Thermal-electrochemical parameters of a high energy lithium-ion cylindrical battery

Abstract

To accurately predict the lifetime of commercial cells, multi-physics models can be used, however the accuracy of the model is heavily reliant upon the quality of the input thermodynamics and kinetic parameters. The thermal properties and the variability of the transport and thermodynamic properties with temperature and state-of-charge (SoC) in a high energy 21700 cylindrical cell were measured. The parameters are used in a DFN and 0D thermal model, and the model was tested against experimental data from the commercial cell. The results demonstrate an improved model fit by 27% when including the parameter dependency upon SoC and temperature, compared to without. The maximum power is limited by the negative electrode, which has lower diffusion coefficients and current exchange density over the full SOC window compared to the positive electrode, particularly at 50% and 80% SoC (x=0.45 and 0.85), reflected in high activation energies of up to 60 kJ K-1 and low diffusion coefficients of 5 x 10-13 cm-2 s-1 at 25 °C. At 45 °C, the reaction rate increases to greater than that of the positive, diffusion also increases, 2 x10-12 cm-2 s-1, but is still limiting. This work provides for the first time an electrochemical and thermal experimental dataset for a high energy cell, and provides insights into the rate limitations and prediction errors.

A continuum of physics-based lithium-ion battery models reviewed

“…Despite this, it is common in the literature to model this process using a linear (Fickian) diffusion A c c e p t e d M a n u s c r i p t equation (i.e. one with constant diffusivity), which is quite an unrealistic assumption (see, for example, the differences between [20] and [94]). Moreover, it has been argued by Bazant and others, e.g.…”