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As the EV and battery market continues to grow, understanding and mitigating battery thermal runaway remains a critically important area of research. Under controlled experimental conditions, researchers have employed a range of different techniques to initiate battery fires and understand both how and why they occur. These tests give important information about how a battery cell catastrophically fails under abuse conditions. However, recognizing the changes in the internal structure of the cell is vital to understanding the mechanisms of thermal runaway which enables the development of effective mitigation strategies. During the last decade, X-ray imaging has emerged as an important diagnostic tool for battery degradation, electrochemical performance, and safety diagnostics. Researchers use X-ray imaging to directly observe the internal changes in the cell during all stages of thermal runaway. Depending on the initiation method, it can sometimes take minutes, hours, or days for a cell to undergo failure. However, the actual final reactions that cause thermal runaway occur over fractions of a second. High-speed cameras, operating at up to 40,000 frames per second, can capture the interactions between electrodes at the final moments of thermal runaway. In this article, the basics of high-speed X-ray imaging and how this technique has been applied to investigating battery thermal runaway are discussed. [ABSTRACT FROM AUTHOR]

This article discusses the dual challenges of modeling and predicting thermal runaway (TR) in li-ion batteries. It explores the current challenges of TR modeling, the methods for progressing from single cells to battery packs, and future directions involving the use of probabilistic methods and ML/AI to tackle this multifaceted issue. Accurate prediction of TR events remains a major challenge, especially because of the cell-to-cell variability, but also due to parametrization, which requires complex experimentation or exhaustive experimental data for training data-driven ML models. Continued research and innovation in modeling and predictive techniques are essential for ensuring safer and more reliable battery systems. [ABSTRACT FROM AUTHOR]

We depict here that the value of the relaxed magnetization follows a unique path for each temperature below the phase transition temperature ( T c 2 ) for pristine C a 3 C o 2 O 6 and its substituents. Here we propose a way to access these paths by cyclic thermal manipulations. Thus the magnetization corresponding to each temperature below T c 2 can be utilized in multilevel data storage that has a potential application in the thermal memory cell. Furthermore, these results were compared with another route used in the thermal memory cell and were proven more efficient and faster than the latter one. [ABSTRACT FROM AUTHOR]

Acoustic ultrasound interrogation and deformation measurements have been used simultaneously as supplementary battery monitoring methods during external overheating and external short-circuit safety tests of LG INR-18650 MJ1 (NMC 811-G-SiOx) Li-ion cells. The short-circuit experiments showed that the MJ1 technology is protected against this type of thermal abuse by the current interruption device (CID) integrated in the positive terminal of the cell. The results indicate that the strain gage signal is able to provide very rapid alert for this type of battery safety breach due to an abrupt change of the cell pressure. It precedes the time of the increase of the skin temperature by an order of magnitude. The thermal stability experiments carried out in adiabatic rate calorimeter on completely charged and overcharged batteries at open circuit conditions, showed that the MJ1 technology is susceptible to self-heating by slow internal exothermic reactions starting above 60 °C. The subsequent process of thermal runaway starts when the temperature exceeds 140 C. The results from the extended monitoring of the cells during the thermal stability tests showed that the acoustic ultrasound interrogation data combined with data mapping and clustering of the signal provides advantageous indication for early detection of slowly approaching battery safety breach events. [ABSTRACT FROM AUTHOR]

Isothermal microcalorimetry is used to study the heat flow of lithium-ion cells to provide insight into active material characteristics and to provide data required for a thermal optimization on the cell and system level. Recent research has shown the application of this technique to cells during high cycling rates, for example fast charging. However, the limitation of isothermal microcalorimetry is the low-pass characteristic of the measured heat flow, introduced by the thermal inertia of the setup and the calorimeter itself. To solve this problem, we introduce an optimized cell holder design and a novel data processing method for a time-resolved measurement of highly dynamic heat flow profiles. These are described in detail and validated using a synthetic power profile applied to a dummy cell. Experiments on a graphite-lithium half-cell illustrate the improvement of the method and the optimized cell holder when compared to the state-of-the-art setup, demonstrating the 3.6 times faster time response, which was further improved using a post-processing deconvolution technique. The thus improved time resolution provides the acquisition of more detailed features than currently shown in the literature and allows an accurate correlation of the thermal signals to electrochemical features like, e.g., the differential voltage of the cell. [ABSTRACT FROM AUTHOR]

