Publications
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2026
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RSER
Renewable and Sustainable Energy Reviews, 241, 117225, 2026.Abstract
Lithium-ion batteries (LIBs) are increasingly used in electric vehicles and large-scale energy storage systems. However, their long-term operational safety remains a critical bottleneck, especially as batteries experience progressive aging during extended service. This review examines how primary aging pathways, including high temperature, low temperature, high C-rate cycling, and overcharge/over-discharge conditions, affect aging reactions and consequently influence thermal runaway (TR) behavior. Specifically, these aging pathways trigger different side reactions and produce characteristic gas signals, such as hydrogen, carbon oxides, and hydrocarbons. These gas signals can reflect the internal aging state of batteries and help explain changes in TR characteristics and overall thermal safety behavior. As the relationship among aging pathways and TR characteristics is strongly path-dependent, gas evolution is reviewed here as a bridge linking aging mechanisms with thermal safety assessment. Moreover, the review further examines how gas signals can be integrated with machine learning methods to support TR diagnosis and early warning. This combined perspective helps improve the safety design and operation of LIBs.
2025
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JES
Journal of Energy Storage, 125, 116855, 2025.Abstract
With the increased demand of lithium-ion batteries in aviation and high-altitude applications, understanding battery safety at low-pressure conditions becomes paramount. This study aims to comprehensively investigate the effects of ambient pressure and charging rate on the thermal runaway behaviors and corresponding gas generation dynamics of commercial 18650-type LiNi₁/₃Co₁/₃Mn₁/₃O₂ (NCM) cells triggered by electrical abuse, employing an accelerating rate calorimeter. The results indicate that low ambient pressure leads to an earlier opening of the safety valve and a shortened delay time of violent thermal runaway, which limits electrolyte ejection outside the cell. Due to the greater participation of electrolytes during thermal runaway, the maximum temperature and gas generation amount both increases at low ambient pressure conditions. Besides, it is found that an elevated charging rate intensifies the thermal runaway process, increasing the potential for thermal runaway hazards, as indicated by the increased generation of flammable gases. Furthermore, the Arrhenius law is employed to evaluate the gas generation dynamics of LIBs during thermal runaway by comparing the activation energy and pre-exponential factors. Therefore, the rate constants for various operation pressures and charging rates are proposed. Significantly, the rate constants show a notable increase at low-pressure conditions, highlighting the higher TR risk in such conditions.
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CRPS
Cell Reports Physical Science, 6(5), 102563, 2025.Abstract
The widespread application of lithium-ion batteries in electric vehicles is hindered by safety concerns, notably thermal runaway. Understanding gas generation during thermal runaway is crucial for battery safety design, early fault detection, and fire hazard assessment, but existing kinetic models remain inadequate. We investigate gas generation behavior of 18650-type LiNi₁/₃Co₁/₃Mn₁/₃O₂ cells across varied states of charge, constructing a training dataset to develop a chemical reaction neural network model that autonomously explores unknown reaction pathways and corresponding chemical kinetic parameters. By incorporating an additional non-linear neural network to predict the mean molar weight of generated gases, the model trains a chemical kinetic mechanism comprising 7 species and 16 reactions. The resulting mechanism accurately predicts key parameters, including gas generation rates and amounts, during thermal runaway. This methodology addresses the current limitations in thermal runaway gas prediction, providing a robust framework for enhancing battery safety.
2024
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JPS
Journal of Power Sources, 600, 234237, 2024.Abstract
Lithium-ion batteries are susceptible to thermal runaway incidents at high-temperature abuse and overcharging conditions. This study employs an experimental approach that combines an accelerating rate calorimetry with a battery testing system to investigate thermal runaway behaviors in 18,650-type LiNi₁/₃Co₁/₃Mn₁/₃O₂ cells at high temperatures, particularly during constant current constant voltage (CCCV) charging at rates of 0.2C, 0.5C, 1C, and 2C. The results reveal that cells coupled with charging behavior exhibit a greater potential for thermal runaway at high temperatures, and increased charging rates lead to increased irreversible heat and promoted side reactions, which ensure advanced thermal runaway events and enhanced heat and gas generation capacity in the cell. Furthermore, owing to the combined influences of stage of charge and the promoting effect of charging current on side reactions, the total heat and gas production and the charging rate exhibit a nonlinear relationship. Eventually, after the completion of charging, the relationship between gas generation rate and heat generation rate can be characterized by two linear growth stages. The initial stage displays consistent gas generation rates despite variations in charging rates, and the subsequent stage demonstrates different gas generation rates with increased charging rates, suggesting alterations in side reaction pathways.
