Full-Range Simulation of a Commercial LiFePO₄Electrode Accounting for Bulk and Surface Effects: A Comparative Analysis

Abstract

The variable solid-state diffusivity (VSSD) and the resistive-reactant (RR) models that focus on different physical phenomena are used to investigate the solid-state transport (bulk effects) and electronic conductivity (surface effects) of LiFePO 4 (LFP). For the first time, the models are effectively validated against experimental galvanostatic discharge data over a full range of applied currents. To achieve a reasonable degree of accuracy, particle-level parameters are estimated by fitting to experimental data obtained under low-rate discharge conditions, whereas electrode-level properties are derived based on high-rate conditions. Particle size distribution turns out to play a pivotal role in determining the rate capability of the electrode determined by the VSSD and a revised version of the RR model. Based on the full-range comparative study, both the resistive-reactant effect and bulk-related rate limitations prove to contribute significantly to the electrode polarization, especially at high C-rate. The resistive-reactant effect is expected to increase in an electrode made of smaller LFP particles.

Mesoscopic Modeling of a LiFePO4Electrode: Experimental Validation under Continuous and Intermittent Operating Conditions

“…Previous modeling and experimental analyses of commercial LFP electrodes similar to that done here considered diffusion to be the determining factor at the end of charge/discharge; 27 Ultrafast charge/discharge of optimized LFP electrodes has also confirmed fast Li mobility in the bulk of LFP. 7,56 In order to assess a diffusion-limited scenario, we extended the mesoscopic model to account for the intra-unit diffusion along with a unimodal log-normal distribution for resistance.…”

“…[29][30][31][36][37][38][39] The dominant mechanism is determined by factors such as particle size and shape, 33,42 quality of ionically and electronically conductive coatings, synthesis route, structural defects, electrode formulation and microstructure, 43 temperature, applied potential/current 38,39 and the conditioning cycles or the cycling history. 32 Core-shell-type 14,44 and non-ideal solid-solution 26,27 models have been used to describe the juxtaposition of the two phases in a single particle observed during chemical lithiation/delithiation. However, in most cases they fail to provide an accurate physical picture of the process (i.e., filling of b channels in the Pnma space group of olivine crystal structure).…”

An Inverse Method for Estimating the Electrochemical Parameters of Lithium-Ion Batteries

“…Farkhondeh et al 49 fitted experimental data for Li/LFP half-cells for these three regions. The authors were able to determine the regions where each of the cell parameters is the most influential on the battery's behavior.…”

Three-dimensional Multi-Particle Electrochemical Model of LiFePO4 Cells based on a Resistor Network Methodology

“…This process has not totally been understood yet; hence, different mathematical models including core-shell [4][5][6], phase field [7][8][9], resistive reactant [10,11], and variable solid-state diffusivity [12,13] models have been proposed in the literature. Among these models, the VSSD model is simple yet physically descriptive that simulates the two-phase behaviour of the LFP by a concentration dependent diffusion coefficient [12].…”

“…Among these models, the VSSD model is simple yet physically descriptive that simulates the two-phase behaviour of the LFP by a concentration dependent diffusion coefficient [12]. Moreover, this model can predict the operating voltage of smallsized LFP batteries from low to high operating rates when it is incorporated in the Newman pseudo two-dimensional (P2D) model [13]. Incorporating this approach in P2D model, however, results in relatively slow simulations and therefore is not suitable to be integrated in the full-sized pouch configuration battery models or control simulations.…”