Rational design of A-CNTs/KxMnO2 and Ti3C2Tx/MoO3 free-standing hybrid films for flexible asymmetric supercapacitor

A flexible quasi-solid-state asymmetric supercapacitor (ASC) with high energy density has been designed and fabricated, exploiting a self-assembled Ti3C2Tx/MoO3 composite as the negative electrode and interpenetrating A-CNTs/KxMnO2 nanowires networks as the positive electrode. The negative electrode exhibits excellent capacity (371 C g-1 or 715 C cm-3 at 1 A g-1) and cycle stability (89.5% after 6000 cycles), which is attributed to the synergistic effect of high conductive two-dimensional (2D) Ti3C2Tx nanosheets and high pseudocapacitive MoO3 nanobelts because Ti3C2Tx can effectively alleviate the volume effect of MoO3 during the charge/discharge process. The positive electrode shows improved rate capability and capacitance with K+ ions pre-intercalation, which effectively enlarges and stabilizes the diffusion channel of the electrolyte cations. The A-CNTs/KxMnO2// Ti3C2Tx/MoO3 ASC exhibits a high capacitance of 65.5 F g-1 (107.1 F cm-3) and a high energy density of 36.4 Wh kg- 1 (59.5 Wh L-1) at a power density of 863.5 W kg- 1 (1410.9 W L-1) with expanded operation voltage up to 2 V in the aqueous electrolyte, showing excellent cycle stability with capacitance retention of 91.7% after 6000 charge/discharge cycles. This work provides a simple but effective strategy for the development of the nextgeneration flexible supercapacitors with high energy and power densities.