Numerical simulations based on the porous electrode theory [1] are commonly used to describe and predict the rate performance of lithium ion batteries. This, however, requires that the relevant properties of the electrolyte and the porous electrode are available for a given electrolyte as a function of electrolyte composition (solvents, salt concentration) and temperature.

Unfortunately, very few of these parameter sets for typically used binary electrolytes can be found in the literature (e.g., Reference [2]), with the exception of the electrolyte conductivity, which can be determined quite easily. Therefore, over the past years, we have focused on developing methods to quantify the following parameters needed for numerical models: i) the thermodynamic factor (1+dln(f_±)/dln(c)) [3], which is derived from the mean molar activity coefficient f_±; ii) the effective ionic conductivity of porous electrodes by means of AC impedance spectroscopy [4]; iii) the binary diffusion coefficient, D_±; and, iv) the lithium ion transference number, t₊ [6].

In this contribution we will present the various measurement methods, compare the resulting parameters with the literature, and also present the temperature dependence of the thermodynamic and transport parameters.

 

References

[1] J. Newman, K. E. Thomas-Alyea, Electrochemical Systems, 3^rded. (2004), Wiley-Interscience, Hoboken.

[2] L.O. Valøen, J. N. Reimers, J. Electrochem. Soc. 152(2005) A882.

[3] J. Landesfeind, A. Ehrl, M. Graf, W. A. Wall, H. A. Gasteiger, J. Electrochem. Soc. 163(2016) A1254.

[4] J. Landesfeind, J. Hattendorff, A. Ehrl, W. A. Wall, H. A. Gasteiger, J. Electrochem. Soc. 163(2016) A1373.

[5] A. Ehrl, J. Landesfeind, W. A. Wall, H. A. Gasteiger, J. Electrochem. Soc. 164(2017) A826.

[6] A. Ehrl, J. Landesfeind, W. A. Wall, H. A. Gasteiger, submitted.

 

Acknowledgements

We gratefully acknowledge the funding by the Bavarian Ministry of Economic Affairs and Media, Energy, and Technology for its financial support under the auspices of the EEBatt project as well as funding by the German Ministry for Education and Research in the framework of the project ExZellTUM II (funding number 03XP0081).