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A Research On Synthesis And Electrochemical Properties Of Li(NiMn)(1-x)/2CoxO2Cathode Material For Lithium Ion Battery

Posted on:2015-02-03Degree:MasterType:Thesis
Country:ChinaCandidate:Z L WangFull Text:PDF
GTID:2251330422472068Subject:Chemistry
Abstract/Summary:PDF Full Text Request
At present, the most widely used cathode materials for lithium ion battery isLiCoO2. As a result of its high cost and toxic nature, alternative cathode materials areexplored constantly to replace a series of positive cobalt materials. Composite cathodematerials containing Ni and Mn are generally superior to LiNiO2and LiMnO2and thusbecome an important research object in cathode material field on account of theabundant reserves and the nontoxic property. In this paper, because of the wide materialsource and cobalt reduction, cathode material LiNi0.5Mn0.5O2was chosen as the mainstudy object, which will trend to be cheaper and eco-friendly.This paper is based on the research of LiNi0.5Mn0.5O2which was prepared byco-precipitation method and one time sintering process. And, various analysis testmethods such as TG-DTA, LPSA, XRD and galvanostatic charge-discharge wereintroduced to study the effects of the experimental factors on theparticle-size-distribution, structure and electrochemical properties of the cathodematerial. In which the experimental factors such as feeding mode of precipitation agent,pH value, cooling pattern, addition of lithium content, calcinations time and evencalcinations temperature were taken into account. According to the TG-DTA analysis,no weight loss sustained its continuance when the temperature reached at800℃in themixtures of Li2CO3and the precursor body, which means the formation of theLiNi0.5Mn0.5O2compound. XRD analysis indicates that the cathode materials hasα-NaFeO2type structure, the intensity ratios of I(003)/I(104)were1.382,1.741and1.662for800℃,850℃and900℃respectively, which can be considered as theindicators of higher ordering of cations between the layered structure of the cathodematerials obtained at850℃and900℃than that of the material prepared at800℃. Inaddition, galvanostatic charge-discharge analysis shows that the sample ofLiNi0.5Mn0.5O2obtained by parallel addition manner of precipitation agent played thebest electrochemical performance, in which, the sample was calcined at900℃for10hunder a condition of pH=11, Li:M=1.1:1and was cooled to temperature in the air.LiNi0.5Mn0.5O2exhibits a discharge initial capacity of148mAh/g at a discharge rate0.15C in the voltage range of2.5-4.5V, the capacity maintained at149mAh/g after30cycles and the specific discharge capacity retention is100.68%.Under the optimized process conditions, systematic investigation was conductedon the electrochemical performance of Li(NiMn)(1-x)/2CoxO2with different x values. The results turned out from the experiments showed that the cathode material ofLiNi0.4Co0.2Mn0.4O2exploits the best electrochemical performance. The capacitymaintained at154.2mAh/g after30cycles at a discharge rate0.15C in the voltage rangeof2.5-4.5V.
Keywords/Search Tags:lithium-ion batteries, cathode material, co-precipitation, LiNi0.5Mn0.5O2, electrochemical performance
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