Facile hydrothermal synthesis of porous MgCo2O4 nanoflakes as an electrode material for high-performance asymmetric supercapacitors

Abstract

In this work, porous MgCo₂O₄ nanoflakes (MgCo₂O₄ NFs) and MgCo₂O₄ nanocubes (MgCo₂O₄ NCs) have been successfully synthesized through a simple hydrothermal method combined with a post calcination process of the precursor in air. The morphology of the MgCo₂O₄ samples can be easily tuned by changing the hydrothermal temperature and reaction time, respectively. The porous MgCo₂O₄ NFs with an average pore size of 12.5 nm had a BET specific surface area up to 64.9 m² g⁻¹, which was larger than that of MgCo₂O₄ NCs (19.8 m² g⁻¹). The MgCo₂O₄ NFs delivered a specific capacitance of 734.1 F g⁻¹ at 1 A g⁻¹ and exhibited a considerable rate performance with 74.0% capacitance retention at 12 A g⁻¹. About 94.2% of its original capacitance could be retained after 5000 charge–discharge cycles at a constant current density of 5 A g⁻¹. An asymmetric supercapacitor (ASC) was assembled by using MgCo₂O₄ NFs as the positive electrode and AC as the negative electrode, and the ASC had a wide operation voltage of 1.7 V and a high energy density of 33.0 W h kg⁻¹ at a power density of 859.6 W kg⁻¹. Such outstanding electrochemical performances make the MgCo₂O₄ NFs a promising candidate for supercapacitor applications. In addition, the simple and scalable synthesis method can be extended to the preparation of other metal oxide-based electrode materials.