Structural and Electrochemical Investigations on Nanocrystalline High Entropy Spinel Oxides for Battery‐Like Supercapacitor Applications

Abstract

Abstract High entropy oxides (HEOs) are a novel class of materials with a stable single‐phase structure that is often entropy stabilized and possess many interesting functional properties. In this work, we report a nanocrystalline spinel‐based high entropy oxide (SP‐HEO) ‐ (Al 0.2 Co 0.2 Cr 0.2 Mn 0.2 Ni 0.2 ) 3 O 4 and present an assessment of its electrochemical performance. A reverse co‐precipitation (RCP) method was used for synthesis, followed by a suitable heat‐treatment/calcination step that was adjusted to form a single‐phase nanocrystalline powder. Structural characterisation revealed that the single‐phase system was stable upto 850 °C. Nitrogen adsorption studies showed a large specific surface area of 90 m 2 g −1 in the case of the SP‐HEO calcined at 550 °C. The SP‐HEO powders were investigated as electrodes for battery‐like supercapacitor behaviour in an aqueous alkaline electrolyte ‐ KOH. The SP‐HEO powder calcined at 550 °C exhibited the highest specific capacity of 318 mAh g −1 at a current density of 1 A g −1 . The high electrochemical performance of the mesoporous SP‐HEO makes it a promising electrode material for energy storage devices.