锂硫电池中转化反应规律及其催化强化机制研究

Li-S batteries are with the merits in high theoretical energy density of 2600 Wh/kg, low cost of sulfur materials, high natural abundance, and environmental benignity. The multi-electron reaction nature renders Li-S battery with ultrahigh theoretical energy density, and leads to complex redox mechanism as well. However, the mechanism understanding is still limited regarding the complex liquid phase redox reactions and liquid-solid conversions. Meanwhile, the electrochemical performances including the energy efficiency and the power density are hindered by the slow redox reaction kinetics of sulfur-containing species. . This project proposes to investigate the redox reaction mechanism in Li-S batteries, and develop the electrochemical catalysts that can intensify the redox reactions. In situ methods including spectroscopy and microscopy together with electrochemical tests will be adopted to understand the redox mechanisms in Li-S batteries. The intensification effect and mechanism of electrochemical catalysts on the conversion of sulfur-containing species will be verified as well. This project intends to develop new-type of cathode/separator materials based on the effective electrochemical catalysis concept, and to improve the performance of lithium sulfur batteries, especially in high active materials loading, rapid reaction kinetics, and high cyclic stability. This project would bring new insights on the redox reactions of Li-S batteries, and may also shed some light on other energy storage system based on conversion reactions.

锂硫电池具有理论能量密度高（2600 Wh/kg）、原料价格低廉等优点，但其多电子转化反应机制复杂，含硫组分液-液、液-固转化反应的动力学慢，影响锂硫电池的能量效率，功率特性。.本项目针对锂硫电池含硫组分转化反应机制不明、动力学慢的问题，提出通过原位的电化学、谱学、显微手段，探究锂硫电池中含硫组分的转化反应规律，通过电化学催化剂的设计实现对该转化反应过程的强化及调控，进而获得具有催化转化功能的正极/隔膜核心材料。本项目对开发具有高负载量、快速反应动力学、高稳定性特征的锂硫电池具有指导意义，对其他基于转化反应的储能系统也具有启发价值。

在锂硫电池中，转化反应动力学带来了一系列性能瓶颈。包括充放电反应过程中液-液，液-固转化过程中的严重极化及其带来的锂硫电池能量效率低、倍率性能较差、稳定性较低等的问题。事实上，目前关于锂硫电池中含硫组分转化反应的研究工作非常少。尤其是锂硫电池中对催化转化过程的深入认识及其调控原理及途径非常欠缺。这方面科学理解的缺乏导致目前尚无有效手段来解决锂硫电池中正极反应动力学受限导致的包括正极硫负载量低、大电流充放电能力差、电解液比例过高等问题。.基于以上考虑，本项目针对锂硫电池体系开展下列研究：.（1）针对锂硫电池硫转化动力学缓慢、硫利用率低，发展了非均相和均相催化剂的设计原则，提出了均相辅催化剂设计思路，实现了对于硫转化动力学的基础理解，有效提高了硫转化动力学过程。.（2）此外，针对锂硫电池工作过程中金属锂负极的腐蚀和枝晶生长问题，开展了金属锂固液界面设计和调控工作，有效揭示了金属锂固液界面形成机制，提出了人工固液界面设计和电解液溶剂化调控固态电解质膜思路。.在硫转化动力学调控与强化和金属锂负极保护两方面研究工作的推动下，有效推进了锂硫电池的研究进展。基于本项目的研究成果，已在 J Am Chem Sci, Adv Mater, Angew Chem Int Ed, Energy Environ Sci, Chem等国内外期刊上发表 SCI 论文 69篇（其中一作及通讯作者论文52篇），总他引近 6000次。