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This study proposes a probabilistic quantification technique that applies an expert inference method to warn of the risk of a fire developing into a thermal runaway when a lithium-ion battery fire occurs. Existing methods have the shortcomings of low prediction accuracy and delayed responses because they determine a fire only by detecting the temperature rise and smoke in a lithium-ion battery to initiate extinguishing activities. To overcome such shortcomings, this study proposes a method to probabilistically calculate the risk of thermal runaway in advance by detecting the amount of off-gases generated in the venting stage before thermal runaway begins. This method has the advantage of quantifying the probability of a fire in advance by applying an expert inference method based on a combination of off-gas amounts, while maintaining high reliability even when the sensor fails. To verify the validity of the risk probability design, problems with the temperature and off-gas increase/decrease data were derived under four SOC conditions in actual lithium-ion batteries. Through the foregoing, it was confirmed that the risk probability can be accurately presented even in situations where the detection sensor malfunctions by applying an expert inference method to calculate the risk probability complexly. Additionally, it was confirmed that the proposed method is a method that can lead to quicker responses to thermal runaway fires. [ABSTRACT FROM AUTHOR]

This paper provides insights into the four key behaviors and mechanisms of the aging to failure of batteries in micro-overcharge cycles at different temperatures, as well as the changes in thermal stability. The test results from a scanning electron microscope (SEM) and an energy-dispersive spectrometer (EDS) indicate that battery failure is primarily associated with the rupture of cathode materials, the fracturing and pulverization of electrode materials on the anode current collector, and the formation of lithium dendrites. Additionally, battery safety is influenced by environmental temperatures and the battery's state of health (SOH), with failed batteries exhibiting the poorest stability and the highest mass loss rates. Under isothermal conditions, micro-overcharge leads to battery failure without thermal runaway. Thus, temperature stands out as the most influential factor in battery safety. These insights hold significant theoretical and practical value for the development of more precise and secure battery management systems. [ABSTRACT FROM AUTHOR]

Battery thermal management system (BTMS) is essential for maintaining batteries in electric vehicles at a uniform temperature. The aim of the present work is to propose most suitable cooling for BTMS. The most significant factors in battery thermal management are operating temperature, reliability, safety, and battery life cycle. The experimental setup is designed and fabricated for that purpose. In experimental work, thermal performance parameter, i.e. variation of maximum cell temperature in battery pack with natural and forced convection, is studied and compared at three different charging rates low (1 C), moderate (2 C), and high (3 C). The numerical model for natural and forced convection battery thermal management is developed using Ansys 22.1. For the present work, the cylindrical cell Li-ion battery pack is considered and simulates the cooling effect due to natural convection and forced convection. For the various flow rate of air, the cooling effect is investigated and efficient flow velocity is obtained by a numerical model for two climatic conditions. Further, the cooling performance of the battery pack with and without fin for optimum velocity is simulated. Based on experimentation, it is seen that forced convection gives better results as compared to natural convection. The temperature drops from 60.46 °C to 43.03 °C (28.82%) at 1 C, 65.81 °C to 48.01 °C at 2 C (27.06%), and 67.05 °C to 50.4 °C (24.77%) at 3 C heat generation rate when forced convection is used for cooling purpose. In the numerical studies, charging of Li-ion cell at 1.5 C rate is studied. Using forced convection maximum temperature is reduced by 27.26% when the inlet velocity is kept 2 m s−1 when ambient is 27 °C. Using fin, battery cell maximum temperature is reduced by 39.23%, as compared with natural convection. Using fin at 27 °C atmospheric temperature, battery cell maximum temperature is reduced by 39.23%, as compared with natural convection, and when the atmospheric temperature reaches to 41 °C, the maximum temperature is reduced to 51.26 °C (12.75%). [ABSTRACT FROM AUTHOR]

