高性能锂电正极材料LiV_3O_8-MWCNTs的制备与性能

Preparation and properties of LiV_3O_8-MWCNTs as high performance cathode materials for lithium-ion battery

利用低温液相法合成了钒酸锂-多壁碳纳米管(LiV_3O_8-(w)MWCNTs)(w分别为0、1%、2%、3%、4%和5%)复合正极材料.采用X-射线衍射(X-ray diffraction,XRD)和扫描电镜(scanning electron microscope,SEM)对复合材料的晶型和结构进行了表征.XRD分析结果表明,复合材料仍为单斜晶系;SEM图谱显示,LiV_3O_8材料附着在MWCNTs的网状结构上,且使颗粒细化;通过恒流充放电测试、循环伏安(cyclic voltammetry,CV)及交流阻抗谱(electrochemical impedance spectroscopy,EIS)技术对材料的电化学性能进行了研究,结果表明,按LiV_3O_8质量百分比复合3%MWCNTs的LiV_3O_8-(3%)MWCNTs复合材料具有最佳的电化学性能,在0.1 C充放电倍率条件下,其首次放电比容量为364.5 m Ah/g,循环50次后放电比容量仍有292.2 m Ah/g,容量保持率为80.2%,而纯LiV_3O_8材料的首次放电比容量为308.2m Ah/g,循环50次后容量保持率仅为55.4%;采用MWCNTs与LiV_3O_8复合可使锂离子在材料颗粒间的电荷转移阻抗变小,有利于Li+的嵌入和脱出.

Lithium trivanadate-multiwalled carbon nanotube（ LiV3O8-（ w） MWCNT）（ w = 0,1%,2%,3%,4%,5%） composite cathode materials are synthesized by low temperature liquid reaction. The crystal structures and microstructures are investigated by X-ray diffraction（ XRD） and scanning electron microscope（ SEM）. XRD analyses show that the LiV3O8-（ w） MWCNTs are still monoclinic. The SEM images show that the LiV3O8 is attached to the network structure of MWCNTs,and the LiV3O8 particles are refined. The electrochemical properties are also characterized with charge-discharge cycling performance,cyclic voltammetry（ CV） and electrochemical impedance spectroscopy（ EIS）. The results show that LiV3O8-（ 3%） MWCNTs have the best electrochemical properties whenthe mass percentage of MWCNTs is 3 % in the composite,exhibiting a high discharge capacity of 364. 5 mA h/g maintaining a stable capacity of 292. 2 mA h/g within 50 cycles at the charge-discharge rate of 0. 1 C,and having the capacity retention of 80. 2%. However,in the pure LiV 3 O8,the discharge capacity is 308. 2 mA h/g,and the capacity retention is only about 55. 4% after 50 cycles. Finally,the EIS results show that the lithium-ion chargetransfer resistance decreases greatly when LiV 3 O8 is coated with NWCNTs,which is favorable for fast lithium-ion intercalations/deintercalations in the composite materials.