Effect of ultrasonic irradiation on structure and electrochemical properties of LiMn_2O_4 thin films cathode material for Li-ion micro-batteries

摘要

Two kinds of spinel LiMn_2O_4 thin film for lithium ion micro-batteries were successfully prepared on polycrystal Pt substrates by spin coating methods, which were carried out under ultrasonic irradiation (USG) and magnetic stirring (MSG), respectively. The microstructures and electrochemical performance of LiMn_2O_4 thin films were characterized by thermogravimetry analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and galvanostatic charge-discharge measurements. It was found that the crystalline structure of USG samples grew better than that of the MSG samples. At the same time, higher discharge capacity and better cycle stability were obtained for the LiMn_2O_4 thin films of USG at the current density of 50 μAh/cm~2 between 3.0 and 4.3 V. The 1st discharge capacity was 57.8 μAh/cm~2-μm for USG thin films and 51.7 μAh/cm~2-μm for MSG thin films. After 50 cycles, 91.4% and 69% of discharge capacity could be retained respectively, indicating that ultrasonic irradiation condition during spin coating was more suitable for preparing spinel LiMn2O4 thin films with better electrode performance for lithium ion micro-batteries.