• The dynamics of the thermal runaway front in large-scale Li-ion batteries are deduced theoretically. • The velocity of the front yields a 1/2 power relationship between the thermal conductivity and reaction rate. • Freezing thermal runaway front is possible in theory and validated by experiments. • Heat dissipation enlarged by heat transfer time delay is critical for the freeze. Large-scale lithium-ion batteries are favored in electric vehicles and energy storage stations; for instance, BYD blade batteries and CATL Kirin batteries are popular. A tiny defect will trigger thermal runaway from a local point towards the other parts of the battery, and the boundary between the failure region and the intact region is called the "thermal runaway front," of which the dynamics are still unclear. Herein, this paper deduces two formulas for the moving speed (v TR) of the thermal runaway front by applying the principles of energy conservation (Formula I) and flame front (Formula II); formulas for the thermal runaway front velocity (v TR) are derived. The velocity v TR conforms to the 1/2 power of the heat conductivity and reaction rate in both formulas. Data regression for the experimental data demonstrated that the overall estimation error was 10 % using Formula I and 25 % using Formula II. As the zero velocity value indicates the termination of thermal runaway propagation, further derivations reveal that forced cooling can suppress thermal runaway as long as the heat dissipation power is higher than the heat generation power. Sufficient heat dissipation time is achieved by the time delay of heat transfer in the long run of thermal runaway propagation. The formula for the dynamics of thermal runaway propagation universally applies to various large-scale lithium-ion batteries, assisting the safe design of high-energy batteries and providing new insights into suppressing battery thermal runaway by the heat transfer delay effect. [ABSTRACT FROM AUTHOR]

Thermal runaway introduces a significant challenge in the widespread application of lithium-ion batteries, necessitating advanced early-warning technologies to ensure safety, particularly during charging. Only monitoring the temperature and voltage limit the performance of diagnostic algorithms. The expansion behavior of batteries, which is linked to their operating status, offers a vital indicator of safety. In this study, the evolution of multidimensional signals during overcharging experiments at different current rates is comprehensively investigated. The result shows that the abnormal expansion force can be detected at temperatures as low as 35.4 °C, which achieves an early warning signal 11 min earlier than the onset of battery thermal runaway. The effect of charging rate on battery safety is comprehensively analyzed, showing that the time interval between the warning signal of the expansion force and temperature increases steadily from 151 s to 682 s as the charging rate decreases. However, the charging rate hardly affects the stage of charge boundary of venting, which is around ±118 %. These insights are crucial for understanding early warning mechanisms in overcharged batteries, offering valuable guidance for enhancing the safety of electric vehicles and energy storage systems. • Force signal offers early warning 682 s before battery thermal runaway. • Abnormal expansion force can be detected at a minimum temperature of 35.4 °C. • Effect of charging rate on battery safety is comprehensively analyzed. • Charging rate hardly affects stage of charge boundary of venting. • Force signal can be utilized as an overcharge warning indicator at high rates. [ABSTRACT FROM AUTHOR]

Thermal management is a crucial parameter in lithium-ion batteries to maintain the temperature of the batteries within safer working limits. If the optimum working temperature is not maintained, it triggers thermal runaway conditions and causes them to propagate heat from one cell to another within pack level configurations. In battery thermal packaging, several government norms such as GB 38031/32 has suggested that for optimum thermal packaging, there should be a significant delay in the thermal runaway trigger point which can prevent a vehicle from going into catastrophic failure since the driver gets a preventive alert for the high-rise temperature of a cell at an early stage. Delaying thermal runaway occurrence can be effectively achieved by using an integrated layer of PCM. However, present conventional PCMs have a lower thermal conductivity which poses instability in delaying thermal runaway trigger point. This can be improved by using graphene-enhanced composite phase change material, in which the percentage of added extended graphene (EG) determines the improvement in thermophysical property, concisely thermal conductivity of CPCM. The current study examines thermal runaway in widely used cathode materials, LiNiMnCoO 2 (NMC) and LiFePO 4 (LFP), within a typical large format prismatic cell profile with a commonly used heater-assisted test. The thermal runaway trigger point is monitored for the cases of cell without CPCM and with CPCM to find potential improvement in the delay point. Thermal runaway modeling and statistical safety regime response show that submerging batteries in a CPCM can delay thermal runaway onset by 20 min. When scaling up to a 7S1P battery module level, it is concluded that the smallest addition of EG in CPCM can delay the thermal runaway trigger point and reduce peak temperatures in the battery module over 66 to 113.2 min, which strategically complies with battery safety norms. • The safety regime response of Li-Ion cell is investigated for different cathodic chemistry. • A comprehensive validated four equation battery thermal abuse model is developed. • Thermal behavior of battery with varying composite phase change material thermal conductivity is investigated. • A novel statistical approach is shown to find the most effective TMS parameter. [ABSTRACT FROM AUTHOR]

