Thermal Runaway Of Lithium-ion Batteries Research Articles

Research Progress on the Safety of LIBs Separators

Over the years, the electrification of transport has forced improvements in energy storage batteries. Lithium-ion batteries (LIBs) are widely used in aerospace, smart devices, electronic communications, and transport because of their high capacity, good cyclability, and environmental friendliness. However, battery safety is a massive issue in people's daily lives. LIBs occasionally suffer from spontaneous combustion and explosion. This is mainly caused by short circuits within the battery. The diaphragm, as the material separating the positive and negative electrodes, prevents the positive and negative electrodes from coming into direct contact, thus avoiding short circuits. The performance of the diaphragm determines the safety of LIBs. Therefore, this paper first introduces the causes of the thermal runaway of lithium-ion batteries and its relationship with diaphragms. Then, this paper presents the essential characteristics and types of high-safety diaphragms. Finally, this paper also summarises the physical and chemical modification methods of diaphragm materials in LIBs. This will help improve the safety of lithium-ion batteries, increase the electrification of transportation, and eliminate concerns about using LIBs.

Performance of sandwich type fire-resistant flexible composite phase change material PEE@EBF for battery thermal management and runaway protection

To mitigate the risks of overheating and thermal runaway in lithium-ion batteries, this study proposes a novel sandwich-type fire-resistant flexible composite phase change material (CPCM), referred to as PEE@EBF. The core material (PEE) was created by melt-blending paraffin wax (PW), expanded graphite (EG), and ethylene–vinyl acetate copolymer (EVA). The outer layer, a fire-resistant coating (EBF), was applied to the surface of PEE and consists of epoxy resin (EP), boron nitride (BN), and the composite flame retardant (CFR). Test results demonstrated that PEE@EBF maintained structural integrity, exhibiting no significant deformation or leakage after being heated at 80 °C for 5 h. PEE@EBF also displayed a high latent heat of 166.6 J/g, thermal conductivity of 0.8 W/(m∙K), and excellent electrical insulation properties. Furthermore, it achieved a UL94 V-0 flame retardant rating, with notable reductions in peak heat release rate (PHRR) and peak smoke production rate (PSPR) by 67.8 % and 81.8 %, respectively. During long-term cycling at 4C, the peak temperature (PT) and maximum temperature difference (MTD) of batteries in the module incorporating PEE@EBF were reduced by 11.8 °C and 4 °C, respectively, compared to natural convection cooling. In addition, the heat generated during the battery thermal runaway was efficiently absorbed and transferred by PEE@EBF, delaying the irreversible thermal runaway process by 633 s. This indicated that the sandwich-type PEE@EBF was suitable for thermal management and fire protection in lithium-ion batteries or energy storage devices.

Relevance-Based Reconstruction Using an Empirical Mode Decomposition Informer for Lithium-Ion Battery Surface-Temperature Prediction

Accurate monitoring of lithium-ion battery temperature is essential to ensure these batteries’ efficient and safe operation. This paper proposes a relevance-based reconstruction-oriented EMD-Informer machine learning model, which combines empirical mode decomposition (EMD) and the Informer framework to estimate the surface temperature of 18,650 lithium-ion batteries during charging and discharging processes under complex operating conditions. Initially, based on 9000 data points from the U.S. NASA Prognostics Center of Excellence’s random battery-usage dataset, where each data point includes three features: temperature, voltage, and current, EMD is used to decompose the temperature data into intrinsic mode functions (IMFs). Subsequently, the IMFs are reconstructed into low-, medium-, and high-correlation components based on their correlation with the original data. These components, along with voltage and current data, are fed into sub-models. Finally, the model captures the long-term dependencies among temperature, voltage, and current. The experimental results show that, in single-step prediction, the mean squared error, mean absolute error, and maximum absolute error of the model’s predictions are 0.00095, 0.02114, and 0.32164 °C; these metrics indicate the accurate prediction of the surface temperature of lithium-ion batteries. In multi-step predictions, when the prediction horizon is set to 12 steps, the model achieves a hit rate of 93.57% where the maximum absolute error is within 0.5 °C; under these conditions, the model combines high predictive accuracy with a broad predictive range, which is conducive to the effective prevention of thermal runaway in lithium-ion batteries.

