Abstract
Galvanostatic intermittent titration technique (GITT) – a popular method for characterizing kinetic and transport properties of battery electrodes – is predicated on the proper evaluation of electrode active area. LiNi0.5044Co0.1986Mn0.2970O2 (NCM523) material exhibits a complex morphology in which sub-micron primary particles aggregate to form secondary particle agglomerates. This work proposes a new active area formulation for primary/secondary particle agglomerate materials to better mimic the morphology of NCM532 electrodes. This formulation is then coupled with macro-homogeneous models to simulate GITT and half-cell performance of NCM523 electrodes. Subsequently, the model results are compared against the experimental results to refine the area formulation. A single parameter, the surface roughness factor, is proposed to mimic the change in interfacial area, diffusivity and exchange current density simultaneously and detailed modeling results are presented to provide valuable insights into the efficacy of the formulation.
Highlights
Amongst the aforementioned cathode materials in the NMC family, Li(Ni0.33Mn0.33Co0.33)O219 and Li(Ni0.5Mn0.3Co0.2)O220 have already been adopted for commercial use
The authors reported three different computations for Li diffusion coefficient values based on cell geometric area, BET surface area and electrochemical active area
It is apparent that Galvanostatic Intermittent Titration Technique (GITT) and Electrochemical Impedance Spectroscopy (EIS) have emerged as robust electrochemical techniques for battery material characterization
Summary
Amongst the aforementioned cathode materials in the NMC family, Li(Ni0.33Mn0.33Co0.33)O219 and Li(Ni0.5Mn0.3Co0.2)O220 have already been adopted for commercial use. Titration Technique (GITT) and Electrochemical Impedance Spectroscopy (EIS) to determine the diffusion coefficient of Li ions in spherical NCM523 Both these methods require the accurate quantification of electroactive area for subsequent computation of diffusivity. It becomes imperative to design first an accurate mathematical descriptor of active area for NCM523 electrodes This estimate is coupled with macro homogeneous performance models to simulate GITT and half-cell performance of NCM523 electrodes. The objective of this work is to extract accurate kinetic and transport properties from experimental GITT datasets which can be further used in half-cell performance studies. The model serves two purposes; firstly, it refines battery material property data extraction from experimental GITT/half-cell performance datasets; and secondly, it can be used as a predictive tool to estimate NCM523 battery performance under different operating conditions. Redistribution subject to ECS terms of use (see ecsdl.org/site/terms_use) unless CC License in place (see abstract)
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