The characteristics of thermal runaway in batteries exhibit significant differences depending on their states of charge (SOCs), posing considerable challenges in accurate and timely warning for thermal runaway accidents. This paper conducts an experimental investigation into the external expansion force, voltage, and temperature behaviours of batteries under different SOCs under thermal abuse scenarios. The expansion force signal was found first to exhibit abnormal characteristics (with an indicator value of 5 N/s), offering an earlier warning signal >642 s prior to thermal runaway, when the battery back temperature is merely approximately 318.15 K. To analyse the main causes of abnormal expansion, ultrasonic nondestructive tests were performed and suggested that a higher SOC intensify the side reactions and cause gas generation inside batteries. Notably, compared to normal-charged batteries (0% ≤ SOC ≤ 100%), over-charged batteries (SOC > 100%) are more sensitive to expansion force than normal-charged batteries. Furthermore, compared with voltage and temperature signals, the early warning time of the expansion force rises with the increase in the SOC of an overcharged battery, in contrast to normal-charged batteries. Finally, a novel hazard classification safety warning strategy for battery failure is effectively proposed. These novel findings hold substantial practical implications for creating more accurate early warning systems for battery thermal runaway, enhancing the safe and reliable operation of battery systems. • Effect of SOC on multidimensional signal evolution is comprehensively revealed. • Expansion force can serve as an early warning signal of battery failure. • Expansion force evolution of batteries with different states of charge is revealed. • Nondestructive tests are conducted to analyse the main causes of abnormal expansion. • A novel warning strategy with hazard classification for battery failure is proposed. [ABSTRACT FROM AUTHOR]

In this work, a composite cooling system including composite phase change material(CPCM) and liquid cooling is designed for battery pack, and the effects of coolant flow rate, battery spacing, thermal conductivity of CPCM, channel number of cooling plate on the safety performance of battery pack under thermal runaway propagation are studied. The results reveal that: (1)Coolant flow rate increase mainly delays the thermal runaway propagation on both sides of cooling plate. When the coolant flow rate is 0.029 m/s, the thermal runaway propagation time through the cooling plate is 32.9s, which is extended by 1.84 times than that at 0.009 m/s (2)Battery spacing increase delays thermal runaway propagation and changes the propagation path. (3)Thermal conductivity reduction of CPCM can significantly delay thermal runaway propagation, because the heat is concentrated in the periphery of the battery and is hard to transfer though CPCM and cooling plate. (4)Compared with other influence factors, channel number of cooling plate has less influence on the overall thermal runaway propagation time. When the channel number is between 5 and 1, the total thermal runaway time changes within 25.5s–27s. The conclusions in this work are helpful to design a safer thermal management system for lithium-ion battery packs. • A novel composite cooling strategy is designed for cylindrical battery pack. • Effects of different factors on the thermal safety of the battery pack are studied. • Thermal runaway propagation path and time of the battery pack are analyzed and obtained. [ABSTRACT FROM AUTHOR]

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 LiNi 1/3 Co 1/3 Mn 1/3 O 2 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. • TR characteristics at thermal-electrical abusive conditions are revealed. • The effects of charging rates on heat and gas generation are investigated. • The promoted impacts of irreversible heat on TR is clarified. • The nonlinear relationship between heat release and gas generation is elucidated. [ABSTRACT FROM AUTHOR]

We have combined simulation experiments and instance analysis to thoroughly study the influence of thermal radiation of cell phone system on its lithium-ion batteries (LIBs). Researches show that high power central processor or memory will make a thermal field (above 60 °C), which has a detrimental effect on LIBs through thermal radiation and heat transfer. The coil structure and electrode materials of LIBs would be destroyed, when LIBs close to an enhanced thermal field without effective heat dissipation. External thermal radiation usually results in the hard swelling of pouch LIBs, which can be reasonably attributed to the wrinkle of pole piece, coil structure deformation, delamination of the active materials. Serious deterioration of LIBs will occur after a long-term operation under the external high-temperature, leading to the decomposition of electrolyte, generation of Li dendrites, and separator closure. It causes of the heat accumulation of LIBs and then thermal runaway. Through this study may raise the attention to the thermal design and reliability of LIBs, improving the safety of the product. Illustration: This article systematically considers the cell phone thermal system and the battery itself to discover the failure reason of LIBs. External thermal radiation from high power components results in the hard swelling of pouch LIBs after a long-term operation. [Display omitted] • This work systematically considers the cell phone thermal system and the battery itself to discover the failure reason of LIBs. • External thermal radiation from high power components of cell phone have been measured, which results in the hard swelling of pouch LIBs. • Simulation experiments and instance analysis thoroughly illustrates deterioration of LIBs will occur under the external high-temperature. • Guidance towards best design practices for the thermal dissipation and LIBs applicaiton is proposed. [ABSTRACT FROM AUTHOR]