Study on cooling efficiency and mechanism of lithium-ion battery thermal runaway inhibition by additives enhanced water mist based on boiling heat transfer theory

In recent years, fire and explosion accidents caused by thermal runaway (TR) of lithium-ion batteries (LIB) have occurred frequently, which has become one of the main obstacles restricting its development. Therefore, it is urgent to develop fire extinguishing agents with high cooling efficiency to inhibit the growth of TR. The water mist is an effective choice, but it shows poor performance with the rise in cell temperature under TR. In this study, two additives, KCl and the nonionic fluorocarbon surfactant FC-4430, were added to the water mist to improve the cooling efficiency. In addition, the inhibition effect exerted by the modified water mist during the whole process of lithium-ion battery TR was experimentally investigated. Furthermore, the influence of water mist with additives on the Leidenfrost effect in the high temperature range was deduced, and the reinforcement cooling mechanism was analyzed by heat transfer theory. The results show that KCl and FC-4430 can increase the initial cooling rate in the high temperature range by 48.6%–120%. The reinforcement mechanism is attributed to changing the medium's physical parameters with additives. On the one hand, the Leidenfrost point of the droplets on the cell surface is increased, which in turn extends the temperature range of the nucleate boiling stage, and on the other hand, the heat flux density and heat transfer of the water mist in the film boiling state are increased.

MOS-based Gas Sensors for Early Alert of Thermal Runaway in Lithium-ion Batteries

MOS-based Gas Sensors for Early Alert of Thermal Runaway in Lithium-ion Batteries

Visualization of stepwise electrode decomposition in a nail penetrated commercial lithium-ion cell using low-temperature synchrotron X-ray computed tomography

The transition towards zero carbon emissions in power generation hinges on the integration of efficient electrical energy storage systems, with lithium-ion batteries (LIBs) positioned as a pivotal technology. While generally safe, deviations in their operational guidelines due to manufacturing defects or misuse can lead to critical safety concerns, notably thermal runaway (TR) events. Internal short circuits (ISCs) are primary initiators of TR within LIBs. For abuse testing, ISCs are often triggered by nail penetration. This study explores the morphological changes and mechanisms underlying ISC-induced TR in LIBs using operando synchrotron X-ray computed tomography (SXCT) at subzero temperatures. A novel cryogenic setup was developed to control a stepwise temperature increase in the damaged sample while monitoring electrochemical characteristics and simultaneously enabling acquisition of high-resolution SXCT images. The findings reveal that conducting nail penetration at minus 80 °C prevents immediate TR, enabling detailed analysis of subsequent structural and electrochemical behavior during controlled thawing. Thus, the initiation of TR processes at localized ISC sites has been observed, evidenced by voltage fluctuations and morphological changes, such as cathode material cracking and decomposition. These results underscore the importance of temperature control in mitigating TR risks and provide critical insights into the internal dynamics of LIBs under abusive conditions. The developed cryogenic SXCT methodology offers a powerful tool for non-destructive, high-resolution investigation of battery failure mechanisms, contributing to the enhancement of LIB safety.

Investigation and optimization of battery thermal management system based on composite phase change material and variable wall liquid cooling plate

To mitigate the risk of thermal runaway in lithium-ion batteries, an efficient battery thermal management system (BTMS) assumes paramount importance. A BTMS based on composite phase change material (CPCM) and variable wall liquid cooling plate (LCP) is proposed in this research. The numerical model of the BTMS was established and experimentally validated. The influence of the wall of LCP on battery temperature was investigated, and the efficiency of phase change material (EOP) index was proposed to assess the efficacy of CPCM. The genetic algorithm was employed to optimize the structure of the CPCM, and the influence of flow rate on the maximum temperature of the battery pack was studied. The results demonstrate a reduction of 1.81 °C in the maximum temperature of the battery pack upon implementation of the variable wall LCP. The optimized EOP achieves a value of 0.07 °C/g, resulting in a temperature difference of 0.56 °C. Furthermore, maintaining the maximum temperature of the battery pack below 40 °C only requires a water flow rate greater than 0.89 g/s. These results can serve as a valuable reference for the development of battery thermal management systems utilizing CPCM and liquid-cooling.

