Two-dimensional Co3O4 thin sheets assembled by 3D interconnected nanoflake array framework structures with enhanced supercapacitor performance derived from coordination complexes

• 2D Co3O4 thin sheets were synthesized by simple pyrolysis of a CoC2O4·2H2O thin sheet precursor.
• The novel thin sheets synthesized at 500 °C for 6 h exhibit a high specific capacitance of 1500 F g−1 at 1 A g−1.
• Excellent cycling stability of 99.3% capacitance retention after 2000 cycles.
• The asymmetric supercapacitor produced a high energy density of 15.4 Wh kg−1 at a power density of 0.8 kW kg−1.

Two-dimensional (2D) Co3O4 thin sheets assembled by 3D interconnected nanoflake array framework structures were first synthesized from nanoflake array-assembled porous cobalt-oxalate coordination complex thin sheets by means of direct pyrolysis in the air and the synthesis is simple and facile to implement scale-up for various application. The products exhibit excellent pseudocapacitive performance in an alkaline medium, holding great promise in supercapacitors (SCs). The electrochemical properties of the obtained Co3O4 thin sheets were evaluated by cyclic voltammetry (CV), galvanostatic charge–discharge measurement (CP) and electrochemical impedance spectroscopy (EIS) in 2.0 M KOH solution. Temperature has an obvious effect on the performance of the products. Impressively, the thin sheets synthesized at 500 °C for 6 h used as electrode materials for SCs exhibit a specific capacitance as high as 1500 F g−1 at 1 A g−1 and even 828 F g−1 at 10 A g−1, as well as remarkable cycling stability with 99.3% of its initial capacitance retained after 2000 continuous charge–discharge cycles at a current density of 5 A g−1. In addition, the assembled asymmetric system using the obtained Co3O4 thin sheets at 500 °C for 6 h as positive electrode and activated carbon as negative one can produce a high energy density of 15.4 Wh kg−1 at a power density of 0.8 kW kg−1. The hierarchical architectures of the products with hierarchical porosity and interconnected channels as well as the synergistic effect between their compositions provide several advantages including a large contact surface area, short ion diffusion path and good charge transport, which validate these thin sheets promising potential for a wide range of applications in energy storage.

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