A theoretical method is introduced that calculates the electrolyte-transport properties using Onsager-Stefan-Maxwell (OSM) theory (concentrated-solution theory) and the generalized-Darken relation. OSM theory is used to relate binary diffusivities to the transport properties of the electrolyte, including transference number, ionic conductivity, and Fickian diffusivity. The generalized-Darken relation is proposed to calculate the binary diffusivities of multicomponent systems from self-diffusivities. Finally, an example is demonstrated to show the details of how this method can be used to estimate transport properties. The calculated properties were reasonably close to the previously reported experimental values. © The Author To develop a physics-based lithium-ion battery model or battery management systems, accurate estimation of electrolyte transport properties are essential. This is especially true as new high-energy cells are designed with thick electrodes wherein electrolyte transport dominates the end of discharge at high current densities.However, the experimental measurements of the electrolyte properties are not trivial because it requires well-controlled experimental apparatus to obtain accurate values. Depending on the technique used, the estimation of the transport properties can be very sensitive to both natural and induced convection when estimating the diffusion coefficient. In addition, solvent reduction; inevitable when using lithium metal electrodes in electrochemical techniques, results in side reactions, and gas formation, leading to convolution of the obtained data. To properly describe mass transport in a solution, n(n − 1)/2 transport properties are necessary for n chemically distinct species because the system has n(n − 1)/2 binary diffusivities (D ij ).2 In a general lithium-ion battery, the electrolyte includes a cation, an anion, and a solvent; therefore, three independent transport properties are required. The cation transference number relative to the solvent t 0 + , ionic conductivity κ, and Fickian diffusivity D serve to describe the mass transport of the electrolyte. 3,4 In this work, we introduced a novel method of evaluating the electrolyte-transport properties using the Onsager-Stefan-Maxwell (OSM) theory (concentrated-solution theory) 2-10 combined with the generalized-Darken relation. 11,12 This method provides a way to estimate transport properties with minimized experimental measurements. The key to this method is converting self-diffusivities to binary diffusivities of multicomponent systems using the generalized-Darken relation. After the conversion, OSM theory can be used to calculate the electrolyte transport properties from the binary diffusivities. This paper is intended to provide the details of this conversion and evaluate its accuracy. As an example, we demonstrate the applicability by calculating the three transport properties of LiPF 6 in PC, and show that the estimated properties compare favorably with published literature data.
Onsager-Stefan-Maxwell (OSM) Theor...