Demystifying Charge Transport Limitations in the Porous Electrodes of Lithium‐Ion Batteries

Abstract

A possible strategy to give a simultaneous boost to the energy and power attributes of the current generation of lithium‐ion batteries is developing thick porous electrodes with a high loading of active material alongside optimal percolation networks for the ions and electrons. However high the insertion capacity and kinetics of the single particle lithium‐insertion materials, the energy and power density of the cell can be capped by the ionic and electronic transport limitations in the porous electrode. In this work, a physical picture grounded in experiment and theory is proposed to spotlight and quantify the pivotal role of the micro‐scale porosity and active‐material loading in determining the tortuosity, effective transport properties, and performance limitations of porous electrodes. The outcome is a phenomenological picture coupled with a theoretical framework for the deconvolution of the relative shares of the electronic and ionic transport limitations over short and long ranges regarding the performance limitation of lithium‐ion batteries.

Constructive versus Destructive Heterogeneity in Porous Electrodes of Lithium-Ion Batteries

“…We used an empirical formalism in analogy with Peukert’s law , to quantify the sensitivity of the energy or capacity ( Y ) to the (dis)­charge current in single-layer and bilayer electrodes (Figure S3)­ where Y j can be the (dis)­charge energy or capacity at the C-rate I j . α > 0 and β > 0 are the two series of constants, which are refined via a least-square fitting of the experimental data at different C-rates, i.e., I j = 1/2, 1, 2, and 3 (Figure S4).…”

“…Although the common belief is usually to link the heterogeneity with the destructive impacts on battery performance, our results highlight the potential constructive role of heterogeneity in designing high-power and long-lasting electrodes. Please be advised that the slurry composition and the details of the processing conditions can significantly impact the microstructural details of the resulting porous electrodes . As such, care should be taken before generalizing the findings reported here to other electrode systems.…”

A limitation map of performance for porous electrodes in lithium-ion batteries

“…The physico-structural properties of the 16 electrodes are presented in Table S1. As introduced in our previous work (Hamed et al, 2020), we used an empirical formalism in analogy with the Peukert's law to quantify the sensitivity of the energy (Y ) of the NMC electrodes to the discharge current: 3)…”

“…The 48 sets of experimental voltage-capacity plots from the 16 NMC622 electrodes discharged at three different C-rates (C/5, 1C, 5C) were compared against the simulation outputs. The only modification compared to the original model developed by Doyle et al (Doyle et al, 1993) is the incorporation of multiple groups of active-material particles with different sizes (Figure S2) and contact resistances to the electronic and ionic percolation network of the electrode (Hamed et al, 2020). A summary of the model framework and its main parameters are shown in Tables S3 and S4, respectively.…”

“…dqh = U p + U s + U l . The latter depends on the quality of the local contacts between the electronic and ionic percolation networks and the active-material particles (Hamed et al, 2020;Jiang et al, 2020;Morelly et al, 2018). The exact composition of the total polarization from the aforementioned three polarization subsets, Y i = ll OPEN ACCESS materials but also on the electrode recipe, preparation steps, and (dis)charge current (Besnard et al, 2017;Du et al, 2010;Nyman et al, 2010;Tian et al, 2019).…”