Preperation,Characterization And Electrochemical Test Of Nickel Sulfides Electrode Materials

Supercapacitors,as a new type of power storage device,have high power density,excellent cycle stability and fast charge-discharge performance.These excellent performances make the application prospect of supercapacitors in high-power equipment,electric vehicles,wearable electronic devices and other fields highly concerned by the majority of researchers.Among all kinds of electrode materials reported for supercapacitors,pseudo capacitance materials have been able to achieve good energy density and excellent cycle stability at a high power density,which is very promising for application.This article mainly takes nickel sulfide as the research object,synthesize these materials through different methods,different conditions.The samples with different particle size were synthesized,microstructure and electrochemical properties of nickel sulfide electrode material,and the system of preparation conditions on the particle size was studied,and the influence of the microstructure,as well as the particle size and microstructure on its electrochemical properties also was explored.The following are the main research results:?1?A simple and mild solvothermal method was proposed to prepare cabbage-like alpha phase NiS particles with hierarchical structure,and the influence of solvothermal time on their microstructure and the influence of annealing temperature in argon on their electrochemical properties was studied.When the solvothermal time reached 9 h,the surface of cabbage-like alpha NiS particles formed cross-wiggling bands,and the gaps between the bands were filled with NiS nanoparticles with a particle size of about50 nm.After annealing in argon at 400 ^o C,these particles exhibited excellent electrochemical properties.It exhibited 1887 F g^-11 at the current density of 1 A g^-1,and still keep 1144 F g^-11 at the current density of 10 A g^-11 at the current density of 5 A g^-1,the capacitance retention rate is 95%after 1000 cycles.The cabbage-like?-NiS particles and rGO particles were assembled as asymmetric supercapacitors.The energy densities of the asymmetric supercapacitors were 48.67 Wh kg^-11 and 19.32 Wh kg^-1displayed at the power densities of 800 W kg^-11 and 8000 W kg^-1,respectively,reflecting its good applying prospect.?2?Due to the metallic properties of nickel sulfides and the large specific surface area of graphene,we prepared the?-NiS nanoparticles by microwave-assisted method,added graphene to provide growth points for NiS nanoparticles,and added the quenching step in the ice-water mixture to rapidly cool the NiS nanoparticles to avoid agglomeration.The particle size controlled in the range of about 50-300 nm was successfully achieved,and the electrochemical properties of the nanoparticles with different particle sizes were studied.Although the prepared materials have good capacity and low impedance,the rate performance of these materials is relatively general,and a great defect of cycle capability have been exposed.The cycle retention rate of nickel-base sulfide materials prepared by microwave-assisted and modified through various methods are all lower than 30%.It is necessary to further improve the preparation method and findmore quickly,efficiently and cheaply synthesizing methods.?3?This part of experiment modified the nickel-based sulfides through preparing precursor with special structure which may result in better electrochemical properties and adding Cobalt element,and then sulfide the precursor by microwave-assisted methods to improve the electorchemical performance of the material which synthesized last chapter.Through solvothermal method,we achieved incorporating the Co element and constructed coral porous structure of precursor,but the microwave heated the precursor too quickly so that we failed maintain the porous structure,the particles broke down and became similar directly by microwave assisted preparation of nickel-base sulfide granular structure,covering reduced graphene oxide at the same time,improve the condition of its grain stack.Although the structure of the precursor was not maintained,the electrochemical properties of the cobalt-nickel sulfide prepared by the two-step method were greatly improved compared with those prepared by the microwave-assisted method.In the future research work,we hope that researchers can keep the structure of the precursor on the basis of using microwave vulcanization method,and further improve the electrochemical properties of the material.