Solid electrolyte interphase (SEI) film resistance is an important parameter in the study of charge transfer kinetics of a Li-ion battery. The passive film affects diffusion process of Li-ions. As such, it becomes essential to include film resistance in battery modelling. However, the traditional method of estimating the SEI film resistance is costly and time consuming. An indirect approach based on Ohm’s law is thus presented in this paper. It relies on determining the interfacial polarisation from the difference of open-circuit voltage measured immediately after switching off the applied current and the equilibrium voltage. The technique is simple, easy to implement and can be used for a quick estimation of SEI film resistance with reasonable accuracy. For instance, average value of SEI film resistance for commercial LFP battery cell is measured as 0.004 Ohm · m2 , which was found to be consistent with the values determined using the impedance spectroscopy techhnique in the published literature for lithium-carbon film electrodes.

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