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JES
Journal of Energy Storage, 80, 110201, 2024.Abstract
This study investigates the gas generation characteristics and explosion limits of the gas generated by 18650-type LiNi₁/₃Co₁/₃Mn₁/₃O₂ (NCM) cells during thermal runaway (TR) at different states of charge (SOCs). An accelerating rate calorimeter is employed to initialize TR, together with an airtight jar for gas measurement. Based on the detected gas composition for NCM cells, the corresponding explosion limits are computed and further compared with those of LiFePO₄ (LFP) and LiNi₀.₈₀Co₀.₁₅Al₀.₀₅O₂ (NCA) cells. The results reveal that the gas generation rates are slightly higher for NCM cells with lower SOCs prior to the violent TR processes compared to those for high-SOC cells, primarily due to the elevated reaction temperature. Moreover, during violent TR, multiple-peak features are observed for the gas generation rate curves, especially at high-SOC conditions. On the other hand, typical Z-shaped explosion limit curves are observed for all generated mixtures. As the cathode material varies from NCM to LFP and NCA, the explosion limits shift from high-temperature regions to low-temperature regions. In contrast to common beliefs that the generation gas at high SOCs is more explosive, non-monotonic responses of the explosion limit curves are found with respect to cell SOC. The significance of minor components of the generated gas, including ethylene and ethane, in reducing the explosivity of the mixture, is highlighted through sensitivity analyses.
2023
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IJHE
International Journal of Hydrogen Energy, 48(97), 38484-38495, 2023.Abstract
Intake temperature and pressure fluctuations prior to main ignition are one of the reasons affecting the efficiency of internal combustion engines. In this study, the effects of temperature and pressure fluctuations with varied amplitudes and frequencies on the exergy loss of hydrogen auto-ignition processes were numerically investigated in an adiabatic constant-volume system at engine-relevant conditions. The results revealed that the increase in temperature fluctuation amplitudes primarily decreases the exergy loss due to chemical reactions, and the exergy loss due to incomplete combustion remains unchanged. Specifically, the total exergy loss is reduced by approximately 1.5% with a temperature fluctuation amplitude of 100 K at a frequency of 2 ms⁻¹. Furthermore, with the same temperature fluctuation amplitude, increasing the frequency of temperature fluctuation from 2 ms⁻¹ to 7 ms⁻¹ leads to a 0.7% increase in the total exergy loss. On the other hand, the effects of pressure fluctuation on the exergy loss of hydrogen auto-ignition processes are negligible compared with those of temperature fluctuation. Through chemical kinetic analysis, it is found that temperature fluctuation promotes the consumption pathway of O₂ to generate OH, rather than the collision with H to produce HO₂. Consequently, the reduced mole fraction of HO₂ inhibits the related HO₂-consumption reactions, including HO₂+H=OH + OH and HO₂+HO₂=H₂O₂+O₂. Moreover, with temperature fluctuation, due to the lower fraction of third-body collision molecules, H₂O, the reactivity of the third-body reaction, H + O₂+M=HO₂+M, is decreased. The reduced reaction rates of these reactions lead to decreased total exergy loss, indicating that the fuel energy conversion process may benefit from temperature fluctuation.
2022
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Energy
Energy, 241, 122941, 2022.Abstract
Syngas, containing mostly CO and H₂, has variant explosion properties for the specific contents. For a further understanding, a comparative study on the turbulent explosion characteristics of syngas between CO-enriched (the mole ratio of CO was 70%) and H₂-enriched (the mole ratio of H₂ was 70%) were conducted at different equivalence ratios (φ, from 0.4 to 3.0) and turbulent intensities (u′_rms, from 0 to 1.309 m/s). The peak value of maximum explosion pressure (p_max) was attained in the stoichiometric explosion of H₂-enriched syngas but in fuel-rich explosion of the CO-enriched, the growth extents of p_max seemed more sensitive to u′_rms for H₂-enriched syngas compared to CO-enriched syngas. The lowest values of explosion duration (t_c) was attained in fuel-rich explosions for both CO-enriched and H₂-enriched syngas but different corresponding φ to the lowest t_c, the phenomena were analyzed from the aspects of ignition delay time, laminar burning velocity, intrinsic instabilities, and flame/turbulence interaction. Finally, the pressure rising was comparatively observed, the maximum pressure rise rate ((dp/dt)_max) expressed more similar variation regulations to t_c rather than p_max, which meant flame propagation speed plays a more important role on the evolution of pressure rising.