Optimization Of Prepa Ration Process Of LiFePO₄ Cathode

Lithium-ion batteries are widely applied in more and more fields in the 21st century.Lithium iron phosphate battery has been favored as battery cathode for its high safety and cycle stability.However,the low density,poor electronic conductivities and slow lithium ion diffusivity limit its application.At present,the research on LiFePO4 battery is mainly focuses on the preparation and the modification of LiFePO4 material with different nanostructures.Few reports are on the prep aration process of electrode,which contributes a great deal to the industrial production of lithium ion battery and their performance.In this paper,the influence of tap density,slurry preparation method and the coating parameters of LiFePO4 on the performance of lithium batteries were investigated.The results are as follows:Three kinds of LiFePO4 with different particle size distributions were mixed by ball milling.The results show that the tap density of mixed powders with different particle sizes is higher than their individual counterparts.The tap density of mixed material with a mass ratio of 3:7 reaches up to 1.37 g/cm3 and its specific volumetric capacity up to 152.6 mAh/cm3 with 1 C rate when the particle size of 1.5?m and 4?m were selected.At the same time,it has improvements of 13.8%and 8.5%over individual samples of 1.5?m and 4 ?m.Moreover,the mass ratio of the mixing was optimized to be were studied 1:3.The optimized sample displayed the tap density of 1.4 g/cm3 and specific volumetric capacity 130 mAh/cm3.Two factors in the slurry preparation process were studied.It was found that the appropriate mixing order and solid content can effectively improve the electrochemical performance of the battery.The initial discharge capacity of battery is 132 mAh/g at 1 C rate and the initial coulombic efficiency reaches up to 95.1%when semi-dry mixing was used.the specific capacity of the battery reaches up to 126.3 mAh/g when the solid content was 35%.The influences of the film thickness and the roller pressure on the electrochemical performance were studied.The optimized film thickness of the electrode was determined to be 120 ?m with the specific capacity of 145.8 mAh/g at 1 C rate.The apparent lithium ion diffusion coefficient reaches 1.76�10-12 cm2/s.When the roller pressure was 6?8 MPa,the higher electrochemical capacity could be obtained.The initial discharge capacity is 130 mAh/g at 1 C rate when film thickness is 90?m.