摘要
Anion exchange reaction is an effective strategy for generating more stable porous structures. The continuous growth of two-dimensional nanosheet structures on the one-dimensional nanowire array generated by anion exchange reactions helps to produce a synergistic effect, improve electrical conductivity, and accelerate REDOX kinetics. In addition, the core–shell structure composed of homologous metal sulfides will uniformly and better match the lattice rows and more uniform physicochemical properties, improve stability and cycle life, and bring higher specific capacitance.
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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 677.3 C 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 (560.3 C g−1) and 15 A g−1 (536.2 C g−1), respectively. Additionally, at a current density of 1 A g−1, the battery demonstrates extended cycle life of 5,000 cycles with a capacitor retention rate of 92.3 % at a current density of 5 A g−1. The assembled NiCo2S4@NiCo2S4//AC battery exhibits exceptional electrochemical performance (43.46 Wh kg−1 at 770.7 W kg−1). However, how to ensure the uniformity and high quality of the core–shell structure through post-processing during the preparation process, and how to improve the packaging technology during use to ensure the integrity of metal sulfides in extreme environments remain a key issue. We will continue to explore this in subsequent experiments. This study introduces innovative prospects for the large-scale industrial manufacturing of positive electrode materials tailored for supercapacitors and applications involving energy storage.