Battery Fire Research Articles

Inhibition effect and extinguishment mechanisms of YS1000 microemulsion for lithium iron phosphate battery fires

The inhibition of Lithium ion battery (LIB) fires has attracted more and more attention from the public. However, an effective fire-extinguishing agent used for LIB fires has not been reported. The use of water mist containing additives for LIB fires is a promising method. In this work, the YS1000 microemulsion was prepared. A fine water mist fire extinguishing system was established to study the extinguishment efficiency of the fire-extinguishing agents for LIB fires. The fire suppression efficiency of pure water, F-500 fire extinguishing agent, and YS1000 microemulsion for the 32135-type lithium iron phosphate battery (LFP) were compared in this paper. The fire extinguishment mechanism of YS1000 microemulsion was revealed by thermo gravimetry, differential scanning calorimetry, mass spectrometry (TG-DSC-MS) combined technology. The results showed that it took more than 30 s for pure water to extinguish the LFP fire. In the case of pure water, three batteries went into thermal runaway (TR). It only took less than 1 s for YS1000 microemulsion to extinguish the fire. In the process of extinguishing the fire, only one battery experienced TR. Compared with pure water, the total heat dissipation of YS1000 microemulsions to the batteries increased by 79 %. The YS1000 microemulsion extinguished the LFP battery fire mainly depending on phosphoric acid decomposing product of YS1000 microemulsion at high temperature. The phosphoric acid could eliminate H∙ and OH∙ free radicals in the flame. Research results are expected to provide a significant reference for the design of fire-extinguishing agents used for LIB fires.

Experimental Investigation of the Effect of Flame-Retardant Additive Dimethyl Methylphosphonate on Combustion Behaviors of Electrolytes

Abstract Adding flame-retardant additives to electrolytes can significantly enhance the safety of lithium-ion batteries. To clarify the effects of flame-retardant additive dimethyl methylphosphonate (DMMP) on electrolyte flammability under practical battery fire conditions, experimental studies are conducted on an electrolyte pool fire setup. It is observed that the flame of carbonate solvent is blue, while the flames of electrolyte and electrolyte with DMMP addition are yellow, due to the formation of phosphorus-containing particles in the flame. With 30 wt% DMMP addition, the combustion duration, combustion mass ratio, and flame height decrease significantly by 40%. The electrolyte achieves non-flammability when the additive fraction increases to 40%. It is observed that with DMMP addition the charred layer forms on the surface of electrolyte liquid, and slows down the heat and mass transfer between the gas and electrolyte liquid. This is the flame-retardant mechanism of DMMP in the condensed phase. The flame spectrum results show that with LiPF6 and DMMP addition the OH emission intensities are weakened dramatically. This is because LiPF6 and DMMP decompose to the radicals containing phosphorus, which can scavenge the vital radicals (H and OH), and then suppress the combustion chain branching reactions. This is the flame-retardant mechanism of LiPF6 and DMMP in the gas phase.

The efficiency of dodecafluoro-2-methylpentan-3-one in suppressing NCM 811 lithium-ion battery fire

With the increase in the specific energy of lithium-ion batteries (LIBs), fire accidents occur more frequently; however, the effective and clean suppression of LIB fires remains a challenge. In the present work, the efficiency of dodecafluoro-2-methylpentan-3-one (C6F12O) in suppressing high energy density (HED) ternary LIB fires is experimentally investigated. It is found that C6F12O can efficiently extinguish the HED battery and its module fire. As the flow rate increases, the extinguishment time decreases and the peak temperature decreases, but the cooling efficiency for the long-term process is reduced. When the C6F12O spray can completely cover the thermal runaway (TR) area, its extinguishing and cooling effect is the best. For the HED module, the application of C6F12O effectively increases the TR trigger temperature, reduces the TR peak temperature, and decreases heat production. The application of water mist enhances the cooling of extinguished LIBs, the combination of C6F12O and water mist extends the TR propagation time of the fully charged LIB module to 1.4 times that without suppression, and the total TR heat production is reduced by 1423.1 kJ. These results provide guidance for the design of inhibitor volume fractions for HED LIB fires.

