锂离子电池正极材料LiVPO_4F的合成及分析  

Preparation and Characterization of LiVPO_4F Cathode Material Used as Lithium-ion Battery

作　　者：马锐[1] 蔡芬峰[1] 水淼[1] 舒杰[1] 

机构地区：[1]宁波大学材料科学与化学工程学院,浙江宁波315211

出　　处：《热加工工艺》2012年第16期89-94,共6页Hot Working Technology

基　　金：国家自然科学基金项目(51104092);教育部科学技术研究重点项目(210083)

摘　　要：通过2步高温固相反应来合成LiVPO4F正极材料。第一步是将五氧化二钒、磷酸二氢铵和乙炔黑在N2的保护下合成中间体VPO4(即为α);第二步是VPO4和LiF进一步反应生成单相LiVPO4F。考察了乙炔黑不同的过量百分比(过量25%时,合成的LiVPO4F为β1,过量50%时,合成的LiVPO4F为β2)对产物组成和电化学性能的影响。结果表明:β1的产物组成和电化学性能优于β2。XRD测试表明:所合成的LiVPO4F属于三斜晶系,其晶胞参数:a=0.5173nm、b=0.5309 nm、c=0.7250 nm;红外测试表明:LiVPO4F的吸收峰主要是由V=O、O-V-O和PO4基团引起;SEM测试表明:样品β1颗粒均匀度优于样品β2,平均粒径为2μm左右。电化学测试表明:β1和β2在第一个循环的充电比容量分别为82.2、99.2 mAh/g,放电比容量分别为71.7、58.5 mAh/g,19周后,其充电比容量分别为64.7、58.8 mAh/g,放电比容量分别为在62.4、52.0 mAh/g。LiVPO4F的平均脱锂电位在4.3 V以上,平均嵌锂电位在4.15 V左右。这说明,样品β1具有更好的电化学性能。以上综合表明,LiVPO4F作为一种锂离子电池正极材料具有良好的稳定性和可逆性。LiVPO4F was prepared by two-step high temperature solid state reaction method.In the initial step,V2O5,NH4H2PO4,and acetylene black reacted under a nitrogen atmosphere to yield the trivalent vanadium phosphate,VPO4.In the second incorporation step,the VPO4 reacted with LiF to yield the single phase LiVPO4F.The effects of mass excess of acetylene black on the microstructure and the electrochemical properties were investigated.The final samples prepared by 25% mass excess of acetylene black was named as β1.The resulting products prepared by 50% mass excess of acetylene black was named as β2.The final results show that the product purities and electrochemical properties of β1 are superior to β2.X-ray diffraction（XRD） patterns show that LiVPO4F synthesized by 25% mass excess of acetylene black has a triclinic structure.The crystallographic parameters of the prepared LiVPO4F powders are as follows,a=0.5173 nm,b=0.5309 nm,c=0.7250 nm,which are similar to the results as reported in the literatures.Infrared（IR） spectra show that the absorption peaks of LiVPO4F are attributed to stretching and bending of V=O,O-V-O and PO4.SEM images show that the particle distribution of β1 is superior to β2,and the particle size of β1 is about 2 μm.The electrochemical test show that the initial charge and discharge capacities of β1 is about 82.2 mAh/g and 71.7 mAh/g,and the initial charge and discharge capacities of β2 is about 99.2 mAh/g and 58.5 mAh/g.After 19 cycles,the charge and discharge capacities of β1 is about 64.7 mAh/g and 62.4 mAh/g and the charge and discharge capacities retain of β2 is about 58.8 mAh/g and 52.0 mAh/g.The average charge and discharge voltages of LiVPO4F are approximately 4.3 and 4.15 V,respectively.It suggests that LiVPO4F prepared by using 25% mass excess of acetylene black show better electrochemical properties.All these results indicate that LiVPO4F used as cathode material for lithium-ion batteries has preferable stability and reversibility.

关 键 词：锂离子电池 正极材料 LIVPO4F 固相法 

分 类 号：TM912.9[电气工程—电力电子与电力传动]