Abstract
Electrolyte transport capability is a critical measure of battery function for both current Li-ion technology and chemistries beyond Li-ion. Ion transport plays a vital role in fast-charging, lithium plating, and performance under extreme temperature and cycling conditions. Though traditional electrolytes have been widely studied, current experimental methods do not allow for simple measurements of transport properties, often requiring large electrolyte volumes, long experiment times, and a dilute assumption. In this research, we developed analytical models that accurately predict apparent diffusion coefficient and transference number from numerical models of electrolyte ion concentrations in a lithium symmetric cell. The first analytical model utilized one-dimensional diffusion to predict the transient response of lithium concentration in the bulk electrolyte to an applied current. The second analytical model predicted lithium-ion concentration decay in a Li/Li cell at the electrode surface following a brief current pulse. The analytical models were used to fit numerical finite difference simulations of Li/Li cell performance to predict transport properties. This result suggests that current pulse methods can be applied to experimentally ascertain electrolyte diffusion properties. A new diagnostic is under development for characterizing electrolyte transport properties, diffusion coefficient and transference number, using the current pulse method applied to an in situ symmetric Li/Li cell. This diagnostic utilizes Fourier transform infrared spectroscopy and attenuated total reflectance to measure transport properties with low volumes of electrolyte and short experiment times. This capability may enable simple and rapid measurement of transport properties for electrolyte candidate screening and enrich broader understanding of electrolyte transport.
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