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The Research On Preparation And Electrochemical Performance Of LiFePO4/Whisker CNT

Posted on:2015-10-19Degree:MasterType:Thesis
Country:ChinaCandidate:J YaoFull Text:PDF
GTID:2181330422477780Subject:Materials Processing Engineering
Abstract/Summary:PDF Full Text Request
LiFePO4is one of prominent cathode materials for Lithium ion battery,and hasgain popularity,Because of low cost and high safety.However, LiFePO4cathodessuffer from poor electronic conductivity and low ionic diffusivity leading to highinitial capacity losses and poor rate capabilities in low temperature or in the case oflarge current discharge,which hinder its practical application in some areas.As a newtype of one-dimensional nano-materials, Whisker carbon nanotube not only has largelength-diameter ratio and high electrical conductivity,but so they are not twining,notcrooked and has well dispersing performance, etc. Based on the research aboutLiFePO4at home and abroad,and the research of our laboratory.Thinking about thedefects of LiFePO4and the advantages of whisker carbon nanotube,This paper doessome modified research to improve the electrical conductivity and ionic mobility ofLiFePO4through of doping whisker carbon nanotube.At the same This paper hascarried on the comparative study with normal carbon nanotubes, conductive graphite,and other conductive materials.(1) Whisker carbon nanotubes have been treated by graphitization in a hightemperature.Graphitization treatment can make carbon atoms of whisker carbonnanotubes arrange orderly by layer, get a clear layered internal structure.And it caneffectively remove the impurities from whisker carbon nanotubes, make its purityincrease from97%to100%.(2) Doping different proportion whisker carbon nanotubes in LiFePO4through themethod of ball-milling. found that the whisker carbon nanotubes are not twining,notcrooked and be mixed well with LiFePO4. Whisker carbon nanotubes can form theconductive bridge or three-dimensional network structure in in the cathode materialparticles. When adding3%Whisker carbon nanotubes,LiFePO4has the highestdischarge specific capacity,0.1C for the first time, specific capacity is150mAh/g,capacity remain at a rate of99%after50cycles.(3) Mixing LiFePO4with respectively3%the three different carbon nanotubesthrough the method of ball-milling.The internal resistance of button battery made with the3%whisker carbon nanotubes is97m.0.2C for the first time, specificcapacity is100mAh/g, only be of60%of the theoretical specific capacity.After50cycles, its capacity keep at a rate of85%. Its Performance is superior to of thesamples doped SDK-VGCF and traditional carbon nanotubes.(4) Mixing LiFePO4with respectively3%the three different conductive agentsthrough the method of ball-milling,found that both conductive graphite and DENKABLACK, compared with the shape of whisker carbon nanotubes, they can not form aconductive bridge and three-dimensional network spatial structure effectively.0.5Cfor the first time, specific capacity of the shape of3%whisker carbon nanotubes is140mAh/g.After50cycles, its capacity maintains at a rate of97%.
Keywords/Search Tags:Lithium ion battery, LiFePO4, Whisker carbon nanotubes, Modify
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