Mg2+ ion-powered hybrid supercapacitor with β-MnO2 as a cathode and α-Fe2O3 as an anode

Commercial electrochemical supercapacitors are expensive, toxic, and have inadequate energy density at a high power density. To overcome above complications, researchers are focusing on aqueous magnesium-ion-based supercapacitors via bivalent Mg 2+ ions. Herein, the facile hydrothermal method was employed for the synthesis of the β-MnO 2 and α-Fe 2 O 3 electrodes, which are confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopic (XPS) techniques. We fabricated a Mg 2+ -based hybrid supercapacitor (Mg-HSC) with β-MnO 2 as a cathode, α-Fe 2 O 3 as an anode, and 1 M MgSO 4 as an electrolyte; β-MnO 2 exhibited a specific capacitance of 1867 F/g while α-Fe 2 O 3 showed 1896 F/g. The good performance is attributed to small ions of Mg 2+ and its bivalent nature. The Mg-HSC exhibited excellent specific capacitance of 230.0 F/g at 1 A/g current density in a wide voltage range of 0 to 1.7 V. The Mg-HSC showed 82.1 Wh/kg energy density at 6153.8 W/kg power density. Moreover, this configured device showed superior long-term cycling stability with capacitance retention of >96.2% over 5000 cycles at 15 A/g current density. The facile synthesis method of electrode materials and the bivalent MgSO 4 yield into the high-performance hybrid supercapacitor which can compete with current electrochemical energy storage devices. • β-MnO 2 //MgSO 4 //α-Fe 2 O 3 supercapacitor with high specific capacitance of 230.0 F/g at 1 A/g and 96.2% retention over 5000 cycles. • Facile syntheses of α-Fe 2 O 3 for as an anode material and β-MnO 2 as a cathode material via hydrothermal method. • Implementation of α-Fe 2 O 3 as an anode material in a multivalent electrolyte.