Fabrication of LiMnPO4-MWCNT cathode material via vapor phase hydrolysis and its electrochemical properties

摘要

Olivine-structured LiMnPO4-MWCNT cathode materials are fabricated via vapor phase hydrolysis without calcination process and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption-desorption isotherm analysis, galvanostatic charging-discharging test, and electrochemical impedance spectroscopy (EIS). All XRD results show LiMnPO4 and multi-walled carbon nanotubes (MWCNTs) coexisted in the obtained sample. The appropriate temperature to synthesize LiMnPO4 cathode material is 200 A degrees C, and MWCNT addition accelerates growing of (020) plane. SEM shows MWCNTs have been coated onto the surface of LiMnPO4 and the morphology of LiMnPO4 can be tuned from fragment to long strip by varying MWCNT contents. EIS results indicate that MWCNTs are able to accelerate the diffusion of Li+ ion across LiMnPO4-MnPO4 boundary, so galvanostatic charging-discharging test indicates that the initial capacity of LiMnPO4-MWCNT composites is higher than that of LiMnPO4. The best initial discharge capacity is 113 mAh/g (0.1 C) when MWCNT addition is 5 % due to the synthetic effect of improved electrochemical performance and relatively small dimensions.