Overdischarge Analytics of Li-Ion Cells Using a Reference Electrode Configuration

Although lithium-ion batteries are driving the prosperity of the rechargeable world, safety catastrophes under extreme conditions are still one of the main challenges. Overdischarge is a common electrical abuse that may arise in a Li-ion battery pack when an extreme cell voltage imbalance occurs. The electrode cross-talk under an overdischarge scenario is still an open question. To fill this gap, Li-ion pouch cells with reference electrode configurations are fabricated to decouple anode and cathode characteristics from full cell performances. Electrode potentials vs. Li/Li+ at discharge, relaxation and charge phases are measured and interpreted. State of health deterioration is tracked through temperature, volume and impedance monitoring. Surface microscopic characterizations are implemented to explore morphologies and chemical states of electrodeposition. Electrolyte transformation and gas generation are determined using the gas chromatography-mass spectroscopy technique. This study reveals an implicit cathode-centric degradation mechanism in overdischarge extremes, providing a new perspective on overdischarge mitigation strategies.