Two-dimensional transition metal carbide (TiV)CT MXene as high performance electrode for flexible supercapacitor.

MXenes have gained widespread interest in flexible supercapacitor due to their rich electrochemical activity and free-standing electrode structure. However, it has been a challenge to obtain an electrode with high (mass and volumetric) specific capacitance, high rate and long cycle life simultaneously. Herein, we have prepared a novel few-layer double transition metal carbide (TiV)CT MXene. Multivalent V atoms with high electrochemical activity were constructed in stable MC-type MXene to obtain the (TiV)CT electrode with excellent performance in flexible supercapacitors. The (TiV)CT film has an excellent specific capacitance of 387F g (1625 mF cm) at 1.0 A g, and 267 F g (1121 mF cm) even at a high current density of 20.0 A g, demonstrating superior rate performance (69%). Moreover, the capacitance of the (TiV)CT film remains stable during 100,000 cycles. The symmetric supercapacitor assembled using (TiV)CT film has high energy and power densities, up to 5.6 Wh kg and 5210.3 W kg. And the all-solid-state (TiV)CT flexible SC maintains stable electrochemical performance after 200 bending cycles. This work shows the huge potential of (TiV)CT in flexible supercapacitor, and provides a new idea for the design of high performance flexible electrodes.