高比能硫基复合材料的设计、电化学性能及界面特性研究

Lithium-sulfur ( Li-S )battery has been receiving more attention due to its high theoretical energy density of 2600Wh/kg. However, there are still some serious problems for sulfur cathode in organic electrolyte, including the lower utilization and poor cycle performance of sulfur active material, which become a big barrier for the research and development of lithium-sulfur battery. In order to develop a novel system of Li-S battery with high-energy density and stable cycle performance, this project focuses mainly on the following issues: (1) Fabrication of sulfur/macroporous carbon composite cathode encapsulated by porous titanate. For the design composite cathode, macroporous carbon is employed to load sulfur to ensure high-loading, and porous titanate to restrain the dissolution of polysulfides. Sulfur/macroporous carbon composite cathode encapsulated by porous titanate is expected to demonstrate a high specific capacity and stable cycling performance. (2) Introduction of Digital holographic interferometry in the secondary battery systems. Digital holographic interferometry is employed to study the interface reaction process between the composite cathode and electrolyte, and then clarify the electrochemical reaction mechanism of Li-S batteries. Under the guidance of mechanism, further research is to develop matching electrolyte for sulfur/macroporous carbon composite cathode encapsulated by porous titanate. (3) Preparation of sulfur/mesoporous carbon microtubes arrays composite cathode encapsulated by porous titanate. Combining with the matching electrolyte, it is expected to develop a novel system of Li-S batteries of high energy density and good electrochemical performance.

锂/ 硫二次电池是最具发展潜力的新型高能化学电源体系之一。但是，硫正极材料存在的活性物质偏低和循环性能较差等缺点制约了锂/硫电池的快速发展。本课题以开发具有高能量密度和稳定循环性的锂/硫电池新体系为目标，拟开展以下研究工作: (1) 构建多孔钛酸盐填充封装的硫-大孔碳复合正极材料，其中以大孔碳负载硫，以多孔氧化物将溶解的多硫化物限定在孔道内，实现硫-碳复合正极材料高比容量和良好的循环稳定性的结合; (2) 引入数字全息术来研究锂/硫电池的固液界面特性，揭示充放电过程中硫-碳复合正极和电解液界面间的相互作用机制，研发出和硫-碳复合材料相匹配的有机电解液. (3) 在上述研究成果的基础上，制备多孔钛酸盐封装的硫-介孔碳微米管阵列复合正极材料，并结和匹配电解液,以开发出具有高能量密度和良好电化学性能的锂/硫电池新体系。

锂硫电池由于其高能量密度而成为下一代高能锂电池的首选，其能否商业化的关键是如何制备具有高比能和卓越循环稳定性的硫正极材料。传统的构建硫基复合正极材料的改性手段，虽然显著的改善了硫正极的电化学性能，但是进一步应用中仍然存在难以完全限定多硫化物的溶解、倍率性能差、电化学性能过分依赖于载体材料的结构和合成过程等一系列问题。针对以上问题，本项目在执行过程中，主要完成了以下工作：1）首先系统研究了球磨法在硫基复合正极材料合成中的应用，进而采用球磨法制备了一系列表面包覆的硫/碳纳米管复合正极材料，包括金属氧化物、金属氢氧化物、石墨烯和无定型碳等，极大的改善了锂硫电池的电化学性能，并可以实现大量合成；2）设计了一种聚多巴胺修饰的亲水性隔膜，并应用于锂硫电池，极大的改善了硫正极材料的循环稳定性；3）提出了电化学活性碳间层的设想，进而合成了具有高容量的氮硫共掺杂的石墨烯作为间层并应用于锂硫电池，极大的提高了锂硫电池的整体比能量和倍率充放电性能；4）将数字全息技术成功应用到了锂离子电池的研究中，比如磷酸亚铁锂-石墨体系，发展了一种原位检测的技术。在本项目的资助下，共发表SCI论文13篇，申请专利1项。