Research progress of aerogel used in lithium-ion power batteries

In recent years, with the rapid development of clean energy vehicles (i.e., electric vehicles and hybrid electric vehicles) and electrochemical energy storage stations, safety accidents have significantly increased. However, the abuse conditions such as overheating, overcharging, mechanical abuse, short circuits, etc., can result in thermal runaway of lithium-ion batteries (LIBs). Severe thermal runaway can lead to battery fire and even explosion, thereby threatening the safety of personnel. The application of a few aerogels to the thermal insulation layer between the cells of the lithium-ion battery modules can strengthen the safety of batteries. Among many aerogels, oxide aerogels show excellent insulation and high-temperature resistance. Therefore, aerogels, especially oxide aerogels, have aroused widespread research interest. This paper introduces the mechanism of thermal runaway of LIBs and systematically reviews several important oxide aerogels and the derived composites, especially those based on SiO2, Al2O3, and ZrO2 aerogels. The mechanical strength and high-temperature resistance of those aerogels are discussed. The application of aerogel in LIBs is also investigated in detail, and the all-around effect is caused by the introduction of aerogel materials. In addition, the thermal protection safety strategy of aerogel thermal insulation layers is proposed. It is supposed that this review could enable readers to deepen their understanding of this field.

Nanoporous Aramid Nanofiber Separators with High Modulus and Thermal Stability for Safe Lithium-Ion Batteries.

Developing high-safety separators is a promising strategy to prevent thermal runaway in lithium-ion batteries (LIBs), which stems from the low melting temperatures and inadequate modulus of commercial polyolefin separators. However, achieving high modulus and thermal stability, along with uniform nanopores in these separators, poses significant challenges. Herein, the study presents ultrathin nanoporous aramid nanofiber (ANF) separators with high modulus and excellent thermal stability, enhancing the safety of LIBs. These separators are produced using a microfluidic-based continuous printing strategy, where the flow thickness can be meticulously controlled at the micrometer scale. This method allows for the continuous fabrication of nanoporous ANF separators with thicknesses ranging from 1.6 ± 0.1µm to 2.7 ± 0.1µm. Thanks to the double-side solvent diffusion, the separators exhibit controllably uniform pore sizes with a narrow distribution, spanning from 40 ± 5nm to 105 ± 9nm, and a high modulus of 3.3 ± 0.5GPa. These nanoporous ANF separators effectively inhibit lithium dendrite formation, resulting in a high-capacity retention rate for the LIBs (80% after 240 cycles). Most notably, their robust structural and mechanical stability at elevated temperatures significantly enhances LIB safety under transient thermal abuse conditions, thus addressing critical safety concerns associated with LIBs.

Review of Flame Behavior and Its Suppression during Thermal Runaway in Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are extensively utilized in electric vehicles (EVs), energy storage systems, and related fields due to their superior performance and high energy density. However, battery-related incidents, particularly fires, are increasingly common. This paper aims to first summarize the flame behavior of LIBs and then thoroughly examine the factors influencing this behavior. Based on these factors, methods for suppressing LIB flames are identified. The factors affecting flame behavior are categorized into two groups: internal and external. The paper then reviews the flame behavior within battery modules, particularly in confined spaces, from both experimental and simulation perspectives. Furthermore, methods for suppressing battery flames are classified into active and passive techniques, allowing for a more comprehensive analysis of their effectiveness. The paper concludes with a summary and outlook, offering new insights for future research and contributing to the development of safer and more efficient battery systems.

Experimental study on thermal runaway and flame eruption characteristics of NCM523 lithium-ion battery induced by the coupling stimulations of overcharge-penetration

