Sonochemical synthesis of battery-type ZnCo2O4 electrode material with huge specific surface area for advanced hybrid supercapacitors

Abstract

Sonochemistry is a novel and efficient method for the synthesis of electrode materials within micro-/nano-scale. In this work, the ZnCo 2 O 4 nanoparticles (NPs) and chain-like ZnCo 2 O 4 nanostructures , namely ZnCo 2 O 4 –7.5 and ZnCo 2 O 4 –9.5, were sonochemically prepared by controlling the pH value of reaction system combined with an extra calcination . The ZnCo 2 O 4 –7.5 NPs exhibited a larger specific surface area (SSA) of 148.77 m 2 g −1 , and presented better electrochemical properties such as a high specific capacity ( C s ) of 331.2C g −1 under 2 A g −1 along with 82.5 % rate performance at 10 A g −1 . As for the ZnCo 2 O 4 –9.5 nanostructure , it delivered an inferior C s of 274.8C g −1 and showed a moderate rate capability with 75.6 % capacity retention, accordingly. The hybrid supercapacitor (HSC) device was assembled using such ZnCo 2 O 4 –7.5 NPs (ZnCo 2 O 4 –9.5 nanostructure) as cathode and activated carbon (AC) as anode to explore the application potential in the field of electrochemical energy storage . After 7000 cycles at the current density of 8 A g −1 , both ZnCo 2 O 4 –7.5//AC and ZnCo 2 O 4 –9.5//AC HSCs showed outstanding cyclic stabilities with 100.4 % and 105.1 % of initial capacity retention, respectively. Meanwhile, the ZnCo 2 O 4 –7.5//AC HSC delivered a high energy density ( E d ) of 38.1 W h kg −1 at the power density ( P d ) of 1002.0 W kg −1 , and it could still hold 26.3 W h kg −1 at the higher P d of 9136.5 W kg −1 . In contrast, the ZnCo 2 O 4 –9.5//AC HSC presented a slightly inferior E d of 36.8 W h kg −1 at 1104.7 W kg −1 . The both types of ZnCo 2 O 4 –7.5 and ZnCo 2 O 4 –9.5 electrode materials demonstrate excellent electrochemical property, and they can be expected to show brilliant application potential in the field of electrochemical energy storage & conversion when served as electrode materials for high-performance hybrid supercapacitors . ZnCo 2 O 4 nanostructures with large specific surface area were prepared via an initial sonochemical method with an extra annealing treatment. These ZnCo 2 O 4 materials exhibited battery-type electrochemical response with a huge capacity of 331.2C g −1 at 2 A g −1 in 2 M of KOH electrolyte. The assembled ZnCo 2 O 4 nanoparticles//AC hybrid supercapacitor delivered a high energy density of 38.1 W h kg −1 at the power density of 1002.0 W kg −1 . • ZnCo 2 O 4 nanostructures with large surface area were sonochemically prepared. • A high specific capacity of 331.2C g −1 at 2 A g −1 was delivered. • No capacity decay over 7000 cycles at a high current density of 8 A g −1 . • The HSC device delivered an energy density of 38.1 W h kg −1 at 1002.0 W kg −1 .