Comparison of monitoring gas evolution in commercial Li-ion batteries: Differential electrochemical mass spectrometry versus operando internal non-destructive gas sensors

Lithium-ion batteries (LIBs) face capacity degradation and safety risks from internal gas evolution. This study compares differential electrochemical mass spectrometry (DEMS) and in-situ non-dispersive infrared (NDIR) gas sensors for monitoring gas in graphite/NMC811 batteries. DEMS enables real-time gas detection but relies on carrier gases and causes 49.7 % capacity loss in small cells. NDIR sensors in 800 mAh pouch cells offer continuous, non-destructive monitoring with <1 % capacity loss, detecting gas accumulation and consumption. NDIR proves robust for operando gas monitoring in high-capacity LIBs, aiding failure mechanism analysis and safety improvement.