The re-stacking of Ti 3 C 2 T x-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 Mn0 2 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.

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