Role of magnetism present in the cobaltites (ACo2O4 A = Co, Mn, and Fe) on the charge storage mechanism in aqueous supercapacitor

Abstract

Recent reports on supercapacitor devices have shown that magnetic fields can alter the storage performance of these devices. To identify the origin of alteration of supercapacitive properties under magnetic field, recently, we have stressed upon the effect of the local environment of magnetised electrode material and proposed that two magnetic field-driven forces; Lorentz force and magnetic gradient force ∇F are active simultaneously in an electrochemical process. However, the impact of external magnetic fields on diffusive and/or capacitive storage of metal oxides is not known yet. Further, magnetism possessed by electrode material and its effect on the storage mechanism under magnetic field is also not explored yet. Here, we have found that the magnetic field contributes to double-layer capacitive storage and largely depends upon the magnetic features of electrode material. It is also observed that the surface area of electrode material does not contribute to total capacitance under the magnetic field. Based on the results, electrolyte’s convection due to Lorentz force induced by the magnetic field and thereby its effect on improving the capacitive storage is ruled out. Further, we have also shown that the local magnetic environment under magnetic field is crucial for any change in the supercapacitive properties.