锂硫电池中石墨烯基致密化电极的可控构建及储能机制研究

Li-Sulfur （Li-S）batteries are promising next-generation energy storage devices with high energy density. But the corresponding real energy density is much lower than the theoretical value due to the insulting property of sulfur and the large amount of carbon nanomaterials used in the cathode. This project is proposed to solve the bottleneck Li-S battery, which can be concluded as low density and low sulfur loading of the electrode. Starting from the construction of densified sulfur/graphene composite materials, the "thick and dense" electrode is fabricated to realize the configuration of high performance Li-S batteries. Specifically, H2S and graphene oxide are selected as typical sulfur source and starting materials, and we focus on the following research topics: 1) densified sulfur/graphene composite materials with high sulfur content is fabricated and the pore structure, pore volume and packing density are well controlled. The free-standing electrode with no current collector and binder is constructed by the densified sulfur/graphene materials. 2) The transport of Li ion and the confinement of polysulfide in the "thick-dense" electrode is simulated to realize the balance of the transport of Li ion and the confinement towards polysulfide, which can maximize the energy density and power density. 3) Develop and optimize the configuration of Li-S batteries towards real applications. This proposed project can provide new insight into the fabrication of novel sulfur/carbon electrode, and pave the avenue towards high energy density Li-S battery. It also presents a new solution for the control of pollutants from power plants and the novel application of coal resources.

锂硫电池作为下一代高能量储能器件，具有超越目前锂离子电池的应用潜力。由于硫的特殊性质和碳纳米材料的大量使用，锂硫电池的真实能量密度远低于预期。本项目聚焦锂硫电池中电极材料密度低、负载少的瓶颈，通过组装致密化硫/石墨烯电极材料，构建“厚密”电极，以应用为导向实现高能量密度锂硫电池的器件集成。结合山西煤炭产业特点，将以硫化氢为代表的化合物作为硫源，与石墨烯等碳纳米材料相结合：1）发展高硫含量的致密化硫/石墨烯复合电极材料，优化其孔隙结构，实现其孔隙度、孔径、密度等参数的可控调节；发展制备一次成型块体电极的方法。2）通过模拟计算，研究锂离子及多硫化锂在多孔厚密电极中的传质和限域平衡，提出优化的厚密电极结构参数。3）发展高能量密度锂硫电池的器件集成。本项目的实施对推动高体积容量锂硫电池的基础研究以及实用化具有重要意义，也将为燃煤污染气体的有效治理和煤炭资源的高附加值应用提供新的思路和解决方案。

本项目聚焦锂硫电池中厚密电极的可控构建和结构优化，结合山西煤炭资源产业优势，进一步发展了可溶性纳米硫的制备方法，实现了高硫载量硫/碳复合电极材料的制备；结合理论计算，对锂硫电池充放电过程产物与碳基网络的相互作用与传质机理进行深入研究，为碳基电极材料的构建及结构调控提供了理论依据；提出面向锂硫电池厚密电极中穿梭效应的解决方案，在锂硫电池中引入吸附-催化作用，加快多硫化物的转化，降低穿梭效应，提高锂硫电池的循环寿命和能量密度，为构建高质量和高体积能量密度锂硫电池奠定基础。基于本项目研究工作，进一步创新地提出了将污染气体与新能源技术有机结合的研究思路，首次提出Li-NO2电池的构建策略，并验证了其充放电机理，实现了其可逆充放电，为下一代高能量密度储能技术提供了良好思路。对锂硫电池中碳基材料的作用进行了系统梳理，提出碳材料对多硫化物“围追堵截”的四大作用机制，对碳基电极设计具有重要指导意义；提出锂硫电池中功能阻挡层的“类细胞膜”特性，强调阻挡层在锂硫电池中的重要作用。本项目在Advanced Energy Materials、Energy Storage Materials、ACS Applied Materials & Interfaces、Science Bulletin等SCI期刊发表论文12篇（引用215次），其中一篇入选ESI高被引论文，一篇作为封面论文发表；申请中国发明专利2项。