磷酸钒锂正极材料的合成与性能研究

本文以LiOH·H2O,NH4VO3,NH4H2PO4和柠檬酸等为原料采用流变相法成功地合成了磷酸钒锂化合物。利用XRD,TEM等手段对目标产物的结构和形貌进行了表征,结果表明:在800℃煅烧的样品具有单一纯相的单斜晶体结构。晶体颗粒分布在200~500nm范围,而且在颗粒表面包覆了一层碳,有利于材料的导电率的改善。对该材料的电化学性质进行了测试,实验发现:800℃煅烧的样品在0.1C和1C倍率电流条件下,首次放电比容量分别高达122.8和107mAh·g-1,经过30次循环后容量衰减很少。交流阻抗谱证实了800℃煅烧的样品具有较高的电导率。本文对800℃煅烧的样品具有较好电化学性能的原因进行了初步讨论。

Synthesis and Electrochemical Characteristics of Cathode Materials Li3V2(PO4)3

A novel theological phase method was used to synthesize nanocrystalline Li_3V_2(PO_4 )_3 compound.In this and the Li_3V2(PO_4 )_3 was obtained by sintering precursor at different temperature for 8 h in flowing argon.The Li_3V_2(PO_4 )_3 has been characterized by XRD and TEM techniques,the compound synthesized at 800℃ take on pure monoclinic crystal structure,the particle size of the samples are ranged from 200～500 nm and there is a layer of carbon particles on the surface of Li_3V_2(PO_4 )_3 particles,which is available for enhancing the conductivity of Li_3V_2(PO_4 )_3.The influence of sintering temperatures on electrochemical properties of Li_3V_2(PO_4 )_3 has been investigated also,the results showed that the Li_3V_2(PO_4 )_3 synthesized at 800℃ exhibited the highest initial discharge capacity (122 mAh·g~(-1) at 0.1C and 107 mAh·g~(-1) at 1C,respectively) and good capacity retention in the voltage range of 3.0～4.3 V.The electrochemical impedance spectroscopy (EIS) showed that the sample synthesized at 800℃ behaved the higher conductivity.The reasons for the excellent electrochemical performance of the carbon coated Li_3V_2(PO_4 )_3 calcined at 800℃ cathode material were presented also.