A high-performance asymmetric supercapacitor device based on CoO@CoAl-LDH hierarchical 3D nanobouquet arrays

Abstract

CoO and CoAl layered double hydroxide (CoAl-LDH) are both promising active electrode materials for pseudocapacitors. It is of great significance to integrate the advantages of both materials and design ingenious electrode structures to achieve high electrochemical performance. Herein, 3D core–shell CoO@CoAl-LDH nanobouquet arrays on Ni foam were fabricated via two-step hydrothermal growth methods, where CoAl-LDH nanoflakes regularly grew on the surface of CoO nanosheets. The composite exhibits superior specific capacitance (2031.2 F g⁻¹ at 1 A g⁻¹) and desirable cycling stability (88.2% after 5000 cycles at 16 A g⁻¹). Asymmetric supercapacitors (ASCs) devices were also assembled using an as-synthesized CoO@CoAl-LDH composite as a positive electrode and activated carbon (AC) as a negative electrode. The electrochemical test of ASCs provides a specific capacitance of 195.6 F g⁻¹ at 1 A g⁻¹, and the devices retained approximately 85% of the capacitance after 5000 cycles. The ASCs display a high energy density of 69.55 W h kg⁻¹ at a high-power density of 800 W kg⁻¹ and remained at 29.2 W h kg⁻¹ even at a higher power density of 12 800 W kg⁻¹. The electrochemical mechanism was discussed. This work offers a meaningful perspective to explore the possibility of supercapacitor applications of LDH-based materials.