Long-Term Study on the Impact of Depth of Discharge, C-Rate, Voltage, and Temperature on the Lifetime of Single-Crystal NMC811/Artificial Graphite Pouch Cells

This work examined the impact of depth discharge (DOD), C-rate, upper cut-off voltage (UCV), and temperature on lifetime single-crystal NMC811/Artificial Graphite (AG) cells. Cells were cycled at C/50, C/10, C/5, or C/3, 25, 50, 75, 100% DOD room (RT, 20 ± 2 °C) 40.0 0.1 °C. The UCVs 4.06 4.20 V. After 12000 hr cycling, experiments such as electrochemical impedance spectroscopy (EIS), Li-ion differential thermal analysis (DTA), ultrasonic mapping, X-ray fluorescence (XRF), capacity analysis, synchrotron computed tomography (CT) scans, cross-section scanning electron microscopy (SEM) carried out. We showed that loss increased slightly with cells V UCV have superior retention control compared to SEM, CT show microcracking positive electrode mass did not occur regardless DOD, UCV. DTA mapping no C-rate dependency for electrolyte changes “unwetting.” Finally, a simple square-root time model was used SEI growth in