The thermal runaway of lithium-ion batteries under extreme coupled abuse conditions has seriously hindered the sustainable development of lithium-ion new energy vehicles. To reveal the complex thermal runaway behavior mechanism of overcharged lithium-ion batteries induced and by nail penetration, In this paper, a coupled stimulated thermal runaway experimental platform was built, and experimental studies of overcharge-penetration coupled stimulated thermal runaway and flame eruption dynamics were carried out on 18650-type NCM523 lithium-ion batteries from macro and minutiae viewpoints, in which the states of charge (SOC) of the overcharged batteries were 100 %, 105 %, 110 %, 115 %, 120 %, 125 %, 130 %, 135 %, 140 %, 145 % and 150 %. The results showed that the maximum battery surface temperature during overcharging increased from 32.7°C at 100 % SOC to 66.1°C at 150 % SOC, an improvement of 102 %. The thermal runaway battery temperature increased from 529.0°C at 100 % SOC to 657.1°C at 150 % SOC, an increase of 24.2 %. The thermal runaway maximum flame temperature increases from 485.5°C at 100 % SOC to 983.9°C at 150 % SOC, an improvement of 102.6 %. The flame area of medium overcharged> high-level overcharged> low-level overcharged batteries and the flame area of thermal runaway increased by 22213.95 cm2 compared to the maximum of 100 % SOC, and the flame propagation speed of the batteries after thermal runaway showed that the greater the SOC, the stronger the intensity of the flame. The higher the degree of overcharging, the higher the danger of thermal runaway on the side of the battery and near the positive electrode, and the danger of thermal runaway in overcharged lithium-ion batteries increases with the increase of SOC.

Series arc-induced internal short circuit leading to thermal runaway in lithium-ion battery

With the widespread implementation of battery energy storage systems (BESSs), significant attention has been focused on issues involving electrical safety. The series arc hazard caused by loose connectors between batteries has become a serious problem. However, research findings for the evolution process of the series arc and the related hazard principle are still unclear. Therefore, in this study we focus on the series arc at the negative terminal of a 20 Ah prismatic lithium-ion battery, establish an experimental platform for the arc, and conduct research on the hazards process. Our results indicate that the arc can induce the thermal failure of the battery when the power supply voltage is 300 V and the circuit current is 15 A. Through a battery voltage analysis, computed tomography scans, and jellyroll disassembly, we uncover the evolution process and hazard laws of series arcs and clarify the failure pathways of arc-induced battery faults. The hotspots formed by arc melt the casing and cause electrolyte leakage. In addition, the heat transfer from the battery terminal to the jellyroll induces separator melting and internal short circuits in batteries. These cause an internal short circuit between the anode and the cathode, as well as combustion of the leaked electrolyte, which give rise to distinct thermal runaway behavior under different states of charge. By comparing runaway behavior with failures triggered by external heating, we clarify that the series arc is a novel risk factor that induces failure. This study addresses the gap in research related to arc effects on battery safety. This is crucial to the development of safe battery systems that do not present arc hazards.

Characterization of pristine and aged NMC lithium-ion battery thermal runaway using ARC experiments coupled with optical techniques

Battery thermal runaway (TR) challenges battery applications due to safety considerations, potentially endangering consumers. Understanding the process is crucial to defining first alarm strategies that indicate the risk of TR and designing systems to mitigate this problem. For this reason, the present paper aims to characterise key variables of the venting and thermal runaway processes. Experimental tests were conducted in an accelerating rate calorimeter (ARC) using the heat wait seek (HWS) protocol, which tracks the battery temperature after detecting an exothermic reaction during the seek period. The maximum temperature rise rate and peak temperature that the calorimeter can achieve are 15 °C/min and 300 °C. Two optical accesses in the ARC were modified to use optical techniques such as Schlieren double pass and infrared. The results cover 3 different cell conditions: Pristine cells at state of charge (SOC) 100 %, pristine cells at SOC 50 %, and aged cells at SOC 100 %. For statical purposes, each cell condition was repeated 5 times. The aged battery was cycled to boost solid electrolyte interface growth. The images obtained were post-processed, with a specific methodology for each optical technique, and according to the parameters intended to be obtained. The main result shows that for higher SOC, the exothermic reaction is detected earlier than for SOC 50 %, which was only detected in an advanced TR stage (higher temperature rise rate). Therefore, the battery system capability to detect plays a crucial role in safety. Safety actuation time is reduced by ∼ 40 % for SOC 50 %. However, the energy to manage during this situation is lower (∼42 %), depending on the mass inside the battery, revealing the importance of a good venting cap design. Infrared images have shown higher particle temperatures for higher SOC, about 150 °C higher than the SOC 50 %. The particle velocity, in this case, achieved 30 m/s.

