新型二维多孔过渡金属氮化物的可控合成及储能特性研究

The transition metal nitrides have great potential in a variety of applications especially in supercapacitors and lithium-ion batteries due to their unique combination of metallic and ceramic properties. Recently, two-dimensional transition metal carbides - Mxenes, have received lots of interest as novel energy storage materials. However, there is no report of the nitrides Mxenes with the same structure. This work designed two novel routes to activate the A layers and to weaken the bonds between A and MX layers by forming a substitutional solid solution and intercalating small ions into MAX layers, where the intercalation will be accelerated under hydrothermal condition. Finally two-dimensional transition metal nitrides will be obtained through etching the intercalated MAX compounds by diluted acid or base. At the same time, by using first-principles theoretical calculations and experimental characterization of the lamellar microstructure, surface condition, pore distribution and electrochemical properties of the nanosheets, the structure-activity relationships and the mechanism of electrochemical energy storage of this material will be revealed, which will benefit to the optimizing the structure controlling of the nitrides MXenes. An electrode based on the nanosheets with, flexibility, high volumetric capacity, high cycle life, high power density, the ability of tolerating high charging/discharging rate and high safety can be expected in this work as a result. Through this study, we can not only explore a novel universal route to exfoliate MAX compounds to nanosheets, but also provide basic knowledge of new excellent materials for lithium-ion battery.

过渡金属氮化物兼具金属和陶瓷的特征，在超级电容器和锂离子电池领域显示出良好的应用前景。近年来，二维过渡金属碳化物（MXenes）作为一类新型储能材料引起了广泛关注，但具有类似结构的氮化物MXenes却未见报导。本项目拟采用固溶活化MAX化合物和离子插层撑开MAX层间结构的方法，并借助水热条件促进离子插入，从而实现稀酸或碱刻蚀掉A层获得二维多孔过渡金属氮化物。同时采用第一性原理理论计算和实验表征片层的微观结构、表面状态、孔隙分布和电化学性能，以揭示该材料的构效关系和电化学储能机制，进而优化氮化物MXenes的结构和组分控制，获得具有柔性、高体积比容量、高循环寿命、高功率密度、快速充放电特性且安全性高的电极材料。通过此项研究，不仅可以发展MAX 化合物的高效、通用剥离技术，获得新型、潜力巨大的氮化物MXenes，并且可为新型锂电池和超级电容器电极材料的研制奠定理论和实践基础。

二维过渡金属碳化物或氮化物（MXene）因为具有特殊的层状结构、丰富的表面官能团、优异的导电性，在储能、电磁屏蔽、催化等领域都展现出良好的应用前景，近年来引起了国内外学者的广泛关注。然而，目前研究主要集中在碳化物MXene，对于导电性更好的氮化物MXene关注较少，此外单层或少层MXene的高效制备也较难实现。.因此本项目主要针对氮化物MXene和MXene的制备开展了深入研究，并探索了MXene在储能、催化及忆阻器领域的应用。首先获得了高纯度且粒度可控的Ti2AlN，Ti3AlC2及Ti2SC等MAX相化合物粉末（即MXene前驱体）的批量制备方法，阐明了MAX相化合物的锂离子脱嵌机制和剥离机制，获得了能用于锂离子电池的高性能MAX电极材料；获得了少层氮化物MXene纳米片及少层碳化物MXene的高效制备方法；阐明了碳化物MXene的电化学储能机制，获得了超级电容器用高容量高稳定性MXene电极材料；获得了MXene材料的催化特性和电学特性，阐明了MXene材料在光催化、电催化及忆阻器领域的应用前景；获得了钛酸锂/石墨烯等一系列性能优异的锂离子电池电极材料。.这一工作不仅在MAX及MXene材料的制备、性能及应用等方面积累了大量的基础研究数据，阐明了该类材料的电化学储能机制及催化机制，同时分析了其在储能、催化及人工智能领域的应用潜力，为MAX及MXene材料的制备与应用提供了理论与数据支撑，具有较为重要的科学意义和应用前景。