Well-defined hollow tube@sheets NiCo2S4 core–shell nanoarrays for ultrahigh capacitance supercapacitor

Abstract

Reasonable design of electrodes with well-defined nanostructure is the central aspect in the practical application of high-performance supercapacitors. Herein, hollow tube@sheets NiCo₂S₄ core–shell nanoarrays are rationally constructed to the free-standing electrode by in situ growing ZIF-67 on Co-precursor nanorods array and sequentially performing anion-exchange (S²⁻) and cation-exchange (Ni²⁺). The well-defined nanostructures can shorten the ion transport path in the charging–discharging process, increase the specific surface area and electrochemical active cites, which help in improving electrochemical performance. Therefore, the unique tube@sheets NiCo₂S₄ core–shell nanoarrays exhibit intriguing electrochemical performance and show excellent areal capacitance of 11.3 F cm⁻² (3227.94 F g⁻¹) at a current density of 2 mA cm⁻² (2 A g⁻¹). The assembled asymmetric supercapacitor device delivers a high energy density of 0.42 mW h cm⁻² at a power density of 2.1 mW cm⁻² and displays outstanding cyclic stability (90.2% retention after 5000 cycles). Consequently, the well-defined nanostructure engineering strategy is beneficial for designing active electrode materials for efficient energy storage devices.