锂离子电池正极材料LiW_xV_3O_8的合成与性质研究

Synthesis and properties of lithum-ion battery cathode material LiW_xV_3O_8

以LiOH.H2O,V2O5,WO3以及柠檬酸为原料采用流变相法合成了锂钒氧化合物LiWxV3O8(x=0,0.01,0.03,0.05).利用XRD对目标产物的结构进行表征,结果表明:掺杂前后LiWxV3O8均为单斜结构,但掺杂后晶胞参数a和c值与纯相LiV3O8相比略有增加,有利于锂离子在晶体结构中的迁移.同时,对该材料的电化学性质进行测试,结果发现:掺杂后样品的循环性能相对纯相LiV3O8均有所提高,尤其是LiW0.01V3O8电化学性能最为优异,首次放电比容量达238 mAh/g,经过40次循环后容量为185 mAh/g.交流阻抗谱也表明了LiW0.01V3O8具有较小的电荷传输阻抗.对LiW0.01V3O8具有较好电化学性能的原因进行了初步讨论.

A novel rheological phase method was used to synthesize layered LiWxV3O8（x=0,0.01,0.03,0.05） compounds,In this route,LiOH·H2O,V2O5,WO3 and citric acid were selected as starting materals to prepare targeted samples.The microstructure characteristics of the materials were intensively characterized by X-ray diffraction（XRD）.The results indicated that the LiWxV3O8（x=0,0.01,0.03,0.05） compounds took on monoclinic crystal structure.Compared with LiV3O8 compound,the LiWxV3O8（x=0.01,0.03,0.05） showed expanded crystal lattices,and the expansion was more significant along the a-axis and c-axis,which was available for lithium transferring and intercalating/de-intercalating.The electrochemical tests showed that the doped samples exhibited the stable cycling properties,furthermore LiW0.01V3O8 showed the best characteristics among the as-prepared materials,which exhibited high initial discharge capacity of 238 mAh/g and remained 185 mAh/g at cycle 40.The results of electrochemical impedance spectroscopy（EIS） showed that LiW0.01V3O8 performed the low charge-transfer impedance.The reasons for good electrochemical performance of LiW0.01V3O8 cathode material were also presented.