In situ monitoring and sensing of gas generation during internal short circuits in Li-ion batteries using Raman spectroscopy and fiber bundle signal collection

This study employs a needle penetration test on Lithium-ion batteries (LIBs) to investigate gas generation during internal short circuits, using a Multi-Reflection Cavity-Enhanced Raman Spectroscopy system, which integrates a fiber bundle consisting of 48 fibers (105 μm inner diameter) arranged in a linear configuration to enhance gas detection sensitivity. To comprehensively analyze the correlation between gas evolution and battery performance, infrared thermography and voltage measurements were conducted in parallel, providing insights into temperature and voltage variations during internal short circuits. Experimental results revealed a sudden voltage drop and a rapid temperature rise that subsequently stabilized, suggesting the short circuit lasted only a few seconds. The sensor detected the continuous generation of CH₄, C₂H₄, and H₂, with gas evolution persisting over time. These findings demonstrate the potential of advanced Raman-based sensors for real-time safety monitoring and diagnostics in lithium-ion batteries.