Thermal Runaway Characteristics and Gas Composition Analysis of Lithium-Ion Batteries with Different LFP and NCM Cathode Materials under Inert Atmosphere

Abstract

During thermal runaway (TR), lithium-ion batteries (LIBs) produce a large amount of gas, which can cause unimaginable disasters in electric vehicles and electrochemical energy storage systems when the batteries fail and subsequently combust or explode. Therefore, to systematically analyze the post-thermal runaway characteristics of commonly used LIBs with LiFePO4 (LFP) and LiNixCoyMnzO2 (NCM) cathode materials and to maximize the in situ gas generation during battery thermal runaway, we designed experiments using an adiabatic explosion chamber (AEC) under an inert atmosphere to test LIBs. Additionally, we conducted in situ analysis of the gas components produced during thermal runaway. Our research findings indicate that after thermal runaway, NCM batteries produce more gas than LFP batteries. Based on battery gas production, the degree of harm caused by TR can be ranked as follows: NCM9 0.5 0.5 > NCM811 > NCM622 > NCM523 > LFP. The primary gas components during thermal runaway for both NCM and LFP batteries include H2,CO,CO2,C2H4, and CH4. The gas produced by LFP batteries contains a high proportion of H2. The high concentration of H2 results in a lower flammability limit (LFL) for the gas generated by LFP batteries during TR compared to the mixed gas produced by NCM batteries. Therefore, in terms of battery TR gas composition, the order of hazard level is LFP > NCM811 > NCM622 > NCM523 > NCM9 0.5 0.5 0.5. Although experimental results show that LFP batteries have superior thermal stability and lower gas production during large-scale battery thermal runaway events, considering gas generation composition and thermal runaway products, the thermal runaway risk of LFP batteries may be higher than that of NCM batteries. Although LFP batteries are considered very safe, our research results have once again drawn researchers’ attention to LFP batteries. These gases can also serve as detection signals for battery thermal runaway warnings, providing a cautionary note for the future development of electrochemical energy storage and the renewable energy sector.

Comparative study on the thermal runaway characteristics of Li(NixCoyMnz)O2 batteries

“…The total CO + CO 2 content in the battery is 62.49 ± 4.09 %. The findings reported in previous studies [ 5 , 23 ], where CO + CO 2 levels fluctuate by approximately 60 %, are consistent with the results of this study. The volume percentage of H 2 ranges from 16.29 % to 23.23 %.…”

“…The battery fixture and the AEC used for thermal runaway (TR) testing of batteries are shown in Fig. 1 and Figure A1 [ 23 , 30 , 31 ]. This experimental chamber was part of the lithium-ion battery cell/module safety testing apparatus developed by Professor Minggao Ouyang's research group at Tsinghua University.…”

“…The GC-MS-QP2020 NX is a gas chromatography-mass spectrometry (GC-MS) instrument that combines the separation capabilities of gas chromatography with the mass analysis capabilities of a quadrupole mass spectrometer. The instrument's scanning rate can reach 20,000 U/sec, with a sensitivity of Signal-to-Noise ratio (S/N) ≥ 185 [ 23 ].…”

“…Until now, three distinct types of experimental environments have been identified for investigating thermal runaway [ 23 ]:…”

Early Detection of Li-Ion Battery Thermal Runaway Using Commercial Diagnostic Technologies

“…The hydrocarbons detected by these two sensors are generated from the evaporation and decomposition of organic electrolyte solvents and carbon-containing components that initiate at lower temperatures (<160 °C). [41][42][43][44][45] This was confirmed with the MS measurements shown in Fig. 6, where multiple hydrocarbons were detected during thermal decomposition of the electrolyte and electrodes.…”