Solid-state batteries are often considered to have superior safety compared to their liquid electrolyte counterparts, but further analysis is needed, especially because the higher specific energy of a solid-state lithium metal battery results in a higher potential temperature rise from the electrical energy in the cell. We construct a model of the temperature rise during a thermal ramp test and short circuit in a large-format solid-state LCO∣LLZO∣Li battery based on measurements of thermal runaway reaction thermochemistry upon heating. O2 released from the metal oxide cathode starting at ∼250 °C reacts with molten Li metal to form Li2O in an exothermic reaction that may drive the cell temperature to ∼1000 °C in our model, comparable to temperature rise from high-energy Li-ion cells. Transport of O2 or Li through the solid-state separator (e.g., through cracks), and the passivation of Li metal by solid products such as Li2O, are key determinants of the peak temperature. Our work demonstrates the critical importance of the management of molten Li and O2 gas within the cell, and the importance of future modeling and experimental work to quantify the rate of the 2Li+1/2O2→Li2O reaction, and others, within a large format solid-state battery. [ABSTRACT FROM AUTHOR]

To simultaneously optimize the battery design, reduce risk, and maintain safety margin, it is important to design from the ground up based on test determined cell-specific thermal runaway behavior as a function of heat output and analysis of the expelled gases. These data will inform the analytical models used for design optimization. Here we analyze the thermal runaway behavior of the 134 A-h GS Yuasa Li-ion cell (LSE134) using a novel large format fractional thermal runaway calorimeter and gas collection methodology. Results indicate an average total thermal runaway energy yield of 2.86 MJ, or 1.6 times the stored electrochemical energy; this follows an assertion commonly found in literature that energy yield scales linearly with capacity. The average fractional energy distribution was 2% through the cell body, 53% through the electrode winding, and 45% through the ejecta material and gases. Lot-to-lot variability in heat output was also identified. Additionally, it was found that an average of 416.6 SL of gas was generated which is approximately 3.1 l A-h−1 . The exhaust gas was determined to be a mixture of carbon dioxide, methane, ethane, oxygen, hydrogen, and other short chain hydrocarbons. Carbon dioxide was the largest component by volume with a range of 41% to 52% followed by hydrogen which ranged from 28% to 41%. Larger cells appear to result in strong ejecta flow driven events with higher fractions of the total energy delivered via the flow as compared to smaller format Li-ion cells (e.g. 18650 and 21700). [ABSTRACT FROM AUTHOR]

At discharge, a battery releases the stored energy of the redox chemical reaction partially by passing electric current throughout the external circuit, and partially dissipating it in the form of heat. The amount of that heat depends on the discharging current. This heat primarily warms the battery itself. Knowing its total amount as well as the heat flow is important for the safety of batteries, especially lithium-ion ones. In battery engineering practice, it is often suggested that the heat flow P follows the Joule-Lenz law that together with the Ohm law has the form P = I² R (I is the current and R is the battery’s internal resistance); we showed that this is not true. Both total heat and heat flow can be determined relatively easily by applying general ideas of thermochemistry and thermodynamics when the battery operates under projected use conditions by comparing the dependencies of the open circuit voltage (OCV) and voltage profile of the discharging battery upon the state of charge (SoC) or depth of discharge (DoD). Although the theoretical background is universal, being applicable to any kind of battery, our paper presents the results of examining three lithium-ion batteries of extensively used chemistries: lithium iron phosphate-graphite, lithium cobalt oxide-graphite, and lithium nickel cobalt aluminum oxide-graphite. Particular attention is given to the effect of the entropy of the reactions on batteries’ thermal behavior. [ABSTRACT FROM AUTHOR]

