High-rate-capability asymmetric supercapacitor device based on lily-like Co3O4 nanostructures assembled using nanowires

Abstract

Following the growing demand for high-efficient energy storage systems, high-current-density supercapacitor devices are needed; however, their development is still a challenge. An electrode material with high electronic conductivity and abundant ion channels is an important area of research. Herein, hierarchical lily-like Co₃O₄ nanostructures constituted using nanowires with a large L/D ratio on Ni foam were in situ synthesized using a simple solvent-thermal method and subsequent sintering treatment. The as-prepared Co₃O₄ precursor was composed of nanowires with a ∼50 nm average diameter and ∼70 L/D ratio. The product morphology was well maintained after thermal treatment, and the product was transformed to cubic Co₃O₄ during this process. Co₃O₄/Ni exhibited excellent rate capability and cycling performance, which showed a specific capacitance of 1600 F g⁻¹ even at a relatively high 10 A g⁻¹ current density that barely declined after 5000 cycles. Furthermore, the assembled asymmetric supercapacitor device using the as-prepared Co₃O₄/Ni and activated carbon showed a high specific capacitance at a high current density (108.1 F g⁻¹ at a current density of 0.5 A g⁻¹, 96.4 F g⁻¹ at 10 A g⁻¹ and 77.9 F g⁻¹ even at 50 A g⁻¹) and displayed a long-term cycling stability performance (10 000 cycles) with a high energy density (34 W h kg⁻¹) at a high power density of 1963 W kg⁻¹. The superior performance of lily-like Co₃O₄ nanostructures on Ni foam is proposed to be attributed to benign electronic conductivity and the presence of abundant ion transport channels. Therefore, these experimental results suggest the potential application of cobalt-based oxides in a high-current-density electrochemical system.