Modifications of MXene layers for supercapacitors

Abstract

The re-stacking of Ti3C2Tx-MXene layers has been prevented by using two different approaches: a facile hard templating method and a pore-forming approach. The expanded MXene obtained by using MgO nanoparticles as hard templates displayed an open morphology based on crumpled layers. The corresponding electrode material delivered 180 F g−1 of capacitance at 1 A g−1 and maintained 99% of its initial capacitance at 5 A g−1 over five thousand charge-discharge cycles. On the other hand, the MXene foam prepared after heating a MXene-urea composite at 550°C, showed numerous macropores on the surface layer and a complex open 3D inner-architecture. Thanks to this foamy porous structure, the binder-free electrode based on the resulting MXene foam displayed a great capacitance of 203 F g−1 at 5 A g−1 current density, 99% of which was retained after five thousand cycles. In comparison, the pristine MXene –based electrode delivered 82 F g−1, only, in the same operating conditions. An asymmetric device built on a negative MXene foam electrode and a positive MnO2 electrode exhibited an attractive energy density of 16.5 Wh kg−1 (or 10 Wh L−1) and 160 W kg−1 (or 8.5 kW L−1) power density. Altogether, the enhanced performances of these nano-engineered 2D materials are a clear demonstration of the efficiency of the chosen synthetic approaches to work out the re-stacking issue of MXene layers.