Lithium-ion battery research has historically been driven by power and energy density targets. However, the performance of a lithium-ion cell is strongly influenced by its heat generation and rejection capabilities which have received less attention. The development of adequate thermal metrics able to capture the anisotropic thermal conductivity and uneven internal heat generation rates characteristic of lithium-ion cells is therefore paramount. The Cell Cooling Coefficient (CCC), in W.K-1, has been introduced as a suitable metric to quantify the rate of heat rejection of a given cell and thermal management method. However, there is no standardised methodology defining how to measure the heat generation capabilities of a cell. In this study, we applied the CCC empirical methodology to evaluate the rates of irreversible heat generation at various operation conditions, providing maps which give a complete insight into cell thermal performance. The maps derived show how the most important operational variables (frequency, C-rate, SOC and temperature) influence the cell thermal performance. These maps can be used along with the CCC by pack engineers to optimise the design of thermal management systems and to down select cells according to their thermal performance. [ABSTRACT FROM AUTHOR]

Lithium-ion battery packs are made by many batteries, and the difficulty in heat transfer can cause many safety issues. It is important to evaluate thermal performance of a battery pack in designing process. Here, a multiscale method combining a pseudo-two-dimensional model of individual battery and three-dimensional computational fluid dynamics is employed to describe heat generation and transfer in a battery pack. The effect of battery arrangement on the thermal performance of battery packs is investigated. We discuss the air-cooling effect of the pack with four battery arrangements which include one square arrangement, one stagger arrangement and two trapezoid arrangements. In addition, the air-cooling strategy is studied by observing temperature distribution of the battery pack. It is found that the square arrangement is the structure with the best air-cooling effect, and the cooling effect is best when the cold air inlet is at the top of the battery pack. We hope that this work can provide theoretical guidance for thermal management of lithium-ion battery packs. [ABSTRACT FROM AUTHOR]

Owing to their versatility in cell formats, lithium-ion cells are widely used in energy storage systems. The pouch format cell architecture allows easy adaptability to a manufacturer's application needs. This study aims to characterize the interplay between cycle life aging and off-nominal conditions. Single pouch cells aged to different capacity fade (CF) levels and modules aged to 20% CF were subjected to overcharge tests. Fresh cells and fresh and aged modules were subjected to external short tests. Under overcharge conditions, fresh cells experienced thermal runaway under 1C overcharge but exhibited only swelling under C/3. Overcharged cells with 10% CF experienced swelling and thermal runaway, while cells with over 15% CF experienced swelling and venting through pouch sidewall rupture. It can be conjectured that cells with over 15% CF did not experience thermal runaway due to the relative loss of active material. Under external short, single cells exhibited slight swelling, charring of the anode tab and crumbling of the cathode. Fresh and aged modules subjected to C/3 overcharge experienced catastrophic thermal runaway. Although aging slightly delays the onset of thermal runaway, the fresh module went into catastrophic thermal runaway under external short, whereas the aged one did not. [ABSTRACT FROM AUTHOR]

With the wide application of lithium-ion batteries (LIBs), it is important to understand the internal heating effects and thermal runaway behavior of such batteries to evaluate their thermal safety and improving thermal management systems. The heat generation of LiCoO2/graphite LIBs under various conditions was compared using calorimetry and electrochemical methods. The heat generation results of the two methods in the process of charging/discharging at different current rates were consistent, but the calorimetry method is simple, convenient, and more feasible. The greater the working current, the greater the irreversible heat generation. Through the identification of the thermal runaway behavior, it was found that the change of the onset temperature of self-heating reactions fluctuates in a narrow range. Thermal runaway after battery degradation is more likely to be triggered by the degradation of thermal stability. [ABSTRACT FROM AUTHOR]

