A Study on the Lithium-Ion Battery Fire Prevention Diagnostic Technique Based on Time-Resolved Partial Discharge Algorithm

A critical review of lithium-ion battery safety testing and standards

The lithium-ion battery (LIB) is widely used as an energy storage device for electric vehicles (EV) due to its advantages, such as high energy density and long lifespan. However, LIB for EV can be exposed to mechanical abuse such as vehicle collision, which causes thermal runaway due to extreme mechanical deformation. Therefore, it is necessary to predict the internal short circuit (ISC) of the LIB cell under mechanical loading conditions and to analyze the mechanical, electrical, and thermal responses after ISC. In this paper, the starting point of ISC is predicted using a two-way mechanical-electrical-thermal coupled analysis method. At the same time, mechanical responses, along with the effects of the ISC area on electrical and thermal responses of the LIB cell, were analyzed. ISC was defined as failure of the separator. The separator’s failure was calculated considering material nonlinearity. Considering the indentation test results, the finite element method (FEM) analysis could accurately predict the starting point of ISC. In the order of cylindrical, hemispherical, and conical indenters, ISC occurred quickly, and the ISC area was large. The larger the ISC area, the greater the voltage drop, current, and joule heat, and the higher the maximum temperature.

Electric vehicles (EVs) are becoming more popular due to concerns about fuel shortages and environmental pollution. Lithium-ion batteries are the preferred power source for EVs because they have high energy and power densities. Ensuring the efficient, safe, and reliable operation of these batteries has been a significant focus of research in recent decades. One major concern that can affect Li-ion battery performance is thermal runaway, which can cause dangerous battery fires. Internal short circuits (ISCs) are believed to be the root cause of thermal runaway incidents in batteries, making early detection of spontaneous ISCs a critical diagnostic task. This study presents a new and simple early ISC detection method for a Li-ion cell based on the augmentation of the state space of an Extended Kalman Filter (EKF) that includes voltage and surface temperature observations. The framework allows for an estimation of the cell's internal ISC state while remaining computationally efficient. The proposed approach is demonstrated in a simulated environment using dynamic stress tests that reflect a practical battery working cycle. The results demonstrate that the method can promptly detect ISC occurrences.

Safety of Li batteries is a major concern for many applications. One of major safety concerns is thermal runaway due internal short circuits created because of dormant internal defects. New processes, designs, and materials are being investigated to improve safety of batteries, particularly to prevent thermal runaway due to internal short circuits (ISC). The challenge is how to evaluate these improvements as existing methods using external triggers, such as nail or blunt rod penetration, crush, and heating, are widely known to be deficient. In response to this challenge, we have developed a very thin and small “thermal switch” to be implanted in a Li-ion cell for triggering ISC on demand to see if the cell goes to thermal runaway. This “thermal switch” or “ISC emulator device” consists of very thin layers of copper, wax, aluminum, and separator that are all compatible with the Li-Ion chemistries. The ISC device is inactive when is placed anywhere in a cell during its fabrication; the cell could be cycles many times without any performance issues. ISC device is activated by applying heat to raise the temperature of the thermal switch to tunable 45°C-60°C to melt the thin layer of wax and create a current path between positive and negative electrode and or current collectors. The ISC device can create any of 4 types of internal short circuit: +ve current collector to –ve current collector, anode active to +ve current collector, cathode active to –ve current collector, and anode active to cathode active. The ISC device can work in any li-ion cell format (cylindrical can and prismatic pouch/can). With support from DOE’s Vehicle Technologies Office, we have demonstrated that more than ISC devices are triggered in a cell creating ISC. In laboratory testing, the activated device can handle currents in excess of 300 A to simulate hard shorts (< 2 mohms). Phase change melting has been 100% successful during trigger tests to go from non-conducting to conducting. Experiments have shown that the creating ISC in cells can lead to thermal runaway depending on the type of internal short circuit is created, the safety measures in the cell, and the chemistry. We have provided more than 300 ISC devices to several cylindrical and pouch cell manufacture to implant them into their cell for evaluation of their safety supplying them to their clients for evaluation. The ISC device has been able to initiate thermal runaway in portion of the cells tested. In this paper, we provide details of the ISC device and the results of triggering the device. We believe that the ISC device a useful research tool for evaluating the safety of lithium ion batteries in response to inherent internal defects. Figure 1