Thermal runaway and soot production of lithium-ion batteries: Implications for safety and environmental concerns

Global energy shortages are becoming increasingly severe, and lithium-ion batteries are becoming an important substitute for fossil fuels. However, thermal runaway of a battery is a significant factor impacting battery industry development. Here, we conducted tests on battery thermal runaway using a combustion test chamber, analysing the effects of natural aging and state of charge (SOC) on battery thermal runaway. Additionally, EDS and XPS were used to analyse the soot particles formed during thermal runaway. Four stages in thermal runaway, e.g., battery bulge, smoke release, jet fire, and fire extinction. LiFePO4 with a higher SOC is more likely to cause thermal runaway. In addition, natural aging has an obvious impact on the intensity of thermal runaway. The gas products generated during a battery fire are identified as C1–C4 hydrocarbons. The soot generated by battery combustion presents a typical “core-shell” structure. The soot surface exhibits C–C, C–O, and O–H bonds, while the soot from early manufactured batteries also contains O–CO and π bonds. Soot contains not only C and O but also trace amounts of Li, F, P and Fe. These results reveal the characteristics of soot emission during thermal runaway of batteries, providing valuable insights for evaluating their toxicity and environmental impact.

Pyrolysis-based modelling of 18650-type lithium-ion battery fires in thermal runaway with LCO, LFP and NMC cathodes

This study presents a modelling approach for simulating fires in thermal runaway and here, it is applied to 18650-type batteries with LCO, NMC, and LFP cathodes at 100% SOC. The model assumes a single-step pyrolysis, where a solid lumped substance, representing the battery components, degrades into volatiles which are vent gases here. Coupling an in-house MATLAB code and FDS solver, a parameter estimation using Bayesian optimization was performed to fit the simulated mass loss and heat release rate to the experimental measurements. One-step kinetics are used for vent gas combustion, with CO yield obtained from literature and soot yield determined via 1-D diffusion flame simulations with CRECK kinetic mechanism in Cantera solver. 3-D simulations using the obtained models yielded maximum values of flame temperature, CO2 and H2O mole fractions, velocity, radiative heat flux, and flame height as 2520 K, 0.47, 0.15, 10.08 m/s, 13.29 kW/m2, and 0.62 m, respectively. The novelties associated with this approach are that, unlike the past studies, there is no need to model the thermal runaway process prior to flaming and, the resulting heat release rate is experimentally verified which makes further analyses, such as flame temperature, height and heat emissions possible.

Determination of lithium in the blood of the deceased by inductively coupled plasma mass spectrometry in a case of lithium-ion battery fire

In this study, a case of lithium-ion battery fire is presented. The blood of the deceased was analyzed for lithium (Li) using ICP-MS (inductively coupled plasma mass spectrometry). When compared to normal individuals in the same region, the deceased had much higher levels of Li in their blood. Therefore, conducting quantitative analyses of Li in the bodies of individuals who die in lithium-ion battery fire can provide valuable information into the specific circumstances surrounding their deaths.

Preparation of a novel environmental-friendly lithium-ion battery fire suppression microcapsule and its fire extinguishing mechanism in coordination with ABC dry powder

Lithium-ion battery fires are one of the main bottlenecks hindering the industrialization development of lithium-ion batteries. The existing fire extinguishing materials can not completely solve the problems of lithium-ion battery cooling, reignition, pollution and so on. Therefore, it is imperative to develop efficient and environmentally friendly fire extinguishing materials. In this paper, environmentally friendly CTS-SA@F7A-Novec 1230 microcapsule fire extinguishing agent with good flame retardant properties was prepared by coating heptafluorocyclopentane (F7A) and perfluorohexanone (Novec 1230) fire-extinguishing materials by the complex coalescence method using chitosan (CTS) and sodium alginate (SA) as the shell material, and the fire-extinguishing effects of the three methods, namely, N2+ABC dry powder + microcapsule (NAM), N2+ABC dry powder (NA), and N2(N), were comparatively analyzed. The research results indicate that, CTS-SA@F7A-Novec 1230 microcapsules were well formed and had excellent thermal stability; The peak heat release rate (PHRR) of CTS-SA@F7A-Novec 1230 microcapsules decreased by 22.56 w/g after the addition of CTS-SA@F7A-Novec 1230 microcapsules to the composite battery materials, and the temperature TPHRR corresponding to PHRR increased by 18.09 °C accordingly, which resulted in a good flame retardant property of the materials; The cell cooling effect was ranked as NAM > NA > N, and the maximum cell surface temperatures under these three methods were reduced by 10.34%, 17.30% and 18.68%, respectively, compared with the thermal runaway experimental data; The fire extinguishing effectiveness was ranked as NAM > NA > N. The maximum flame temperature was reduced by 52.10%, 40.53%, and 23.95%, and the flame extinguishing time was shortened by 71.02%, 64.12%, and 22.48%, respectively, with these three methods compared to the thermal runaway flame data. Based on this, the three-phase synergistic extinguishing mechanism of gas, liquid and solid under the NAM method is revealed, which provides an important reference for the design of extinguishing agents and extinguishing methods for lithium-ion batteries.

