钾离子电池长寿命石墨基负极材料的结构设计与性能研究

可用石墨做负极是以资源广泛、成本低廉而新近受到关注的钾离子电池的一大优势，但储钾过程中高达60%的层间体积膨胀引起的循环性能衰减严重制约了石墨在钾离子电池中的实际应用。本项目以制备具有长循环寿命的钾离子电池石墨基负极材料为目标，紧紧围绕减小/缓冲层间体积膨胀这一核心科学问题，提出了碳层呈同心多面体结构的石墨化多面体炭、纳微结构的石墨/无定型炭复合材料和柔性自支撑结构的薄片石墨/石墨烯复合膜三条具有高稳定性的石墨基负极材料的结构设计新思路。拟分别采用液态碳源气相碳化-高温石墨化、纳米石墨/有机碳源分散液喷雾干燥-碳化、薄片石墨/氧化石墨烯分散液抽滤成膜-热还原制备三种石墨基负极材料；研究制备工艺对材料的结构和储钾性能的影响，实现可控制备，并揭示其构效关系；阐明石墨基负极材料的储钾机制及其减小/缓冲石墨层间体积膨胀的原理；制备出具有长循环寿命的石墨基负极材料，为钾离子电池的发展奠定材料基础。

The availability of graphite as anode is a great advantage of potassium-ion batteries (PIBs), which have attracted much attention recently due to the wide resources and low cost. However, the interlayer volume expansion of up to 60% during the potassium storage causes serious cycle degradation, restricting the practical application of graphite in PIBs. In this study, we aim at the graphite-based anode materials with ultra-long cycle life for PIBs and closely focus on the crucial scientific issue of reducing/buffering interlayer volume expansion. Three new ideas for structure design on highly stable graphite-based anode materials are proposed: graphitized polyhedral carbon with concentric polyhedral structure, graphite/amorphous carbon with nano-micro structure, and flexible, free-standing thin graphite sheets/graphene composite film. Here, the three kinds of graphite-based anode materials are going to be prepared by vapor carbonization and high-temperature graphitization of liquid carbon source, spray drying and carbonization of nano graphite/organic carbon source dispersion, and filtration of thin graphite sheets/graphene oxide dispersion to film followed by thermal reduction, respectively. The influence of the preparation process on the structure and potassium storage performance of the materials will be studied to achieve the controllable preparation and reveal the structure-activity relationship. The potassium storage mechanism of the graphite-based anode materials will be clarified and how the materials reduce/buffer the graphite interlayer volume expansion will be demonstrated. The graphite-based anode materials with ultra-long cycle life will be prepared to lay a material foundation for the development of PIBs.