基于二维导电网络的过渡金属氧化物@煤沥青基氮掺杂石墨烯材料的性能调控及其界面作用机制

Our country is rich in coal tar pitch resources. However, the effective and high value-added utilization technology of coal tar pitch is scarce, and the added value of products is low, then have become a bottleneck problem of sustainable development for coking industry. The coal tar pitch used as raw material is carbonized in a limited range of tripolycyanamide and in situ formed g-C3N4, and then the nitrogen-doped graphene with two-dimensional conductive network are constructed. The computational methods that are suitable for describing the surface effects and carrier transport mechanism of transitional metal oxide materials are proposed, and the effect of nitrogen-doped graphene coating layer on the electrochemical performance of transitional metal oxide materials and the factors affecting structure stability and carrier transport performance of the materials are illuminated. The transitional metal oxides@coal tar pitch-based nitrogen-doped graphene materials are synthesized controllably by a self-organization method. In combination with the in situ and ex situ electrochemical techniques, the electrode reaction kinetics between the materials and electrolyte at the surface/interface and structural evolution of the materials during the intercalation and deintercalation of lithium are revealed. The interface interaction mechanisms between transitional metal oxides and coal tar pitch-based nitrogen-doped graphene are understood, and the mechanism on preparation, construction and performance regulation of coal tar pitch-based nitrogen-doped graphene are broken. The research results of this project contribute to achieving the functional design and preparation of high-performance transitional metal oxides@coal tar pitch-based nitrogen-doped graphene materials under the guidance of theory system, and then improve the utilization value of secondary resources.

我国煤沥青资源丰富，但缺乏煤沥青高效高附加值利用的技术，产品附加值低，已成为制约焦化行业可持续发展的瓶颈问题。项目以煤沥青为原料，提出煤沥青在三聚氰胺和原位生成的g-C3N4空间限域下碳化，构筑二维导电网络的氮掺杂石墨烯。采用第一性原理建立适用于描述过渡金属氧化物材料表面效应和载流子输运机制的计算方法，阐明氮掺杂石墨烯包覆层对过渡金属氧化物材料的电化学性质的影响机制以及影响材料结构稳定性和载流子输运性能的因素。利用液相自组装方法可控合成过渡金属氧化物@煤沥青基氮掺杂石墨烯材料，结合电化学原位及非原位技术，揭示材料与电解液表面/界面处的电极反应动力学及材料锂化过程中的结构演化，明晰过渡金属氧化物和煤沥青基氮掺杂石墨烯的界面作用机制，突破煤沥青基氮掺杂石墨烯材料的制备、结构及性能调控机理，实现理论指导下高性能过渡金属氧化物@煤沥青基氮掺杂石墨烯材料的功能化设计与制备，提升二次资源利用价值。

我国煤沥青资源丰富，但缺乏煤沥青高效高附加值利用的技术，产品附加值低，已成为制约焦化行业可持续发展的瓶颈问题。项目以煤沥青为原料，通过纳米碳酸钙模板法成功合成了多孔碳，提出煤沥青在三聚氰胺和原位生成的g-C3N4空间限域下碳化，构筑二维导电网络的氮掺杂石墨烯。以煤沥青基碳材料作为包覆层，以双金属氧化物为研究对象，制备了高性能的煤沥青基多孔碳@钴基双金属氧化物作为锂离子电池负极材料。利用静电纺丝技术，成功制备了由一维无定形的氮原子掺杂的纯硬碳和软碳/硬碳复合碳纤维材料，研究了其储锂性能。通过静电纺丝方式在软碳/硬碳复合无定形碳纤维材料中掺入适量的过渡金属氧化物(MOx)，合成了C-M复合纤维材料和C-M-MOx自支撑电极作为锂离子电池负极材料。然后利用第一性原理计算，建立过渡金属氧化物材料的电子结构与宏观性能之间的内在联系，阐明氮掺杂碳包覆层对过渡金属氧化物材料的电化学性质的影响机制以及影响材料结构稳定性和载流子输运性能的因素。利用电化学ex-situ XRD技术并结合Rietveld精修技术研究煤沥青基材料本征的反应动力学及材料脱嵌锂过程中的结构演化，明晰此类材料的嵌脱锂反应机理。结合第一性原理方法对锂离子在材料内部脱嵌过程中的扩散路径进行研究，计算各传输通道的活化势垒，研究锂离子嵌入脱出动力学问题，最终确定其储锂机制。利用原位/非原位技术等多种原位手段相结合，揭示材料与电解液表面/界面处的电极反应动力学，材料锂化过程中的结构演化，解决过渡金属氧化物和煤沥青基碳的界面作用机制问题，找到材料的失效机制和容量衰减原因，实现理论指导下高性能、高稳定性的过渡金属氧化物@煤沥青基碳材料的功能化设计与制备。

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