Active Modulated Electroconvection and Current Response in Polymer Electrolyte Solutions

Abstract

Active modulations of charge-selective interfaces are highly emphasized in electrodeposition and liquid batteries, where the overlimiting current response is linked to dendrite formation on battery electrodes and electrochemical energy storage correlated with electroconvection. However, the overlimiting ion transport with surface topology and polymer electrolytes is poorly understood in electrochemical engineering at present. We perform a global analysis of the flow patterns, energy spectra, instantaneous and statistical morphology of electroconvection flow (ECF) that exists for polymers and surface patterning by high-resolution direct numerical simulations with nonlinear Poisson–Nernst–Planck–Navier–Stokes (PNP–NS) schemes. The coupling of the electric field and patterning mode with the elastic field gives rise to new instabilities and a completely new mechanism for the current response and system energy distribution. Polymer macromolecules exhibit notable active modulation, dividing I-V (current-voltage) curves into several new branches characterized by energy sources or energy sinks at varying voltage amplitudes. The instantaneous results reveal chaotic multiscale vortices and charge ribbons that separate and merge in a highly irregular manner. In addition, neutral polymer macromolecules act as flow stabilizers, and energy spectral densities (SEDs) suggest that the power law exponential decays over narrower spatiotemporal scales than in Newtonian fluids. Owing to the distinction from purely electrokinetic instability-induced modes, the patterning dominant mode enhances ion mass transfer and cancels the horizontal line at a low voltage limit. The relevant results provide comprehensive physical insight into active modulated electroconvection and affect the design of electromembrane platforms.

Keywords: Ion-selective membrane, Electroosmotic flow, Patterning surface, Electrohydrodynamic, Polymer, ionic transport, electroconvection, Viscoelastic fluid