Surrogate Model for the Effect of Charge State in Lithium-ion Battery Fires

Recently, the demand for eco-friendly energy sources, including batteries, has increased rapidly owing to growing climate and environmental problems. However, battery fire accidents are also increasing, and many researchers are focusing on the safe use of batteries and their flammability characteristics. Owing to the multiple battery types, conducting experiments is difficult in all cases, so various methods to model battery fires are being attempted. This study focuses on the effect of charge states and models surrogate fuels for battery thermal runaway. Three surrogate fuels were selected based on the battery components, and a method of increasing the oxygen concentration was adapted to model the effect that occurs when the charge states of a battery fire increases. As a result, the temperature and pressure increased in all cases, and it appears that the explosion caused by the battery thermal runaway can be simulated by the model. One of the results of this study is that ethane exposed to a high temperature not only contributes to the physical explosion of the battery but also increases the risk of chemical explosion as it decomposes in to H<sub>2</sub> and CH<sub>4</sub> .

Composite structure failure analysis post Lithium-Ion battery fire

The use of composite materials has expanded significantly in a variety of sectors. In road transport,lithium-ion batteries (LIB) are the most commonly used.It is standard practice for batteriesto be housed within a metal enclosure, whichprotects and enables extinguishment in the event ofThermal Runaway (TR). Composite materials have been shown to contribute to lightweighting in many vehicle structures and their use inbattery enclosures has been growing in recent years - with the aim of reducing the weight of the battery assembly and positively impacting vehicle range.This work develops Finite Element (FE) models to assess thermal and mechanical damage and failure mechanisms during a TR event considering a section of a composite battery enclosure. Experimental data for a cylindrical 18650 lithium-ion battery fire is studied and used to define representative thermal loading. This validated loading profile is applied to a composite specimen and material temperature data is used to appraise damage. Finally, the predicted damage isused to predict and quantify the residual failure mechanism and strength of the specimen post battery fire. Results have shown the presence of damage from a single cell runaway can potentially reduce the strength of the specimen by 20% while multi-cell runaway can potentially reduce the strength by 56%. The predictive simulation capability herein could be used as a design tool for battery fire protection of composite enclosures, potentially reducing the need for corrective action, minimising the number of physical tests to support design and certification, as well as aiding in the interpretation of physical test results.

Evaluation of Fire Spread and Suppression Techniques in Micro-Mobility Battery Packs

Lithium-ion battery packs used in micro-mobility devices, such as e-bikes and e-scooters can lead to substantial safety hazards should a single cell go into thermal runaway. In this paper we explore the extent and severity of e-mobility battery fires resulting from a single cell thermal runaway failure and evaluate various suppression techniques a user may attempt to implement if they experience a battery fire at home. We tested a household water hose as well as different fire blankets deployed both before the forced thermal runaway event and after initiation. The water hose was unable to supply a sufficient amount of water to extinguish the thermal event, however, the average pack temperature was decreased and the cell-to-cell propagation rate was slowed. Neither fire blanket tested was able to contain the flames or debris ejected from the battery packs and both acted to hold in the heat from the event, increasing the temperature, rather than allowing it to dissipate. In addition, we also demonstrated how various design approaches, such as added thermal insulation between cells, can help prevent cell-to-cell propagation and reduce the severity of a battery pack failure.

