Particle size mediated investigation of various physicochemical properties of kaolinite clay for fabricating the separator layer of green capacitors

This article reports size fractionation of a natural clay namely kaolinite for fabricating cost-effective green separator material for energy storage devices. kaolinite is reportedly biocompatible and abundantly available in nature, which makes it cost-effective. Such a low-cost clay is found to be in the nano regime when treated in a ball-milling machine for a prolonged duration (12 h). The enhancement in porosity and surface area have also been observed in the treated nano-clay, which subsequently renders it's dielectric constant (similar to 5000 at 40 Hz frequency) remarkably. Henceforth, it can be argued that crystallinity and aspect ratio (S/V) has a prominent impact on the electrical properties of this natural clay. Cyclic voltammetry and galvanostatic charging-discharging measurements depict high specific capacitance (similar to 185 F g(-1)) in the nano-clay sample without the presence of any redox peak making it a good separator material. The slow electrical discharge rate also approves the storage property of this clay sample quite effectively. Abundance, augmented permittivity with a relatively low tangent loss, high specific capacitance and significant resistivity through the material make this nano-clay material a promising 'green' dielectric separator for energy storage applications.