Laser‐Cutting Fabrication of Mxene‐Based Flexible Micro‐Supercapacitors with High Areal Capacitance

Abstract Flexible micro‐supercapacitors (MSCs) in the form of a thin sheet are anticipated to be the thinnest possible structure. High energy storage capacity is an added merit of such devices and is also important for practical applications. In this work, we devise double‐side MSCs by using a UV laser to cut interdigital patterns in a 20‐μm‐thick Ni foil with both sides coated with MXene films. Because of the laser beam penetration and the use of MXene slurry to coat films with a high mass loading of ∼3 mg cm⁻², both surfaces of the Ni sheet can be exploited for energy storage, achieving a high areal capacitance of 52 mF cm⁻². Moreover, the fabrication of multiple coplanar MSCs in series or parallel can be accomplished via one‐step laser cutting process. In addition to the symmetric design that has a voltage window of 0.6 V, we make asymmetric MSCs by assembling two set of Ni finger electrodes coated with porous carbon or Zn as negative electrodes, and MXene as positive electrodes. The carbon//MXene MSC reaches a broader voltage window of 0.8 V, and the voltage of Zn//MXene hybrid MSC can be further increased to 1.1 V. Our study provides a new strategy to increase the areal energy density of thin sheet MSCs with limited area.