锂硫电池中表面共价接枝离子液体聚合物粘结剂的结构设计及其电化学行为研究

Owing to the high energy density, low cost, and environmental friendliness, lithium–sulfur (Li–S) batteries are considered as a promising candidate to alternate routine Li–ion batteries applied in portable electronics and electric vehicles. However, the dissolution and shuttling of polysulfide intermediates are responsible for rapid capacity decay during cycling. Polymer binders, an important component in sulfur electrode, are generally electrochemically inactive, non-conductive as well as dissolubility in electrolyte, which leads to the difficulty in maintaining the structural integrity and stability of electrode. Moreover, the knowledges on the effect of polymer binder on diffusion behavior of polysulfides and the transformation mechanism of polysulfides is still rudimentary. Hence, the design and regulation of polymer binder structure give a great chance to mitigate the shuttle effect of polysulfides and propel its redox kinetics, improving the electrochemical performance of sulfur cathode..Present project aims at achieving high-performance sulfur cathode in Li–S battery. Based on the forceful electrostatic incorporation between positively charged cation polymer backbone and negatively charged polysulfide anion, the ionic liquid polymer grafted graphene with high mechanically elasticity, high adhesion, high electronic/ionic conductivity and strong polysulfide immobilization is will designed through ionic liquid polymer chemically covalent bonding on graphene. Combining the molecular simulation calculation and experiment process, the relationship between structure of polymer binder and diffusion behavior of polysulfides as well as electrochemical performance will be studied and analyzed by the design and regulation of ionic liquid structure units, which further guide the structure design of binder. In addition, the diffusion and conversion behavior of polysulfides also will be researched through theoretical calculation and in situ characterization, which will be beneficial for improving the understanding in physical-chemical mechanism of polysulfide transformation. Therefore, this project can provide a new insight on the design of binder for Li-S batteries, which can build a solid theoretical basis for high-performance lithium-sulfur battery.

锂硫电池具有远高于锂离子电池能量密度的显著优势。然而，充放电过程中多硫化物的溶解和穿梭会造成锂硫电池性能的快速衰减。粘结剂作为正极的重要组成部分，通常是不导电和无活性的，且在电解液中易溶解，不利于维持正极结构的完整和稳定，而且，粘结剂结构与多硫化物扩散行为的关系以及对于多硫化物转化机制的认识目前仍然缺乏深入研究和理解。.本课题以实现高性能锂硫电池正极为目的，拟提出在石墨烯表面通过化学共价接枝方法制备石墨烯接枝的离子液体聚合物粘结剂，计划采用分子模拟和实验相结合，利用阳离子聚合物骨架与多硫化物之间强的相互作用，通过对离子液体结构单元设计，研究聚合物结构与多硫化物扩散行为以及电池电化学性能之间的关系，并反馈指导高性能粘结剂的构建，最终实现粘结剂结构的优化。并在此基础上，进一步通过理论计算和原位表征，研究多硫化物转化过程，明确多硫化物转化的物理化学机制，为高性能锂硫电池打下坚实的理论基础。

锂硫电池具有远高于锂离子电池能量密度的显著优势。然而，充放电过程中多硫化物的溶解和穿梭、以及缓慢的动力学转化过程会造成锂硫电池性能的快速衰减。粘结剂作为正极的重要组成部分，通常是不导电和无活性的，且在电解液中易溶解，不利于维持正极结构的完整和稳定，而且，对于多硫化物扩散行为以及多硫化物转化机制的认识目前仍然缺乏深入研究和理解。.基于以上考虑，本项目针对锂硫电池体系开展了如下研究：.（1）针对锂硫电池多硫化物扩散、动力学转换缓慢等难题，提出了通过在聚合物粘结剂的大分子结构中引入氧化还原活性基团，介导硫的转化过程；同时通过反应界面设计和均相/非均相催化剂引入，实现多硫化物的快速转换。.（2）针对锂硫电池中金属锂负极的腐蚀和枝晶生长问题，开展了金属锂沉积行为机制、固液界面调控、人工固态电解质界面膜设计等工作，进一步推进了锂硫电池的研究进展。.本项目在锂硫电池正极和负极两方面的工作，进一步推进了锂硫电池的研究进展。基于本项目的研究成果，已在Adv Mater, Adv Energy Mater, Angew Chem Int Ed, Energy Storage Mater, Chem等国内外期刊上发表SCI论文26篇（其中一作及通讯作者论文10篇），总他引1450次。