Thickness-independent capacitance of vertically aligned liquid-crystalline MXenes

Yu Xia; Tyler S Mathis; Meng-Qiang Zhao; Babak Anasori; Alei Dang; Zehang Zhou; Hyesung Cho; Yury Gogotsi; Shu Yang

doi:10.1038/s41586-018-0109-z

Thickness-independent capacitance of vertically aligned liquid-crystalline MXenes

Nature. 2018 May;557(7705):409-412. doi: 10.1038/s41586-018-0109-z. Epub 2018 May 16.

Authors

Yu Xia¹, Tyler S Mathis², Meng-Qiang Zhao^{2

3}, Babak Anasori², Alei Dang^{1

4}, Zehang Zhou^{1

5}, Hyesung Cho¹, Yury Gogotsi⁶, Shu Yang⁷

Affiliations

¹ Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, USA.
² Department of Materials Science and Engineering and A.J. Drexel Nanomaterials Institute, Drexel University, Philadelphia, PA, USA.
³ Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA, USA.
⁴ School of Materials Science and Engineering, Shannxi Engineering Laboratory for Graphene New Carbon Materials and Applications, Northwestern Polytechnical University, Xi'an, China.
⁵ State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu, China.
⁶ Department of Materials Science and Engineering and A.J. Drexel Nanomaterials Institute, Drexel University, Philadelphia, PA, USA. gogotsi@drexel.edu.
⁷ Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, USA. shuyang@seas.upenn.edu.

PMID: 29769673
DOI: 10.1038/s41586-018-0109-z

Abstract

The scalable and sustainable manufacture of thick electrode films with high energy and power densities is critical for the large-scale storage of electrochemical energy for application in transportation and stationary electric grids. Two-dimensional nanomaterials have become the predominant choice of electrode material in the pursuit of high energy and power densities owing to their large surface-area-to-volume ratios and lack of solid-state diffusion^1,2. However, traditional electrode fabrication methods often lead to restacking of two-dimensional nanomaterials, which limits ion transport in thick films and results in systems in which the electrochemical performance is highly dependent on the thickness of the film^1-4. Strategies for facilitating ion transport-such as increasing the interlayer spacing by intercalation^5-8 or introducing film porosity by designing nanoarchitectures^9,10-result in materials with low volumetric energy storage as well as complex and lengthy ion transport paths that impede performance at high charge-discharge rates. Vertical alignment of two-dimensional flakes enables directional ion transport that can lead to thickness-independent electrochemical performances in thick films^11-13. However, so far only limited success^11,12 has been reported, and the mitigation of performance losses remains a major challenge when working with films of two-dimensional nanomaterials with thicknesses that are near to or exceed the industrial standard of 100 micrometres. Here we demonstrate electrochemical energy storage that is independent of film thickness for vertically aligned two-dimensional titanium carbide (Ti₃C₂T _x ), a material from the MXene family (two-dimensional carbides and nitrides of transition metals (M), where X stands for carbon or nitrogen). The vertical alignment was achieved by mechanical shearing of a discotic lamellar liquid-crystal phase of Ti₃C₂T _x . The resulting electrode films show excellent performance that is nearly independent of film thickness up to 200 micrometres, which makes them highly attractive for energy storage applications. Furthermore, the self-assembly approach presented here is scalable and can be extended to other systems that involve directional transport, such as catalysis and filtration.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.
Research Support, Non-U.S. Gov't