Polypyrrole–MXene coated textile-based flexible energy storage device

Recently, more and more researchers have devoted their efforts to developing flexible electrochemical energy storage devices to meet the development of portable and wearable electronics. Among them, supercapacitors (SCs) have been widely studied due to their high specific capacitance and power density. However, most flexible SCs often use traditional carbon materials and transition metal oxides as electrode materials. In this paper, we used an easy and low-cost way to fabricate a flexible supercapacitor based on a new type of two-dimensional material, transition metal carbides, nitrides, or carbonitrides (MXenes). By taking full advantage of the hydrophilicity and metal conductivity of MXene nanosheets, an extremely simple "dipping and drying" method was used to achieve conductive textile electrodes with a specific capacitance of 182.70 F g^-1, which is higher than reported for carbon nanotubes (CNTs) and active carbon. To further improve the capacitive performance of the MXene-based electrode and avoid the poor oxygen oxidation of MXene, polypyrrole (PPy) was electrochemically deposited on the surface of MXene textiles, thus producing a PPy-MXene coated textile electrode with a specific capacitance of 343.20 F g^-1. In addition, a symmetrical solid-state supercapacitor based on MXene-PPy textiles was assembled, which achieved an energy density of 1.30 mW h g^-1 (power density = 41.1 mW g^-1). This work introduces a new type of MXene-based textile SC, which provides a promising candidate for flexible and wearable energy storage devices.