For the U.S. Department of Defense, high-performance power sources are a critical technology for current and future gun-fired munitions. Molten salt thermal batteries are the reserve power source of choice for many weapon systems due to their high power density, proven long shelf life, and capability to function across a wide range of operating environments. The incorporation of nanomaterials into thermal battery components offers the potential to produce batteries with performance improvements, such as higher voltages at increased current densities. In this study, nanoscale iron disulfide (FeS2) was synthesized using a fully scalable, high energy milling method, and characterized utilizing SEM, XRD, ICP-OES, BET surface area analysis, TGA-DSC, and other techniques. Nanostructured cathode mixtures containing the nanoscale FeS2 and LiCl-KCl eutectic salt electrolyte were pressed into electrode pellets. Their electrochemical performance was then characterized as compared to standard FeS2 cathode electrode pellets currently used in industry. Single cell thermal battery discharge testing, polarization type scans, and pulse load capability were used to compare cell performance for better understanding of best-use applications for these materials. Compared to control cells, the cells utilizing nanostructured cathodes provided higher power response, with respect to both voltage and runtime. [ABSTRACT FROM AUTHOR]

The energy density of traditional Li-Si/FeS2 thermal batteries, which multiple cations are contained in molten salt electrolyte, is limited by the deficiency of Li+ in cathode when a high discharge current is applied. To address this issue, LiCl-KCl is taken as an example to build a functional gradient structure through Li-Si/FeS2 thermal batteries. By levering the Li+ concentration in cathode and preventing the formation of high concentration polarization resistivity as well as molten salt precipitation, the energy density of Li-Si/FeS2 single cell with a discharge current of 500 mA cm-2, increase from 157.0 Wh kg-1 to 218.4 Wh kg-1 at 450 °C (with an increase ratio of 39.1%), compared with the original one. Similarly, a 25.6% raise is observed at 525 °C. Moreover, the effects of LiCl-rich electrolyte and the functional gradient structure on the electrochemical performance of Li-Si/FeS2 single cells are discussed and classified. [ABSTRACT FROM AUTHOR]

Approaches for thermal management of lithium-ion (Li-ion) batteries do not always keep pace with advances in energy storage and power delivering capabilities. Root-cause analysis and empirical evidence indicate that thermal runaway (TR) in cells and cell-tocell thermal propagation are due to adverse changes in physical and chemical characteristics internal to the cell. However, industry widely uses battery management systems (BMS) originally designed for aqueous-based batteries to manage Li-ion batteries. Even the “best” BMS that monitor both voltage and outside-surface temperature of each cell are not capable of preventing TR or TR propagation, because voltage and surface-mounted temperature sensors do not track fast-emerging adverse events inside a cell. Most BMS typically include a few thermistors mounted on select cells to monitor their surface temperature. Technology to track intra-cell changes that are TR precursors is becoming available. Simultaneously, the complex pathways resulting in cell-to-cell TR propagation are being successfully modelled and mapped. Innovative solutions to prevent TR and thermal propagation are being advanced. These include modern BMS for rapid monitoring the internal health of each individual cell and physical as well as chemical methods to reduce the deleterious effects of rapid cell-to-cell heat and material transport in case of TR. [ABSTRACT FROM AUTHOR]

The operating temperature of a battery strongly affects overall chemical reactions, ion transport, intercalation and deintercalation process, and consequently, efficiency, cycle life, and degradation of battery systems. Therefore, thermal management for battery systems should be optimally designed to secure a highly efficient and reliable operation of the battery systems, which requires characterization and analysis of heat generated during operation. In this paper, a thermal model that includes irreversible and reversible heat source terms is developed and then incorporated into a reduced-order electrochemical model (ROM). The model is validated against the heat generation rate of a large format pouch type lithium-ion battery measured by a developed calorimeter that enables the measurement of heat generation rate and entropy coefficient. The model is seen to be in good agreement with the measured heat generation rates up to 3C from −30 °C to 45 °C. The analysis includes the effects of C-rates and temperatures on the two heat source terms generated during charging and discharging. [ABSTRACT FROM AUTHOR]

