快速充放锂电池的离子扩散机理及其固体电解质界面的理论设计

以电动汽车为代表的新能源汽车是未来交通工具发展的方向，但是电池动辄几小时的充电时间限制了电动汽车的大规模推广。高离子迁移率的电解质及稳定高效的固体电解质界面是快速充放电锂电池的基本材料基础。本项目拟通过第一性原理分子动力学模拟和密度泛函理论计算，系统的研究锂离子在不同液体电解质中的扩散过程，总结出液体电解质中可能存在的几种锂离子扩散方式及其对应的基本条件，并归纳出锂离子扩散方式与离子电导率之间的关联，以期从基本物理机制上解释最近实验中发现的高锂盐浓度电解质中的反常的超快扩散行为。在此基础上，深入研究具有“反常超快锂离子扩散”特征的高浓度电解质与电极界面膜的形成过程、锂离子扩散特点、界面稳定性等问题，并进一步通过高通量的计算设计寻找改善固体电解质界面膜性能和稳定性的有效途径，为新型可快速充放电锂电池需求的高离子迁移率电解质及固体电解质界面膜的选取和性能改进提供相关的科学依据。

New energy vehicles such as electric vehicles are the new transport with good prospects for the development. However, waiting hours to recharge the batteries limit the large-scale applications of electric vehicles. The high mobility rate electrolytes and stable solid electrolyte interfaces are the basic materials for the rapid charging lithium batteries. This project focus on the diffusion processes of lithium ion in the liquid electrolytes and solid electrolyte interfaces by the first principles molecular dynamics simulations and density functional theory calculation. We first summarize the different lithium ion diffusion mechanisms in the liquid electrolytes, and conclude the basic conditions and key parameters in the different lithium ion diffusion mechanisms, especially in the ultrafast diffusion mechanism with high concentration of lithium salt. Base on the liquid electrolytes with “unusual ultrafast lithium ion diffusion” mechanism, we deeply discuss the formation processes of solid electrolyte interfaces, the microstructure and chemical composition of solid electrolyte interfaces, the lithium ion diffusion in the solid electrolyte interfaces, and the stability of the solid electrolyte interfaces. We will find an effective way to improve the performance and stability of the solid electrolyte interfaces by the theoretical design. Our project can provide suggestions and scientific basis for the high mobility rate electrolytes and solid electrolyte interfaces for fast charging lithium batteries.