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Study On Synthesis And Electrochemical Characteristics Of LiNi1/3Co1/3Mn1/3O2 Cathode Material For Lithium Ion Batteries

Posted on:2007-09-05Degree:MasterType:Thesis
Country:ChinaCandidate:X F LuoFull Text:PDF
GTID:2121360185480764Subject:Physical chemistry
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Lithium-ion batteries (LIB) with high energy density, power capability and long cycle life are used to power portable electronic devices such as cellular phones and laptop computers and have long been considered as possible power source for electric vehicle (EV), hybrid electric vehicle (HEV) and high efficiency energy-storage systems. Layered LiCoO2 is the most widely used cathode material in the present-day commercial Li-ion batteries. However, due to its high cost and toxicity, considerable effort has been expended over the past decade to find possible alternatives to LiCoO2. Recently, LiNi1/3Co1/3Mn1/3O2 as a special case among the Li[NixCo1-2xMnx]O2 series which x is 1/3 has attracted a great deal of interest in the investigation of cathode materials of LIB to replace the presently popular LiCoO2 because the combination of Ni, Co, Mn can provide advantages such as high reversible capacity, stable cycling performance, good thermal stability, excellent rate capability and low cost. It is considered to be one of the best candidates of positive electrode material for hybrid electric vehicle (HEV) power source system. In this dissertation,the studies on the synthesis, morphology, structure and electrochemical performance of LiNi1/3Co1/3Mn1/3O2 as cathode materials for lithium ion batteries were carried out systemically and in detail.In this paper, the uniform spherical metal hydroxide (Ni1/3Co1/3Mn1/3)(OH)2 was prepared via hydroxide co-precipitation. This paper represents details of the optimized spherical (Ni1/3Co1/3Mn1/3)(OH)2 formation process by control reaction time, pH, amount of chelating agent, etc., during co-precipitation reaction. The results indicated that the optimum conditions for spherical (Ni1/3Co1/3Mn1/3)(OH)2 were that the pH of the aqueous solution was 10.5, the NH3/M was 0.8 and the reaction time was 16h.Layered spherical LiNi1/3Co1/3Mn1/3O2 powders with high tap-density were successfully synthesized by mixing uniform co-precipitated spherical metal hydroxide, (Ni1/3Co1/3Mn1/3)(OH)2 with LiOH?H2O followed by heat-treatment. The mixture was pre-heated at 480℃for 5h, then at 650℃for 9h. XRD examination revealed that the synthetic temperature of the cathode material with good electrochemical properties could be as low as 700℃. The effects of calcination temperature, time and Li/(Ni+Mn+Co) ratio on the structural and electrochemical properties of the LiNi1/3Co1/3Mn1/3O2 were characterized by the Rietveld refinement associated with electrochemical studies. The results got from the experiments showed that the sample of LiNi1/3Co1/3Mn1/3O2 which were sintered for 18h at 850℃after a serials of pre-heat...
Keywords/Search Tags:lithium ion batteries, cathode material, hydroxide co-precipitation, layered structure, LiNi1/3Co1/3Mn1/3O2, electrochemical properties
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