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As a class of promising 2D material, MXenes are widely applied to energy storage systems (ESSs) due to metallic conductivity and high electrochemical activities, but the restacking problem during electrode preparation restricts their electrochemical performances. Herein, polyaniline nanofibers (PANINFs) are used as conductive interlayer spacers to induce the self‐assembly of MXene (Ti3C2Tx)‐based electrode. The favored sandwiched porous structure is formed due to the electrostatic adsorption and hydrogen bond interaction between the positively charged PANINFs and the negatively charged Ti3C2Tx nanosheets, which provide abundant accessible sites and facilitate the diffusion of ions. As a result, the flexible freestanding Ti3C2Tx/PANINFs composite electrode exhibits high conductivity (1373.3 S cm–1) and excellent gravimetric capacitance of 645.7 F g–1. Due to the enhanced structural stability, it achieves impressive cycling stability of 98% capacitance retention after 5000 cycles, which is significantly improved from that of pristine Ti3C2Tx electrode (84.6%). This work provides a feasible strategy for the structure regulation and performance enhancement of MXene‐based supercapacitors, which has great potential in energy storage systems. [ABSTRACT FROM AUTHOR]

Polypyrrole (PPy) has received extensive attention in supercapacitor electrodes due to its promising electrochemical activity, while the poor cycling stability and densely packed structure limited its electrochemical performance. Herein, we demonstrate the fabrication of flexible and freestanding PPy@bacterial cellulose (BC)/MXene composite film with significantly enhanced electrochemical performance. PPy nanoparticles were uniformly deposited on BC nanofibers via in situ polymerization, and assembled with highly conductive MXene (Ti3C2Tx) nanoflakes through strong interfacial interactions. BC as a biological template can effectively disperse PPy nanoparticles. The intercalation of PPy@BC nanofibers into Ti3C2Tx layers constructs hierarchically packed nanofibrous structure, which provides extensive accessible electrochemical active sites. Freestanding PPy@BC/Ti3C2Tx (PBM) electrode exhibits superior specific capacitance (gravimetric and areal capacitance of up to 550 F g−1 and 879 mF cm−2, respectively) and excellent capacitance retention of 83.5% after 10,000 cycles. In addition, the symmetric supercapacitor assembled by PBM papers present a high energy density of 33.1 W h kg−1 (power density of 243 W kg−1) and excellent capacitance retention. The elaborately designed nanostructure and PPy-Ti3C2Tx hybridization make great contribution to the enhanced electrochemical performance, which provide a feasible method for the fabrication of conductive polymer-based high-performance flexible supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

With the development of wearable and portable electronic devices, there is growing demand for ultrathin high-performance electromagnetic interference (EMI) materials with desirable mechanical properties. In this study, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) oxidized cellulose nanofibers (TOCNFs) were used to fabricate ultrathin and flexible Ti3C2Tx/TOCNF composite films with a nacre-like layered structure via a simple vacuum-assisted assembly. These composite films present excellent mechanical strength (up to 212 MPa) and Young's modulus (up to 7 GPa) due to their strong intermolecular interaction and hierarchically aligned structure, which is superior to the state-of-the-art MXene-based functional materials. Furthermore, the Ti3C2Tx/TOCNF composite films exhibit high electrical conductivity (up to 2837 S m−1) and an outstanding EMI shielding effectiveness (SE) of 39.6 dB at a very low thickness of 38 μm. The possible synergistic mechanisms enhancing the mechanical properties and EMI shielding performance are discussed. The design and fabrication of Ti3C2Tx/TOCNF composite films provide a versatile strategy for ultrathin high-performance EMI shielding materials with desirable mechanical properties, which have great potential for various applications, especially in flexible, wearable and portable electronics. [ABSTRACT FROM AUTHOR]