Y-doped Li3V2（PO4）3 cathode materials were prepared by a carbothermal reduction（CTR） process.The properties of the Y-doped Li3V2（PO4）3 were investigated by X-ray diffraction（XRD） and electrochemical measurements.XRD studies showed that the Y-doped Li3V2（PO4）3 had the same monoclinic structure as the undoped Li3V2（PO4）3.The Y-doped Li3V2（PO4）3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram（CV）, and electrochemical impedance spectra（EIS）.The optimal doping content of Y was x=0.03 in Li3V2-xYx（PO4）3 system.The Y-doped Li3V2（PO4）3 samples showed a better cyclic ability.The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Y-doping.The improved electrochemical perormances of the Y-doped Li3V2（PO4）3 cathode materials were attributed to the addition of Y3＋ ion by stabilizing the monoclinic structure.
Cr-doped Li3V2（PO4）3 cathode materials Li3V2-xCr（PO4）3 were prepared by a carbothermal reduction（CTR） process. The properties of the Cr-doped Li3V2（PO4）3 were investigated by X-ray diffraction （XRD）, scanning electron microscopic （SEM）, and electrochemical measurements Results show that the Cr-doped Li3V2（PO4）3 has the same monoclinic structure as the undoped Li3V2（PO4）3, and the particle size of Cr-doped Li3V2（PO4）3 is smaller than that of the undoped Li3V2（PO4）3 and the smallest particle size is only about 1 1μm. The Cr-doped Li3V2（PO4）3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram （CV）, and electrochemical impedance spectra（EIS）. The optimal doping content of Cr was that x=0.04 in the Li3V2-xCrx（PO4）3 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li3V2（PO4）3 cathode materials are attributed to the addition of Cr^3＋ ion by stabilizing the monoclinic structure.
Li3V2（PO4）3 samples were synthesized by sol-gel route and high temperature solid-state reaction. The influence of Li3V2（PO4）3 as cathode materials for lithium-ion batteries on electrochemical performances was investigated. The structure of Li3Va（PO4）3 as cathode materials for lithium-ion batteries and morphology of Li3V2（PO4）3 were characterized by X-ray diffractometry （XRD） and scanning electron microscopy （SEM）. Electrochemical performances were characterized by charge/discharge and AC impedance measurements. Li3V2（PO4）3 with smaller grain size shows better performances in terms of the discharge capacity and cycle stability. The improved electrochemical properties of Li3V2（PO4）3 are attributed to the refined grains and enhanced electrical conductivity. AC impedance measurements also show that the Li3V2（PO4）3 synthesized by sol-gel route exhibits significantly decreased charge-transfer resistance and shortened migration distance of lithium ions.
LiNi0.6Co0.2Mn0.2O2 was prepared from LiOH·H2O and MCO3(M=Ni,Co,Mn)by co-precipitation and subsequent heating. XRD,SEM and electrochemical measurements were used to examine the structure,morphology and electrochemical characteristics, respectively.LiNi0.6Co0.2Mn0.2O2 samples show excellent electrochemical performances.The optimum sintering temperature and sintering time are 850℃and 20 h,respectively.The LiNi0.6Co0.2Mn0.2O2 shows the discharge capacity of 148 mA·h/g in the range of 3.0-4.3 V at the first cycle,and the discharge capacity remains 136 mA·h/g after 30 cycles.The carbonate co-precipitation method is suitable for the preparation of LiNi0.6Co0.2Mn0.2O2 cathode materials with good electrochemical performance for lithium ion batteries.
Y-doped LiVPO4F cathode materials were prepared by a carbothermal reduction（CTR） process. The properties of the Y-doped LiVPOaF samples were investigated by X-ray diffraction （XRD） and electrochemical measurements. XRD studies show that the Y-doped LiVPOaF samples have the same triclinic structure as the undoped LiVPO4F. The Li extraction/insertion performances of Y-doped LiVPO4F samples were investigated through charge/discharge, cyclic voltammogram （CV） , and electrochemical impedance spectra（EIS）. The optimal doping content of Y is x=0.04 in LiYxV1-xPO4F system. The Y-doped LiVPO4F samples show a better cyclic ability. The electrode reaction reversibility is enhanced, and the charge transfer resistance is decreased through the Y-doping. The improved electrochemical performances of the Y-doped LiVF＇OaF cathode materials are atlributed to the addidon of Y^3＋ ion by stabilizing the Iriclinic structure.
