新型二维碳化物晶体MXene的储能研究

发布时间：2018-03-03 06:31

本文选题：二维晶体　切入点：MXene　出处：《河南理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：新型高性能储能材料的设计、合成与应用研究被视为解决当今世界能源和环境问题的重要课题。MXene是一类新型的二维过渡金属碳化物,经过短短四年的研究,成为一种极具潜力的新型储能材料并引起广泛关注。首先,本论文利用第一性原理研究了24种MXene的电子结构和形成能。结果表明:表面裸露的MXene均具有导电性能,选择A金属活性高的MAX相较易于刻蚀制备相应的MXene。其次,利用第一性原理研究了Ti2C的储氢性能。结果表明:Ti2C的储氢方式分为三类:化学吸附(1.7 wt%)、Kubas吸附(3.4 wt%)和物理吸附(3.4 wt%)储氢。分子动力学模拟表明,在300-400 K,Kubas氢分子能够可逆吸附和脱附。此外,Sc2C的储氢也包含了物理吸附、Kubas吸附和化学吸附三种方式,理论储氢量为9.0 wt.%。再次,利用第一性原理研究了高锂浓度下V2CO2的储锂性能,结果表明:(1)单层Li吸附时,随着x增大,结构H1H2-V2CO2Lix向H1T-V2COLix转变,并伴随着一系列体积的变化。这种结构转变的实质,是高浓度锂原子诱导V2C表面的氧原子重新排列。(2)多层Li吸附时,随着锂浓度增加,氧原子迁移到两层锂原子层之间,形成一个三明治吸附结构,该结构与Li2O单质结构非常相似。因此,此阶段可能通过相转变反应生成V2C和Li2O。在插层和相转变机制的共同作用下,V2CO2的理论比容量高达1470 mAh g-1。(3)根据是否发生结构转变,不同OMX(MXene functioned by O groups)储锂的行为可分为三类,即V-类,Nb-类和Ti-类。层厚变化率φ可作为判断OMX储锂分类的参数。最后,制备了ex-Ti3C2和in-Ti3C2晶体并测试了其电化学性能。结果表明,在1 C的倍率下,in-Ti3C2的可逆比容量为123.6 mAh g-1,高于ex-Ti3C2的比容量,说明增大晶格常数c是提高MXene比容量的有效方法之一。
[Abstract]:The design, synthesis and application of new high-performance energy storage materials are regarded as an important subject to solve the energy and environmental problems in the world. MXene is a new type of two-dimensional transition metal carbide, which has been studied for a short period of four years. In this paper, the electronic structure and formation energy of 24 kinds of MXene have been studied by first principle. The results show that all the surface exposed MXene have conductive properties. The MAX phase with high activity of metal A is easier to be etched to prepare the corresponding MXene.Secondly, The hydrogen storage properties of Ti2C were studied by first principle. The results show that the hydrogen storage methods of Ti2C are divided into three types: chemical adsorption (1.7wt), Kubas adsorption (3.4wt) and physical adsorption (3.4wt.). Kubas hydrogen molecules can be adsorbed and desorbed reversible at 300-400 Kas. In addition, the hydrogen storage of Sc2C also includes physical adsorption Kubas adsorption and chemical adsorption. The theoretical hydrogen storage capacity is 9.0 wt. thirdly, the lithium storage properties of V _ 2CO _ 2 at high lithium concentration have been studied by first principle. The results show that with the increase of x, the structure of H _ 1H _ 2-V _ 2CO _ 2Lix and a series of volume changes are accompanied by a series of volume changes during the adsorption of the monolayer Li. The essence of this structural transition is when the oxygen atoms on the surface of V _ 2C are rearranged. With the increase of lithium concentration, oxygen atoms migrate to the two layers of lithium atoms to form a sandwich adsorption structure, which is very similar to the simple structure of Li2O. V2C and Li _ 2O-V _ 2C and Li _ 2O. the theoretical specific capacity of V _ 2CO _ 2 under the interaction of intercalation and phase transition mechanism is as high as 1470 mAh g ~ (-1) ~ (3). According to the structural transition, different OMX(MXene functioned by O groups can be classified into three types of lithium-storage behaviors. The thickness change rate 蠁 can be used as a parameter to judge the classification of lithium storage in OMX. Finally, ex-Ti3C2 and in-Ti3C2 crystals have been prepared and their electrochemical properties have been tested. The reversible specific capacity of Ti3C2 at 1 C is 123.6 mAh g-1, which is higher than that of ex-Ti3C2, indicating that increasing the lattice constant c is one of the effective methods to increase the specific capacity of MXene.
【学位授予单位】：河南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB34

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