Preparation Of Transition Metal Sulfide Nanomaterials And Study On Their Supercapacitive Performances

As an ideal pseudo-capacitive electrode material,transition metal sulfide have become a major kind of positive materials candidate for asymmetric supercapacitor.In this paper,we paid attention to the synthesis of nickel,manganese,cobalt and molybdenum transition metal sulfides.What's more,their electrochemical behaviors and applications in supercapacitors were also investigated.The morphologies of the synthesized samples depend on the hydrothermal reaction conditions,such as the ratio of precursors,the reaction temperature and the reaction time.What's more,the morphology of the samples will further directly influence the electrochemical performance of the as-prepared samples.In this paper,by optimizing reaction conditions,we obtained superior electrode materials which have wonderful capacitance,excellent rate performance and well cycling performance.The main research contents are as follows:1.A facile hydrothermal method was designed to synthesize a novel structure that micro-flowers decorated with nanoparticles.The micro-flowers structure consists of enormous cross-linked flat hexagon nanosheets with sufficient internal space,providing fluent ionic channels and enduring volume change in the electrochemical storage process.As expected,the Mn S/Nix Sy(NMS)material delivers good specific capacitance(1073.81 F g-1 at 1 A g-1)and good cycling stability of 82.14% retention after 2500 cycles(10 A g-1).Furthermore,the assembled asymmetric supercapacitor could achieve a high energy density of 46.04 W h kg-1 with excellent cycling performance(89.47% of capacitance retention even after 10000 cycles).The remarkable electrochemical behaviors corroborate that the NMS can serve as an advanced electrode material.2.Co9S8/Mo2S3 nanorods on Co S2 laminar arrays(Co S2-Co9S8/Mo2S3,defined as Co1Mo1)were synthesized via one step hydrothermal method for high performance supercapacitors.The Co1Mo1 hybrid was in-situ grown on Ni foam(NF).The nanorods and laminar arrays constructed 3D network with stable structure,maintaining highdurability during electrochemical reactions.What's more,this Co1Mo1 hybrid electrode combined the merits of both cobalt sulfides(the high capacity)and molybdenum sulfides(the excellent cycling stability).As expected,the Co1Mo1//NF hybrid exhibited excellent capacitance(2777.5 F g-1 at 1 A g-1),wonderful rate performance(81.46% from 1 to 50 A g-1),as well as superior stability(100% at 10 A g-1 after 8500 cycling)when used as single electrodes.The Co1Mo1//AC device was also assembled,showing high energy density(56.56 W h kg-1)with well power density(850 W kg-1).When combined two Co1Mo1//AC devices in series,six colored led bulbs which were in parallel can be lighted(green LED,working voltage greater than 3 V),further corroborated the possibility of the Co1Mo1 electrode for practical application.3.A facile two-step strategy is developed to synthesized Nix Sy(Ni3S4 and Ni S2)/Mo S2 nanomaterials as high performance electrode materials,which are defined as Ni2Mo1.The Ni2Mo1 material has best loose structure,which is benefiting for ion diffusion,and thus endows it the superior electrochemical performances.What's more,this hybrid electrode material could well combine the advantages of both nickel sulfides(the high capacitance)and molybdenum disulfide(the excellent cycling stability).The as-synthesized Ni2Mo1 electrode delivers a high specific capacitance(1525 F g-1 at 1 A g-1)with excellent cycling stability(88.24% of capacitance retention after charge-discharge for 8000 times).Most significantly,the constructed Ni2Mo1//AC asymmetric supercapacitors(ASCs)devices with a wide voltage window of 1.7 V could reach a wonderful energy density(51.71 W h kg-1 at a power density of 1700 W kg-1)with excellent cycling performance(92.31% of capacitance retention even after 10000cycles).High power density and energy density could facilitate fast charge and discharge,as expected,the combined two Ni2Mo1//AC ASCs devices in series could power four red led bulbs for 16 min,and subsequently light one red led bulb for 5 min,conforming its possible for practical application.This general strategy provides a facile and cost-effective method to design the metal sulfides composites electrode,which could be applied in energy storage field.