Facile synthesis of an accordion-like Ni-MOF superstructure for high-performance flexible supercapacitors

Metal-organic frameworks have received increasing attention as promising electrode materials in supercapacitors. In this study, we have successfully synthesized a novel accordion-like Ni-MOF superstructure ([Ni-3(OH)(2)(C8H4O4)(2)(H2O)(4)]center dot 2H(2)O), for the first time, and used it as an electrode material for supercapacitors. The supercapacitors with the novel electrode exhibited excellent electrochemical performance. For example, the accordion-like Ni-MOF electrode showed specific capacitances of 988 and 823 F g(-1) at current densities of 1.4 and 7.0 A g(-1), respectively, while maintaining outstanding cycling stability (capacitance retention of 96.5% after 5000 cycles at a current density of 1.4 A g(-1)). More importantly, the accordion-like Ni-MOF and activated carbons were assembled into a high-performance flexible solid-state asymmetric supercapacitor with a specific capacitance of 230 mF cm(-2) at a current density of 1.0 mA cm(-2). The cycle test showed that the device can offer 92.8% capacity of the initial capacitance at 5.0 mA cm(-2) after 5000 cycles with little decay. The maximum energy density of the device can achieve 4.18 mW h cm(-3) and the maximum power density can also achieve 231.2 mW cm(-3).