Low Frequency Impedance Spectroscopy – Modeling Study on the Transferability of Solid Diffusion Coefficients

<div class="section abstract"><div class="htmlview paragraph">Modeling of lithium iron phosphate electrodes calls for appropriate extensions of established model approaches. An electrochemical pseudo two-dimensional and a single-particle model are enhanced to address the phase separating behavior of this material with a variable solid state diffusion model. A particle size distribution model tackles the heterogeneity of the electrode microstructure. Both models are embedded in a framework to describe multi-layer electrode designs featuring segregated material properties. The models are parameterized following literature replicating a good match with measured discharge curves at low, medium and high currents. A simplified version of the rigorous model shows the effort of reparameterization, the computational advantage of model order reduction techniques, the model accuracy and application scope. The impact of the electrode morphology is investigated using the full model by simulating variants of porosity and particle size distribution in single and bi-layered electrodes. The simulations reveal porosity changes, and electrode layering plays a minor role as solid diffusion in lithium iron phosphate particles dominates the cell behavior. This is underlined by results from varied particle size distributions that strongly influence the predicted cell capacity.</div></div>

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Parameterization of an Electrochemical Battery Model Using Impedance Spectroscopy in a Wide Range of Frequency

Chen,

Wurzenberger

2024

SAE Technical Paper Series

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<div class="section abstract"><div class="htmlview paragraph">The parameterization of the electrochemical pseudo-two-dimensional (P2D) model plays an important role as it determines the acceptance and application range of subsequent simulation studies. Electrochemical impedance spectroscopy (EIS) is commonly applied to characterize batteries and to obtain the exchange current density and the solid diffusion coefficient of a given electrode material. EIS measurements performed with frequencies ranging from 1 MHz down to 10 mHz typically do not cover clearly isolated solid state diffusion processes of lithium ions in positive or negative electrode materials. To extend the frequency range down to 10 μHz, the distribution function of relaxation times (DRT) is a promising analysis method. It can be applied to time-domain measurements where the battery is excited by a current pulse and relaxed for a certain period. By means of curve-fitting techniques, the pulse-relaxation measurement can be transferred in a function suitable for the DRT analysis, which is the basis for constructing additional low-frequency impedance points.</div><div class="htmlview paragraph">In this work, the EIS measured in the frequency domain and the simulated EIS derived from the time-domain measurement by the DRT method are combined to cover all electrochemical processes of the battery, especially the lithium-ion diffusion in the electrodes. The electrical equivalent circuit model (ECM) consisting of resistors, ZARC elements and Warburg elements in the frequency domain is applied to fit the EIS curve and identify the P2D model parameters. By investigating the intercalation processes using the distribution function of the differential capacity (DDC) technique, particles with different particle sizes are considered and their corresponding solid diffusion coefficients are identified by the established ECM. The consistency between time- and frequency-domain data is elaborated based on a model of a commercial automotive cell.</div></div>

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Low Frequency Impedance Spectroscopy – Modeling Study on the Transferability of Solid Diffusion Coefficients

Cited by 3 publications

References 28 publications

Efficient Parametrization of Electrochemical LIB Models

Efficient Parametrization of Electrochemical LIB Models

High load Operation of Lithium-Ion Batteries – Modeling Study on a LiFePO <sub>4</sub> Graphite Cell

Parameterization of an Electrochemical Battery Model Using Impedance Spectroscopy in a Wide Range of Frequency

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