Arbitrary deformable and high-strength electroactive polymer/MXene anti-exfoliative composite films assembled into high performance, flexible all-solid-state supercapacitors

Flexible all-solid-state supercapacitors (ASSSs) are excellent energy storage devices for portable/wearable electronics, although the development of an excellent comprehensive performance film electrode for the extraordinary flexible ASSSs still faces a great challenge. Here, bendable, foldable and anti-exfoliative Ti3C2Tx MXene-based films utilized as supercapacitor electrodes are reported. Polyaniline/Ti3C2Tx composites (i-PANI@Ti3C2Tx) were prepared by in situ oxidant-free polymerization of aniline on Ti3C2Tx nanosheets with p-phenylenediamine (PPD) as an initiator. Lignosulfonate (Lig) and Ti3C2Tx were constructed into a compact composite (Lig@Ti3C2Tx) film based on the hydrogen bonds formed between Lig and Ti3C2Tx. The Lig@Ti3C2Tx/i-PANI@Ti3C2Tx(5/5) hybrid film was produced by vacuum-assisted filtration of the mixed two composite dispersions. The as-prepared films can be arbitrarily deformed (such as bending and folding). They show high tensile strength and vertical-plane (the plane of film) tensile strength with 33.2 and 0.28 MPa for the i-PANI@Ti3C2Tx film, 75.4 and 0.77 MPa for the Lig@Ti3C2Tx film, and 53.7 and 0.58 MPa for the Lig@Ti3C2Tx/i-PANI@Ti3C2Tx(5/5) film (those of Ti3C2Tx film are 17.4 and 0.21 MPa), respectively. The enhanced vertical-plane tensile strength of the as-prepared composite films indicates that the large binding force generated between the Ti3C2Tx nanosheets can effectively prevent the exfoliation of films. The electrodes of the as-prepared i-PANI@Ti3C2Tx, Lig@Ti3C2Tx and Lig@Ti3C2Tx/i-PANI@Ti3C2Tx(5/5) films assembled into symmetric flexible ASSSs can deliver excellent specific capacitances of 310 F g(-1) (similar to 1001 F cm(-3)), 271 F g(-1) (similar to 881 F cm(-3)) and 295 F g(-1) (similar to 959 F cm(-3)), respectively. In addition, the corresponding supercapacitors exhibit ultrahigh energy densities of 34.8, 30.6 and 33.3 W h L-1, respectively. It is expected that the as-prepared MXene-based films can be applied in various fields, such as electromagnetic-interference shielding and batteries. Furthermore, the as-prepared flexible ASSSs can be practically used as a wearable energy storage device.