Extending the calendar life of LiNi_0.8Co_0.1Mn_0.1O₂-based lithium-ion batteries via low-temperature storage

In this study, we investigated the calendar aging pattern based on NCM811 cathode cells and proposed that LT storage is more conducive to prolonging the service life. First, through electrochemical tests, it is found that the degree of self-discharge increases with increasing storage time, and storage SOC, which applies to both full and half cells. Cells stored at LT shows less decay than at RT. Second, in situ EIS tests reveal a greater interfacial impedance at LT, which decreases instantaneously after returning to RT. Accordingly, we hypothesize that the smaller self-discharge rate at the LT is caused by the larger Li transfer impedance and smaller parasitic reaction rate. Finally, by performing long-cycling teats on the cells after storage, we find that LT storage does not disrupt the cycling stability. X-ray diffraction (XRD) analysis revealed no change in the crystal structure of the NCM811 cathode. Moreover, no fragmentation of the active material particles is observed by scanning electron microscopy (SEM). The cryogenic storage should be considered for long-distance transportation cells or energy storage cells to extend the calendar life.

March 2024