MXenes系储能材料的先进制备手段与储能机制综述

Review on advanced preparation methods and energy storage mechanism of MXenes as energy storage materials

二维层状过渡金属碳化物(氮化物)MXenes以其独特的物理和化学性能成为新型储能器件电极材料的重要候选材料,目前研究最广泛的MXenes材料为美国Drexel大学Gogotsi课题组于2011年以MAX相陶瓷材料Ti_(3)AlC_(2)为前驱体制备的Ti_(3)C_(2)T_(x)。结合本课题组对Ti_(3)C_(2)T_(x)/SnO_(2)复合材料储锂性能的探索,本文综述了近年来二维与三维MXenes作为储能材料的新型制备手段,分析了三维MXenes及复合体系的储能优势,然后总结了目前比较主流的MXenes能量存储机制。大量资料表明:目前主要以HF或者LiF+HCl作为刻蚀剂,制备手风琴结构或类黏土结构的二维MXenes,采用不同改性手段减少二维MXenes纳米片重复堆积、形成良好对齐的交替排列结构是提高其电化学性能的有效策略;而制备三维体系的MXenes及复合材料则主要使用模板法,此类结构除了可抑制纳米片叠合之外,还有丰富的通道,有利于电解质的快速扩散与载流子的快速传输,再加上MXenes优异的电导率(约10^(5) S/cm)、低的锂离子扩散能垒以及独特的金属离子吸附特性,使其能够成为理想的活性材料或电极。最后,本文对MXenes系储能材料的未来机遇和挑战进行了简要的展望。

The growing family of MXenes,i.e.,layered transition metal carbides and/or nitrides,has become an important candidate of electrode materials for new-concept energy storage devices due to their unique properties.Presently,the most widely studied MXenes material is Ti_(3)C_(2)T_(x),which was etched from the MAX phase ceramic material Ti_(3)AlC_(2) by the Gogotsi team of Drexel University.Herein,proceeding from our exploration of the lithium storage performance of Ti_(3)C_(2)T_(x)/SnO_(2),the novel preparation methods of MXenes with different microstructures were reviewed.Afterward,several main energy storage mechanisms of MXenes were discussed.The literature showed that two-dimensional MXenes with accordion or clay-like structures are mainly prepared with HF or LiF+HCl as etchants.Reducing the stack of 2D nanosheets and forming an alternate alignment structure effectively improves the electrochemical performance of 2D MXenes.Meanwhile,the template method is mainly used to prepare three-dimensional MXenes and their composites.In addition to inhibiting the accumulation of nanosheets,3D MXenes have abundant micron channels,which is beneficial to the diffusion of electrolytes and the transport of carriers.Coupled with their excellent electrical conductivity(≈10^(5) S/cm),low lithium-ion diffusion energy barrier,and unique metal ion adsorption characteristics,we believe that 3D MXenes have great potential to become an ideal active material or electrode of secondary batteries.Finally,the opportunities and challenges of MXenes'series energy storage materials were presented.