The Early Detection of Faults for Lithium-Ion Batteries in Energy Storage Systems Using Independent Component Analysis with Mahalanobis Distance

In recent years, battery fires have become more common owing to the increased use of lithium-ion batteries. Therefore, monitoring technology is required to detect battery anomalies because battery fires cause significant damage to systems. We used Mahalanobis distance (MD) and independent component analysis (ICA) to detect early battery faults in a real-world energy storage system (ESS). The fault types included historical data of battery overvoltage and humidity anomaly alarms generated by the system management program. These are typical preliminary symptoms of thermal runaway, the leading cause of lithium-ion battery fires. The alarms were generated by the system management program based on thresholds. If a fire occurs in an ESS, the humidity inside the ESS will increase very quickly, which means that threshold-based alarm generation methods can be risky. In addition, industrial datasets contain many outliers for various reasons, including measurement and communication errors in sensors. These outliers can lead to biased training results for models. Therefore, we used MD to remove outliers and performed fault detection based on ICA. The proposed method determines confidence limits based on statistics derived from normal samples with outliers removed, resulting in well-defined thresholds compared to existing fault detection methods. Moreover, it demonstrated the ability to detect faults earlier than the point at which alarms were generated by the system management program: 15 min earlier for battery overvoltage and 26 min earlier for humidity anomalies.

Dry water: Toward an ideal extinguishant for lithium-ion battery fire

Developing an environment-friendly, high-cooling, non-conductive, and low-cost extinguishant has been the focus on fighting lithium-ion battery (LIB) fires. In this work, dry water (DW), a powdered material containing copious amounts of liquid water, was first studied as an extinguishant for LIB fires. Benefiting from the core-shell structure and dispersibility properties as a dry powder, DW shows a high electric breakdown voltage, which enables it to overcome the conductivity drawback of liquid water. Moreover, although the endothermic enthalpies of DWs are only about 82.4–95.7 % of liquid water, their water evaporation rates are faster than liquid water, which brings DWs a better cooling effect than liquid water in suppressing thermal runaway propagation. Thus, DW combines the advantages of both liquid water (high cooling ability) and dry powder (low conductivity), and presents a great application potential to control LIB fires.

Experimental study on the inhibition effect of water mist containing additives on the thermal runaway of lithium battery

The water mist (WM) is currently an important environmentally friendly fire extinguishing agent, offering a distinct advantage in efficiently cooling and inhibiting the thermal runaway (TR) behavior of lithium battery (LIB). Numerous studies have explored the additives of WM to extinguish LIB fires more efficiently. However, the inhibition mechanism of WM containing additives on TR of LIB has not been revealed clearly, and the principle of adding additives remains to be further studied. In this study, three types of non-ionic surfactants are examined and their effects on the maximum temperature during TR and the cooling time of WM are compared. The results indicate that foam induced by the additives has certain advantages in mitigating LIB TR. Further the defoamer is used to modify the foaming performance of the additive solution, and it is found that an appropriate increase in the brittleness of the foam can greatly decrease the highest temperature of the battery during TR moment. These findings can serve as a valuable reference for future applications of WM with additives in the design of battery fire suppression systems.

Characterisation of Smoke Particles from Lithium-Ion Battery Fire: Morphology, Size and Composition

The electrification of the transport sector is a necessary step to reduce the concentration of greenhouse gas emissions (GHGs) in the atmosphere in order to mitigate climate change. Li-ion batteries (LIBs) are considered a key enabling technology and are crucially important for the green energy transition. However, LIBs may pose safety concerns, as demonstrated by the recurrent fire accidents involving electric vehicles, according to news reports from recent years. Several studies concentrated mainly on the identification, composition and flammability of vented gases during LIBs thermal runaway and fires. Scarce work about the particle emissions during a LIB fire can be found in the literature. To fill up this research gap, in this study, we characterised smoke particles from Li-ion battery fire using Scanning Electron Microscopy/Energy Dispersive X-ray spectroscopy (SEM/EDX) and X-ray Diffraction (XRD) to evaluate their size, morphology, crystallographic and chemical composition. Our results show that battery fire smoke particles contain chemical components and crystallographic phases that are toxic for health and environment. Moreover, we confirm the presence of (ultra) fine particles, reported previously, which due to their small size are inhalable and can therefore pose a serious risk to human health. Recommendations for further experimental studies are outlined to establish e.g. a correlation between smoke particles emissions and battery SOC, chemistry, abuse scenario, etc.

