Diffusion Coefficients and Kinetic Rate Constants of Phase Changing Electrode Materials using Physics-based Models: A Descriptive Study

Abstract

The simplified gravimetric intermittent titration technique (GITT) model, proposed by Weppner and Huggins in 1977, remains a popular method to determine the solid-state diffusion coefficient ( ) and the electrochemical kinetic rate constant ( ). However, more realistic and conceptually descriptive models have appeared recently, taking advantage of the increased availability of computational power. Building improved batteries requires an understanding of internal battery dynamics, particularly the charge transport mechanisms in porous electrodes. Solid-state diffusion is typically the slowest and, hence, the mechanism that determines rate in lithium-ion battery (LIB) and sodium-ion battery (SIB) electrodes. Therefore, understanding the kinetic rate constant (k) and the solid-state diffusion coefficient (D₁) is crucial for designing battery electrodes for maximum power and energy efficiency. To ascertain the solid-state mass transport characteristics, it is crucial to establish experimentally precise and confirmed characterisation methods.