With the growing usage of lithium-ion (Li-ion) batteries in various applications from stationary applications to automotive industries, their ageing mechanism and its influencing factors have become a big concern today. Ageing may be defined as deterioration in the performance of the battery due to irreversible physical and chemical changes like internal resistance rise, electrolyte decompositions, electrodes cracking and solid electrolyte interphase (SEI) modification/growth. The aim of this research article is to study and analyse the behaviour of SEI layer growth at the anode using a novel non-invasive magnetic field probing (MFP). A 3-d model based upon well-known John Newman’s pseudo 2-d approach has been developed in COMSOL Multiphysics®. It is observed that the magnetic field response (MFR) is inversely related to SEI growth. Anode’s state of charge (SoC) response with SEI layer and MFR is also studied.