Lithium ion batteries (LIBs) are the mostly used energy storage systems because of their high energy density and excellent cycle life. Recently, as the more expanding application fields of LIBs from portable devices to electric vehicle (EV) and energy storage system (ESS), the demands for better LIBs increase. Energy density is one of the most important required performances of batteries. A high energy density in batteries can be achieved by increasing the capacity of the electrodes or by increasing the working potential of the cathode materials. In the field of field of anode materials, research is underway to increase capacity, because the capacity of graphite widely used as anode in commercial LIBs is limited (~372mAh/g). Transition metal oxides such as CoO, Co3O4, NiO, FeO and Fe2O3 have attracted great attention due to their high theoretical capacity (700~1500 mAh/g) based on the conversion reaction mechanism. Mn-based oxides are the promising anode materials for lithium ion battery due to low cost, lower operating voltage compared to the Co, Ni, Fe and Cu based oxides and their high theoretical capacity (MnO : 756 mAh/g, Mn3O4 : 934 mAh/g, Mn2O3 : 1018 mAh/g, MnO2 : 1232 mAh/g). Many groups reported that nanostructured manganese oxides show higher capacity than theoretical capacity based on the conversion reaction mechanism. However, their exact reaction mechanisms are not yet clear and information about the reaction mechanism of MnO2 is more insufficient compared to other manganese oxide materials, MnO, Mn3O4 and Mn2O3 because they have focused on the synthesis method of materials to improve their electrochemical performances. Chen et al. reported that electron energy loss spectra (EELS) and selected area electron diffraction (SAED) results propose that MnO2 is only partially reduced to LiMn3O4, instead of being reduced to Mn [1]. Furthermore, Fang et al. reported that the LixMnO2 (X=0.96) and Li2MnO2 are observed by ex situ X-ray diffraction (XRD) but MnO is not observed until Li2MnO2 is fully reduced to metallic Mn and Li2O at 0V. From high resolution transmission electron microscopy (HRTEM), Mn is one of the end products of discharge to 0V, while MnO is the end product of recharge for MnO2 at 3.0V [2]. Recently, by cyclic voltammetry, MnO2 is reduced to Mn via MnO intermediate and the oxidation of Mn0 to Mn2+ and Mn2+ to Mn4+ occur during charge [3,4]. But cyclic voltammetry cannot provide obvious evidence of phase formation. In our report, to propose the detailed reaction mechanism of MnO2, we synthesize ordered mesoporous MnO2 and use synchrotron-based X-ray techniques, high resolution transmission electron microscopy (HRTEM) and electrochemical techniques. Our new proposed reaction mechanism suggest experimentally that, for the first time, the formation of the MnO intermediate during 1st discharge and the further oxidation of Mn2+ to higher oxidation state during charge are involved in the reaction mechanism of MnO2. Therefore, we provide a better understanding of the reaction mechanism of MnO2 anode for Li ion batteries. More details will be discussed in the meeting. Reference s : [1] C. Chen, N. Ding, L. Wang, Y. Yu, I. Lieberwirth, Journal of Power Sources. 189 (2009) 552–556 [2] X. Fang, X. Lu, X. Guo, Y. Mao, Y.-S. Hu, J. Wang, Z. Wang, F. Wu, H. Liu, L. Chen, Electrochemistry Communications. 12 (2010) 1520-1523 [3] M. Kundu, C.C. Albert Ng, D.Y. Petrovykh, L. Liu, Chem. Commun. 49 (2013) 8459-8461 [4] J. Chen, Y. Wang, X. He, S. Xu, M. Fang, X. Zhao, Y. Shang, Electrochimica Acta. 142 (2014) 152-156

