Preparation And The Electrochemistry Properties Study Of LiNi_0.5Mn_0.5O₂ As Cathode Material For Lithium Secondary Batteries

With the development of science and technology, battery has more and more importanteffect in high technology area, the new electron product is applied in more and more field. Liionbattery has been paied much attention because of the high voltage , high power capacity ,low consumption, without memory effect , without pollution,small volume , small internalresistance , few self discharging , many circulation numbers and so on. At present, LiCoO2 andLi-Co-Ni-O have become the main cathode material in commercial lithium-ion batteries,however, because of the high cost, toxicity, resource shortage and polluting environment ofLiCoO2, researchers have been searching for alternative materials. They made extensivelystudy on LiNiO2, LiMn2O4 and LiMnO2 as LiCoO2 alternatives. Although they have obtainedlots of progress in making those materials in many aspects, they have not found an excellentmaterial to alternate LiCoO2. So researchers pay their attention to multi-substitution and hopeto get a new compound material, which has become a focus and developing direction onbattery study. layered LiNi0.5Mn0.5O2 material has a lot of merit , and causes concerns amongscience worker in recent years because of low cost, abounding natural resources and beneficialto the environment.In this paper, layered LiNi0.5Mn0.5O2 material is selected as research object and is studiedon its preparation method, synthesis condition and electrochemical property in detail.Using the high temperature solidoid mehod and co-precipitation method synthesized theLiNi0.5Mn0.5O2,we find that synthesizing LiNi0.5Mn0.5O2 by the co-precipitation method hasbetter properties. In order to look for the best route of the co-precipitation method of theLiNi0.5Mn0.5O2, we study the rubbing time, PH, ultrasonic disposal, reaction time andtemperature, cooling patterns, which affect structure of material and electrochemistry property.Through the experiment, we find a better synthesis condition and optimize synthesis route.We analyze element property, material structure and electrochemistry property by XRD,Raman, ICP, XPS and CV. The result of experiment indicates that the LiNi0.5Mn0.5O2 sample,which was synthesized by LiOH as lithium source, by Ni(NO3)2·6H2Oand Mn(Ac)2·4H2O asnickel and manganese source, by Li: Mn: Ni=1.1:1:1,dealed with by strong oxidizer, calcinedat 900℃for 12h, dealed with quenching at normal temperature, has the best electrochemicalproperties. The analysis result of ICP indicates that there are only Ni2+, almost Mn4+ and avery few Mn3+, which close to perfect theoretical value . On electrochemistry propertyaspect, discharging at 0.3C, the reversible capacity reachs 86mAh·g-1, after 20 loop cycles, itstill get to 54mAh·g-1.