Electromigration in Lithium Whisker Formation Plays Insignificant Role during Electroplating

Plating of metallic Li results in deposition of needle‐like structures, whose prevention is a fundamental challenge that currently restricts the development and application of high energy Li‐metal rechargeable batteries. Over the last decades, a number of mechanisms were proposed to explain morphological instabilities of planar crystallization fronts. The suggested reasons for non‐uniform deposition include Li⁺ concentration gradients in the nutrient phase, accelerated electromigration to the tip of the growing needle, specific nucleation behavior, mechanical properties of the solid‐electrolyte interphase, and many more. Here, we unravel the role of electromigration currents by adding indifferent cations (TBA⁺, TEA⁺) to screen for non‐uniform electric fields, thus, suppressing migration‐driven mass‐transfer. Nearly full exclusion of electromigration currents showed no impact on the morphology of electrodeposited lithium. Therefore, the role of electromigration seems negligible, and electric field edge effects are undoubtedly not the main driving force for filament growth during Li plating.