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Preparation And Research Of Olivine LiFePO4 Cathode Materials

Posted on:2015-08-12Degree:MasterType:Thesis
Country:ChinaCandidate:S L YanFull Text:PDF
GTID:2321330518971173Subject:Applied Chemistry
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Olivine-type LiFePO4,exists as phosphorus ore in nature,is considered to be one of the most potential cathode materials in development and application for lithium-ion batteries.The material with a higher theoretical specific capacity of 170mAh/g and good thermal stability is environmentally friendly.But It has not been applied in large-scale commercial field because of its own structure,poor ion conductive and electronic conductive.At present,carbon coated and metal ion doping are considered the most effective and direct method to improve the poor conductive and low rate performance of LiFePO4.In this paper,LiFePO4/C composite materials were synthesized by rheological phase method using two different iron source?FeC2O4 and FePO4?then,doped Ti and Ni in LiFePO4 respectively.The materials were characterized by XRD,SEM and other electrochemical test.The results show that the LiFePO4/C with 15 wt%carbon synthesized by FeC2O4 had the largest initial specific capacity of 132 mAh/g at 700 ? sintering temperature and after 30 cycles,the capacity retention is above 95%.When we use FePO4 as iron source,the best sintering temperature is 600 ?,the lithium iron phosphate/C showed a large initial discharge specific capacity of 13 8mAh/g in 0.1 C,the retention is above 95%after 30 cycles.When doped 20wt%?mole rate of LiFePO4?Ti4+ in LiFePO4/C,the material showed a large initial discharge specific capacity and a good cycle performance in both 0.1 C and 1C.They were 146 mAh/g and 118mAh/g,the retentions were 97%and 98%after 30cycles.The LiFePO4/C doped with 0.05 Ni2+?mole rate of LiFePO4?also showed a great initial discharge specific capacity of above 156 mAh/g in 0.1 C while 122 mAh/g in 1 C,the retentions of them were 95%and 99%.
Keywords/Search Tags:LiFePO4, Rheological phase method, Carbon coated, Metal ion doping
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