Preparation And Study Of A New Kind Of Cathode Material LiFePO₄for Lithium-ion Battery

LiFePO₄, as a new generation of cathode material for lithium-ion battery, has becomemore concerned because of its low cost, environmental friendly, thermally stable, safetyand excellent cycle performance and so on since the late20th century. However, as anupstream industry, its main drawback such as low electronic conductivity, poorperformance at low temperature have been obstacles for the development to the largescale applications field such as hybrid electric vehicles. so it’s necessary to searcheffective approaches for the downstream industry and better development.Firstly, the olivine-structured lithium iron phosphate（LiFePO₄）was prepared bysolid-state method by using constituents of Li resource Li₃PO₄, Fe resourcesFePO₄^*xH₂O and Fe power in this paper. each optimal Process parameter such ascalcining temperature, calcining time, carbon amount and atmosphere have beendiscussed. The effectes of process parameter for the samples’performance were discussedby XRD, SEM analysis and electronic conductivity test, and have made a contrast amongthe materials. The results show that the materials is well crystallized and keep excellentperformance at the condition of650℃,7hours and4%C content.We have improved the program of atmosphere as the key. The result indicates thatreducing flow produced by the breakdown of sucrose independently driven by N2canreplace the traditional atmosphere of Ar/H2, which will reduce the synthesis costs largely.Secondly, with the carbon-coat methods by inorganic carbon（the mixture of acetyleneblack and graphite） and organic carbon（sucrose）, the peformence affected on the twoC-resource were also discussed. It shows that there is no crystalline and amorphousstructure of carbon in the XRD patten, and adding less carbon will not affect the thecrystal structure of LiFePO₄/C.what’more, the initial discharge specific capacity reached142.9mAh/g at0.1C in the latter conditions and the coulomb efficiency remained98.1%which showed better performance than the former；The influence of Ti-doping on properties of LFP products were also discussed. The result clearly shows the the specificcapacity of Ti-doped LFP is higher than the undoped one. Ti is replace Fe according tothe mixture ratio Ti of and iron（Ⅱ） and the XRD analysis shows that the samples by Ti-doping is pure well-ordered olivine phase with no impurities.Finally, The electronic conductivity of carbor-coated and Ti-doping were also tested. Itshows that the electronic conductivity are greatly improved to10^-3and10^-2in contrast tothe pure LiFePO₄, which is10^-710^-9S/cm. The samples exhibit excellent performancebecause of the improvement of electronic conductivity.