金属有机框架材料担载石墨烯复合硫电极材料的构筑与机理研究

Lithium/sulfur (Li/S) batteries have attracted increasing interest with high energy density, low cost and environmentally benign. However, some technic problems still need to be resolved such as fast capacity fading, short cycle life and poor stability, because of the existing defects of poor conductivity and easily dissolved sulfur loss of the sulfur electrode. The project aims to develop a new system Li/S battery with high energy density and high stability, which is focused on graphene/sulfur composite materials based on the metal-organic frameworks with special structure. Novel carbon/sulfur composite electrode materials are prepared through optimization of preparation methods and composition formulation. The interface characteristics are studied including the stability of chemical and electrochemical stability, capacity of charge exchange and ion transport, and physical configuration of interface films of the sulfur composite materials. The interaction and micro structural changes of the sulfur composite electrodes are analyzed using spectroscopy and quantum simulation. It will help to understand the electrochemical behavior and improve the electrochemical performance and the compatibility between electrode and electrolyte. Material optimization and electrode formation are studied to develop the Li/S battery samples with high energy density, stable and reliable, and good cycle performance.

锂硫二次电池虽具有能量密度高、价格低廉、环境友好等特点，但由于硫电极材料导电性差、易溶解损失等缺陷，导致其存在容量衰减快、循环寿命短及稳定性差等亟待解决的难题。本课题以开发具有高能量密度和稳定循环的锂硫二次电池新体系为目标，重点采用具有特定结构特征的金属有机框架材料作为主体，担载石墨烯复合单质硫，通过对合成方法、组成配比的优化，构筑得到新型硫复合电极材料；对其界面特性进行研究，分析硫复合材料的化学与电化学稳定性、电荷交换与离子输运能力及其界面膜的物理构型；结合谱学和量化计算分析硫复合电极材料组分间的相互作用、微结构变化，明确其电化学行为特性，提高硫复合电极的整体电化学性能并改善其与电解液材料的相容性；进一步通过材料优化、电极成型的研究，研制出具有高能量密度、稳定可靠和良好循环特性的锂硫电池样品。

锂硫电池比传统锂离子电池具有更高的理论比能量和更优秀的低温性能，同时硫在自然界中储量丰富，价格低廉，容易获取，且对环境友好，因而是当前新型二次电池研究体系中的热点。然而，多硫化物的溶解，体积膨胀，结构破坏和锂金属负极枝晶问题一直制约着锂硫电池的实用化进程。构建高稳定性的锂硫电池正极材料，优化锂硫电池的整体结构是开发高性能锂硫电池的基础。本项目从开发制备新型的锂硫电池正极材料和锂硫电池相关组成材料入手，优化它们的物理化学属性，设计出新型的锂硫电池构造，研制出了具有高能量密度、稳定可靠和良好循环特性的锂硫电池样品。