The current work aims to understand and model thermal runaway (TR) events in lithium-ion (LIB) 18650 cells within the context of aircraft battery applications. The primary goal is to comprehend the phenomenon and discuss strategies for mitigating its consequences during aircraft operation. TR is modeled using Arrhenius kinetic equations and is implemented in both lumped parameters (Matlab SimulinkTM), and 3D CFD simulations (Ansys FluentTM) using User Defined Functions. To validate the thermochemical model, cells are initially simulated in an oven test, where a cell is exposed to a temperature-controlled atmosphere, triggering exothermic reactions. With a strong correlation between lumped parameters and 3D models, the latter is simulated under battery module installation conditions. An internal short-circuit is then implemented within the cell to observe how thermal runaway is triggered by an internal heat source. The trigger cell is subsequently placed in a battery module assembly to assess the dominant heat transfer modes and the likelihood of TR induction from one cell to its neighbors. This work's main objective and innovation are to compare different materials in which cells are immersed while observing the main heat transfer parameters for each material. Three conditions are tested: ceramic paper fiber and G7 as solid separators, and no separator material, where air fills the gaps between cells. The analysis of heat transfer modes reveals radiation's dominance in the case of air interstice, suggesting the possibility of using a special coating to reduce the cell surface emissivity as an alternative to decrease the likelihood of TR propagation. Thus, two values of surface emissivity were tested in the case of air. Considering a cell triggered by an internal short-circuit, a thermal runaway temperature spike is not observed in any of the four cases. However, the air interstice case with regular emissivity is the most critical one, with the closest cell reaching peak temperatures as high as 136 °C in 490 s. The ceramic paper fiber is considered the best separator material, as it postpones the temperature increase in the closest cell while also being lighter than G7. The results and discussions concerning heat propagation presented herein can serve as guidelines for developing strategies to mitigate thermal runaway in battery modules. [ABSTRACT FROM AUTHOR]

• "Two birds with one stone" strategy is raised to obtain the balanced properties. • 3D micro-nanostructure of CoS 2 /doped carbon aerogel is rationally designed. • Such structure shows superior cycling and rate property than many metal sulfides. • Utilizing this micro-nanostructure dramatically promotes the thermal safety of cell. • The favorable Li+/Na+ storage actions and related reaction kinetics are discerned. Up to now, lithium/sodium ion batteries (LIBs/SIBs) are deemed as the ideal candidates for traditional fossil energy. However, the absence of suitable Li+/Na+ reservoirs and the hazard of thermal runway have plagued their usages. Using Li 4 Ti 5 O 12 or TiO 2 anode promotes the thermal safety of LIBs/SIBs but reduce their electrochemical property. How to achieve the balanced performances has been an urgency. Here, we have delicately designed a 3D micro-nanostructure of CoS 2 /doped carbon aerogel (CoS 2 @NCA), via "killing two birds with one stone" strategy. When used as LIBs anode, CoS 2 @NCA delivers a high capacity of 639.5 mAh g−1 after operating at 1 A g−1 for 250 cycles, giving a low-capacity attenuation rate of 0.048 % per cycle. Meanwhile, the reduced maximum temperature and maximum heating rate of thermal runaway (TR) are observed for cell. When used as SIBs anode, CoS 2 @NCA delivers a high capacity of 620.9 mAh g−1 at 100th cycle as working at 1 A g−1. Likewise, the activation energy for TR is promoted. Overall, the utilization of CoS 2 @NCA enables the superior and safe energy storage. The cell with CoS 2 @NCA anode shows better electrochemical property and superior thermal safety. [Display omitted] [ABSTRACT FROM AUTHOR]

