Highly Stabe Core-Shell Heterostructures by Homologous Metal Sulfides for Supercapacitors

Abstract

Transition metal sulfide (TMS) demonstrates significant potential as an anode material for supercapacitors due to its abundant REDOX reaction capabilities and high conductivity. This paper presents the design and construction of a homologous TMS core-shell heterostructure using a hydrothermal method for asymmetric supercapacitor (ASC) cathode materials. The anion-exchange reaction produces a one-dimensional NiCo2S4 nanowire array featuring enhanced structural stability and increased active sites, along with a three-dimensional heterogeneous structure incorporating two-dimensional NiCo2S4 nanosheets. This configuration creates a synergistic effect that yields higher conductivity and accelerated REDOX kinetics. Furthermore, the utilization of homologous TMS in both core and shell structures results in superior lattice matching and more uniform physicochemical properties, thereby minimizing stress concentration issues related to material compatibility, improving stability, and delivering higher specific capacitance and cycle life. The NiCo2S4@NiCo2S4 electrode, functioning as a binder-free electrode for the supercapacitor, achieves a high specific capacitance of 1128.8 F g-1 at a current density of 1 A g-1. It maintains impressive capacitance retention rates of 82.7% and 79.2% at 10 A g-1 (933.9 F g-1) and 15 A g-1 (893.6 F g-1), respectively. Additionally, at a current density of 1 A g-1, the battery demonstrates extended cycle life of 1,000 cycles with a capacitor retention rate of 92.3%. The assembled NiCo2S4@NiCo2S4//AC battery exhibits exceptional electrochemical performance (43.46 Wh kg−1 at 770.7 W kg−1). This study introduces innovative prospects for the large-scale industrial manufacturing of positive electrode materials tailored for supercapacitors and applications involving energy storage.

Keywords: heterostructure, transition bimetal sulfides, electrochemical energy storage, relieved phase transition, volumetric change