Novel Methodology of General Scaling-Approach Normalization of Impedance Parameters of Insertion Battery Electrodes – Case Study on Ni-Rich NMC Cathode: Part II. Detailed Analysis Using a Transmission Line Model

Here, we extend the general approach shown in PART-1 to a detailed analysis of the measured data using our previously published physics-based transmission line model (TLM). We construct general relationships between the TLM parameters and the electrode mass. We then systematically check the scaling properties of all model parameters by fitting the measured impedance responses of 8 NMC-NMC cells with different masses (thicknesses) of NMC cathodes ranging from 2.3 to 58.5 mg per 2 cm 2 of geometric electrode surface. We consider in detail all deviations of the measured spectra from the idealized spectra predicted by the model. Among other things, we discuss the high-frequency inductive effects, the ambiguities in the analysis of the low-frequency diffusion phenomena, and the effects of non-ideal capacitive properties (the so-called constant-phase elements) on the shape of the measured spectra. We also report an unexpected additional feature observed in measurements on thin (light) electrodes: a diffusion arc due to the diffusion of lithium in the electrolyte in the micropores of the NMC aggregates in the material used. Finally, we present a detailed dependence of all model parameters on the mass (thickness) of the electrode and discuss the potential practical significance of such an analysis.