The Synthesis And Electrochemical Performances Of The Nanostructured Materials Ag_0.33V₂O₅and Li₃V₂（PO₄）₃

ABSTRACT:Vanadate as the cathode materials has the advantages of stability, high theoretical capacity, high-rate capability and so on. When the silver vanadium oxides are used as the cathode materials, the batteries have very poor cycling capability, which constrain their applications just in the primary batteries. Lithium vanadium phosphate method of solid phase sintering-temperature is too high, and poor electrical conductivity. This work is focus on synthesizing nanostructured silver vanadates by a sol-gel route, synthesizingLi3V2(PO4)3by solid state sintering method. As follows:(1) Using V2O5, citric acid and AgN03as raw material, the Ag0.33V2O5nanorods are prepared by sol-gel method.The products contains no impurity phase, and are small and uniform particles. The Ag0.33V2O5nanorods have good stability and cycle performance. under the discharge density100and200mA/g, the material can reach the maximum capacity of247and210mAh/g, respectively., These capacity can reach211and189mAh/g after30laps cycle.The Ag0.33V2O5pro form better cycle stability than other vanadate silver material which had the very beenreported.(2)Using LiF as source of Li, V2O5, NH4H2PO4, oxalic acid and oleic acid used as raw materials, the Li3V2(PO4)3/C composite material is systhesis through solid phase sintering method after ball mill. The temperature is700℃much lower than the reported, but the materialhas a high degree of crystallinity, and no impurity phase generated. The product is nanomaterial, the partical is uniform, between tens to hundreds of nanometer. In this method, the nano flake Li3V2(PO4)3/C composite material under2.54.7V charging and discharging a maximum capacity of182.2mAh/g, charge and discharge the highest available under2.54.3V128.2mAh/g, it is close to with theoretical capacity. Decreases after30laps cycle, capacity is not much, it means that the stability of the material is good, but the highest potential4.7V lower attenuation is much greater than4.3V, three Li ion will show out on the material of the structure stability has a certain impact.(3)V2O5, ammonium dihydrogen phosphate, acetylene black are used as the raw material, and the VPO4precursor is synthesized by carbon thermal reduction method.Then the VPO4is reacted with LiF to get the L13V2(PO4)3· LiVPO4F composite materials. Structure characterization results show that750℃sintering product of3h contains two kinds of target materials. Electrochemical performance test results show that the L13V2(PO4)3· LiVPO4F composite materials have the Li3V2(PO4)3good cycle stability and rate performance advantages, and includes LiVPO4F discharge at around4.2V when discharge platform, which make up the Li3V2(PO4)3in2.5-4.7V to the defects of no apparent when charging and discharging platform. The material under the discharge density of0.1C can get the specific capacity of152mAh/g, and even current increase to8C can still obtain specific capacity of about100mAh/g.