Construction of a High-Performance Three-Dimensional Structured NiCo2O4@PPy Nanosheet Array Free-Standing Electrode for a Hybrid Supercapacitor

Asymmetric supercapacitors (ASCs) with free-standing electrodes have attracted extensive attention due to enhanced power density, high energy density, long-term stability, and low inner resistance. Herein, a three-dimensional (3D) hierarchical nanosheet array electrode (CC@NiCo2O4@PPy), consisting of a polypyrrole (PPy) thin film shell and spinet NiCo2O4 as the core, was prepared on carbon cloth (CC) via a simple two-step electrodeposition. Since the protection of the highly conductive pseudocapacitive PPy shell, the integrated electrode delivers an enhanced specific capacitance (1687.2 F or 257.8 mAh g(-1) at 1 A g(-1)) and a high cycling stability (91.9% capacitance retention after 10,000 cycles at 10 A g(-1)). We further demonstrate the ASC based on CC@NiCo2O4@PPy/6 M KOH/active carbon, which can be cycled over 10,000 times with 80% retention at 4 A g(-1). Moreover, the prepared ASCs present a favorable rate capability with high energy densities of 46.5 and 31 Wh kg(-1) at power densities of 725 and 7246 W kg(-1), respectively. Our work provides a viable approach to construct a hierarchical 3D structure under ambient conditions and opens possibilities for adopting it in hybrid supercapacitors.

Automated summary

The study successfully prepared a three-dimensional hierarchical nanosheet array electrode on carbon cloth through a simple two-step electrodeposition method, which achieved enhanced specific capacitance and cycling stability while protecting the highly conductive pseudocapacitive shell. The prepared ASCs exhibited excellent performance in terms of high energy density and good cycling stability.