Hierarchical CoNb2O6@CoOOH core-shell composite on carbon fabric for aqueous supercapacitor anode with high capacitance and super-long life

With the great success in developing high-performance cathode materials for hybrid aqueous supercapacitors, there is an urgent need to explore anode materials with excellent electrochemical performance to replace the currently used carbon anodes of low specific capacitance in order to increase the energy density of the supercapacitors. In this paper, we report a hierarchical CoNb2O6@CoOOH core-shell composite on carbon fabric prepared by the in-situ conversion from CoNb2O6 to CoOOH via an electrochemical activation strategy, which possesses CoNb2O6 nanoparticles “core” and CoOOH nanosheets “shell” supported by carbon fabric. When used as the anode of supercapacitors, the CoNb2O6@CoOOH core-shell composite exhibits a high specific capacitance of 1015.67 F g−1 at a current density of 2 A g−1 in 6 mol•L−1 KOH aqueous solution as well as excellent rate capability. Additionally, the anode delivers a super-long life at a current density of 15 A g−1 with the capacitance retention of approximately 100% after 40,000 cycles. The outstanding comprehensive electrochemical performance may be attributed to the synergistic effect of efficiently using all the desired functions of CoNb2O6 and CoOOH components in the unique hierarchical structure of the composite, which contributes to a larger electrochemical active surface area and a more stable electrochemical process.