Electrolyte Composition Influence on Oxygen Reduction and Evolution in Li-Air Cells

Abstract

The lithium-air battery is a promising next generation energy storage technology, yet the current combinations of electrolytes and electrodes have been unable to demonstrate long-term efficient cell cycling. Major issues include the decomposition of electrode and electrolyte materials and high overpotentials for the oxidation reaction. While there is significant work exploring the possibility of catalyzed electrodes to reduce cell overpotentials and encourage reversibility, there is a lack of understanding about how to select appropriate complementary electrolyte systems. In this study we employ data from hundreds of Li-air cells to reveal meaningful relationships between electrolyte composition (solvent, salt, oxygen solubility and concentration), oxygen reduction kinetics and mass transport properties. Data from practical coin-type cells are compared to fundamental studies using flat disc electrodes to prove the validity of the method. Findings are supported by molecular dynamics simulations to elucidate the interaction of various electrolyte components. The relationships derived in this work form necessary criteria for downselecting electrolyte systems with the most desired properties. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.