Charging Induced Electrode Layer Fracturing of 18650 Lithium-Ion Batteries

Lithium-ion batteries are considered fully charged when they are charged to the battery manufacturer's specified cut-off voltage using the specified cut-off C-rate. To assess the consequences of going beyond this charged state, four types of 18650 lithium-ion battery cells were charged from 100% state of charge until the cells' internal safety mechanisms were triggered, or thermal runaway occurred. The electrical, thermal, and mechanical behavior of the cells was monitored and compared using X-ray computed tomography, visual inspection, cross-sectional analysis, and scanning electron microscopy/energy dispersive X-ray spectroscopy analysis. In some samples, a unique degradation mechanism - electrode layer fracturing is identified, which is shown and discussed.