Li-ion batteries have been positioned like one of the best storage devices today there is a satisfactory combination of electrodes and electrolytes to be used for rechargeable Li-ion batteries in the electronic market due to their high energy densities (e.g. portable media, computers and small equipment), however, it is overriding to account for numerous problems related with transport mechanisms of charge and mass that significantly affect their capacities and power. The understanding of these mechanisms is complex due to various kinetic and transport phenomena interacting within the battery, and the difficulty of estimating local variables such as concentrations, potential, among other.

Mathematical modeling based on porous electrode theory [1] has been a powerful tool to understand and optimize the functioning performance of these devices. Nevertheless, the role of each component in the porous matrix of the electrode has not been accounted for since under this perception the battery is described as a whole identity [2, 3]. In this direction, the effect of electrode composition (i.e. variation of active and inactive material) on rate capabilities cannot be explained by these models.

In the present work, a macroscopic model is proposed relying on the assumption that the electrode is a porous solid matrix where active and inactive components should be separately expressed but interacting in solid and liquid phases. This enables to account for the experimental discharge of a semi cell Li °/1M LiPF₆ in 1:1:1 EC:DMC:EMC/LiFePO₄:PVDF-Csp considering effective transport parameters and the kinetic proposal taking in count the active material fractionin the cathode composition.

Acknowledgements:

I. Santos is grateful to CONACYT for the scholarship granted to pursue his doctoral studies.

References:

[1] Newman, J. and W. Tiedemann, AIChE Journal, 21 (1975) 25-41

[2] West, K., T. Jacobsen, and S. Atlung, Journal of The Electrochemical Society, 129 (1982) 1480-1485

[3] Farkhondeh, M., et al., Physical Chemistry Chemical Physics, 16 (2014) 22555-22565.