SILAR synthesized α-Fe2O3 thin film anode for the development of all binder-free, high-performing Mg-ion asymmetric supercapacitors

Abstract

Divalent-ion electrolyte-based supercapacitors (D-ISCs) have been gaining prominence due to their affordability and potential to deliver superior electrochemical performance as compared to single-ion electrolyte-based supercapacitors. Moreover, to satisfy the high energy demands of advanced electronic devices, a rational combination of electrodes and electrolytes in D-ISCs is required to enhance their power and energy densities further. Therefore, the present work describes the development of all binder-free magnesium-ion supercapacitor (Mg-ISC) using α-Fe2O3 as an anode and MnO2 thin films as a cathode. The binder-free thin films are fabricated using the SILAR method, allowing for direct formation of uniform and nanocrystalline thin films on the substrate, confirmed through structural and morphological analysis. Individually, both α-Fe2O3 and MnO2 thin film electrodes employed as anode and cathode exhibit excellent electrochemical properties, achieving a specific capacitance (Csp) of 381 F g−1 and 587 F g−1 at 0.2 mA cm−2, respectively, and confirms that both electrodes can be effective and reversible host materials. Furthermore, the developed Mg-ISC delivers a remarkable Csp of 234 F g−1 at a current density of 0.2 mA cm−2. Moreover, the aqueous Mg-ISC achieves a significant energy density of 105.2 Wh kg−1 at a high-power density of 619.4 W kg−1, suggesting that the device can deliver both high energy and power simultaneously. Moreover, Mg-ISC retained 86 % of its capacitance through 10,000 cycles at 5 mA cm−2. The current work lays the basis for developing D-ISC that are safe, sustainable, and provide improved electrochemical performance for a wide range of applications.