Mechanism of Storage Process for Graphite/LiCoO2 and Graphite/Li(Ni1/3Co1/3Mn1/3)O2 Batteries

Two kinds of 2H-graphite/LiCoO2 and 2H-graphite/Li(Ni1/3Co1/3Mn1/3)O2 batteries were studied in parallel. The test contents include: macroscopic observation before and after storage, performance changes before and after storage, including the change of capacity with storage time, the relationship between capacity decay rate and storage time and charge degree (SOC%), charge–discharge curve before and after storage, internal resistance, relationship between capacity and cycle period after storage, overcharge performance, and thermal stability, etc. The fine structure and microstructure of the positive and negative active materials and diaphragms of the two kinds of batteries before and after storage and the micro-morphology of the electrode surface were tested and analyzed. The I101/I104 diffraction intensity ratio of Li(Ni1/3Co1/3Mn1/3)O2 was also measured to solve the Li/Ni atomic mixed occupation parameters. On the basis of these experimental results, the temperature effect and charge effect of battery performance degradation are summarized, and the corresponding relationship between the storage performance of the two kinds of batteries and the fine structure of electrode active materials is summarized by table comparison. Finally, the attenuation mechanism of battery storage performance is discussed.