Deep eutectic solvents (DES) are environmentally-friendly electrolytes that are gaining interest for electrodeposition and energy storage applications. In these applications, metal electrodeposits with smooth, non-dendritic morphology are desired and thus effective strategies for suppressing roughness evolution are critically needed. A commonly employed and rather effective strategy for suppressing roughness evolution in metal electrodeposition is the use of electrolyte additives; however, the availability of such additives in DES electrolytes is limited and so is the understanding of the mechanisms through which additives suppress roughness amplification in DES media. In the present contribution, we demonstrate that polyethylenimine (PEI) is an effective electrolyte additive that suppresses roughness evolution during Cu electrodeposition in ethaline DES. PEI, due to its adsorption–deactivation properties, exhibits a unique hysteresis response during voltammetric studies of Cu electrodeposition – this response is analyzed using a mathematical model incorporating the relevant PEI transport, surface adsorption and deactivation processes. The model provides guidelines for selection of optimal conditions (e.g., PEI concentration) for effective suppression of roughness amplification in Cu electrodeposition.

深共晶溶剂（DES）是环保型电解质，在电沉积和能量存储应用中引起了人们的兴趣。在这些应用中，需要具有光滑，非枝晶形态的金属电沉积物，因此迫切需要有效的抑制粗糙度演变的策略。抑制金属电沉积过程中粗糙度发展的一种常用且相当有效的策略是使用电解质添加剂。然而，这种添加剂在DES电解质中的可用性受到限制，因此对添加剂抑制DES介质中粗糙度增加的机理的理解也受到限制。在本文稿中，我们证明了聚乙烯亚胺（PEI）是一种有效的电解质添加剂，可抑制乙胺DES在Cu电沉积过程中的粗糙度演变。由于PEI具有吸附-失活特性，因此在伏安法研究Cu电沉积时表现出独特的磁滞响应-使用包含相关PEI传输，表面吸附和失活过程的数学模型来分析该响应。该模型为选择最佳条件提供了指导（例如。，PEI浓度）可有效抑制铜电沉积中粗糙度的放大。