The Effect of Discharge Products on the Impedance Spectra in Li-Air Batteries with Organic Electrolyte

Abstract

The effects of discharge products on the impedance spectra of Li-air batteries with organic electrolyte are studied using finite element simulations. The finite element simulations are based on the theory of concentrated solutions and the complex impedance spectra are computed by linearizing the partial differential equations that describe the mass and charge transport in Li-air batteries. These equations include the oxygen diffusion equation, the Li drift-diffusion equation, and the electron conduction equation. The reaction at the anode and cathode are described by Butler-Volmer kinetics. The total impedance of a Li-air battery increases by more than 200% when the response is measured near the end of the discharge cycle as compared to on a fresh battery. The resistivity of the deposition layer significantly affects the deposition profile and the total impedance. Using electrolytes with high oxygen solubility and concentrated oxygen gas at high pressures will reduce the total impedance of Li-air batteries.