An Ultrahigh Energy Density Flexible Asymmetric Microsupercapacitor Based on Ti 3 C 2 T x and PPy/MnO 2 with Wide Voltage Window

Ti 3 C 2 T x MXene, as a new 2D material, with unique physical and chemical properties, is ideal for building high performance miniaturized electrochemical energy storage devices. However, the operating voltage window of Ti 3 C 2 T x based microsupercapacitor (MSC) in symmetric structure is very narrow (≤0.6 V), which affects its practical application. Herein, a flexible asymmetric microsupercapacitor (AMSC) based on Ti 3 C 2 T x //polypyrrole (PPy)/MnO 2 is reported, where Ti 3 C 2 T x is deposited on graphite paper (GP) by electrophoresis method as negative electrodes, MnO 2 and PPy are electrochemically deposited on GP successively as positive electrodes, and polyvinyl alcohol/sulfuric acid (PVA/H 2 SO 4 ) as the quasi‐solid electrolyte. This AMSC based on Ti 3 C 2 T x //PPy/MnO 2 operates at 1.2 V voltage window, which is two times wider than symmetric Ti 3 C 2 T x based MSC. And its maximum areal capacitance and areal energy density can reach up to 61.5 mF cm −2 and 6.73 µWh cm −2 respectively. Moreover, three above AMSCs in series connection can turn on three lights after being charged. And the AMSC also shows high flexibility under mechanical bending level (bending angle with 0°–180°). The flexible AMSC based on Ti 3 C 2 T x //PPy/MnO 2 with ultrahigh energy density is a promising candidate for exploiting and fabricating next‐generation miniature integrated energy storage devices.