Cobalt based Metal Organic Framework/Graphene nanocomposite as high performance battery-type electrode materials for asymmetric Supercapacitors

•A novel nanocomposite of Co-based MOF and graphene was fabricated (CoMG5).•The CoMG5 nanocomposite shows high surface area and conductivity.•The CoMG5 nanocomposite shows excellent supercapacitive performance.•The CoMG5 nanocomposite was used as a cathodic material in an asymmetric supercapacitor. Recently, development of advanced materials of metal-organic frameworks (MOFs) has attracted attention for the fabrication of supercapacitors (SCs) because of their high surface area and high level of porosity. However, poor electrical conductivity and weak mechanical properties of the MOFs have restricted their applications in the field. In this study, a one-step, in-situ synthesis of Cobalt-based MOF with graphene (CoMG nanocomposite) was employed to overcome the poor properties of MOFs. Accordingly, when the nanocomposite (CoMG5) was use as a supercapacitor electrode material, a specific capacitance (CS) of 549.96 F g−1 was observed in a three-electrode system with 6 M KOH electrolyte when scan rate was 10 mV s−1 in the cyclic voltammetry (CV) test. This CS value is higher than that of pristine Co-MOF (CoM) and graphene (G) owing to the synergistic effects between CoM and G in the nanocomposite. Moreover, the CoMG5//carbon active (CoMG5//CA) asymmetric supercapacitor assembled in a 6 M KOH electrolyte with the potential window of 1.7 V showed a high energy density of 8.10 Wh kg−1, the power density of 850 W kg−1 and good cycle lifetime, i.e. after 1000 charge/discharge cycles at 1 A g−1, 78.85% of its initial specific capacitance was retained. So that, two devices connected in series could light up an LED for more than 10 minutes continuously. This suggests that CoMG5 nanocomposite is possibly a new promising alternative material for production of high-performance energy storage devices. [Display omitted]