锂硫电池正极材料的复合结构的设计

This project aims to design and synthesize capsule structured sulfur composite electrodes for high performance lithium sulfur batteries through controlling the microstructure and the interaction between the two components of the capsules. In the project, we will study the design, controlled synthesis method and mechanism of nano-sized sulfur/crumpled graphene capsule structure to mitigate problems related to the sulfur shuttle effect, volume expansion from sulfur to lithium sulfide, sulfur content in the composite and material density, thus to optimize the composite’s electron transfer and ion diffusion. We will also study the microstructure change induced by the volume fluctuation of sulfur during charge and discharge and the deposition of polysulfide. We will design multi-compartment structure in the capsule to separate the sulfur nanoparticles by engineering the interaction between the functional groups on graphene and sulfur during synthesis. We will also induce chemical bonding between graphene and sulfide to control the size and morphology of the polysulfide deposition products. We will build the interconnection between the capsule structure and the material properties and summarize the effect of the microstructure of the capsules on the electrochemical performance of sulfur composite electrodes. Overall, this project will pave way to high performance lithium sulfur battery cathodes.

本项目的研究目标是设计合成具有胶囊结构的锂琉电池硫电极材料，实现对胶囊结构的微观结构和组分相互作用的调控，进而提高复合材料的电化学性能。综合考虑硫电极中的硫的穿梭效应、硫到硫化锂转变的体积膨胀、硫含量和材料密度等问题，研究纳米琉颗粒/纸团石墨烯胶囊结构的设计、可控制备和形成机理，实现对复合材料的电子传导、离子扩散的调控；阐明胶囊结构中琉在充放电过程中膨胀收缩导致的复合材料结构变化的和多硫化合物溶解沉积的调控机制，用石墨烯表面官能团和硫的相互作用，设计在石墨烯纸团内部构筑分隔硫纳米颗粒的多仓室结构，并通过石墨烯的表面与硫化物的化学键作用调控硫和硫化锂沉积的尺寸和形貌；建立胶囊结构与材料性能的内在联系，掌握胶囊结构影响电化学性质的规律，为制备具有高比容量、高倍率、长循环寿命的锂琉电池的新型琉电极材料提供理论和实验依据。

锂硫电池在电动汽车和大型储能系统中具有广阔的应用前景。但是，由于硫、锂硫化物导电性差以及锂多硫化物的穿梭效应等带来的巨大挑战，使其市场发展受到严重阻碍。本项目热还原法和喷雾干燥法制备合成了两种具有胶囊结构的纳米硫颗粒-纸团石墨烯硫电极复合材料。实验结果表明，该材料具有良好的倍率性能和良好的循环稳定性。这主要得益于褶皱还原石墨烯宿主与硫正极间强的相互作用、褶皱还原石墨烯适宜的微孔和介孔结构以及褶皱还原石墨烯表面丰富的表面氧官能团。作为拓展研究内容，本项目还研究了碳纳米管/硫柔性正极的制备、石墨烯（rGO）与金属锂或金属钠的自组装，并对其结构进行了表征与测试、并探究了其在锂硫电池和锂、钠金属电池中应用。该项目为制备具有高比容量、高倍率、长循环寿命的新型锂琉电池提供理论和实验依据。通过该项目总共发表SCI论文18篇、发明专利8项。培养博士研究生两名，硕士研究生三名，其中一人已取得博士学位，两人取得硕士学位。