Carrasco-Busturia David, Lysgaard Steen, Jankowski Piotr, Vegge Tejs, Bhowmik Arghya, García-Lastra Juan María
Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs., Lyngby, Denmark.
ChemSusChem. 2021 May 6;14(9):2034-2041. doi: 10.1002/cssc.202100163. Epub 2021 Apr 6.
Deep eutectic solvents (DESs) have emerged as an alternative for conventional ionic liquids in aluminum batteries. Elucidating DESs composition is fundamental to understand aluminum electrodeposition in the battery anode. Despite numerous experimental efforts, the speciation of these DESs remains elusive. This work shows how ab initio molecular dynamics (AIMD) simulations can shed light on the molecular composition of DESs. For the particular example of AlCl :urea, one of the most popular DESs, we carried out a systematic AIMD study, showing how an excess of AlCl in the AlCl :urea mixture promotes the stability of ionic species vs neutral ones and also favors the reactivity in the system. These two facts explain the experimentally observed enhanced electrochemical activity in salt-rich DESs. We also observe the transfer of simple [AlCl (urea) ] clusters between different species in the liquid, giving rise to free [AlCl ] units. The small size of these [AlCl ] units favors the transport of ionic species towards the anode, facilitating the electrodeposition of aluminum.
深共熔溶剂（DESs）已成为铝电池中传统离子液体的替代品。阐明DESs的组成对于理解电池阳极中的铝电沉积至关重要。尽管进行了大量实验，但这些DESs的物种形成仍然难以捉摸。这项工作展示了从头算分子动力学（AIMD）模拟如何能够揭示DESs的分子组成。对于最常用的DESs之一AlCl₃:尿素的具体例子，我们进行了系统的AIMD研究，表明AlCl₃:尿素混合物中过量的AlCl₃如何促进离子物种相对于中性物种的稳定性，并且还有利于系统中的反应性。这两个事实解释了实验观察到的富含盐的DESs中增强的电化学活性。我们还观察到简单的[AlCl₃(尿素)₃]簇在液体中不同物种之间的转移，产生游离的[AlCl₄]⁻单元。这些[AlCl₄]⁻单元的小尺寸有利于离子物种向阳极的传输，促进铝的电沉积。