Simulation of lithium-ion battery thermal runaway considering active material volume fraction effect

The multi-physics solver BatteryFOAM couples with the side reaction model for thermal runaway (TR) simulations, including the electrolyte decomposition (E) and solid electrolyte interface layer decomposition (SEI), and the reaction of the electrolyte with graphite intercalated lithium (NE-E) and the reaction of positive electrode active material with the electrolyte (PE-E). This solver is used to study the lithium-ion battery (LIB) TR at different conditions. The published experimental results are used to validate the effectiveness and practicability of BatteryFOAM in predicting the temperature under constat high temperature. We also discuss the reactant concentration, reaction rate, and heat release rate during the LIB TR. The influences of the external factor of the equal equivalent heat transfer (h) on the battery TR is considered, and the sequence in which the battery reaches the critical temperature rising rate (RTR, 60 K/min) and the separator failure temperature (Tsep) is predicted. The results demonstrate that overall the exothermic reaction peaks arise sequentially from SEI decomposition, PE-E reaction, NE-E reaction, and electrolyte decomposition, and NE-E reaction has three exothermic peaks induced by other three side reactions. PE-E reaction contributes more heat for fuse energy to trigger TR, but the NE-E reaction and electrolyte decomposition mainly accounts for the runaway energy. In addition, increasing SEI and electrolyte decomposition intensity is found no effect on the TR temperature. Besides, the rapid reaching to RTR is caused by the high heat release rate of positive electrode active material with electrolyte. Results further show that reducing the fNE−E within 5.0 % will significantly reduce TR risk.

Seawater submersion for cylindrical lithium-ion batteries thermal runaway prevention

Lithium-ion batteries (LIBs) are currently used in various electric vehicles, including electric boats. To assess the risk of fire due to thermal runaway of the LIB during the operation of ferries, seawater can be used as a cooling fluid for the LIB to prevent thermal runaway as it is abundant. However, the seawater could corrode the electrodes of the battery, which would lead to toxic wastewater. Prevention of thermal runaway of lithium-ion batteries by submersion in seawater needs to be investigated to clarify the corrosion that could lead to toxic wastewater. In this study, fully charged, pristine 18650 NMC Li-ion cells were submerged in synthetic seawater (SSW) to investigate the corrosion effect compared to deionized (DI) water. The results showed that SSW induced rapid voltage discharge, leading to corrosion on the electrodes and toxic effluents, while DI water maintained the stability of the cells and did not cause any corrosion effect. In addition, the prevention of thermal runaway was investigated by exposing fully charged LIB to extreme overheating conditions. The liquid submersion system was activated by rapid voltage drop monitoring to evaluate its effectiveness in preventing thermal runaway (TR). The investigation of TR prevention by SSW submersion showed that the TR process can be effectively prevented. In addition, no corrosion effect was observed during submersion in SSW as the battery voltage was not applied. This study shows that seawater can be used to prevent TR in LIB and does not cause environmental problems comparable to water.

Experimental study on the thermal runaway and flame dynamics of NCM811 lithium-ion batteries with critical thermal load under variable penetration condition

With the diversification of lithium-ion battery (LIB) application scenarios, the thermal runaway (TR) mechanism of LIBs under complex nail penetration conditions has become increasingly complex, becoming one of the key bottlenecks restricting the safe prevention and control of TR of LIBs. In this paper, an experimental platform for coupled stimulations of heat-penetration on LIBs was built, aiming to study the effects of penetration depth (4.5 mm, 9 mm, 13.5 mm, 18 mm), penetration diameter (3.3 mm, 5.3 mm, 7.3 mm), and nail material (steel, ceramic) on TR under 100 °C. The results showed that with the increase of penetration depth, the maximum temperature of cell will decrease. From 4.5 to 18 mm, the maximum temperature of cell with 100% SOC decreased from 867.6 °C to 711.1 °C, a decrease of 18.04%. When penetration depth is 4.5 mm, and the diameter of steel nail is 7.3 mm, the temperature of cell is the highest and the thermal hazard is the highest. The maximum temperature of TR jet flame, the propagation speed of TR flame, and the area of TR jet flame all increase with the increase of penetration depth. When penetration depth is 18 mm, and the diameter of ceramic nail 7.3 mm, the flame temperatures of the 75% SOC and 100% SOC cells were 952.4 °C and 913.4 °C, respectively, which were higher than those of 932.0 °C and 906.5 °C when induced by a steel nail. The ceramic nail increased the fire risk of TR in LIBs. The mass loss increases with the increase of penetration depth and penetration diameter, and the mass loss under ceramic nail stimulation is greater than that under steel nail stimulation. More than 60% of particles with a diameter less than 10 μm are found to contain toxic substances (such as LiF) in the ejected particles, which can enter the human and cause damage the human body. The research results have important guiding significance for the intrinsic safety design of LIBs.

