Enhancing Cation Diffusion and Suppressing Anion Diffusion via Lewis-Acidic Polymer Electrolytes

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• 作者：Brett M. Savoie ; Michael A. Webb ; Thomas F. Miller III
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2017
• 出版时间：February 2, 2017
• 年：2017
• 卷：8
• 期：3
• 页码：641-646
• 全文大小：551K
• ISSN：1948-7185

文摘

Solid polymer electrolytes (SPEs) have the potential to increase both the energy density and stability of lithium-based batteries, but low Li⁺ conductivity remains a barrier to technological viability. SPEs are designed to maximize Li⁺ diffusivity relative to the anion while maintaining sufficient salt solubility. It is thus remarkable that poly(ethylene oxide) (PEO), the most widely used SPE, exhibits Li⁺ diffusivity that is an order of magnitude smaller than that of typical counterions at moderate salt concentrations. We show that Lewis-basic polymers like PEO favor slow cation and rapid anion diffusion, while this relationship can be reversed in Lewis-acidic polymers. Using molecular dynamics, polyboranes are identified that achieve up to 10-fold increases in Li⁺ diffusivities and significant decreases in anion diffusivities, relative to PEO in the dilute-ion regime. These results illustrate a general principle for increasing Li⁺ diffusivity and transference number with chemistries that exhibit weaker cation and stronger anion coordination.