Measurement of Li-Ion Battery Electrolyte Stability by Electrochemical Calorimetry

Abstract

© The Author(s) 2017. Published by ECS. All rights reserved. Recent work describing the use of high precision coulometry combined with isothermal heat flow calorimetry has shown promise in studying electrolyte reactivity in Li-ion batteries. In this paper we describe what we term an "integration/subtraction" technique for determining the electrolyte reactivity as a function of cell voltage in Li-ion full pouch cells. We apply this method to the characterization of a base electrolyte blend of ethylene carbonate and ethyl methyl carbonate (EC/EMC 3/7 w/w) with 1 M LiPF6. We then show how the parasitic thermal power and coulombic efficiency are affected by the addition of the reactive carbonates vinylene carbonate and 1-fluoro-ethylene carbonate to the base electrolyte. We show how this method can discriminate the effectiveness of additives used in Li-ion cells as a function of cell voltage and cycle life.