Wei Shuya, Cheng Zhu, Nath Pooja, Tikekar Mukul D, Li Gaojin, Archer Lynden A
Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA.
Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853, USA.
Sci Adv. 2018 Mar 23;4(3):eaao6243. doi: 10.1126/sciadv.aao6243. eCollection 2018 Mar.
Electrodeposition is a widely practiced method for creating metal, colloidal, and polymer coatings on conductive substrates. In the Newtonian liquid electrolytes typically used, the process is fundamentally unstable. The underlying instabilities have been linked to failure of microcircuits, dendrite formation on battery electrodes, and overlimiting conductance in ion-selective membranes. We report that viscoelastic electrolytes composed of semidilute solutions of very high-molecular weight neutral polymers suppress these instabilities by multiple mechanisms. The voltage window Δ in which a liquid electrolyte can operate free of electroconvective instabilities is shown to be markedly extended in viscoelastic electrolytes and is a power-law function, Δ : η, of electrolyte viscosity, η. This power-law relation is replicated in the resistance to ion transport at liquid/solid interfaces. We discuss consequences of our observations and show that viscoelastic electrolytes enable stable electrodeposition of many metals, with the most profound effects observed for reactive metals, such as sodium and lithium. This finding is of contemporary interest for high-energy electrochemical energy storage.
电沉积是一种在导电基底上制备金属、胶体和聚合物涂层的广泛应用的方法。在通常使用的牛顿液体电解质中，该过程从根本上说是不稳定的。潜在的不稳定性与微电路故障、电池电极上枝晶的形成以及离子选择性膜中的超极限电导有关。我们报告称，由非常高分子量的中性聚合物的半稀溶液组成的粘弹性电解质通过多种机制抑制了这些不稳定性。在粘弹性电解质中，液体电解质能够在无电对流不稳定性的情况下运行的电压窗口Δ被显著扩展，并且是电解质粘度η的幂律函数，即Δ ∝ η 。这种幂律关系在液体/固体界面处的离子传输阻力中也有体现。我们讨论了我们观察结果的影响，并表明粘弹性电解质能够实现多种金属的稳定电沉积，对于活性金属（如钠和锂）观察到的影响最为显著。这一发现对于高能电化学储能具有当代意义。
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