A hybrid electrical energy storage system (EESS) consisting of supercapacitor (SC) in combination with lithium-ion (Li-ion) battery has been studied through theoretical simulation and experiments to address thermal runaway in an electric vehicle. In theoretical simulation, the working temperature of Li-ion battery and SC has been varied from 0 to 75 °C in steps of 25 °C and the effect of the variation is observed on the output current, voltage and power of Li-ion battery and SC for a calculated load using the standard driving cycle. Further, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) have been performed to investigate the effect of temperature on SC. EIS measurements of SC indicate a low equivalent series resistance of 0.095 Ω at 25 °C. CV measurements indicate a high value of capacitance of 56.65 F/g at 25 °C for a scan rate of 5 mV s−1. Through theoretical simulation of EESS, a temperature increase ( $$ \Delta T $$ ) of 0.41 °C is calculated considering an initial peak of 10-s duration for the case of EESS without SC, whereas the use of SC reduces $$ \Delta T $$ to 0.025 °C. Further, optimal size calculation for hybrid EESS is done to achieve the least cost, wherein Li-ion battery capacity has been varied from 0 to 200 Ah and the SC capacity has been varied from 0 to 5 F in MATLAB simulation. The optimal combination is obtained as 30 Ah capacity of Li-ion battery and 3 F capacity of SC by connecting load across hybrid EESS for a duration of 3600 s.

Safe, powerful and reliable lithium batteries are required for an extensive market penetration of electric vehicles and stationary energy storage systems. In operation, lithium batteries are continuously generating and dissipating heat. Therefore, an appropriate thermal management is necessary to provide best electrochemical cycling conditions and avoid battery performance losses and thermal runaway. The rational design of thermal management systems should be based on quantitative information for thermal behavior, heat generation and dissipation of batteries in operation. Both regular and irregular battery use as well as accidents have to be realistically simulated by experiments in the laboratory. Calorimetry and thermography are excellent analysis tools to provide data for batteries applied in different operation modes under various environmental conditions. Simultaneously, (hazardous) reactions of battery materials and correlated pressure changes can be analyzed. The thermal runaway with inflammation and even explosion of a Li-ion cell in a larger battery pack is the worst case scenario which must be avoided in commercial applications under all circumstances. In order to get more insight into the character of exothermic reactions, that trigger the thermal runaway, combined experimental and computer simulation approaches were used. Accelerating Rate Calorimeters (ARC) are perfect tools for in-operando investigations of the cells during electrochemical cycling under isoperibolic and adiabatic conditions and for so-called heat-wait-seek tests. Heating under adiabatic conditions will eventually either stop the cell from cycling or lead to thermal runaway depending on the cycling parameters

Benefiting from the merits of high energy density, wide operating voltage, and rapid ion transport dynamics, lithium-ion batteries (LIBs) have become increasingly widespread in electric vehicles, energy storage, and electronic products. However, the thermal runaway initiated by the internal short circuit (ISC) of the battery causes a serious safety issue. In this work, high-safety LIBs with high-temperature self-interrupting effect are fabricated by employing TiNi-based shape memory alloy (TN-SMA) with shape memory effect (SME) as the current collector to delay thermal runaway. When ISC occurs, the shape recovery of TN-SMA creates a physical gap between cathodes and anodes inside the battery at the initiation of thermal runaway, which effectively blocks the migration of electrons and ions and avoids the catastrophic thermal runaway of the battery. Meanwhile, after nail penetration testing, the pouch cell with TN-SMA as the current collector still maintained a relatively intact appearance and no high-temperature scorching was observed on the aluminum-plastic film of the pouch cell, confirming the strong efficacy in preventing thermal runaway and markedly improving the overall safety of the battery. Finally, through the rational selection of TN-SMA, the as-obtained LIBs show excellent electrochemical performance and high safety. Hence, the TN-SMA as the current collector shows a promising application prospect in high-safety LIBs.