(Invited) Safety of Li-Ion Batteries: Current Challenges in a Policy Context

Batteries are a key technology required to meet our objective for climate neutrality, to reduce dependency on fuel imports as well as to ensure maximum use of renewable electricity. Over 80 GW / 160 GWh of stationary batteries and over 50 million electric vehicles are expected in the EU by 2030. Lithium-ion batteries are expected to dominate the market well beyond 2030, while developments in other technologies will continue in parallel. Battery-related policies are currently of high interest and have to evolve quickly in order to facilitate and accommodate technological progress.With increasing numbers of electric vehicles and batteries in operation and the parallel rise of energy density in lithium-ion batteries, risks related to battery safety e.g., through battery fires, increase. The Joint Research Centre (JRC) carries out research on battery safety to support policymaking and develop fit-for-purpose testing methodologies: the recently proposed Batteries Regulation, aiming at a sustainable battery value chain, foresees new safety requirements for stationary batteries. Another example is the Global Technical Regulation on Electric Vehicle Safety, where a thermal propagation test procedure is being developed with international partners.In this context, thermal runaway initiation methods and criteria for thermal runaway events had been analysed. A rapid heating method and suitable criteria for thermal runaway were applied in a thermal propagation test campaign on full electric vehicles and corresponding battery packs. While a high degree of reproducibility was observed, a difference in severity between pack and vehicle-level tests was found, and gas emissions from the tests are currently being analysed. Figure 1

Characterizing the Cathode Degradation Process from Thermal Abuse in Solid State Batteries

With an ever-increasing reliance on batteries for all aspects of life, safety of energy storage is a growing concern as reported instances of lithium-ion battery (LIB) fires and even a solid-state battery (SSB) fire arise. However, the understanding of battery safety from a fundamental materials level is not well understood. As the push for higher energy density batteries in the electrification of transportation continues, it is imperative to understand how underlying material degradation and failure affects the safety of current and next-generation lithium battery technology.In this study, heat release and corresponding degradation due to external heating are explored for the following battery configurations: All solid-state batteries (ASSBs), SSBs containing a low amount of liquid electrolyte, and LIBs. NMC532 cathode was used in all battery configurations, Ta-doped LLZO was used for the solid electrolyte, and LiPF6 in EC/EMC was used as the liquid electrolyte in the SSB and LIB configurations. Differential scanning calorimetry (DSC) was used to raise microcells to definitive temperatures of interest depending upon their respective exotherm profile. LIB sample heat release was significantly higher than the heat release of the ASSB and SSB, even though the heating temperature range and final temperature were lower for the LIB samples. The disassembled microcell components were then analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis revealed the LIB samples did not show the presence of the fully degraded rock salt crystalline phase after peak heat release, whereas ASSB and SSB configurations revealed the presence of the rock salt phase. Additionally, SEM image analysis shows no degradation of the LIB particles, while ASSB and SSB samples show surface degradation of the high temperature samples. Decomposition of NMC to the rock salt phase involves the release of oxygen, which may undergo an exothermic reaction inside the SSB. These investigations shed light into the expected extent of NMC decomposition at key temperatures and exothermic heat flow peaks for each battery composition. Future work combining these results with further elemental characterization experiments will pave the way for a materials-level understanding that can be incorporated into the initial design and development stages of next generation lithium batteries, impacting the creation of energy storage devices by ensuring commitment to safety from the ground up.