• 1. This paper provides an overview of lithium-ion battery thermal runaway. • 2. This paper categorizes and summarizes control methods for thermal runaway. • 3. This paper summarizes the varying outcomes of thermal runaway. • 4. This paper forecasts strategies for mitigating the thermal runaway propagation. With the escalation of environmental issues, the large-scale application of lithium-ion batteries (LIBs) has become a prominent solution to replace the use of fossil fuels. However, safety issues related to LIBs, particularly thermal runaway (TR) and its propagation, have yet to find robust solutions. This has impeded the application of LIBs in electric vehicle (EVs) to some extent. In this review paper, the factors triggering TR in LIBs, the consequences of TR and the current available methods for mitigating TR are summarized. More specifically in the first part, the major causes of LIB thermal runaway are examined from three primary triggering factors, including mechanical abuse, electrical abuse and thermal abuse. The causation of TR is summarized comprehensively combined with internal short circuit (ISC) and some minor contributing factors. Furthermore, a specific phenomenon called 'spontaneous ISC' has been detailed and analyzed. Secondly, the consequence of TR is analyzed from the perspective of exhaust, jet fire, heat release. Lastly, an analysis and categorization of existing thermal runaway propagation (TRP) control methods for LIBs are conducted from the perspectives of active control and passive control. This paper also provides a comparative summary of control and improvement techniques of battery TR. [ABSTRACT FROM AUTHOR]

The growing demands on high-performance energy systems for emerging technologies drive the advancement of high-density batteries. However, the issue of thermal runaway (TR), particularly in high-density battery, remains a major challenge worldwide. One of the primary hazards associated with TR is the emission of combustible ejections. Therefore, elucidating the TR ejection parameters holds significant meaning. In this study, we propose a novel method to determine the ejection parameters. Based on the principles of momentum conservation, the proposed method is applicable to high-density battery types. For the 52 A h ternary battery, our results indicate the following: 1) the ejection velocity reaches a peak of 210 m/s, a maximum mass loss rate of 0.041 kg/s and a maximum total pressure of 112.325 kPa; 2) the temperature of the particles is 200 °C higher than that of the gas. Furthermore, we have derived empirical formulas that encompass the ejection dynamics, thereby facilitating the modeling of TR degassing and ventilation within a battery pack. This approach overcomes the challenges associated with measuring the ejection parameters in high-density battery TR, such as the extreme temperature, flammability, and multiphase composition. Consequently, this method exhibits great potential to bolster the fire safety and structural design of battery packs. • The velocity, mass loss rate etc. Of NCM battery multiphase ejection are obtained. • Temperature of thermal runaway gas and particle are distinguished. • Empirical formulas of TR ejection are derived for future CFD modeling. [ABSTRACT FROM AUTHOR]

This paper employs density functional theory to investigate transition metal-doped WSSe(Ti–WSSe, Mn–WSSe, Mo–WSSe) gas-sensitive devices, exploring their adsorption and sensing properties towards three characteristic gases of thermal runaway in Li-ion battery, namely H 2 , CO, and CO 2. Results indicate that Ti, Mn, and Mo dopants preferentially anchor to the S-surface of the pristine WSSe monolayer, exhibiting binding energies of −3.145, −1.282, and −3.376 eV, respectively. All three monolayers present significantly improved sensing characteristics, showing chemisorption towards CO. Band structure and density of states analyses reveals the potential of Ti–WSSe monolayer as a resistive CO detection sensor. Furthermore, recovery time calculations are performed to assess the reuse capabilities of the three gas-sensitive devices. Regarding high sensitivity and tunable detection, Mn–WSSe monolayer emerges as potential candidate for H 2 detection, while Mo–WSSe monolayer is more suitable for CO 2 detection. This work lays the foundation for the potential gas-sensitive applications of WSSe monolayer in the field of thermal runaway scenarios, which is expected to advance research in gas sensing domains. In this work, the DFT is employed to systematically investigate the adsorption and sensing mechanisms of major thermal runaway gases (CO, CO 2 , and H 2) on Ti–WSSe, Mn–WSSe, and Mo–WSSe monolayer. The primary objective is to explore their potential application as sensitive components in LIB. The main conclusions are as follows: • Ti, Mn, and Mo dopants tend to anchor on the S-surface of the pristine WSSe monolayer, with E f of −3.145, −1.282, and −3.376 eV, respectively. • The adsorption energy of TM-WSSe is nearly 7 times that of pristine WSSe, indicating that TM atom doped on the WSSe monolayer significantly enhances the adsorption performance. • TM-doped WSSe monolayer exhibits significantly improved electrical conductivity and gas sensitivity. Therefore, for the detection of thermal runaway fault gases, Ti–WSSe, Mn–WSSe, and Mo–WSSe gas sensors possess strong theoretical research support in applications. • Recovery characteristic analysis reveals the promising potential of Ti–WSSe monolayer as a resistive CO sensor. In terms of high sensitivity and tunable detection, the Mn–WSSe monolayer emerges as a potential candidate for H 2 detection, while the Mo–WSSe monolayer is better suited for CO 2 detection. [ABSTRACT FROM AUTHOR]

