固相熔盐法制备高性能改性硅酸亚铁镁储能材料及其电化学性能研究

There have large amount of Li, Na, K, and Mg elements in Qinghai salt lakes. It is benefit for the preparation of transition metal ions doped high-performance modified ferrous magnesium silicate structure materials. MgFeSiO4 has the advantages, such as safe, cheap, environmentally friendly and high specific energy, et. al, which makes it become the hot research spot of new generation for cathode active material of lithium ion battery. However, magnesium ions charge density than lithium ion, and thus more easily salvation. Meanwhile, the intrinsic material with poor dynamic performance has furthermore limit its application in the field of power supply. To improve its performance, we introduced divalent transition metal ions to change the structure and composition of ferrous magnesium silicate materials in the molten salt after solid phase reaction. This project plans to use in situ produce of carbon and the introduction of graphene to construct a three-dimensional conductive network. And in the conductive network the relationship of particle size, mesoporous structure of MgFeSiO4 and the assembly between modified ferrous magnesium silicate and grapheme with their lithium storage properties will be investigated. This relationship and structure construction of materials could help us to achieve effectively higher specific capacity and better power performance. Finally, from the theory and the effect of structure on the electrochemical properties of the material, an effective way should be found to modify electrode material for improved comprehensive electrochemical properties.

青海盐湖中Li、Na、K、Mg等元素含量丰富，这为过渡金属离子掺杂制备高性能改性硅酸亚铁镁结构材料提供方便。硅酸亚铁镁具有的安全、价廉、环境友好、高容量等优点使之成为新一代动力电池正极活性材料的研究热点。然而，镁离子电荷密度大，相较于锂离子更易溶剂化。同时，该材料固有的较差的动力学性能也限制了其在动力电源领域的进一步应用。为提升其电化学性能，我们采用熔盐法制备硅酸亚铁镁。并进一步通过固相反应引入二价过渡金属离子进而改变硅酸亚铁镁材料的结构与组成。同时，将其与利用原位生成的碳和石墨烯的引入构筑出立体导电网络，并在此导电网络中研究改性硅酸亚铁镁的粒径、介孔结构及其与石墨烯不同的组装方式对其储镁特性的影响关系。通过不同结构特征的复合材料的构筑达到有效调控材料的比容量和比功率等电化学性能的目的。最后，从理论上阐述结构对材料电化学性能影响，找到改良电极材料综合电化学性能有效途径。

青海盐湖中蕴藏着极其丰富的镁资源，为熔盐法制备硅酸亚铁镁电极材料提供了极大方便。相对于备受关注的锂离子电池体系，镁二次电池体系低廉的成本、安全以及环境友好的特性，使得镁二次电池在大负荷充放电设备中有着更好的发展前景。然而，镁二次电池体系的研究还较为有限。针对这一科学问题，本项目旨在探索纯相硅酸亚铁镁电极材料的熔盐法制备工艺，并通过调整其组成对其进行改性研究。首先，通过详细考察熔盐法关键技术参数对产物形貌和晶相的影响，确定了最优制备路线，成功制备出纯度高、结晶性优良的硅酸亚铁镁电极材料，并通过碳包覆工艺优化了其在镁离子电池领域的性能；然后，通过改变原料的种类，引入有益的金属离子，通过熔盐法制备出了具有不同比例的锰、镍、钴单一及多元改性硅酸亚铁镁电极材料，详细探索了改性金属对纯相硅酸亚铁镁形貌及物相的影响；并通过溶剂热法，将片状α-Ni(OH)2原位构筑在纯相硅酸亚铁镁的表面，成功制备了具有核壳结构的α-Ni(OH)2@MgFeSiO4复合电极材料；并对改性前后的电极材料进行了超级电容器性能测试。执行项目的三年时间里，发表标注基金资助的SCI收录论文25篇，包括Journal of Materials Chemistry A 3篇，ACS Applied Materials & Interfaces 2篇，Nano Research 1篇，Electrochimica Acta 3篇，还有部分重要数据正在整理中。