THEORETICAL MODELLING AND SIMULATION OF PRISTINE LFP AND Ni DOPED LFP AS CATHODE MATERIAL OF LITHIUM ION BATTERY

Abstract

A simulation model for electrochemical impedance spectroscopy (EIS) of pristine LiFePO4 (LFP), doped with various concentrations of Ni such as LiNi.03Fe0.97PO4 (LFNP3), LiNi.05Fe0.95PO4 (LFNP5) and LiNi.07Fe0.93PO4 (LFNP7) in place of Fe has been developed in COMSOL Multiphysics. The model was studied under constant frequency domain perturbation using AC current impulses of 5-10 mA in frequency range 10kHz-10mHz. The simulated model parameters, which depict ideal conditions were varied one at a time, and then, two at a time to bring them close to experimental performance as extracted from experimental data. Among all the undoped and Ni doped LFP samples, lithium iron phosphate doped with 3% Ni i.e. LiNi.03Fe0.97PO4 comes close to 92% of the theoretical predicted yield [55], which translates to a maximum electrode state of charge of 0.9-0.92. The dielectric constant of pristine LFP, LFNP3, LFNP5 and LFNP7 is dependent on frequency of operation and affects the capacitance of electrode as the frequency domain perturbation is investigated. At low level of doping, the electrochemical performance improves, but on increasing the doping content of Ni more than 5 %, the resistances increase beyond that of pristine LPF.