(Invited) Battery System Safety Design Based on Studying the Runaway in Battery Cell

Lithium ion battery systems towards certain military application such as submarines and torpedoes are considered “fire critical applications”. Meaning a fire in the battery system on board a submarine is equal to a lost submarine with many crewmen dead. There have already been critical lithium ion battery fires on board submarines. In the united states a midget submarine were destroyed about fifteen years ago during the development phase of the submarine delaying the incorporation of lithium ion batteries in to marine platforms in the USA by about ten years even though no one were killed by the fire. Four years ago the Russian spy submarine Loshariks lithium ion battery system caught fire during the new battery systems maiden voyage. The fire started when the submarine were at a depth of about 200m below the surface of Barents ocean and 14 crewmen were killed almost all were high ranking officers. Too, be able to come up with a safe battery system design for the Swedish submarines we concluded that we need a strategy for the battery system design. We studied literature, conducted modelling work and carried out a lot of abuse test to understand what happens when a battery cell fails.What happens when a 21700 battery cell is overcharged? First the cell is heated to about 110-115°C and then the membrane between the anode and the cathode melts. In the next step the CIP opens up and hot gas is released at about 125 - 135°C. The cell self-heat itself, the temperature rises fast to about 190-200 ° C, then the gas caught fire, and a jet flame is formed with a temperature above 1100°C. A huge amount of hot gases mixed with sluggish particles is released from the top of the battery cell at high speed. The sluggish particles are black and look like a lava flow and when analysed they are found to be electric conductive. What is also interesting is that the lava particles slowly releases its heat to the surroundings, thus the particles kept at a high temperature for a relatively long-time. The surface of the battery cell reaches a peak temperature of about 300°C. This information is enough to start the battery module design work.Why is a round lithium battery cell the obvious choice for a safe high performing battery system? A runaway in round 21700 battery cell leads to axial expansion of 1-2mm the radial expiation is taken up by the design materials. A runaway in a prismatic or pouch cell battery the horizontal expansion can be several centimetres leading to an inefficient design to be able to take up the expansion of failing battery cell. To be able to do an efficient design to keep down the weight of the battery system the cells can be part of the mechanical design. When organizing the round battery cells symmetrically in a battery module each battery cell will work as springs in the right design material, thus be able to take up energy from an impact from an object. If the incoming object is a bullet at speed of 900m /s and a weight of 50 gram, the symmetrically organized battery cells will absorb the energy fast and only few of the battery cells in the module will be de destroyed and will start to burn.Finally yet importantly, the round battery cells are in most cases smaller than the prismatic battery cells for the same application thus contains less energy per battery cell.One battery cell can always burn, but a propagation in battery module or system is not an option for “Fire Critical Military Applications”.

(Invited) Stress and Surface Engineering for Dendrites-Suppressing Solid-State Electrolytes

This presentation will discuss a new and general paradigm via stress engineering for enabling all-solid-state batteries that use lithium or sodium (Li or Na) metal anodes. It is well known that all solid-state batteries that replace the highly flammable liquid electrolytes that are presently used will dramatically reduce the incidence of battery fires and enable using metallic anodes. Unfortunately, solid-state electrolytes (SEs) face significant technical challenges, in large part because Li dendrites readily penetrate through SEs, leading to short circuits and cell failure. Completely different from the existing approaches, which either apply high stack pressures or add a buffer layer between Li and the SEs, this approach will suppress dendrites and cracks in SEs by putting the SE surfaces into a state of residual compressive stress via ion implantation. In addition, this talk will present the understanding of surface/grain boundary science and its impact on electrochemistry, as well the future strategies to improve electrodeposition efficiency via surface and stress engineering. Combining the results from spectroscopic and structural characterization, this invited talk will highlight the impact of stress and surface engineering on reversible electrochemistry of the Garnet solid-state electrolytes and provide insights in designing all-solid-state batteries for cycling at room temperature and low stack pressure.

Diagnostics of Safety Hazardous Ageing Conditions for Commercial Lithium-Ion Pouch Cells

