(181o) Stabilizing Electroconvective Flow in Viscoelastic Polymer Electrolytes

Electrodeposition is critical for battery safety and stabilization. In a variety of liquid electrolytes, electrodeposition is determined by hydrodynamic and morphological instabilities, both of which could induce strong electroconvenction at the interfaces. The anode of such battery is prone to shape change and dendritic formation during charging cycles that eventually leads to short-circuit and battery failure. In our study, we find there are two main factors playing important roles in the electrodeposition instabilities. One factor is the viscoelasticity of polymer electrolytes, resulting in the increased voltage window of limiting current regime. The other factor is buoyancy force. In unstable gravitationally configuration, the variation of salt density leads to a Rayleigh-Bernard flow that increases the current. Furthermore, dimensional parameters of the buoyancy effect are studied in the viscoelastic electrolyte system. Visualization experiments at nano/micro scale along with the comparison to theoretical and simulation studies help to quantitatively understand the mechanisms. In our battery applications, adding ultrahigh molecular weight polymers in liquid electrolyte is proven to be effective in stabilizing electroconvective flow at the interface and improving battery performance.