Two-dimensional (2D) nanomaterials have garnered much attention in the past decades in the applications of energy storages. MXenes (Ti3C2TX) are new family of 2D nanomaterials that have shown great potential in energy storage applications due to their unique physical and chemical properties, such as high specific capacitance due to redox reactions of the transition metals. However, MXenes lose a great portion of their properties after restacking of the layers that dramatically blocks the ion diffusion path. Here, we solve the ion diffusion problem of MXenes by introducing the MXene liquid crystal (LC) phase. In the LC phase, MXene plates can be precisely controlled with their orientation, such that they can be oriented in their vertical direction. Supported by the impedance measurements of both the vertically and horizontally aligned MXene samples, we found in the vertical configuration of MXene LC, ion diffusion rate is much faster comparing to that in the horizontal configuration. Based on the orientational control of the 2D nanoplates, we found the specific capacitance has very weak dependence with the sample thickness; our 40µm MXene LC film holds ~90% of capacitance at 1000mv/s of scan rate, while the 200µm film remains ~80%. The MXene LC samples are also extremely stable, showing almost no decay of capacitance after 20,000 cycles scanning at 20A/g for the 200µm thick film. The boosted performance of MXene LC films thus shows great potential of the practical applicaions of MXene materials in energy storage devices, especially for ultrahigh rate supercapacitors.

Liquid crystalline MXenes: Ordered 2D titanium carbide for ultrahigh rate supercapacitors

254th National Meeting (2017)

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