Sonochemical synthesis of CoNi layered double hydroxide as a cathode material for assembling high performance hybrid supercapacitor.

CoNi LDH nanostructures with large specific surface areas were prepared through a facile sonochemical approach in the solutions with different pH values. The CoNi LDH exhibited battery-type electrochemical response with the highest capacity of 740.8C/g at 1 A/g in 2 M of KOH electrolyte. The assembled CoNi LDH//AC hybrid supercapacitor delivered the highest energy density of 35.6 W h kg−1 at the power density of 781.1 W kg−1. [Display omitted] • CoNi LDH nanostructures with large surface area were sonochemically prepared. • A high specific capacity of 740.8C/g at 1 A/g was delivered. • Just a little capacity decay over 5000 cycles at a high current density of 8 A/g. • The HSC device delivered an energy density of 35.6 W h kg−1 at 781.1 W kg−1. Fabricating battery-type electrode materials with large specific surface area and mesopores is an efficient method for enhancing the electrochemical performance of supercapacitors. This method may provide more active sites for Faradic reactions and shorten the ion-diffusion paths. In this study, the CoNi layered double hydroxides (LDHs) with the morphology of nanoflowers and nanoflakes were prepared in solutions with pH values of 7.5 (CoNi LDH-7.5) and 8.5 (CoNi LDH-8.5) via a simple sonochemical approach. These CoNi LDHs possessed large specific surface areas and favourable electrochemical properties. The CoNi LDH-7.5 delivered a specific capacity of 740.8C/g at a current density of 1 A/g, surpassing CoNi LDH-8.5 with 668.1C/g. The hybrid supercapacitor (HSC) was assembled with activated carbon as the anode and CoNi LDH as the cathode to assess its practical application potential in the field of electrochemical energy storage. The CoNi LDH-7.5//AC HSC achieved the highest energy density of 35.6 W h kg−1 at a power density of 781.1 W kg−1. In addition, both HSCs exhibited little capacity decay over 5,000 cycles at a high current load of 8 A/g. These electrochemical properties of CoNi LDHs make them promising candidates for battery-type electrode materials. The current sonochemical method is simple and can be applied to the preparation of other LDHs-based electrode materials with favourable electrochemical performance. [ABSTRACT FROM AUTHOR]