石墨烯活化Li2S薄膜复合材料的制备及作为高容量柔性锂离子电池正极材料的性能研究

Currently, many serious issues restrict the specific energy of rechargeable lithium ion batteries (LIBs), such as high costs, low specific capacities, as well as the safety and limited replacements of metallic lithium anodes in lithium-sulfur batteries. Li2S, an emerging cathode material, has a high capacity of 1166mAh/g being as the lithium source in LIBs. Pairing Li2S and optional anode, the full battery cell develops higher energy density, which is an important issue for flexible, high energy-density, and lithium metal-free LIBs. Specifically, basing on the materials of sulfur film coated graphene prepared in previous work, this project will prepare three dimensional composites, with structures of graphene supporting lithium-sulfide nano films. To research the intimate contact based the structure of mutually inserting in nanoscale, the improvement of electron transport of Li2S activated by high-conductivity graphene, the utilization of Li2S working as cathodes, as well as the electrochemical reaction, cycle performance, rate performance and charge-discharge performance under various current densities will be demonstrated here. Additionally, the flexible LIBs using graphene as current collectors are designed in this project. In conclusion, this work has significantly scientific importance towards the development of high energy-density LIBs.

针对过渡金属基正极材料的高成本低容量以及锂-硫电池负极的不安全性和选择局限性等问题，研究以高容量的Li2S材料（1166mAh/g）作为正极材料选择性匹配负极材料组装成具有柔性功能和高能量密度的锂离子电池是目前二次储能器件研究的重要课题。本项目以前期工作中得到的硫包覆石墨烯纳米片正极材料为切入点，探索使用化学合成方法在石墨烯纳米片层表面支撑二维Li2S纳米薄膜，制备三维纳米复合结构，研究以相互嵌入方式实现两种物质在纳米尺度上紧密结合；研究利用高导电的石墨烯网络充分活化电子传输惰性的硫化锂，提高Li2S作为锂离子电池正极材料的有效利用率；研究硫化锂工作的电化学反应过程、循环寿命、倍率特性和快速充放电性能；研究以石墨烯网络作为Li2S正极的集流体，制备高容量的柔性锂离子电池。该工作对高容量锂离子电池和柔性锂离子电池的研究具有重要的科学意义。

石墨烯作为优异的二维单原子层碳材料在能量转换领域具有重要的应用。本项目研究以能量转换材料和储存为主，主要研究以石墨烯为基础的能量转换功能材料的结构调控和性质研究，通过调控石墨烯-储锂活性物质的界面提高储能材料的利用率和化学反应活性，延长活性材料的使用寿命。研究课题从石墨烯与电化学功能材料相互作用展开进行了一系列研究工作：一是制备了具有石墨烯-Li2S-PEDOT 导电高分子独特的夹层结构的柔性电极，实现石墨烯和导电高分子对Li2S的协同界面活化，增强硫化锂电极的电子传输，限制聚硫离子中间产物的流失，加速离子传输，增强大电流充放电性能；二是研究硫化锂添加剂对石墨烯-硫复合正极材料的性能增强作用；三是研究了一种新方法制备三维纳米多孔石墨烯，并用于填充硫应用于锂硫电池；四是研究石墨烯-阳极活性材料的微纳结构控制，物理化学性质，储锂机制；同时，本项目还研究了石墨烯量子点等其他微观材料的结构控制以及能量转换和电化学性质，开拓其在能量转换领域的应用。