(580b) Electroconvective Flow Mitigation through Viscoelastic Electrolyte Property Modifications

Electrodeposition of metals is a critical process for the commercialization of next generation, energy dense batteries that utilize metallic anodes, such as lithium. The electrodeposition in these systems must be stabilized in order to enable long and safe lifetimes in practical applications. The chemical, morphological and hydrodynamic instabilities in a battery inevitably lead to rough deposition in the form of dendritic structures that significantly hinder safety and performance. Lithium deposition is inherently rough, but this roughness can be enhanced through hydrodynamic instabilities in the electrolyte [1]. Solutions of high molecular weight polymers are an interesting candidate for the suppression of this flow because of their high viscosity coupled with high ionic conductivity. These viscoelastic liquid electrolytes have been shown to reduce the roughness of deposits and influence convection at the interface [2]. This work has been extended to isolate the hydrodynamics from any morphological impacts by using ion-selective membranes. These results demonstrate that when roughness effects are removed the polymers are even more effective in mitigating the overlimiting conductance from electroconvection. However, to understand the polymer influence this talk will focus on the effects of adjusting electrolyte properties through polymer molecular weight changes. By adjusting the size of the polymer additives, the entanglement transition will occur at much different polymer concentrations, along with changes in polymer relaxation times, and ionic conductivity. Additionally, the viscous and elastic components of the electrolytes can be tuned to understand their influence on electroconvective flows in the bulk and interface.

[1] Barkey, D. P., et al. The role of induced convection in branched electrodeposit morphology selection. J. Electrochemical Society 1994, 141, 1206-1212.

[2] Wei, S., Cheng, Z., Nath, P., Tikekar, M. D., Li, G., & Archer, L. A. Stabilizing electrochemical interfaces in viscoelastic liquid electrolytes. Science Advances, 2018, 4(3).