A Non-Linear Electrical Model for Iron Doped Sodium Metal Halides Batteries

In this paper an improved modelling of Sodium Metal Halides Batteries (SMHB) that considers the effects associated to the iron doping, is presented. The proposed nonlinear electrical configuration has been developed analysing both the electrochemical phenomena occurring during the discharging and charging processes and the experimental tests performed on a SMHB. The parameters of the proposed electrical model has been determined referring to step current tests, specifically designed for the identification of the proposed model parameters and performed on a commercial SMHB. In order to put in evidence the improvements achieved, the comparison between experimental and simulation results is presented. In particular, the voltage time evolutions during step currents application, evaluated considering both the proposed SMHB Thevenin model and that recently reported in the technical literature, are shown. The results obtained improves the possibility to mimic the behaviour of SMHB especially at low value of State of Charge, opening new opportunity in the exploitation of this class of electrochemical batteries.