球磨转速对LiMnPO_4/C电化学性能的影响

Effects of milling speed on electrochemical performance of LiMnPO_4/C

采用湿法球磨-喷雾干燥-热处理方法制备了碳包覆的类球形锂离子电池正极材料Li Mn PO_4/C。利用X射线衍射(XRD)、恒流充放电测试、交流阻抗(EIS)和循环伏安(CV),考察了球磨转速对材料的结构和电化学性能的影响,并用场发射扫描电镜(FE-SEM)表征了最佳转速下合成材料的形貌。XRD表征结果表明,不同转速合成的产物均为单相橄榄石结构。SEM表征结果表明,合成材料为一次颗粒镶嵌在导电碳网络之中聚集而成的类球形微米二次颗粒。电化学测试结果表明,合成材料的电化学性能随着转速的提高先增加而后下降。球磨转速为1 250 r/min时合成材料的电化学性能最佳,在0.5C倍率下的放电比容量达到100 m A·h/g,50次循环后容量保持率为94.5%,放电电流从0.1C提高到2C时放电比容量从129 m A·h/g降到96 m A·h/g,表现出较好的循环性能和倍率性能。

The spherical carbon-doped Li Mn PO4/C composites used for cathode material of lithium ion battery were prepared by wet ball-milling-spray drying-heat treatment method.The effects of milling speed on the material structure and electro chemical performance of Li Mn PO4/C were investigated by X-ray diffraction（XRD）,charge-discharge test,electrochemical impedance spectroscopy（EIS）,and cyclic voltammetry（CV）.The morphology of the synthesized material under the best rotation was characterized by field emission scanning electron microscopy（FE-SEM）.XRD results showed that all the composites prepared at different rotational speeds were single-phase olivine structure.SEM result indicated that the spherical composites were composed of nanoparticles,and the nanoparticles were embedded in carbon network.The discharge capacity of the Li Mn PO4/C increased and then decreased with the increase of milling speed.The sample prepared at 1 250 r/min delivered a discharged capacity of 100 m A·h/g with a retention rate of 94.5% after 50 cycles at 0.5 C.When the discharged current increased from0.1 C to 2 C,the discharged capacity decreased from 129 m A·h/g to 96 m A·h/g,showing a good cycle and rate capability.