Experimental study of the strategy of C6F12O and water mist intermittent spray to suppress lithium-ion batteries thermal runaway propagation

Extinguished lithium-ion battery fires can experience temperature rebound and re-ignition, necessitating proper fire extinguishing and cooling measures for battery safety. This study introduces a novel approach that integrates C6F12O and water mist as a strategy to prevent the spread of thermal runaway in lithium-ion batteries, evaluating the fire-suppression and cooling ability under various intermittent spray modes. The findings demonstrate that the strategy has a stronger suppression effect compared to continuous water spray and could prevent the spread of thermal runaway. C6F12O can extinguish fires in just 1 s. During the cooling phase, the cooling capacity generally decreases with increasing cycle period and duty cycle. Among different cycle periods, C6F12O combined with intermittent water mist spray (DC = 0.5, Pt = 2 s) exhibited the most effective cooling, significantly reducing peak temperature and providing the highest heat suppression. In terms of duty cycles, C6F12O combined with intermittent water mist spray (DC = 0.1, Pt = 20 s) achieved the longest cooling duration, lowering the temperature of Cell #3 to below 50 °C. The combination of C6F12O and intermittent water mist spray rapidly extinguishes flames, maximizes the cooling impact of water mist, and ultimately hinders the propagation of thermal runaway.

An Initial Report of Thermal Runaway Resulting in Full-Thickness Foot Burns From Lithium-Ion Battery-Powered Insole.

Lithium-ion batteries are used in many commercial products such as electronics, cell phones, and e-cigarettes. The use of these batteries has become widespread over recent years due to their chargeability and long-lasting performance. Though a rare occurrence, lithium-ion batteries can fail due to myriad battery defects, which can cause fires and burns. One particular concern is that of thermal runaway, a critical failure marked by a sudden exothermic reaction that occurs as a result of damage to the lithium battery. Thermal runaway can produce heat in excess of 1800 °F, causing severe burns to individuals in close proximity. A 39-year-old man presented to an emergency department (ED) with full-thickness burns to his right foot after an episode of lithium-ion battery thermal runaway in his footwarmer. The patient's boot suddenly and unexpectedly caught fire for several seconds prior to being successfully removed. The patient subsequently underwent several weeks of debridements, auto- and homografting, and wound care before eventually making a full recovery. This case highlights the rare, but serious, risk posed by lithium-ion batteries as a result of thermal runaway. This phenomenon can cause devastating full-thickness burns in a matter of seconds. As lithium-ion-powered appliances grow in popularity, stringent safety measures should be implemented to prevent catastrophic injuries. Furthermore, healthcare providers should be made aware of injuries caused by thermal runaway to appropriately treat patients.

Advancements in Li-Ion Battery Safety: A Multiphysics and Deep Learning Approach for Thermal Runaway Prediction

