Construction And Properties Of Zn/Co Based Supercapacitance Electrode Materials

With the increasingly serious environmental problems,the production,storage and utilization of energy has gradually become a hot topic in today's society,it's necessary to develop high-performance,green energy storage technology to rationally and efficiently use energy sources.Supercapacitor?SCs?,as a new environment-friendly energy storage,have attracted much attention in the field of energy and academic circles.Develop electrode materials with high electrochemical performance is a core issue in SCs'filed.In this paper,our studies mainly focused on ZnCo-based hydroxide,oxide,sulfide and their composites,the crystal composition,microstructure and electrochemical properties of materials were systematically analyzed.The specific research contents are as follows:?1?A series of zinc cobalt layered double hydroxide?ZnCo-LDH?hybrid composites were prepared by a simple and cost-effective hydrothermal approach.The effects of Zn:Co molar ratios on its morphology features and pseudocapacitor properties were investigated systematically.It is found that Zn:Co molar ratios plays an important influence on the morphology and electrochemical performance of ZnCo-LDH.An interconnected nanowires structure and a high specific capacitance of 1469.9 F g^-11 at 1 A g^-1 were achieved when the ZnCo molar ratio is 1:2?Zn₁Co₂-LDH?.Moreover,Zn₁Co₂-LDH is further combined with reduced graphene oxide stuck onto Ni foam?Zn₁Co₂-LDH@rGO/NF?to improve its electrochemical properties.Benefiting from the unique structural feature and excellent electrical conductance ability of Zn₁Co₂-LDH@rGO/NF composite,the as-prepared material exhibits an enhanced specific capacitance of 2142.0 F g^-1 at 1 A g^-1.In addition,the assembled asymmetric supercapacitor?ASC?device based on Zn₁Co₂-LDH@rGO/NF delivers a high energy density of 53.2 Wh kg^-1 and excellent long cycling stability.?2?Core-shell ZnCo₂O₄@Ni-Co-S nanosheets composites with microspheres structure for supercapacitors have been successfully prepared through a facile three-step methods involving hydrothermal reaction,subsequent annealing and electrodeposition process.The influences of deposition cycles on its morphology and electrochemical performances were studied in detail.Compared with ZnCo₂O₄ and Ni-Co-S,the electrochemical performance of ZnCo₂O₄@Ni-Co-S been significantly enhanced.The ZnCo₂O₄@Ni-Co-S with six electrodeposition cycles?ZCO@NCS-6?exhibits high specific capacitance values of 1762.6 F g^-1 at 1 A g^-1,and maintained 1655.3 F g^-11 even at 50 A g^-1,showing an excellent rate capability.The constructed ASC device based on ZCO@NCS-6 exhibits the maximum energy density of 37.1 W h kg^-1.Moreover,a red LED was successfully lighted more than ten minutes by our assembled device.All these results reflect the potential practical application value of the composites.?3?ZnCo₂O₄ nanosheet was prepared by hydrothermal method with nickel nitrate and cobalt nitrate as raw materials,urea as precipitant and ammonium fluoride as morphology control agent.Subsequently,ZnCo₂O₄ was converted to Zn-Co-S composite by ion-exchange method.The effects of sulfide time on the electrochemical properties of Zn-Co-S was also discussed.The specific capacitance of synthesized Zn-Co-S-5?ZCS-5,5 hours?composite as high as1496.6 F g^-1 at current density of 1 A g^-1.In addition,the assembled ZCS-5//AC device shows the maximum energy density of 36.2 Wh kg^-1 and maximum power density of 5024.3 W kg^-1.The cycle retention rate of the device was 67.3%after10000 charge-discharge process,demonstrating the research and potential application value of sulfide composite materials in SCs filed.