Need for Revisiting the Use of Magnetic Oxides as Electrode Materials in Supercapacitors: Unequivocal Evidence of Significant Variation in Specific Capacitance under Variable Magnetic Field

Abstract

Abstract A simple question, which remains ignored in the field of supercapacitors is: will the device performance be affected near a magnetic field, if it is fabricated using electrode materials that are also magnetic? It is shown in this paper that the answer is: yes, it will be appreciably affected! The modulation in the specific capacitance is a convoluted picture of variation: diffusion mechanics of solvated cations, Nernst layer at the interface, magnetoresistance, and associated I – V response. The magnetic field also has direct control on the value at which saturation in specific capacitance is observed in such devices. Nearly a 170% increase in energy density at 1 A g −1 is observed by varying the magnetic field from 0 to 5 mT and a ten fold increase in power density is observed at 5 mT when current density is increased from 1 to 5 A g −1 . These results clearly show that electronic circuitry designed using supercapacitors needs to be reworked/designed if it is to be used in or around magnetic environment. To prove the concept and have a complete picture in one article, the paper presents results on nanosized magnetic metal oxides based on the four ferromagnetic elements, Fe, Co, Mn, and Ni.