Thermal Runaway is one of the major safety risks in lithium ion batteries. One of the prime reasons for thermal runaway are Internal Short Circuits (ISCs). The ISC phenomenon is very fast and the battery discharges in a matter of seconds, resulting in an explosion which can propagate to other cells, resulting in additional thermal runaway. Hence it is important to understand which sensors can give earliest warning (integrated with voltage measurement) to give a higher confidence level of detecting the imminent evolution of the thermal runaway due to the ISC. Leveraging prior work in [1] where battery swelling was used to improve SOC estimation, we consider the benefits of force measurement along with temperature measurement for detecting the onset of thermal runaway. As it is shown in Figure 1, the measured force increases at the same instance when there is a voltage drop due to the short. The measured force changed earlier than the installed RTD (resistance thermometer) or thermocouple. The mechanical measurement, therefore, can be used in conjunction with electric measurements to generate a robust detection of internal shorts. A 4.5 Ah NCM - Graphite pouch cell with a built-in ISC device was fabricated for the experiment at the University of Michigan Battery Lab. The ISC device used is similar to the one developed by NREL [2]. During the battery fabrication, a hole is cut in the separator, which is then covered by a Phase Change Material (PCM) trigger. The PCM melts when the temperature reaches its melting point at 55oC, thus creating a gap in the separator, allowing the electrodes to contact and triggering the ISC. This pouch cell was inserted in a cell holder shown in Figure 2. A RTD strip with six sensing elements [3] was placed on the cell. A thermocouple was placed between the current collecting tabs (at the position where the venting will occur). There are four load cells (which measure force) attached to the four corners of the cell holder. The instrumented cell fixture was heated in an Accelerating Rate Calorimeter until the ISC is triggered. The temperatures, terminal voltage and load cells were all sampled at 80 Hz during the experiment. The chronology of events shown in Fig.2 suggests that the ISC leads to local heating and gas generation, which results in battery swelling before the elevated temperature can reach to the surface of the cell. The measured voltage exhibits an initial drop (indicated by t=0 in the graph) but subsequently rises again and continued to fluctuate until reaching zero 6.5s later. The force started rising immediately after the initial voltage drop. Even the thin film RTD located on top of the ISC trigger responded slower than the force, at 0.2s after the initial voltage drop. The accumulated pressure inside the cell then caused the pouch to rupture between the electrical contacts (at the weakest part of the pouch cell). The ultimate burst pressure exceeded the measurement range of the sensor, but the timing of the event was observed by the rapid depressurization at 0.55 s. Finally, the thermocouple temperature increased at 0.60s, most likely due to hot gases venting out over the thermocouple placed between the tabs. An ISC event and the eventual rupture can be detected using measured force earlier than using temperature sensors on the surface of the battery. The actual implementation of the mechanical measurement can be achieved with load sensors in the end plates of a battery module [1], or with strain sensors embedded in the module [3].

