Free-standing MXene film modified by amorphous FeOOH quantum dots for high-performance asymmetric supercapacitor

The rapid development of the portable and wearable electronics creates a high demand for better performance energy storage devices with high areal capacity as well as excellent flexibility. Herein, a free-standing Ti3C2/FeOOH quantum dots (QDs) hybrid film has been designed and synthesized by a simple electrostatic self-assembly, where amorphous FeOOH QDs not only act as pillars to prevent restacking of the Ti3C2 nanosheets but also provide considerable capacitance as active materials. The Ti3C2/FeOOH QDs hybrid film exhibits 2.3 times higher areal capacitance (485 mF cm−2) than the pristine Ti3C2 film and good cycle stability (94.8% retention over 5000 cycles) in neutral electrolyte. Moreover, an asymmetric device has been prepared by combining the hybrid film as negative electrode and MnO2 on carbon cloth as positive electrode, which operates at an output potential difference of 1.6 V. The device delivers the maximum energy density of 40 μW h cm−2 and the maximum power density of 8.2 mW cm−2 with 82% capacitance retention after 3000 cycles. The facile preparation process and excellent electrochemical properties of the free-standing Ti3C2/FeOOH QDs hybrid film make it a promising candidate for constructing high-performance flexible energy storage devices.