Real-time analysis of gases produced by induced failure of lithium-ion batteries

This work reports real-time gas analysis (RTGA) of failing lithium-ion batteries (LIBs) in order to identify how gas emissions proceed during LIB failure. The results reported give insights into the failure behaviour of cells with a range of formats, capacities, cathode chemistries and failure scenarios. Mass spectrometry (MS) was used to analyse relative compositions of H 2 , CO, CO 2 , CH 4 , C 2 H 4 , C 2 H 6 , C 3 H 6 and C 3 H 8 . Fourier transform infrared spectroscopy (FTIR) was used to measure for carbonates commonly used in LIB electrolyte mixtures and HF. 3–5 Ah cylindrical cells with cathode chemistries of nickel manganese cobalt aluminium oxide (NCA), nickel manganese cobalt oxide (NMC) and lithium iron phosphate (LFP) at differing states of charge (SoC) were failed by heating under a nitrogen atmosphere. Nickel based pouch and prismatic and LFP prismatic cells have been failed by overcharging in an air atmosphere. In general, we identified a trend that by MS the major components in failure gases of nickel cells are H 2 , CO and CO 2 . Nickel based cells tend to fail with ignition of failure gases, failure is more aggressive at higher SoC in cylindrical cell tests. For LFP cells the major component by MS is H 2 , unless there is self-ignition in which case CO and CO 2 are much more pronounced. Complex mixtures of ethyl methyl, diethyl, dimethyl and ethylene carbonate have been identified. Nickel based emissions tend to have less carbonates present than unignited LFP emissions. HF was only detected by FTIR in unignited LFP prismatic cells failed by overcharge. • Failing cylindrical cells produce most gas during thermal runaway. • NMC and NCA cells tend to fail more violently than LFP cells. • LFP cells produce large amounts of hydrogen and electrolyte vapour which can ignite. • FTIR has shown HF is present in battery failure gas.