The increasing adoption of Lithium-ion batteries (LIBs) in various applications necessitates an enhanced focus on safety, particularly concerning the thermal runaway (TR) phenomenon. This study introduces a novel framework combining multiphysics modeling and deep learning (DL) to predict TR in cylindrical Li-ion batteries. The primary objective is to prevent catastrophic battery failures by identifying critical thermal conditions leading to TR.Our methodology integrates state-of-the-art convolutional neural networks (CNNs) and the "You Only Look Once" (YOLO) object detection model to classify and detect the evolution of TR stages in LIBs. The CNNs, trained on simulated thermal images generated through comprehensive multiphysics modeling, classify TR into three distinct stages: safe operation, critical condition, and actual TR occurrence. The YOLO model further pinpoints the location of TR heat sources, enhancing the predictive accuracy.The multiphysics model employed captures the coupled thermal and electrochemical behavior of LIBs, focusing on the solid electrolyte interface (SEI) formation/decomposition on the anode as the primary degradation mechanism. The simulated thermal imagery, reflecting real-time battery conditions, serves as a dataset for training our DL models. This combination of physics-based and data-driven approaches allows for a detailed understanding of TR dynamics.In our study, we also explored the efficiency of other neural network architectures, notably ResNet, EfficientNet, and MobileNet for their potential in TR prediction. ResNet, known for its deep residual learning framework, demonstrated proficiency in handling the complex, layered features of thermal images. EfficientNet, optimized for efficiency and accuracy, showed promise in its scalable architecture and balanced depth, width, and resolution, making it a viable alternative for real-time TR detection. The MobileNet known for its lightweight architecture and efficiency on mobile devices, was evaluated for its capability to process thermal images in a resource-constrained environment. It demonstrated a remarkable balance between computational efficiency and predictive accuracy, making it a viable option for real-time TR monitoring in portable LIB applications.While MobileNet, ResNet, and EfficientNet each showed potential in their respective capacities, our primary CNN-YOLO framework emerged as the most effective for TR prediction in this study. Its proficiency in extracting spatial features and detecting anomalies in real-time was critical for early TR identification in LIBs.Results demonstrate high accuracy in predicting TR stages and heat source locations, emphasizing the ability of the integrated approach. The study highlights the importance of thermal management and real-time monitoring in LIBs, offering insights into the thermal behavior under various load conditions. The predictive framework not only advances the fundamental understanding of TR in LIBs but also provides practical implications for enhancing battery safety in applications like electric vehicles and consumer electronics.In conclusion, this work presents a significant stride in battery research, paving the way for safer and more reliable energy storage solutions. The combined multiphysics modeling and DL framework offer a robust tool for predicting and preventing TR in LIBs, contributing to the broader goal of advancing battery technology in the modern energy landscape.

Decomposition Mechanism of Lithium Methyl Carbonate with Electrolyte in the Solid Electrolyte Interphase to Elucidate the Early Stages of Thermal Runaway in Lithium-Ion Batteries

With the growing demand for electric vehicles, the safety of lithium-ion batteries has been greatly emphasized. Thermal runaway caused by the continuous side reactions inside the battery makes it difficult to extinguish fires caused by abnormal activity. The temperature at which a typical thermal runaway begins is around 100°C, the temperature at which several elements in the solid electrolyte interphase (SEI) layer on the anode surface experience thermal decomposition reactions (causing gas generation and heat production). Therefore, to understand the first stage of thermal runaway and increase battery safety, it is necessary to describe the thermal decomposition process of the SEI layer.To investigate the thermal decomposition process of the SEI layer, it is necessary to understand the various organic components. During the initial charging phase, the reduction reaction between the lithium ions and the electrolyte produces a series of components that make up the SEI layer. On the surface of the anode active material, the SEI layer is a thin layer with an overall thickness of 10-50 nm. It is composed of various organic (inner layer) and inorganic (outer layer) elements. Under thermal stress, the unstable organic SEI layer decomposes into an inorganic SEI layer due to its low stability in the presence of heat and gas generation, which is mostly caused by the decomposition of lithium carbonate (ROCOOLi). It is important to note that the most used electrolytes in batteries today are ethylene carbonate and ethyl methyl carbonate (EMC) dissolved in salts based on lithium hexafluorophosphate. Due to the application of EMC, lithium methyl carbonate (LMC) accounts for more than 50% of the SEI layer in the ROCOOLi compounds.This study used both theoretical and experimental techniques to fully elucidate the pyrolysis process of high-purity synthesized LMC with the electrolyte. First, LMC was chemically synthesized using a nucleophilic substitution reaction. Then, in-situ thermogravimetry analysis (TGA)-mass spectrometer(MS), attenuated total reflectance (ATR)- fourier transform infrared (FTIR), and nuclear magnetic resonance (NMR) results along with bond dissociation energy (BDE)/spectral analysis/energy diagrams obtained by density functional theory (DFT) calculations were analyzed to propose the elementary reaction steps involved in the pyrolysis reaction. We propose six elementary reaction steps for the pyrolysis reaction of LMC. To verify the validity of the proposed basic reaction mechanisms, chain reactions involving radicals generated during pyrolysis were finally calculated using GRI-MECH 3.0, and the calculated results were compared with the composition of the actual gas. We hope to utilize the techniques used in this study to obtain the reaction steps of additional SEI components (LEMC, Li2CO3, etc.). The precise mechanisms obtained through modeling studies can be used to predict the self-heating phase of thermal runaway and to develop materials that can stop the SEI decomposition reaction.