Preparation and Characterization of LiMn2O4 Cathodes Surface-Modified by DC Pulsed Plasma Treatment

A study of oxygen dc pulsed plasma irradiation treatment has been carried out on LiMn2O4 powder cathodes to enhance the electrochemical performances of lithium ion batteries. The samples have been characterized by X-ray diffraction, scanning electron microscope, energy dispersion spectroscope and electrochemical measurements. It is found that after undergoing the plasma treatments, the sharp facets of LiMn2O4 particles become smooth due to plasma ion bombardment. The treated electrodes are partially covered by layers with high atomic percent of element F, indicating the reflow of binders. The electrochemical measurements are carried out under harsh conditions, including deep-discharge at low cut-off potential of 2 V and cycling at elevated temperature of 60 degrees C. The results reveal that moderate oxygen dc pulsed plasma treatment can improve the cycling stability of LiMn2O4 powder electrodes in the above mentioned conditions. The enhanced electrochemical performances are attributed to the dense protection layers on electrode surface, which reduce the capacity fading due to the Mn+2 ions dissolution.