Hole transporting layers (HTLs) play a crucial role in the realization of efficient and stable perovskite solar cells (PSCs). Copper phthalocyanine (CuPc) is a promising HTL owing to its thermal stability and favorable band alignment with the perovskite absorber. However, the power conversion efficiency (PCE) of PSCs with a CuPc HTL is still lagging behind highly efficient solar cells. Herein, a p-type tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) is employed as an interlayer between the perovskite and CuPc HTL in all-vacuum deposited PSCs. The F4-TCNQ interlayer improves the conductivity of both MAPbI3 and CuPc, reduces the shunt pathway and facilitates an efficient photoexcited holes transfer from the valance band of the MAPbI3 to the LUMO of the F4-TCNQ. Consequently, the best solar cell device with an F4-TCNQ interlayer achieved a PCE of 13.03% with a remarkable improvement in fill factor. Moreover, the device showed superior stability against thermal stress at 85 °C over 250 h and retained ∼95% of its initial efficiency. This work demonstrates a significant step towards all-vacuum deposited perovskite solar cells with high thermal stability. [ABSTRACT FROM AUTHOR]

There is no universal and quantifiable standard to compare a given cell model's capability to reject heat. The consequence of this is suboptimal cell designs because cell manufacturers do not have a metric to optimise. The Cell Cooling Coefficient for pouch cell tab cooling (CCCtabs) defines a cell's capability to reject heat from its tabs. However, surface cooling remains the thermal management approach of choice for automotive and other high-power applications. This study introduces a surface Cell Cooling Coefficient, CCCsurf which is shown to be a fundamental property of a lithium-ion cell. CCCsurf is found to be considerably larger than CCCtabs, and this is a trend anticipated for every pouch cell currently commercially available. However, surface cooling induces layer-to-layer nonuniformity which is strongly linked to reduced cell performance and reduced cell lifetime. Thus, the Cell Cooling Coefficient enables quantitative comparison of each cooling method. Further, a method is presented for using the Cell Cooling Coefficients to inform the optimal design of a battery pack thermal management system. In this manner, implementation of the Cell Cooling Coefficient can transform the industry, by minimising the requirement for computationally expensive modelling or time consuming experiments in the early stages of battery-pack design. [ABSTRACT FROM AUTHOR]

With the rapid development of high-power and high-energy density lithium-ion batteries, thermal safety has become a critical issue. Due to the fast microstructure change triggered by heat, thermosensitive polymers have aroused increasing attention as thermal shutdown material candidates to prevent the thermal runaway of lithium-ion batteries. In this work, a sandwich-structured polyacrylonitrile/polyethylene oxide/polyacrylonitrile (PAN/PEO/PAN) fibrous membrane with prompt thermal shutdown properties and high thermal stability is prepared using electrospinning technique. The inner layer of the fusible PEO fibrous membrane impart the composite separator with a prompt thermal shutdown function at 80 °C. Meanwhile, the outer layer of the heat-resistant PAN membrane remains thermally stable, even at 200 °C. The large buffering temperature difference (120 °C) between the thermal shutdown temperature and the thermally stable temperature of the composite separator is wider than most of the reported separators and effectively enhances the thermal safety of the lithium-ion batteries. In addition, the PAN/PEO/PAN separator exhibits a higher porosity, better electrolyte wettability, larger ionic conductivity, and lower interfacial resistance compared with a commercial polypropylene/polyethylene/polypropylene (PP/PE/PP) separator. Moreover, the coin cells assembled by the PAN/PEO/PAN separator presents stable cycle performance and excellent rate capability. Therefore, the novel PAN/PEO/PAN membrane shows great potential as a promising candidate for much safer lithium-ion battery separators. [ABSTRACT FROM AUTHOR]

The electrochemical oxidation of HCl to Cl2 plays an important role in the production of polycarbonates and polyurethanes. Recently, the gas-phase oxidation of HCl proved to be significantly more efficient than the current state-of-the-art process based on the oxidation of hydrochloric acid. In experimental investigations of this gas-phase reactor, a limiting current can be observed that is so far not understood but impedes the overall reactor performance. In the present work, a nonisothermal multiphase agglomerate model is developed to investigate the underlying reasons for this limiting behavior in more detail. It is shown that the thermal management of the cell plays a significant role and that minor changes to its thermal resistance lead to the limiting behavior being caused by either flooding of the cathode or dehydration of the membrane and anode. An optimization of operational and structural parameters of the cell based on these insights leads to an increase in the limiting current by more than 90%. Interestingly, under these conditions a third phenomenon, the rate determining Tafel step in the microkinetic reaction mechanism of the HCl oxidation, limits the overall reactor performance. These insights harbor the potential for enormous energetic savings in this industrially highly relevant process. [ABSTRACT FROM AUTHOR]

