Facile fabrication of three-dimensional NiCo2O4 hierarchical nanosheet-wire structure for high-performance supercapacitors†

Abstract

Designing a superior micro–nano structure is conducive to boosting the capacitance performance of electroactive materials. Herein, the three-dimensional NiCo₂O₄ hierarchical nanosheet-wire composite structure (NiCo₂O₄ HNSW) was fabricated by a one-step hydrothermal process followed by calcination. The hierarchical structure consisted of numerous nanowires grown at the end of nanosheets. The unique nanosheet-wire structure can enlarge the contact area between the electrode and electrolyte, accelerate electron transport, expose more active sites, and accelerate the diffusion of the electrolyte ions. The NiCo₂O₄ HNSW electrode displayed an impressive specific capacity of 992.8 C g⁻¹ at 1 A g⁻¹ and demonstrated an outstanding capacity retention of 70.1% at 20 A g⁻¹ for 12 000 charge–discharge cycles. The hybrid supercapacitor demonstrated an energy density of 44.3 W h kg⁻¹ at a power density of 800 W kg⁻¹.