（Author: Alei DANG, Responsible Reader: Weqiang DONG, Tiehu LI）
Alei Dang, a young faculty member from Prof. Tiehu Li’ group in the School of Material Science & Engineering at Northwestern Polytechnical University (NPU) and a postdoctoral fellow (2016/5/1-2018/4/30) from Prof. Shu Yang’s group in the Department of Material Science and Engineering at University of Pennsylvania has recently published a research paper with his collaborators in Nature (IF = 40.137) as a co-author on the design and application of liquid crystalline two-dimensional MXene material in high performance electrode film materials (meanwhile, Nature Chemistry Community has carried out a synchronous report on the results of this work (http://go.nature.com/2L4VLzU)). Entitled as “Thickness-independent capacitance of vertically aligned liquid-crystalline MXenes” (doi:10.1038/s41586-018-0109-z), this work is partially supported by the program “Advanced Visiting Program for Young Faculty Member” from the Personnel Department, School of Material Science & Engineering and Shannxi Engineering Laboratory for Graphene New Carbon Materials and Application at Northwestern Polytechnical University.
Figure 1. Schematic illustration of ion transport in Ti3C2Tx MXene films. a) Ion transport in horizontally stacked (a) and vertically aligned (b) Ti3C2Tx; c, illustration of the surfactant (C12E6)-enhanced lamellar structure of the MXene lamellar liquid crystal (MXLLC). d), illustration of the alignment method used in this work.
New materials and novel fabrication and assembly techniques are fertilizing the burgeoning growth of advanced energy storage devices to feed the huge and hungry market. Compared with two-dimensional graphene materials, MXene is a new member of two-dimensional nanomaterials well-recognized by super-high conductivity (~ 8000 S/cm) that is usually found in metal or graphene, and high energy (pseudo capacitance) and power density characteristics. Though MXene has attracted tremendous attention since its discovery in 2011, there is a long-time contradiction between thickness and capacitance in the field of electrode preparation, especially when pursuing high electrode thickness towards industrial standard (~100 micrometers). This is mainly because the traditional method of electrode preparation often leads to the re-stacking of two-dimensional nanomaterials, which makes the ion transfer rate in the thicker electrode severely restricted, and thus greatly hinders the electrochemical reactions in the electrode materials.
Figure 3. Electrochemical performance of vacuum-filtered MXene papers and MXene lamellar liquid crystal (MXLLC) films
Here we demonstrate thickness-independent EES in vertically aligned 2D titanium carbide (Ti3C2TX) from the MXene family. The vertical alignment was achieved by mechanical shearing of a discotic lamellar liquid crystal (LC) phase of Ti3C2TX. The resulting electrode films show exceptional rate handling and nearly thickness-independent performance up to 200 mm, making them highly attractive for electrochemical energy storage (EES) applications. Furthermore, the self-assembly approach developed here is scalable and can be extended to other systems involving directional transport, e. g. catalysis and filtration.