Electric vehicles that utilize lithium-ion batteries (LIBs) as a power source provides viable solution to realize the decarbonization of transportation sector. However, their future application is severely hindered by the temperature sensitivity of LIBs. Thus, a well-designed battery thermal management system (BTMS) is recommended to ensure proper temperature environment for improving LIBs' performance. Here, the aim is to provide a clear and detailed understanding on the two-phase heat transfer technologies for BTMS, especially given the urgent demands for fast-charging and harsh operating conditions. The fundamentals of BTMS, including battery working principles, adverse temperature effects, and modelling approaches are first analyzed. What's more, typical battery cooling methods are briefly discussed and categorized in terms of working mediums. However, with the ever-growing trend towards high energy density and fast charging, these methods are insufficient to effectively regulate the temperature of batteries. To address the rigorous demands, two-phase heat transfer strategies, with heat transfer rate several orders of magnitude higher than typical BTMS, have gained great interests. The up-to-date progresses of such system based on refrigerant flow boiling, immersion boiling, spray cooling, and other strategies, are comprehensively reviewed. Besides, discussions on battery thermal management studies are presented from the perspectives of heat transfer mechanism, pros and cons, and future insights. This state-of-the-art review is expected to deliver guidance and draw more attention to the development of advanced thermal management approaches in EV applications. • A review of emerging two-phase battery thermal management strategies is presented. • Two-phase heat transfer-based BTMSs effectively control battery temperature. • The mechanism, limitations and future insights of emerging BTMS are discussed. [ABSTRACT FROM AUTHOR]

Thermal runaway (TR), a critical safety issue that hinders the widespread application of lithium-ion batteries (LIBs), is easily triggered when LIB is exposed to thermal abuse conditions. Identifying the characteristics and trigger mechanism of TR induced by external heating is crucial for enhancing the safety of LIBs. Herein, based on overheating experiments, a detailed analysis is implemented from temperature, heat generation, and TR propagation velocity within the battery to reveal the TR triggering mechanisms at the cell level. Compared with the front heating mode, the bottom heating mode always results in severe TR accompanied by higher peak temperature, temperature increment, heat generation, and TR propagation velocity within the battery. The internal heat generation before TR makes a non-negligible contribution to the battery temperature increase and the trigger of TR, accounting for more than 35 %. The external heating quantity, heating power, temperature, and temperature gradient are the critical factors affecting the TR trigger when LIBs are exposed to thermal abuse conditions. TR is triggered by the decrease of the temperature gradient within the battery under the limited external heating quantity. Moreover, a theoretical model describing the battery TR trigger is proposed, revealing different TR triggering mechanisms under varied thermal abuse conditions. [ABSTRACT FROM AUTHOR]

