Fabrication And Electrochemical Performance Of Supercapacitor Based On Metal–organic Framework Derived Cathode Materials

The syntheses of CoS_x@NiCo-LDH and?Ni,Co?Se₂@GO based on ZIF-67precursor and their electrochemical performance as single electrode and in hybrid supercapacitor were investigated.ZIF-67 precursor was employed to fabricate hollow structured CoS_x@NiCo-LDH nanocubes through a two-step process of sulfuration and chemical precipitation.Hollow nanocubes with epitaxial nanosheets offer plenty of open surface sites to contact KOH electrolyte,and the design of CoS_x@NiCo-LDH could integrate the merits of high-capacity NiCo-LDH and highly conductive CoS_x.Therefore,when investigated as anode material of supercapacitor?SC?,CoS_x@NiCo-LDH composite delivers high specific capacitance(680.8 C g^-1,1 A g^-1)together with outstanding cycling stability(80%,3000th cycles,10 A g^-1).Additionally,the CoS_x@NiCo-LDH//AC hybrid supercapacitors?HSC?assembled with positive CoS_x@NiCo-LDH and negative active carbon electrodes,achieves high energy density of 42.81 Wh kg^-1at 800.17 W kg^-1 and excellent capacitance retention(90%,7000th cycles,5 A g^-1).Also,the cruising power of ASC was further highlighted via the triggering of six LED bulbs.The blue and white LED bulbs with working voltage of>3.0 V were separately be lit at least for 3 and 1 minutes,further validating nice energy-storage capacity of as-fabricated CoS_x@NiCo-LDH material.For achieving the long cycle and high capacity of supercapacitive materials,the emphasis lies in ameliorating conductivity,regulating phase content and constructing porous structure.In such case,we synthesize a hierarchical hollow?Ni,Co?Se₂nanocubes@reduced graphene oxide?rGO?via the procedures of co-precipitation,selenation and rGO coating treatments.The hollow structure and ultra-thin nanosheets are conducive to rapid OH-diffusion.The tailored Ni:Co ratio coupled with weak-electronegativity Se are beneficial to adjust the electronic structure of hybrid structure.Meanwhile,the existing porous rGO is not only served as conductive network to improve conductivity,but also used as the structure protector and space separator to maintain structural integrality.Benefited from such merits in the content and morphology,the?Ni,Co?Se₂@rGO electrode is featured with high specific capacity(649.1 C g^-1 at 1 A g^-1),ultrahigh rate performance(75.5%at 20 A g^-1)and outstanding cycling stability(90.5%retention after 5000 cycles at 10 A g^-1).Moreover,the resulting?Ni,Co?Se₂@rGO//activated carbon?AC?hybrid supercapacitor?HSC?achieves high energy density of 52.6 Wh kg^-1 at 803.4 W kg^-1 together with excellent cycling life?¹00%,10000 cycles?,further eliciting the tremendous potentiality of such?Ni,Co?Se₂@rGO material.Those materials are prepared in a simple and environmental-friendly route and the composites fabricated exhibit outstanding electrochemical performance.Therefore,our work provides a new strategy on fabricating transition metal based supercapacitive materials.