Iron trifluoride (FeF3) might be a suitable high-voltage cathode material for high-power thermal batteries due to its high voltage plateau, low cost and low toxicity. In this study, anhydrous FeF3 was synthesized and its applicability as a cathode material for thermal batteries was investigated. Its structure, thermal stability and electrochemical properties were also studied. The synthesized anhydrous FeF3 had a hierarchical structure and a decomposition threshold temperature of 800°C. At a current density of 100 mA cm−2, the Li-B/FeF3 single cell exhibited an initial discharge voltage of 3.20 V and a specific capacity of 81.9 mA h g−1 with a cutoff voltage of 2.0 V. Moreover, multi-walled carbon nanotubes (MWCNTs) were used as the conductive agents, leading to an decreasing of the total polarization from 45 mΩ to 10 mΩ. In specific, the Li-B/ FeF3-MWCNTs single cell exhibited an initial discharge voltage of 3.27 V and a specific capacity of 160.7 mAh·g−1. This work provides a beginning for further applying FeF3 as a high-voltage cathode material for high-power thermal batteries. [ABSTRACT FROM AUTHOR]

Thermal batteries are an established primary battery technology and the most commonly used cathodes in these batteries are transition metal disulfides MS2 (whereM= Co, Ni and Fe). However, understanding the evolution of crystalline phases upon battery discharge has been hindered due to the high temperature operation of these batteries. Here we report an experiment that simultaneously collects powder neutron diffraction and electrochemical data as the battery is discharged. Four regions are observed in the diffraction data and four different cobalt containing phases are observed. Multi-phase Rietveld refinement has been used to monitor the evolution of phases during discharge and this is linked to the battery discharge profile. A new discharge mechanism has been proposed which involves hexagonal CoS instead of Co3S4, and the increase in unit cell parameters on discharge suggests the formation of a sulfur deficient solid solution before transformation to Co9S8. This behavior seems reminiscent of that of NiS2 suggesting that the discharge mechanisms of transition metal disulfides may have more similarities than originally thought. [ABSTRACT FROM AUTHOR]

Thermal runaway of Li-ion batteries is a major safety issue. It is a complex process involving high heat generation, fast temperature rise and significant amounts of generated gas. Modeling thermal runaway will enable a better understanding and earlier detection of the phenomenon. Since the majority of the thermal runaway incidents are triggered by an internal short circuit, this paper presents a model describing lithium-ion battery thermal runaway triggered by an internal short. In this study, two internal short circuit experiments were conducted on two nickel manganese cobalt oxide pouch cells, one that was fully charged and one half charged. The fully charged cell went into a quick thermal runaway, while the half-charged cell evolved only into a slow, self-discharge process. Both of these experiments demonstrate that a huge battery swelling force signal can be detected prior to the surface temperature rise during an internal short circuit event. This thermal runaway model is the first attempt to connect gas generation with force signal, and successfully capture the early stages of thermal runaway, including the early rise of force signal, after parameter tuning. This model's use of force measurement enables higher confidence in the early detection of thermal runaway induced by an internal short. [ABSTRACT FROM AUTHOR]