• Form-stable and flame-retardant CPCM is produced for battery thermal safety management. • The optimum mass ratio of the CPCM is obtained by comprehensive analysis. • CPCM has a positive effect on battery heat absorption and increasing the time between the thermal runaway spread. Phase change materials (PCMs), characterized by zero energy consumption and high energy storage density capability, have a wide range of applications. However, the development of organic PCM is restricted by their low thermal conductivity, easy leakage and high combustibility. In this study, we produced a composite phase change materials (CPCM) with both high thermal conductivity and flame-retardant effect for application in battery thermal safety management. We demonstrated that addition of a porous network structure of EG as a shaping support to increase PA's thermal conductivity, and incorporation of environmentally safe and non-toxic silica-based flame retardant (SiO 2 sol) improved the flame retardant properties. The optimum mass ratio of the CPCM was obtained by comprehensive analysis of the shape and thermal stability, energy storage performance and thermal conductivity. It was also verified by cone calorimetry that the CPCM outperformed pure PA in several aspects: heat release, smoke release rate and emission of toxic gases. The cooling and thermal runaway experiment of the battery module showed that the addition of CPCM had a positive effect on absorption of battery heat and extending the time between the thermal runaway spread of battery modules (21 s increasing to 396 s), providing valuable time for the safe evacuation of people in the event of a runaway fire. [ABSTRACT FROM AUTHOR]

NCM811 (Li(Ni 0.8 Co 0.1 Mn 0.1)O 2) lithium-ion battery (LIB) at 100 °C is in a critical state of internal chemical reaction and external thermal runaway (TR), and the coupled stimulations of nail penetration under such thermal load will accelerate TR, and coupled stimulations have hindered the development of LIBS. In this paper, an experimental platform for coupled stimulations of heat-penetration on LIBs was built, and revealed the thermal runaway acceleration mechanism, explored the influence of the SOC on the TR behavior of the cells when penetration under the critical thermal load condition. The results show that critical thermal load condition reduces the critical SOC for TR to occur, and 25% SOC NCM811 cell still produces a jet flame, elevating the fire risk of thermal runaway when compared to room temperature conditions. And the maximum temperature of 25% SOC cell was elevated by 76.1 °C, which was 18% higher than that of penetration at room temperature. Meanwhile, at critical 100 °C, as the SOC increases from 0% to 100%, the average temperature rise rate of the cell sharply increases from 1.992 °C/s to 93.033 °C/s, and the maximum temperature of cell increases from 125.9 °C to 652.9 °C, and the mass loss increases from 3.332 g to 31.180 g. The 0%SOC cell undergoes slighter TR, generating a lot of smoke but no flame. However, with the SOC increase of 25%–100%, the flame temperature increases from 437.8 °C to 918.5 °C, the flame area rise ratio reaching 281.77%. Combined with the microscopic performance characterization experiments, the dynamics behavior of particle eruption is mainly dominated by the anode graphite. The results of this study provide scientific guidance for the safety prevention of LIBs. • Thermal runaway acceleration mechanism induced by penetration at 100 °C are proposed. • The heat-penetration coupling stimulation increases risk of thermal runaway. • When SOC≥25%, thermal runaway induced by penetration at 100 °C will produce jet flame. • The particle eruption dynamics is mainly dominated by the anode graphite. [ABSTRACT FROM AUTHOR]

Increasing charging rate is an upgrading direction of electrochemical energy storage, which might induce more heat accumulation, posing a higher risk to cause the battery thermal runaway (TR). Driven by this, an experimental investigation was carried out to study the characteristics of TR and gas venting behaviors in commercial lithium iron phosphate (LFP) batteries that were induced by overcharging under different rates. As the charging rate increases, the growth rate of lithium dendrites accelerates, resulting in the earlier formation of large-scale short circuits and a rapid transition to the next stage of the TR chain reaction. However, the temperature rise and the total heat does not increase in proportion to the charge rates. The electrolyte also accelerates its decomposition, and the reaction between the electrolyte and lithium is the main reason of overcharge heat accumulation. It is worth noting that the charging rate for overcharging is positively correlated with the TR violence of batteries and the explosion risk of the ejected gas. The main gases emitted are H 2 , CO, and CO 2 and various alkanes. Specifically, the content of H 2 gas increases significantly with the increase of charging rate. And the H 2 contents for 2C, 1.5C and 1C correspond to 61%, 53% and 50%, respectively. The rapid growth of lithium dendrites results in a significant increase in H 2 generation and earlier capture. This is accompanied by a higher impact pressure and a lower explosion limit (LEL) of the combustible gas mixture, indicating a severer explosion risk. In short, by comparing the TR characteristics and gas products of LFP batteries with different charging rates, which is of great significance for the fire extinguishing design and emergency response of energy storage systems. [ABSTRACT FROM AUTHOR]