Global demand for lithium-ion secondary batteries have been increasing due to new market growth from electric vehicles and power storage systems. Lithium-ion batteries possess high power density, energy density and long cycle life without memory effect and little self-discharge, and have been primary energy storage system for commercial electronics. However, recent accidents regarding battery safety, such as Samsung Note 7 issue, has raised doubt among public about lithium-ion batteries as option for energy storage. Separator is one of the primary component for lithium-ion battery safety. Commercial separators like PE or PP not only possess outstanding mechanical and electrochemical performance, but also have thermal shutdown function that provide safety measure by pore—blocking with melted polyolefin materials. Nevertheless, polyolefin materials suffered serious shrinkage at elevated temperature, which cause internal short-circuited of batteries ; also, polyolefin materials have relatively low electrolyte uptake, and could be major obstacle for future lithium-ion battery application. Hence it’s necessary to design new type of separator that guarantee battery safety and demonstrate better electrochemical performance In this study, we proposed a brand-new method to design composite separator with high thermal stability, electrolyte uptake ability and thermal shutdown function. Polyimide(PI) nanofiber film was used as substrate and produced by electrospinning technique, and ultra-thin Low-Density-Polyethylene(LDPE) layer was laid upon PI by simple spin-coating method. Spin-coating method provided unique advantages such as ultra thin coating layer (less than 1 micron), uniform coating structure and simple process, and was yet been applied for construction of composite film as lithium-ion battery separator. Coating parameter was tuned to obtain the optimized composite separator. Field-emission scanning electron microscope (FE-SEM) was used to investigate morphologies of separators ; Contact angle measurement was conducted to verify electrolyte affinity of different separators ; A.C. impedance method was used to measure conductivities and verify thermal shutdown of separators, and electrolyte uptake of different separators were measured by electrolyte soaking method in an argon-filled glovebox. The composite film had sub-micron average pore size, and possessed excellent physical properties, for instance, high porosity(73%), electrolyte uptake(1300%), ion conductivity(4.3*10-4 S/cm), air permeability(gurley value=0), and thermal stability(no shrink up to 150。C). Thermal shutdown function of composite film was also confirmed by impedance measurement at elevated temperature. It was noticed that physical properties between pristine PI and composite film were similar owning to ultra-thin coating layer, which mitigate performance loss from LDPE coating. Afterward, full cell battery tests were conducted with CR2032 type coin cell (Cathode : LFP, anode : MCMB, electrolyte : 1 M LiPF6 in EC/EMC/DMC=1:1:1+1%VC, 1C=2.4mAh/g). The first cycle charge-discharge curves, rate capability and cyclic performance were conducted. The composite film showed flatter first cycle charge-discharge plateau, better capacity retention at higher C-rate (Composite film :102 mAh/g at 1C, 79% retention, Celgard 2500 : 73 mAh/g, 51% retention , w.r.t. 0.1C), and higher discharge capacity at 0.5C 50th cyclic test. The higher porosity and electrolyte uptake of composite film facilitated ion conduction and were the main cause for enhanced battery performance. With enhanced thermal stability and electrochemical performance, we expected this type of composite separator to be promising for future lithium-ion battery application. Figure 1

Two-way nonlinear mechanical-electrochemical-thermal coupled analysis method to predict thermal runaway of lithium-ion battery cells caused by quasi-static indentation

<p indent="0mm">In order to deal with the increasingly severe global energy crisis as well as serious environmental pollution, it is urgent to develop new energy resources. Although lithium-ion batteries have only been successfully introduced into the market since 1990s, there is still an exponentially growing demand for lithium-ion batteries all over the world. As a considerable novel energy source, lithium-ion batteries have significant potential, which is widely used in electric vehicles, energy-storage systems, metallurgy, ceramic production, glass manufacturing and aviation fuel industries. Among them, the solid-state lithium-ion batteries (SSLIBs) represent a promising evolution in battery technology, offering superior safety, energy density, and longevity compared to conventional liquid electrolyte batteries. Traditional lithium-ion batteries, which use liquid electrolytes, suffer from safety issues such as leakage, flammability and thermal runaway. SSLIBs replace these liquid electrolytes with solid electrolytes, mitigating these risks and enabling higher energy densities due to the ability to accommodate lithium metal anodes. The SSLIB consists of a positive electrode, a negative electrode and a solid electrolyte. Compared with liquid electrolytes, solid electrolytes avoid the direct contact between positive electrodes and negative electrodes, fundamentally eliminating the risk of lithium dendrites piercing the separator, so as to enhance the safety of lithium batteries greatly. Furthermore, the SSLIBs are expected to be a hot spot in future lithium battery research due to the advantages of high energy density, wide operating voltage range and long cycle life. Advancements in SSLIBs technology are crucial for the next generation of electric vehicles, portable electronics, and large-scale energy storage systems, pushing the boundaries of battery performance, safety and sustainability. Solid electrolytes are regarded as the key component of SSLIBs, serving dual functions as both separators and electrolytes. The currently developed solid electrolytes can be divided into two categories: Polymer solid electrolytes and inorganic solid electrolytes, in which the oxide solid electrolytes, as the earliest developed inorganic solid electrolytes, play an indispensable role in the development of solid-state battery industry. The typical oxide solid electrolytes, including sodium super ionic conductor (NASICON), garnet (LLZO), inorganic perovskite (LLTO), and LiPON films, are reviewed in this paper. NASICON, for example, is known for its high ionic conductivity and structural stability. Garnet-type electrolytes, such as LLZO, possess high ionic conductivity and chemical stability with lithium. Inorganic perovskite (LLTO) provides a good balance between ionic conductivity and mechanical strength. LiPON films, widely used in thin-film batteries, have excellent electrochemical stability and compatibility with lithium metal. In addition, the crystal structures and ion-transport mechanism, the solutions to improve conductivity and measures to improve the compatibility between electrodes and electrolytes are introduced, along with a comparation of oxide solid electrolytes. Finally, several suggestions for future development directions are proposed. These include enhancing the ionic conductivity of solid electrolytes, improving the interface compatibility between the electrolytes and electrodes, and developing cost-effective and scalable manufacturing processes. Additionally, further research is needed to understand the degradation mechanisms and long-term stability of solid-state batteries. These recommendations aim to provide a more comprehensive reference for ongoing and future research on oxide solid electrolytes, supporting the broader goal of advancing solid-state lithium battery technology.

