Study On Electrochemical Performance Of LiMoS₂ And VN Nanoparticle As Negative Electrode Materials For Lithium Ion Capacitors

Lithium ion capacitors?LIC?,also known as lithium ion hybrid supercapacitors,is a new type of energy storage devices between lithium ion batteries and supercapacitors,since it combines high power density of supercapacitors and high energy density of lithium ion battery,has fast charge and discharge performance,excellent cycle stability,lightweight and easy to carry and so on.which make them one of the most promising candidates for next generation energy storage devices.This paper designs two systems of lithium ion capacitors cells,include AC//lithium compound systems and AC//lithium free compound systems,and choice LiMoS₂ and VN nanoparticle as the negative electrode material of the two systems.The two materials were prepared by a relatively simple and mild synthesis method,and we also take the test methods such as XRD,SEM and TEM to analyze and characterize the composition and structure of electrode materials,and using the electrochemical workstation and blue electric testing system to comprehensive analysis its electrochemical performance.1.The synthesis LiMoS₂ was carried out by solvothermal method at different temperatures as negative electrode material,commercial activated carbon as cathode material,1 M LiPF₆ dissolve in EC:DMC=1:1 as electrolyte and assembled into lithium ion capacitors.Firstly,we study the structure of LiMoS₂,results show that under the optimum conditions,the prepared LiMoS₂ electrode material has a good crystallinity and a lamellar structure with a large number of pores.This structure is very favorable for the insertion and removal of lithium ions,therefore,the electrochemical properties of lithium ion capacitors assembled with LiMoS₂ materials are excellent.Then,we discuss the effect of LiMoS₂ synthesis temperature on the electrochemical performance of AC//LiMoS₂ lithium ion capacitors,through electrochemical test,the discharge capacity of lithium ion capacitor increases with the increase of LiMoS₂ synthesis temperature,at 180?,AC//LiMoS₂ lithium ion capacitors specific capacity is 88 F/g.2.Ammonium vanadate as raw material,synthesis of precursor V₂O₅ by direct heating method,then heated in ammonia and VN nanoparticles were obtained,high specific surface area activated carbon made from polystyrene?PS?was chosen as the cathode material.In order to improve the preparation efficiency of lithium ion capacitor,preparation of lithium ion capacitor electrode by spraying method.The PS//VN nanoparticles lithium ion capacitors has a large potential window?0-3.5 V?,high energy density and power density?69.2 Wh/kg at3498.9 W/kg?and good cycle stability?keep 70%initial capacity after 1500 cycles?.