Investigation of Microstructural and Electrochemical Changes in the Cathode Electrode of ۱۸۶۵۰ Commercial Batteries

Today, due to the great need for electricity in daily consumption, the need for high energy density batteries as a high efficiency means of energy storage is felt more than ever. Among the various components of lithium ion batteries, the cathode electrode is the limiter of the battery capacity in more cases, and this proves the great importance of conducting extensive research in the field of cathode materials of lithium ion batteries.Li Ni۱-x-y Cox Mny O۲ and Li Ni۱-x-y Cox Aly O۲ provide the highest energy density among the materials that have been used as the cathode electrode of commercial lithium-ion batteries. Despite the high energy density, these two materials do not have good structural stability and cycles, and it is necessary to study the changes that occur in the charge/discharge cycles of these materials in order to find the root and propose a solution. Therefore, in this study, a number of commercial ۱۸۶۵۰ batteries with a capacity of more than ۳۰۰۰ mAh were prepared and subjected to electrochemical impedance spectroscopy before and after charge/discharge cycles. The batteries were also opened before and after charge/discharge cycles and their cathode electrodes were collected and microstructurally studied. According to the results the cycling tests, it was observed that after ۵۰۰ charge/discharge cycles, the capacity of these batteries decreases significantly. By comparing the results of electrochemical impedance spectroscopy before and after the mentioned ۵۰۰ cycles, it was found that the resistance of ion and electron transfer in these batteries has increased significantly. To investigate the reason for this increase in resistance, scanning electron microscope images were taken from the cathode of the opened batteries. In these images, the process of cracking of the cathode particles due to charge/discharge cycles is clearly visible.