Ultralong Co11(HPO3)8(OH)6/Co9S8 hierarchical tubular architectures with highly enhanced electrochemical performance for supercapacitors

Abstract

The electrode materials of supercapacitors with desirable compositions and architectures can promote electrochemical performance. Hierarchical tubular architectures have the beneficial characteristics of being one-dimensional and hollow. Hence, they could be used for high-performance supercapacitors. Herein, we present a simple self-template approach for the preparation of Co₁₁(HPO₃)₈(OH)₆/Co₉S₈ hierarchical tubular architectures as electrode materials in supercapacitors. First, a facile hydrothermal process was carried out to synthesize a Co₁₁(HPO₃)₈(OH)₆ nanofibers template, which was subsequently transformed into Co₁₁(HPO₃)₈(OH)₆/Co₉S₈ hierarchical tubular architectures by a sulfidation reaction. Structural and compositional benefits were guaranteed to deliver boosted electrochemical performance. As expected, the prepared Co₁₁(HPO₃)₈(OH)₆/Co₉S₈ shows a large specific capacity of 609 C g⁻¹ at 4.0 A g⁻¹, an enhanced rate capability and an extended cycling stability with 91% capacity retention at 10 A g⁻¹ for 10 000 consecutive charge–discharge cycles. Furthermore, an asymmetrical supercapacitor based on a Co₁₁(HPO₃)₈(OH)₆/Co₉S₈ cathode and activated carbon anode was constructed for practical application. The constructed device demonstrated a high energy density of 96.9 Wh kg⁻¹ at a power density of 1550 W kg⁻¹ and robust stability of 6000 cycles at 5.0 A g⁻¹ with a mere 3.5% decline. This work establishes a facile path to synthesize hollow architectures and provides a potential candidate for supercapacitors.