Lithium-ion battery development is conventionally driven by energy and power density targets, yet the performance of a lithium-ion battery pack is often restricted by its heat rejection capabilities. It is therefore common to observe elevated cell temperatures and large internal thermal gradients which, given that impedance is a function of temperature, induce large current inhomogeneities and accelerate cell-level degradation. Battery thermal performance must be better quantified to resolve this limitation, but anisotropic thermal conductivity and uneven internal heat generation rates render conventional heat rejection measures, such as the Biot number, unsuitable. The Cell Cooling Coefficient (CCC) is introduced as a new metric which quantifies the rate of heat rejection. The CCC (units W.K-1) is constant for a given cell and thermal management method and is therefore ideal for comparing the thermal performance of different cell designs and form factors. By enhancing knowledge of pack-wide heat rejection, uptake of the CCC will also reduce the risk of thermal runaway. The CCC is presented as an essential tool to inform the cell down-selection process in the initial design phases, based solely on their thermal bottlenecks. This simple methodology has the potential to revolutionise the lithium-ion battery industry. [ABSTRACT FROM AUTHOR]

Heavy duty Li-ion batteries in the electric vehicles suffer from serious safety issues due to their operation in abuse conditions. The worst consequence of these conditions is the thermal runaway, which causes a dramatic rise in temperature and pressure leading to a catastrophic failure of the battery. Therefore, precise determination of thermal runaway behavior of the battery under different abusive scenarios holds critical importance. This paper reviews the understanding of the thermal runaway behavior of Li-ion batteries through experimental routes. The impact of initial conditions (SoC, overcharge and ageing) and design (geometry, material and capacity) of the battery on the severity of thermal runaway is extensively discussed. It is observed that the thermal runaway becomes more severe in high SoC, overcharged and aged batteries, and the mechanism of thermal runaway primarily depends on the battery design. The quantification of the fire-induced hazards is presented in terms of the heat release rate. Further, we observe that the electrical and mechanical abuse conditions induce an internal short circuit in the battery due to a component collapse. We also briefly review the prevention techniques of thermal runaway which include detection modelling, heat dissipation strategies and the use of the non-flammable electrolytes. [ABSTRACT FROM AUTHOR]

An experimental study of the module-to-module thermal runaway (TR) propagation in a multi-modular battery pack is presented here. During the experiment a cell in one of the modules is triggered by heating to study both cell-to-cell and module-to-module propagation. In order to understand the mechanism and gain insight into the thermal hazards of a battery pack system, the thermal characteristics of the cells in different modules are analyzed in detail. Although the TR-propagations are all triggered from the side next to the heater, the results indicate that the thermal characteristics of the modules vary in different phases. The upward direction of burning flame and heat flow highlight the importance of design considerations in a multi-modular battery pack. [ABSTRACT FROM AUTHOR]

In this paper, the pristine and hydrofluoric acid (HF) modified MgO porous fibers are investigated as an immobilizing agent for LiF-LiCl-LiBr molten salt electrolytes. The electrochemical performance of as prepared thermal batteries is evaluated. Compared to pristine MgO porous fibers, significantly reduced electrolyte leakages and the highest ionic conductivity (1.427 S · cm-1) of the electrolyte are obtained when the MgO porous fiber is modified by using 40 mol% (of the MgO fiber) HF solution. Accordingly, the discharge capacity of 456 mAh· g-1 at 1.0 V voltage plateau is obtained. At the same time, the influence of HF modification on the ion transportation is discussed, based on element diffusion and properties of newly formed MgF2. It can be concluded that HF modification is a promising method to improve the performance of MgO porous fibers used as an immobilizing agent for the molten salt electrolyte in thermal batteries. [ABSTRACT FROM AUTHOR]

In this work ZrS3 has been synthesized by solid state reaction in a sealed quartz tube and investigated as a candidate cathode material in Li thermal batteries. The structure of ZrS3 before and after cell testing has been studied using powder X-ray diffraction. A new spinel related material, LiZr2S4, has been identified as the product of the electrochemical process, which can be indexed to a = 10.452(8) Å cubic unit cell. The electrochemical properties of the batteries were investigated at 500°C against Li13Si4 by galvanostatic discharge and galvanostatic intermittent titration technique (GITT). In a thermal Li cell at 500°C a single voltage plateau of 1.70 V at a current density of 11 mA/cm² was achieved with capacity of 357 mA h g-1. Therefore ZrS3 material has some promise as a cathode for Li thermal batteries. [ABSTRACT FROM AUTHOR]

