基于Nafion/LixY(Y：F、N、O、P)复合材料构造Li-S电池中锂负极人工SEI膜及其稳定性的研究

针对锂硫电池中锂负极不稳定，即锂枝晶生长和放电产生的多硫化物溶解在有机溶液中并与金属锂负极发生可持续的副反应，SEI膜易破裂，本项目拟基于Nafion/LixY（Y：F、N、O、P）复合材料，构造锂负极人工SEI膜，研究锂硫电池中锂负极稳定性。应用密度泛函理论和分子动力学模拟探索最有潜力的人工SEI膜的组分构成。设计和制备人工SEI膜，研究人工SEI膜的稳定性，建立其组分和结构与性能关系。采用离线和在线研究相结合，通过表征金属锂负极的形貌、结构、物理性质、化学性质、是否可逆，研究电化学锂沉积过程及锂枝晶微结构的形成机制。结合实验，理论模拟锂枝晶生长过程，揭示锂枝晶生长机制，建立人工SEI膜的成分-结构-性能关系，发展一种有效抑制锂枝晶生长和控制锂负极副反应发生的普适方法。这些研究为科学设计、可控合成高质量人工SEI膜，实现锂负极稳定以及锂硫电池高能量密度和长循环寿命提供科学依据和新思路。

The instability of the Li anode in Li-S batteries originates from the Li dendrite growth, side reactions between the Li anode and polysulfides, which are easily dissolved in organic electrolyte during charge/discharge processes, as well as the fragileness of the SEI film. In this project, we are going to construct an artificial SEI film of the Li anode based on the Nafion/LixY（Y：F、N、O、P）composite materials, and investigate the stability of the modified Li anode in Li-S batteries. First, we are going to determine one or two promising Nafion/LixY（Y：F、N、O、P）composite materials as an artificial SEI film based on the DFT calculation and molecular dynamics simulation. Followed by that, the artificial SEI films will be designed and prepared successfully. Their stability and the structure-property relationships of the artificial SEI film will be investigated and established. By combining off-line approach with in situ observation, the Li plating/stripping behaviors and the formation mechanism of the Li dendrite microstructure will be explored by characterizing the morphology, component, physical properties, chemical properties, reversible electrochemical performance of the Li anode. Subsequently, we will theoretically simulate the growth process of the Li dendrite and propose the formation mechanism of the Li dendrite, revealing the relationship between the component, microstructure, and performance of the artificial SEI films, and develop a general approach to efficiently inhibit the Li dendrite growth and control the side reactions of the Li anode, based on the previous studies. This work could provide an open idea and scientific evidence for rational design and preparation of a high-performance artificial SEI film for the stable Li anode and Li-S batteries with a high energy density and long cycling life.