  Metal electrodeposition in batteries is fundamentally unstable and affected
by different instabilities depending on operating conditions and chemical
composition. Particularly at high charging rates, a hydrodynamic instability
called electroconvection sets in that aggravates the situation by creating
non-uniform ion flux and preferential deposition at the electrode. Here, we
experimentally investigate how oligomer additives interact with the
hydrodynamic instability at a cation selective interface. From electrochemical
measurements and direct visualization experiments, we find that
electroconvection is delayed and suppressed at all voltage in the presence of
oligomers. Our results also reveal that it is important to consider the role of
polymers at the interface, in addition to their bulk effects, to understand the
stabilization effect and its mechanism.
