Pascal Zittlau, Sarah Mross, Dominik Gond, Maximilian Kohns
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引用次数: 0
Abstract
Multi-criteria optimization is used for developing molecular models for ethylene carbonate (EC) and propylene carbonate (PC), organic solvents commonly used in Li-ion batteries. The molecular geometry and partial charges of the solvents are obtained from quantum mechanical calculations. Using a novel optimization strategy that combines systematic variations of the Lennard-Jones parameters with a reduced units approach, the models are fitted to experimental data on the liquid density, vapor pressure, relative permittivity, and self-diffusion coefficient. Since no experimental data for the self-diffusion coefficient of pure EC were available in the literature, they are measured in this work using a gradient-based nuclear magnetic resonance technique. For all pure component properties, excellent agreement between experiment and simulation is obtained. Moreover, the predictive capabilities of the new solvent models are assessed by comparison to experimental data for the liquid density and relative permittivity of mixtures of EC and PC. In addition, molecular models for the anions PF6-, BF4-, and ClO4- in solutions of their lithium electrolytes in PC are developed using experimental data on the solution densities. Finally, the self-diffusion coefficients of LiPF6 in PC and in aqueous solution are predicted and compared, showing that diffusion is much slower in the organic solution due to the formation of larger solvent shells around the ions. Furthermore, an analysis of the radial distribution functions in these solutions suggests that the ions have much less impact on the structure of the solvent PC than on water.
多标准优化用于开发锂离子电池常用有机溶剂碳酸乙烯(EC)和碳酸丙烯(PC)的分子模型。溶剂的分子几何形状和部分电荷是通过量子力学计算获得的。利用一种新颖的优化策略(将伦纳德-琼斯参数的系统变化与还原单元方法相结合),将模型与有关液体密度、蒸汽压、相对介电常数和自扩散系数的实验数据进行了拟合。由于文献中没有纯 EC 自扩散系数的实验数据,因此本研究采用基于梯度的核磁共振技术对其进行了测量。对于所有纯成分的特性,实验和模拟结果都非常吻合。此外,通过与 EC 和 PC 混合物的液体密度和相对介电常数的实验数据进行比较,评估了新溶剂模型的预测能力。此外,还利用溶液密度的实验数据,建立了阴离子 PF6-、BF4- 和 ClO4-在 PC 中的锂电解质溶液的分子模型。最后,对 PC 和水溶液中 LiPF6 的自扩散系数进行了预测和比较,结果表明,由于离子周围形成了较大的溶剂壳,有机溶液中的扩散速度要慢得多。此外,对这些溶液中径向分布函数的分析表明,离子对 PC 溶剂结构的影响远远小于对水的影响。
期刊介绍:
The Journal of Chemical Physics publishes quantitative and rigorous science of long-lasting value in methods and applications of chemical physics. The Journal also publishes brief Communications of significant new findings, Perspectives on the latest advances in the field, and Special Topic issues. The Journal focuses on innovative research in experimental and theoretical areas of chemical physics, including spectroscopy, dynamics, kinetics, statistical mechanics, and quantum mechanics. In addition, topical areas such as polymers, soft matter, materials, surfaces/interfaces, and systems of biological relevance are of increasing importance.
Topical coverage includes:
Theoretical Methods and Algorithms
Advanced Experimental Techniques
Atoms, Molecules, and Clusters
Liquids, Glasses, and Crystals
Surfaces, Interfaces, and Materials
Polymers and Soft Matter
Biological Molecules and Networks.