Electrical conductivity is key to the performance of thermal battery cathodes. In this work we present the effects of manufacturing and processing conditions on the electrical conductivity of Li/FeS2 thermal battery cathodes. We use finite element simulations to compute the conductivity of three-dimensional microcomputed tomography cathode microstructures and compare results to experimental impedance spectroscopy measurements. A regression analysis reveals a predictive relationship between composition, processing conditions, and electrical conductivity; a trend which is largely erased after thermally-induced deformation. The trend applies to both experimental and simulation results, although is not as apparent in simulations. This research is a step toward a more fundamental understanding of the effects of processing and composition on thermal battery component microstructure, properties, and performance. [ABSTRACT FROM AUTHOR]

We present the application of our thermal battery system-level simulator [J. Electrochem Soc., 156, A442 (2009)] in novel multiple-cell thermal analyses. Several model batteries are chosen to demonstrate the simulator's versatility and robustness in developing advanced thermal battery designs. The heat transfer phase-change model and supporting mass balance are modified to improve model consistency. Simulation results are presented from several case-studies covering different battery structures and operating conditions, including low and high current densities, different number of electro-active cells, various internal and external battery geometrical details, the use of salt buffers, external flanges, and inhomogeneous initial conditions in the battery stack. These results show the simulator to be a highly user-friendly and powerful tool for development of complex thermal batteries. Investigation of heat of reactions and joule heating effects unfold insights regarding dominant processes in multiple-cell batteries. Furthermore, these detailed analyses emphasize the need to track solidification dynamics at the sub-cell level and, at the same time, show that thermal battery design should include a significant ingredient of multiple-cell analysis. Altogether, this study presents a first-in-its-kind portable simulator with great flexibility and a capability for supporting the analysis and development of most thermal battery structures and designs. [ABSTRACT FROM AUTHOR]

We present a complete and detailed thermal simulator designed for the computational analysis of thermal batteries from the level of a single cell up to that of the entire system. Our simulator is based on a comprehensive transient and two-dimensional (axisymmetric) mathematical heat-transfer model, with significant flexibility in the geometrical modeling and the materials used. The model accounts for different aspects of heat transfer, including conduction, joule heating, h]eat of reactions, and latent heat of fusion associated with, electrolyte phase change (salt solidification). It is supported by a simplified mass balance involving the current drawn from the battery and accounting for the mass-transfer resistance of each of the cell's components. Results presented include model verification-and-validation calculations as well as single-cell thermal battery simulations performed under realistic operating conditions. The latter reveal the significance of the phase-change process to heat transfer and thus to the prediction of its operation time. Solidification dynamics are found to be different in each of the cell's components, emphasizing the necessity of accounting for details at the subcell level. Additional results uncover the effect of heat of reactions as well as joule heating on single-cell battery thermal behavior. [ABSTRACT FROM AUTHOR]

In this paper, we present a theoretical simulation of 87Rb absorption spectrum in a thermal cm-cell which is adaptive to the experimental observation. In experiment, the coupling and probe beams are configured to copropagate but perpendicular polarized, making up to five velocity selective optical pumping (VSOP) absorption dips able to be identified. A Λ-type electromagnetically induced transparency (EIT) is also observed for each group of velocity-selected atoms. The spectrum by only sweeping the probe beam can be decomposed into a combination of Doppler-broadened background and three VSOP dips for each group of velocity-selected atoms, accompanied by an EIT peak. This proposed theoretical model can be used to simulate the spectrum adaptive to the experimental observation by the non-linear least-square fit method. The fit for the high quality of experimental observation can determine valuable transition parameters such as decaying rates and coupling beam power accurately. [ABSTRACT FROM AUTHOR]

The article offers information on several electrochemical studies. Topics discussed include the use of porous magnesia fibers as immobilizing agent and enhancing the immobilizing effect in thermal batteries, the advancements on the use and application of scanning electrochemical microscopy, and the use of low frequency radio waves to detect electrically active defects in three-dimensional integrated circuits.