Highly Flexible All-Solid-State Supercapacitors Based on MXene/CNT Composites

MXene, a promising electrode material for supercapacitors, has excellent mechanical properties, hydrophilicity, metallic conductivity, and rich surface chemistry. However, the self-restacking of MXene nanosheets due to the strong van der Waals force makes it difficult to assemble them into electrodes. Here, continuous, ultrathin carbon nanotube (CNT) films are introduced as interlayers between MXene layers to prevent self-restacking during the assembly process, and freeze-drying is used to obtain composite films with a layered porous structure. The MXene/CNT composite films exhibit excellent electrochemical performance, and the film asymmetric device based on them delivers an energy density of 7.34 Wh kg–1 at a power density of 50 W kg–1. Moreover, these composite films demonstrate good flexibility and can be spun into fibers to assemble symmetric supercapacitors, showing good cyclic stability with a capacitance retention up to 99% over 5000 cycles. These MXene/CNT composite film electrodes can work under different forms (films or fibers) and have potential applications as flexible and wearable energy storage devices and textiles.