安全電池実現のための適切添加剤を用いた先端的非引火性電解液の理論的設計

本研究的主要目的是通过计算设计一种先进的不可燃电解质，用于实际安全的锂离子电池。为此，我们专注于基于不易燃的磷酸三甲酯（TMP）溶剂的高盐浓度（HC）电解质的稀释。首先，我们旨在研究HC TMP基电解质中固体电解质中间相（SEI）层形成的微观机理。使用Red Moon方法，揭示了大量的盐阴离子位于HC电解质中的SEI表面上，增强了具有SEI盐衍生物质的致密无机层的网络形成。接下来，我们旨在“稀释”这种HC TMP基电解质，以解决其低离子电导率和高粘度。为此，设计了具有高度疏水性的新型氢氟醚（HFE）。使用MD和QM计算，Li+的自扩散常数和离子电导率应显着提高稀释与双（1，1，2，2-四氟乙基）醚（B2 E）和双（五氟乙基）醚（BPE）相比，其他常见的HFE稀释剂。此外，HFE具有在HC TMP基溶液中形成局部浓缩电解质的高能力，导致对形成稳定且致密的无机SEI膜的高期望。最后，通过微观分析SEI膜的组成对其力学性能的影响，研究了SEI膜的弹性。评价SEI的延展性以及每种电解质化合物对SEI稳定性的作用。

The main goal of this study is to design computationally an advanced non-flammable electrolyte for a practical safe Li-ion batteries. For that, we focused on the dilution the highly salt-concentrated (HC) electrolyte based on non-flammable trimethyl-phosphate (TMP) solvent. First, we aimed to investigate the microscopic mechanism of the solid electrolyte interphase (SEI) layer formation in HC TMP-based electrolyte. Using Red Moon methodology, it was revealed that a large amount of salt anions is localized on the SEI surface in HC electrolyte, enhancing the network formation of a dense inorganic layer with SEI salt-derived species. Next, we aimed to “dilute” such HC TMP-based electrolyte in order to address its low ionic conductivity and high viscosity. For that, new hydrofluoroethers (HFEs) were designed with high degree of fluorination. Using MD and QM calculations, self-diffusion constant of Li+ and the ionic conductivity should be significantly improved by dilution with bis(1,1,2,2-tetrafluoro ethyl) ether (B2E) and bis(pentafluoro ethyl) ether (BPE) compared to other common HFE diluents. In addition, HFEs have high ability to form a localized-concentrated electrolyte in HC TMP-based solution, leading to high expectation for the formation of a stable and a compact inorganic SEI film. Finally, the elasticity of the SEI layer was investigated through the microscopic analysis of the composition effect of the SEI on its mechanical properties. The ductility of the SEI were evaluated as well as the role of each electrolyte compound on the SEI stability.