MXene/Graphdiyne nanotube composite films for Free-Standing and flexible Solid-State supercapacitor

MXene with excellent flexibility, metallic conductivity, and ultra-high capacitance, makes a promising electrode for flexible supercapacitor. But the serious restacking phenomenon between MXene layers undesirably limits the ion transport kinetics and substantially reduces ion storage sites, badly restricting the rate capability and storage capacity of supercapacitor. Here, we constructed a free-standing, flexible, structurally 3D-interconnected and hydronium ion penetrable MXene/Graphdiyne nanotube (MG) composite film by employing graphdiyne nanotubes (GDY-NTs) with inherent in-plane pores for horizontal-vertical intercalation among MXene layers. Benefiting from the above synergistic effect, this composite film presents a greatly-improved capacitance of 337.4 F g−1 (337.4 C g−1) and an obviously-enhanced rate capability of 73 %-remaining at 100 mV s−1, which is much better than those of the pure Ti3C2Tx films (230.8 F g−1, 55 %-remaining). Based on it, we developed an asymmetric solid-state flexible supercapacitor with a high energy density of 19.7 Wh kg−1 at the power density of 750 W kg−1 and a capacitance retention of 88.2 % after 10 000 cycles at 8 A g−1. Evidently, this work provides a new route to solve the restacking issue of MXene for high-performance flexible supercapacitor.