Maiti Moumita, Krishnamoorthy Anand Narayanan, Mabrouk Youssef, Mozhzhukhina Nataliia, Matic Aleksandar, Diddens Diddo, Heuer Andreas
Institute of Physical Chemistry, University of Münster, Corrensstrasse 28/30, 48149Münster, Germany.
Forschungszentrum Jülich GmbH, Helmholtz-Institute Münster (IEK-12), Corrensstraße46, 48149 Münster, Germany.
Phys Chem Chem Phys. 2023 Aug 2;25(30):20350-20364. doi: 10.1039/d3cp01236k.
Liquid electrolyte design and modelling is an essential part of the development of improved lithium ion batteries. For mixed organic carbonates (ethylene carbonate (EC) and ethyl-methyl carbonate (EMC) mixtures)-based electrolytes with LiPF as salt, we have compared a polarizable force field with the standard non-polarizable force field with and without charge rescaling to model the structural and dynamic properties. The result of our molecular dynamics simulations shows that both polarizable and non-polarizable force fields have similar structural factors, which are also in agreement with X-ray diffraction experimental results. In contrast, structural differences are observed for the lithium neighborhood, while the lithium-anion neighbourhood is much more pronounced for the polarizable force field. Comparison of EC/EMC coordination statistics with Fourier transformed infrared spectroscopy (FTIR) shows the best agreement for the polarizable force field. Also for transport quantities such as ionic conductivities, transference numbers, and viscosities, the agreement with the polarizable force field is by far better for a large range of salt concentrations and EC : EMC ratios. In contrast, for the non-polarizable variants, the dynamics are largely underestimated. The excellent performance of the polarizable force field is explored in different ways to pave the way to a realistic description of the structure-dynamics relationships for a wide range of salt and solvent compositions for this standard electrolyte. In particular, we can characterize the distinct correlation terms between like and unlike ions, relate them to structural properties, and explore to which degree the transport in this electrolyte is mass or charge limited.
液体电解质的设计与建模是改进锂离子电池开发的重要组成部分。对于以LiPF为盐的混合有机碳酸盐（碳酸乙烯酯（EC）和碳酸甲乙酯（EMC）混合物）基电解质，我们比较了极化力场与标准非极化力场，有无电荷重新标度以模拟其结构和动力学性质。我们的分子动力学模拟结果表明，极化力场和非极化力场具有相似的结构因子，这也与X射线衍射实验结果一致。相比之下，锂周围环境存在结构差异，而极化力场中锂-阴离子周围环境的差异更为明显。将EC/EMC配位统计与傅里叶变换红外光谱（FTIR）进行比较，结果表明极化力场的一致性最佳。对于诸如离子电导率、迁移数和粘度等输运量，在大范围的盐浓度和EC:EMC比例下，与极化力场的一致性也远更好。相比之下，对于非极化变体，动力学被大大低估。通过不同方式探索了极化力场的优异性能，为真实描述该标准电解质在大范围盐和溶剂组成下的结构-动力学关系铺平道路。特别是，我们可以表征同类离子和异类离子之间不同的相关项，将它们与结构性质联系起来，并探索该电解质中的输运在多大程度上受质量或电荷限制。
