Geirhos K, Lunkenheimer P, Michl M, Reuter D, Loidl A
Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany.
J Chem Phys. 2015 Aug 28;143(8):081101. doi: 10.1063/1.4929554.
Finding new ionic conductors that enable significant advancements in the development of energy-storage devices is a challenging goal of current material science. Aside of material classes as ionic liquids or amorphous ion conductors, the so-called plastic crystals (PCs) have been shown to be good candidates combining high conductivity and favorable mechanical properties. PCs are formed by molecules whose orientational degrees of freedom still fluctuate despite the material exhibits a well-defined crystalline lattice. In the present work, we show that the conductivity of Li(+) ions in succinonitrile, the most prominent molecular PC electrolyte, can be enhanced by several decades when replacing part of the molecules in the crystalline lattice by larger ones. Dielectric spectroscopy reveals that this is accompanied by a stronger coupling of ionic and reorientational motions. These findings, which can be understood in terms of an optimized "revolving door" mechanism, open a new path towards the development of better solid-state electrolytes.
寻找能够推动储能设备发展取得重大进展的新型离子导体是当前材料科学面临的一项具有挑战性的目标。除了离子液体或非晶态离子导体等材料类别外，所谓的塑性晶体（PCs）已被证明是兼具高导电性和良好机械性能的理想候选材料。PCs由分子构成，尽管材料呈现出明确的晶格结构，但其分子的取向自由度仍会波动。在本工作中，我们表明，在最著名的分子PC电解质丁二腈中，当用更大的分子取代晶格中的部分分子时，锂离子的电导率可提高数十倍。介电谱表明，这伴随着离子运动和重取向运动更强的耦合。这些发现可通过优化的“旋转门”机制来理解，为开发更好的固态电解质开辟了一条新途径。
