Design,Preparation And Electrochemical Properties Of Transition Metal Sulfide Composite Electrode Materials

At present,environmental problems and energy crisis are becoming more and more serious,so it is urgent to develop new energy storage devices.As a new type of energy storage device,supercapacitor has many advantages,such as high power density,high speed of charge and discharge,long cycle life,no pollution and so on.Electrode material as the core part of supercapacitor,the development of high performance electrode material is the key to improve the performance of supercapacitor.In recent years,nickel-based electrode materials have become the focus of research due to the advantages of rich storage,low cost and high specific capacitance.However,the limited active sites and slow reaction kinetics in electrochemical reaction seriously affect the improvement of electrochemical performance of electrode materials.In order to solve the above problems,high performance transition metal sulfide electrode materials were prepared from the synergy between elements aspects of element doping and the design of composite electrode materials.The main research contents is as follows:1.Zinc-doped Ni_xZn_1-xOH nanosheets were grown on the foamed nickel matrix by a simple two-step hydrothermal method.The nanosheets were uniformly distributed and then vulcanized with sodium sulfide to form cactus-like ZnS/Ni₃S₂?NZS?composites.Its specific surface area was greatly increased,that is,the specific surface area reached 43.08 m² g^-11 and the average pore size was about 20-30 nm.So,electrochemical active sites and reaction kinetics was greatly improved.And it can effectively alleviate the volume change of the material in the process of charge and discharge.As a cathode material for supercapacitors,NZS exhibits a high capacitance of2093 F g^-11 at 1 A g^-1 and excellent rate performance(72%,10 A g^-1).In addition,we assembled asymmetric supercapacitor?ASC?using advanced NZS electrode material as positive electrode and activated carbon?AC?as negative electrode.The device exhibits a high energy density of 51.2 Wh kg^-1(at a power density of 849.4 W kg^-1)in a high voltage range of 0-1.7 V.In addition,two fully charged ASC?in series?can light up four red LED lights.2.Nickel manganese sulfide?NiMn-S-1?is a unique double shell hollow spherical structure prepared by low cost solvothermal method.The synthesized materials have multi-layer thin shell and hollow structure,which facilitate the transport of ions and electrons,facilitate the penetration of electrolyte and alleviate the volume effect in charge and discharge process.This not only improves the electrochemical performance of NiMn-S-1,but also prevents the aggregation of NiMn-S-1.Through testing and calculation,the synthesized NiMn-S-1 electrode has a high specific capacitance of 1240 F g^-1 at the current density of 1 A g^-1 and excellent cycle performance(81%,10 A g^-1).As far as the practical application of electrode materials is concerned,we maked the NiMn-S-1//AC asymmetric supercapacitor using activated carbon as the negative electrode and NiMn-S-1 as the positive electrode.The device has a high energy density of 44 Wh kg^-1(when the power density reached 792 W kg^-1).Therefore,as a pseudo-capacitive material,NZS has great potential for application.To sum up,the research of transition metal sulfide electrode material mainly starts from two aspects:?1?utilizing the synergistic effect between elements;?2?designing the morphology and structure of the material,it shows excellent electrochemical performance.This makes it a promising energy material.