Year: 2026
Type: preprint
Abstract: Classical secondary-current theory predicts a directionally neutral through-thickness reaction distribution when a porous electrode’s effective electronic and ionic conductivities are equal. In a working concentrated electrolyte, the salt-concentration gradient adds a thermodynamic contribution to electrolyte current that shifts this balance. A convention-consistent reduction of the porous-electrode equations shows that, in the quasi-steady weak-depletion onset limit, reaction skew vanishes when the electronic-to-ionic conductivity ratio equals 1/(1+ρe), or 0.390 for the reference electrolyte. Separator-favored reaction therefore persists well below the classical equal-conductivity condition. Full Doyle–Fuller–Newman (DFN) calculations reproduce ∼93% of the predicted boundary displacement across a 2.7-fold change in ρe, although the reduced theory overpredicts skew amplitude away from the boundary; the zero location is the more robust reduced-order result. The boundary does not prescribe the finite-time trajectory: across a 36-condition rate–thickness study, 8 of 17 evaluable trajectories show collector-ward centroid motion followed by separator-ward recovery, and nearly matched cutoff capacities conceal different internal histories. Finally, differencing two depth-resolved stored-lithium profiles at matched delivered capacities recovers the capacity-window-averaged reaction distribution from two states, with predicted through-thickness contrasts reaching ∼33% in 150 µm electrodes.
Source: ChemRxiv
Author: Ramez A. Elgammal
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7204815737