Cobalt pentlandite structured (Fe,Co,Ni)9S8: Fundamental insight and evaluation of hybrid supercapacitor

Abstract

From the perspective of improving energy density, research efforts to design electrode materials that can be used in supercapacitors based on mature transition metal sulfides are already so common and efficient but insufficient. So it is a nice approach to empower the traditional transition metal sulfides with new vitality by composite structures to enrich the family of metal sulfides. In this study, we synthesized a kind of cobalt pentlandite structured (Fe,Co,Ni)9S8 originally existed only in natural ores by relatively mild means, and found that such structured materials have good potential for use in supercapacitors. The optimized (Fe,Co,Ni)9S8 sample presents a remarkably high specific capacity of 135 mAh/g at 1 A/g as well as favorable cycling stability. Density functional theory simulations confirmed the metallic properties of such sample, and Co sites are more favorable for the adsorption of OH–. Moreover, a button-type hybrid supercapacitor was fabricated utilizing our designed electrode material, presenting a relatively high energy density of 50 Wh kg−1 at 1353 W kg−1 and good cyclic stability. Moreover, two such hybrid supercapacitors can power a red LED for 22 min, which has shown its attractive and promising possibilities for practical energy storage devices.