Fabrication of Ti3C2Tx MXene/polyaniline composite films with adjustable thickness for high-performance flexible all-solid-state symmetric supercapacitors

In here, we successfully fabricated flexible Ti3C2Tx (MXene)/polyaniline (PANI) films with adjustable thickness by changing the amount of PANI nanofibers utilized as high-performance supercapacitor electrode materials. Firstly, MXene nanosheets and PANI nanofibers were prepared by the minimum strength stratification method and the redox method, respectively. And then the MXene/PANI films were synthesized by simple physical mixing and suction filtration of these two components. The electrochemical performances of the composite films show that the introduction of PANI nanofibers increases the specific capacitance of the MXene film. The reason is that conductive PANI nanofibers can not only provide a path for charge carriers, but also increases MXene layer spacing beneficial to electrolyte ion infiltration. However, with increasing amount of PANI nanofibers, the specific capacitance of the composite film shows a trend of first increase and then decrease. This fact is a result of that excess PANI nanofibers lead to an increase in the thickness of the composite film, which increases the ion and electron transport paths. The assembled device based on the optimal composite film exhibits a high specific capacitance of 272.5 F g−1 at 1 A g−1 and a capacitance retention rate of about 71.4% after 4000 cycles at 2 A g−1. The devices exhibited a high energy density of 31.18 Wh kg−1 at a power density of 1079.3 W kg−1, indicating that it has excellent energy storage performance.