It is well-known that Lithium-ion cells can have safety issues. A large number of battery fire incidents have been reported the last years within e.g. battery energy storage systems [1], electric and hybrid-electric ships [2], electric vehicles and mobile phones [3]. The causes for these incidents are numerous and can include internal shortage of the Li-ion cell, external shortage of the battery system, over-heating or over-charging. All these causes result in overheating which can lead to an eventual thermal runaway which again could lead to a severe fire and explosion. We report on changes in thermal stability due to different ageing mechanisms in abstract Lian (#176439) and in Lian [4]. A decrease in thermal stability due to battery ageing could be hazardous and might be an end-of-life criteria. It is thus of vital importance to develop diagnostic tools capable of detecting a potentially hazardous drop in thermal stability for aged lithium-ion cells.This study is based on results from a battery life study performed on a large renowned Li-ion pouch cell with an initial capacity of 64 Ah. More than 100 cells were tested following a selected test matrix including different temperatures, currents, and State-of-Charge windows. All cells were tested until they reached a remaining capacity of between 60 to 80 % State-of-Health. A large dataset with diagnostic data was recorded during ageing, including e.g., dQ/dV (incremental capacity analysis) and DC resistances. Thermal properties of selected new and aged cells were studied in an Accelerated Rate Calorimeter (ARC), see Lian (abstract #176439). A post-mortem study of selected new and aged cells was performed to relate the collected diagnostics data to different ageing paths and safety properties. Based on detailed cell characterization, an experimental parameter set for an electrochemical pseudo-two-dimensional (P2D) model was established.Based on the dQ/dV (ICA) analysis, a distinct change in diagnostic patterns was observed for cells aged and cycled at low temperature (5-15 °C) compared to cells cycled at higher temperatures (35 -45 °C). This correlates to the observed differences in thermal stability reported by Lian (abstract #176439). To verify the observed ageing mechanisms from the post-mortem studies, emulated ageing modelling was performed both based on the Alawa tool [5], as well as the P2D model coupled with different ageing mechanisms. References McKinnon, M.B., S. DeCrance, and S. Kerber, Four Firefigheters Injured In Lithium-Ion Battery Energy Storage System Explosion - Arizona, U. Laboratories, Editor. 2020, Underwriters Laboratories: Columbia, MD. p. 66.Norwegian Maritime Authority, Supporting preliminary findings after battery incident. 2019: Norwegian Maritime Authority.BBC, Samsung confirms battery faults as cause of Note 7 fires, in BBC. 2017, BBC.Lian, T., et al., (Invited) Changes in Thermal Stability of Cyclic Aged Commercial Lithium-Ion Cells. ECS Transactions, 2019. 89(1): p. 73-81.Dubarry, M., et al., State of health battery estimator enabling degradation diagnosis: Model and algorithm description. Journal of Power Sources, 2017. 360: p. 59-69.

Investigation of Water Ingress Driven Circuit Board Faults As a Contributory Factor to Battery Thermal Runaway

Recent high-profile examples of battery fires in electric vehicles (EV’s) during the aftermath of Hurricane Ian [1] have led to increased public visibility of the susceptibility of EV batteries to thermal failure due to water immersion or ingress.Although clearly an issue for manufacturers and users of automotive EV’s, this issue poses a particular challenge in the rapidly increasing micromobility market with nearly 800 million battery powered 2- and 3-wheeled vehicles (such as e-bikes or scooters) expected to be in operation by 2040 [2]. With privately owned micromobility vehicles generally not subject to the rigorous servicing or maintenance schedules of automotive EV’s, and fleets of rented e-bikes / scooters subjected to prolonged rough handling and environmental exposure, the risk of failure in these vehicles due to improper handling, water ingress or mechanical abuse is very real.Testing and failure recreation of thermal runaway in lithium-ion based micromobility battery packs within Exponent’s European laboratory (London) has shown that even small amounts of moisture ingress to sensitive electronic components of the battery pack, such as the battery protection circuitry, can lead to thermal runaway of the cells within the battery pack. Such failures are often highly dependent on battery pack design (and physical condition) and may only manifest in the days or weeks after water immersion or ingress.The study presented here investigated specific conditions and behaviours of saltwater ingress-driven circuit board faults in lithium-ion battery packs, and demonstrated localised temperature increases of ~100 °C, even at relatively low fault currents (mA’s), showing the potential for circuit board faults to propagate to cell thermal runaway.Further studies investigated the effect of full, partial and targeted immersion of lithium-ion battery packs in 5 wt% NaCl solution, demonstrating the influence of the volume of water ingress and ingress location within the battery pack on the potential for battery thermal runaway. This paper will also discuss design aspects and/or mitigation methods to protect from such failure modes.[1] - https://content.govdelivery.com/accounts/USDHSFACIR/bulletins/333744b[2] - https://www.faraday.ac.uk/wp-content/uploads/2023/02/Faraday_Insights_16_FINAL.pdf