超级电容器用二维Ti_3C_2T_x过渡金属碳/氮化物材料的研究进展

Recent advance on the 2D Ti_3C_2T_x MXene materials in supercapacitor field

近年来二维过渡金属碳/氮化物(MXene)材料由于其独特的物理/化学性能,在储能领域引起广泛的关注。其中以二维Ti3C2Tx材料的研究最为普遍。MAX相是一类三元氮化物和/或碳化物,其化学式为Mn+1AXn (n=1～3),M代表过渡金属元素(如Sc, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo等),X是碳和/或氮,A主要是IIIA或IVA族元素。根据n不同,MAX相的晶体结构包括3种类型。MAX相中,M-X和M-A键强度都很高。无法通过剪切或其它机械方法分层剥离。由于M-A键比M-X键具有更高的化学活性,可以通过化学刻蚀M-A键并辅助剥离方法获得单层/少层的MXenes材料。表面基团随机分布,对电化学性能有重要的影响。调控表面基团的种类和数量是当前研究的重要内容。本工作介绍了MXene相的基本结构,分析了相结构与性能的关系。总结了通过离子插入、热处理、表面改性、电极设计和元素掺杂等手段改善MXene相材料电化学性能的研究进展,简要介绍了MXenes与碳材料、氧化物、聚合物复合在超级电容器领域中的应用进展。对MXene相材料的结构、制备及电化学性能等方面进行了综述,指出了MXene相材料用于超级电容器领域存在的主要问题及未来的发展方向。

In recent years, two-dimensional(2 D) MXene materials have attracted a great deal of research interests in the field of energy storage, due to their extraordinary physical/chemical properties. The investigation of the 2 D Ti3 C2 Tx is the most prevalent. MAX phase is a kind of ternary nitrides and/or carbide, its chemical formula for Mn+1 AXn(n=1~3), M represents the transition metal elements(such as Sc, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, etc.), X is the carbon and/or nitrogen, A is main IIIA or IVA group elements. According to different n values, the crystal structure of MAX phase includes 3 types. In the MAX phase, the bonds of M-X and M-A are very strong. Therefore, it is impossible to separate the layers by cutting or other mechanical methods. However, because the M-A bond has higher chemical activity than the M-X bond, the single-layer/low-layer MXenes material can be obtained by chemical etching of M-A bond assisted auxiliary method, and the surface terminations are randomly distributed. Surface terminations play an important role in electrochemical performance. Therefore, how to control the type and quantity of surface terminations is an important part in the current research field. The fundamental structure of the MXene phase was introduced and the relationship between phase structure and performance was analyzed in this work. The electrochemical performances of Mxene phase materials improved by ion implantation, heat treatment, surface modification, electrode design and elemental doping were summarized. Meanwhile, in order to further improve the conductivity and cyclic stability of the materials, the application progress of the composites with carbon, oxide and polymer in the field of supercapacitor was briefly introduced. Phase structure, preparation and electrochemical properties of Mxene material were reviewed, the existing problems and future development direction for Mxene phase materials used in supercapacitor fields were pointed out.