基于Fe-MOFs形貌调控及等离子体诱导非金属掺杂制备Li2FeSiO4@C正极材料及储锂机制

Li2FeSiO4 has been considered as a promising candidate for large-scale applications because of its abundance, low cost and high safety, etc. Unfortunately, its low conductivity, thus resulting in poor rate performance, has become a main obstacle to its applications in power battery and energy storage system. In this project, Fe-MOFs precursor will be synthesized by one-step hydrothermal method, which will be further used as iron source and template to prepare Li2FeSiO4@C composite by a plasma-assisted sintering method together with non-metal element doping strategy The as-prepared materials will possess high electronic and ionic transport properties. We will focus on the synthesis mechanism of growth processes of different microstructure and particle size of Fe-MOFs induced by steric hindrance effect. The structure, properties and carbon coating layer change for the target material will be investigated by using different ligands and the effect of ligands on the target structure and properties will be obtained. The process mechanism of the plasma-induced non-metal element doping will be investigated. The non-metal element doping strategy to carbon coating and Li2FeSiO4, or synergistic doping to Li2FeSiO4/carbon will be highlighted. The plateaus, structural and phase variations during the lithium insertion/extraction process will be studied and the lithium storage mechanism of Li2FeSiO4 will be summarized.

Li2FeSiO4正极材料因其资源丰富、成本低、安全性能高等优点备受研究者关注，但其电导率低，倍率性能较差，极大地限制在动力和储能领域的应用。针对上述科学问题，本项目拟采用一步水热法制Fe-MOFs前驱体，并以Fe-MOFs为铁源和模板，通过等离子体辅助烧结技术诱导可控制备非金属掺杂的Li2FeSiO4@C复合材料，显著提升目标材料的电子和离子输运性质。重点深入研究空间位阻效应控制诱导不同结构和形貌的Fe-MOFs的合成机理；对比不同配体制备目标材料结构、性能及碳包覆层的变化，尝试揭示配体对目标材料结构和性能的影响规律；探讨等离子体诱导非金属掺杂过程的作用机制，揭示非金属掺杂碳包覆层、Li2FeSiO4或非金属同时掺杂碳包覆层和Li2FeSiO4协同作用机理；考察目标材料在锂离子脱嵌过程中电位平台、形貌结构及物相变化规律，总结材料的储锂机制。

Li2FeSiO4正极材料因其资源丰富、成本低、安全性能高等优点备受研究者关注，但其电导率低，倍率性能较差，极大地限制在动力和储能领域的应用。针对上述科学问题，本课题以水热反应合成Fe-MOFs，并以Fe-MOFs为铁源构筑多孔碳包覆硅酸亚铁锂复合材料，系统研究了硝酸铁和均苯三甲酸的配比对材料结构、形貌和电化学性能的影响。分别以叶酸和硼酸为氮源和硼源，采用固相法分别构筑了非金属(N、B)掺杂对硅酸亚铁锂的结构进行调控，探讨了非金属(N、B)掺杂对提升材料性能的原因。此外，采用金属离子(Zr4+)对硅酸亚铁锂结构进行调控，硅酸亚铁的倍率性能与循环稳定性能均得到了显著提高。在上述工作基础上，采用碳-银共包覆对硅酸亚铁锂界面进行调控，研究了碳-银共包覆对材料结构、形貌和电化学性能的影响规律。采用喷雾干燥法构筑了多孔硅酸亚铁锂，探讨了硝酸铁和柠檬酸的配比对材料的影响。本课题不但对提高Li2FeSiO4的电导率，开发出的高比容量、安全性较好和能够进行高倍率放电的Li2FeSiO4 正极材料，同时对其它电子电导率较小的电极材料的改性起到一定的借鉴意义。