Three-dimensional MXene/BCN microflowers for wearable all-solid-state microsupercapacitors

Modified MXene (Ti3C2Tx) is attractive as a flexible electrode for wearable energy storage devices. In this work, a convenient and effective method was proposed to change the conventional 2D boron carbon nitride (BCN) nanosheets into three-dimensional 3D BCN microspheres that were obtained by tube furnace drying under N2 flow and annealing. Then, the MXene/BCN microflowers were applied to all-solid-state flexible microsupercapacitors (MSCs) as a high-performance electrode material. It was found that the areal capacitance can reach up to 89 mF cm−2 for a single MSC under 0.5 mA cm−2. Furthermore, the MSCs can achieve remarkable mechanical flexibility such that the capacitance will not be evidently decreased even after bending by up to 180°. In addition, 90.1% capacity retention was obtained even after 10 000 cycles and the highest energy density and power density reached 0.0124 mW h cm−2 (volumetric energy density of approximately 17.7 mW h cm−3) and 3.1 mW cm−2 (volumetric power density of approximately 4.5 W cm−3). These results demonstrate the synthesis of MXene/BCN composite materials with excellent power density and large scalability and can provide distinctive insights into high-performance flexible device storage systems.