Porous MgCo2O4 nanoflakes serve as electrode materials for hybrid supercapacitors with excellent performance

In this work, MgCo 2 O 4 microspheres (MgCo 2 O 4 MSs) and MgCo 2 O 4 nanoflakes (MgCo 2 O 4 NFs) were prepared by one-step and two-step synthetic method, respectively, and combined with a post annealing treatment. Both MSs and NFs electrode materials possessed porous structure and large specific surface areas. The electrochemical properties were evaluated using three-electrode as well as two-electrode systems. The MgCo 2 O 4 NFs delivered a specific capacity of 375.5C g −1 at 1 A g −1 together with a high rate performance (74.9%) at 10 A g −1 , while the MgCo 2 O 4 MSs exhibited 276.3C g −1 at the current density of 1 A g −1 . A hybrid supercapacitor (HSC) device was assembled with a cathode made from MgCo 2 O 4 and an anode made from activated carbon (AC) for evaluation of real applications, and it was able to run over a high voltage window (1.75 V). This MgCo 2 O 4 NFs//AC HSC delivered a high energy density ( E d , 35.4 W h kg −1 ) at 950.6 W kg −1 , and at the highest power density ( P d ) of 8905.0 W kg −1 , it could still hold 25.8 W h kg −1 . On the other hand, the MgCo 2 O 4 MSs//AC HSC device exhibited an E d of 32.4 W h kg −1 at a P d of 1048.0 W kg −1 . Both HSCs exhibited good long-term cycling stability due to no capacity decay over 6000 cycles at 6 A g −1 . The excellent electrochemical performance demonstrates that these MgCo 2 O 4 electrode materials, especially the MgCo 2 O 4 NFs, have great application potential for electrochemical energy storage. This synthesis method is simple and is possibly to be applied in synthesizing other transition metal oxides (TMOs)-based electrode materials with large surface area and outstanding electrochemical performance.