Andersson D, Engberg D, Swenson J, Svanberg C, Howells W S, Börjesson L
Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
J Chem Phys. 2005 Jun 15;122(23):234905. doi: 10.1063/1.1931568.
A quasielastic neutron scattering study has been performed on a polymer gel electrolyte consisting of lithium perchlorate dissolved in ethylene carbonate/propylene carbonate and stabilized with poly(methyl methacrylate). The dynamics of the solvent, which is crucial for the ion conduction in this system, was probed using the hydrogen/deuterium contrast variation method with nondeuterated solvent and a deuterated polymer matrix. Two relaxation processes of the solvent were studied in the 10-400 microeV range at different temperatures. From analysis of the momentum transfer dependence of the processes we conclude that the faster process ( approximately 100 microeV) is related to rotational diffusion of the solvent and the slower process ( approximately 10 microeV) to translational diffusion of the solvent. The translational diffusion is found to be similar to the diffusion in the corresponding liquid electrolyte at short distances, but geometrically constrained by the polymer matrix at distances beyond approximately 5 A. The study indicates that the hindered diffusion of the solvent on a length scale of the polymer network interchain distance ( approximately 5-20 A) is sufficient to explain the reduced macroscopic diffusivity and ion conductivity of the gel electrolyte compared to the liquid electrolyte.
对一种由溶解在碳酸亚乙酯/碳酸亚丙酯中并用聚甲基丙烯酸甲酯稳定化的高氯酸锂组成的聚合物凝胶电解质进行了准弹性中子散射研究。使用非氘代溶剂和氘代聚合物基质的氢/氘对比度变化方法探测了该体系中对离子传导至关重要的溶剂动力学。在不同温度下，研究了10 - 400微电子伏特范围内溶剂的两种弛豫过程。通过对这些过程的动量转移依赖性分析，我们得出结论，较快的过程（约100微电子伏特）与溶剂的旋转扩散有关，较慢的过程（约10微电子伏特）与溶剂的平动扩散有关。发现平动扩散在短距离内与相应液体电解质中的扩散相似，但在距离超过约5埃时受到聚合物基质的几何限制。该研究表明，溶剂在聚合物网络链间距离（约5 - 20埃）的长度尺度上的受阻扩散足以解释与液体电解质相比凝胶电解质宏观扩散率和离子电导率的降低。
