Hierarchical\nVertically Aligned Titanium Carbide (MXene) Array for Flexible All-Solid-State\nSupercapacitor with High Volumetric Capacitance

Abstract

The\ntraditional method for fabricating film electrodes may cause the restacking\nof the nanomaterials, which leads to the severe reduction of specific\nsurface area and hinders the contact of ions with active sites. Herein,\na vertically aligned hierarchical array structure is achieved with\nthe accordion-structured MXene particles as the building block, and\nhigh-performance flexible all-solid-state supercapacitors (ASSSs)\nare fabricated with this original structure. These electrodes not\nonly retain the accordion structure of MXene but also possess a micron-scale\narray structure, which could both avoid the restacking of the two-dimensional\nnanomaterials and facilitate the ion migration and electron transport\nin the solid-state devices. The as-prepared ASSSs exhibited a high\nvolumetric capacitance of 485 F cm^–3 at 1 A cm^–3 with an ultrahigh energy density of 9.6 mWh cm^–3, and a power density of 2800 mW cm^–3 under the optimal conditions, and demonstrate high flexibility and\nweakened correlation between capacitance properties with material\nthickness. This hierarchical array structure achieves a remarkable\nincrease in specific capacitance by ∼200% compared with that\nof the film counterpart, which demonstrates a valid way to design\nelectrodes for electrochemical energy storage and generation devices.