基于无烟煤的异取向微膨化石墨微球制备及储锂性能研究

The anode materials with high capacity have been the focus of research on lithium ion battery, but most of the new anode materials exhibit the increase of Li+ insertion/extraction potential and the decline of electrode density, which are not conducive to the promotion of overall energy density of lithium ion battery. In this project, we introduce a new way to prepare the mildly expanded graphite (MEG) microspheres with different orientations using anthracite as raw material. After ball milling, flotation purification, spray granulation, high temperature carbonization and controllable graphitization, the anthracite will be transformed into MEG microspheres with high capacity, low potential and slightly enlarged interlayer spacing, which is conducive to the diffusion of Li+ in high C-rate and low temperature conditions. Meanwhile, the stress concentration for graphite anode occurred at deep Li+-insertion will also be effectively suppressed because of the MEG with different orientations. Using this new method without oxidant, the irreversible capacity in the first cycle caused by defects and impurity groups can be reduced. Effect of anthracite's structural derivation during carbonization and controllable graphitization processes on morphology, composition, structure and electrochemical properties of MEG microspheres with different orientations will be systematically investigated. R & D of high energy density lithium-ion battery and efficient use of China coal resource will also benefit from the implementation of this project.

高容量负极材料一直是锂离子电池研究的热点，但大多数新型负极材料却表现出明显的嵌/脱锂电位升高和电极压实密度下降现象，不利于锂离子电池整体能量密度的提升。本项目提出以无烟煤为原料，通过球磨细化、浮选纯化、喷雾造粒、高温炭化及可控石墨化制备异取向微膨化石墨微球负极材料。微膨化石墨不仅具有高容量和低电位特性，其增大的层间距也有利于锂离子在高倍率和低温条件下的扩散过程，而取向不同的微膨化石墨微球还能有效抑制石墨负极在深度嵌锂时易出现的应力集中现象。本项目提出的微膨化石墨制备新工艺中，因未使用氧化剂而避免了缺陷和杂质官能团的引入，为降低材料首次循环容量损失创造了条件。项目将系统研究无烟煤在炭化和可控石墨化过程中的结构演变情况及其对异取向微膨化石墨微球的形貌、组成、结构与电化学性能的影响规律，为高能量密度锂离子电池研发及我国煤炭资源高效利用提供理论参考与借鉴。

高容量负极材料一直是锂离子电池研究的热点，但大多数新型负极材料表现出明显的嵌/脱锂电位升高和电极压实密度下降现象，不利于锂离子电池整体能量密度的提升。本项目以无烟煤为原料，通过破碎整形、浮选纯化、喷雾造粒和石墨化制成异取向球形石墨，并通过调节石墨化温度对石墨层间距进行调控，石墨微球负极不仅具有高容量（380mAh/g）和低电位特性，其增大的层间距也有利于锂离子的扩散过程；以石墨微球为基础，将纳米氧化亚硅颗粒引入并分散在石墨微球中，可将复合材料的可逆容量提高到600mAh/g以上；以无烟煤为碳源，通过掺杂和包覆改性制得系列无烟煤基复合负极材料（P/C、P-TiO2-C、P-MoO2-C），均显示出了较高的容量水平和较好的循环稳定性；将无烟煤或淀粉改性后引入锂（钠）离子电池电极材料（PO/C、A-900、a-Sn@C、LVP/C-10）合成工艺中，得到的材料均具有显著改善的容量性能和倍率性能。本项目研究结果不仅能为新型锂（钠）离子电池材料研发提供技术支撑，也极大丰富了电极材料制备技术及无烟煤深加工技术，为高能量密度锂（钠）离子电池研发及我国煤炭资源高效利用提供了理论参考与借鉴。