Shell-strengthened hollow architecture of NiCo2S4 carved through an in-situ reaction Ostwald Ripening mechanism with significantly enhanced electrochemical performance

Abstract

For Faraday supercapacitors, some battery-type electrode materials such as nickel-based materials attract intensive attention by virtue of their high theoretical capacity. However, it is quite difficult for these materials to achieve the satisfied high-rate performance and cycling life concurrently due to the contradiction of their individual requirements to the microscopic structure of materials. In this work, we build a hollow architecture of NiCo2S4 at hydrothermal condition following an in-situ reaction Ostwald Ripening mechanism. The as-prepared NiCo2S4 presents a shell-strengthened hollow structure, satisfying the as-mentioned two requirements: (1) the rich pores in shell and hollow structure plus structural cobalt ions lead to the excellent high-rate performance of NiCo2S4; (2) the dense particulate layer in shell with additional mechanical strength prolongs the cycling life of NiCo2S4. Consequently, the asymmetrical supercapacitors assembled with NiCo2S4 as positive electrode material show both high energy and power densities, and excellent cycling stability.