Small Organic Molecules Regulate Transport-Limited Dendrite Growth in Aqueous Zn Battery Anodes
Year: 2026
Type: preprint
Abstract: Understanding electrochemical crystal growth at high rates and under far-fromequilibrium conditions is important for a broad range of industrial processes, including metal electrowinning, semiconductor plating, and electrochemical energy storage. In particular, transport-limited metal electrodeposition, which often produces aggressive dendritic morphologies, plays a critical role in the behavior of fast-charging battery anodes. Although small organic molecules such as urea are known to influence electrodeposition, their effects have primarily been studied at moderate current densities well below the mass-transport limit. Here, we investigate how urea affects Zn metal growth in concentrated aqueous battery electrolytes (10 M ZnCl2) under explicitly transport-limited conditions. Using operando visualization together with ex situ characterization, we find that urea transforms Zn dendrite structure once its concentration exceeds a threshold. In the absence of organic additives, Zn forms quasi-single-crystalline, needlelike dendrites whose crystallites exhibit apparent orientational correlation across the entire dendrite, over length scales of centimeters. This behavior suggests sustained growth from a small number of initially nucleated crystals. In contrast, above 5 wt.% urea, the dendrites initially lose their long-range orientational correlation before reverting to needle-like propagation. We attribute this transition to urea adsorption on the Zn surface, which modifies the relative kinetics of nucleation and crystal growth. Comparisons with structurally related small molecules indicate that molecular symmetry and functional group selection play an important role in governing this behavior: asymmetrical acetamide yields needle-like growth similar to the additive-free baseline, whereas retaining symmetry with methyl groups using acetone provides a dense morphology that extends cell lifespan. These findings provide new insight into the molecular regulation of electrochemical crystal growth under far-from-equilibrium conditions and may inform strategies for controlling Zn deposition in fast-charging aqueous batteries.
Source: ChemRxiv
Authors: Alex Kretzschmar, Kent J. X. Zheng
Institutions: The University of Texas at Austin, Texas Materials Institute
Language: English
Topic: Aqueous and Flow Batteries
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7213246510