Graphene Ionogel Ultra‐Fast Filter Supercapacitor with 4 V Workable Window and 150 °C Operable Temperature

Abstract The filtering capacitor plays an essential role in the ever‐increasing electronics for current stability in complicated environments. However, because of the low specific capacitance and bulky volume, current filtering devices have difficulty satisfying the harsh temperature environment and small size for supercomputers, electric vehicles, aircraft and so on. Therefore, an ultra‐fast electrochemical capacitor is developed on the basis of vertically oriented graphene iongel electrodes (GI‐EC), which demonstrates excellent alternate current line‐filtering performance with both hot tolerance of up to 150 °C and a wide voltage window of 4 V. Because of the particularly oriented graphene nanosheets induced fast ion transport, this ionic electrochemical capacitor displays a high areal specific energy density of 1784 µF V 2 cm −2 with a phase angle of −80.0° (120 Hz) at 150 °C, which is greater than most of the reported electrochemical capacitors. Moreover, it can filter arbitrary waveforms to smooth direct current signals and works well with a wide frequency range from 10 to 10 4 Hz. The easy integration of GI‐ECs in series or parallel can also further deliver desired capacitances or high voltages. The GI‐EC with high‐rate performance, wide voltage window, and high‐temperature adaptability presents a great promise for universally applicable filtering capacitors.