Analysis of electrolyte imbibition through lithium-ion battery electrodes

Abstract

A quantitative measurement of wettability between the porous electrode and the electrolyte in lithium-ion batteries can greatly improve our understanding of wetting behavior. Although the wetting balance method is widely used to measure the electrolyte transport rate in the porous electrodes, it suffers from several drawbacks and has limited accuracy. We here presented a combined experimental and theoretical investigation of the dynamics of electrolyte imbibition through electrodes. We proposed a novel method to accurately measure the electrolyte imbibition rate. Excellent agreement between the experimental data and the developed analytical model is obtained. The coefficient of penetrance (COP) and the solid permeability coefficient (SPC) are identified as important parameters, i.e., the electrolyte with higher COP value wets faster into an electrode, whereas for an electrolyte, the electrode with higher SPC value is more amenable to be impregnated. The effect of electrolyte salt concentration and electrolyte solvent has been studied in detail. The result suggests that increasing salt concentration adversely influences electrolyte wetting rate, whereas switching from EC-DEC system to EC-EMC system improves electrolyte wetting rate. In addition, for the electrolytes tested in this study, the imbibition into the uncalendered graphite anode is much faster than that into the uncalendered NMC532 cathode.