, rechargeable lithium air (or Li-O2) batteries have attracted considerable interest in recent years as a potential power source for EVs, owing to their high theoretical specific energy. A typical non-aqueous lithium air battery consists of a porous air electrode, a lithium metal anode, and electrolyte containing lithium salt. The electrolyte is generally regarded as a critical component as it is directly related to the stability and the performance of a lithium air battery. While physicochemical properties of potential electrolytes are often discussed, the ability of electrolyte to utilize the oxygen during reversible charge/discharge cycle is rarely explored. In fact, previously reported gas analysis indicated low current efficiency for O2 evolution during charging (Li2O2 → 2Li+ + O2 + e-), accompanied the evolution of byproduct gases such as H2 and CO2.1-2 Furthermore, the O2 revolution (therefore, rechargeability) seemed highly dependable on the choice of electrolyte. In this work, we investigated the oxygen efficiency during discharge/charge cycle in lithium-air using differential electrochemical mass spectrometry (DEMS). We explored various electrolytes that have the potential to prompt reversible electrochemistry in Li-O2 battery. In addition to this, the effect of a catalyst and lithium salt variation on the O2 evolution was investigated. 1) B. D. McCloskey, D. S. Bethune, R. M. Shelby, G. Girishkumar, and A. C. Luntz, J. Phys. Chem. Lett., 2, 1161 (2011) 2) C. J. Barile and A. A. Gewirth, J. Electrochem. Soc., 160, A549 (2013)