Lithium-ion batteries, containing flammable electrolytes, have become safer in many ways since their invention. As the technology matures, energy and power densities increase: the European Council for Automotive R&D set 2030 (cell level) targets for battery electric vehicle energy density of 1000 Wh L-1, with 450 Wh kg-1 specific energy and 1800 W kg-1 peak specific power. This rise in energy and power densities increases the risk of accidental release of energy from the batteries and thermal runaway (TR). Safety is thus a key concern when designing a lithium-ion battery system for electric vehicles (EV).TR relates to fast heating of a battery cell caused by exothermic chemical decomposition reactions of the materials inside the cells. It develops in a cell when heat is generated and cannot be dissipated quickly enough to the surroundings, giving rise to an abrupt (exponential) temperature increase and subsequent reaction rate increase. During TR, various exothermic side reactions can occur, leading to temperature increase, accompanied by pressure increase as electrolyte evaporates and venting. This can result in the emission of highly flammable gas and the formation of toxic atmosphere, as well as, in fire and, in very rare circumstances, in explosion. The corresponding temperature increase in adjacent cells (or modules) might then be sufficient to cause them to also go into TR – leading to a process known as thermal runaway propagation (TRP).Fit-for purpose testing procedures to assess the risks associated with TRP are therefore of utmost importance and the focus should always be the safety of the EV occupants, bystanders, first responders and property. Some tests in current standards and regulations try to simulate internally driven failures (e.g. internal short circuit), but whether these tests are suitable to represent field failures remains an open question.This work will give an insight into two selected TR initiation methods assessed within JRC’s TR initiation and propagation test campaigns, namely (a) localised rapid external heating, as developed and patented internationally by NRC (National Research Council Canada) and (b) ceramic nail penetration, as described in the IEC TR 62660-4 standard. It examines the response of short-stacks of pouch cells extracted from automotive batteries after TR is triggered in a single cell. Experimental data and analysis to better understand how TR propagates and the potential for TRP inhibition will be reported. The potential of inhibiting TRP is explored on 2- and 5-cell assemblies with a multi-layer, porous, composite insulation material between cells. Separating the cells can delay significantly TRP in adjacent cells in modules constructed with pouch cells, whereas TRP may be slowed and even inhibited as the thickness of the multilayer material varies.

Lithium-ion batteries are widely used in electric vehicles and energy storage systems. Sudden fire accident is one of the most serious issue, which is mainly caused by unpredicted internal short circuit. Metal particle defect is a key factor in internal short circuit it will not show an obvious abnormal change in battery external characteristic just like mechanical and thermal abuse. So, a non-destructive testing of battery internal metal defect is very necessary. This study is first time to scan and analyze different types of defects inside a battery by using ultrasonic technology, and it shows the detection capability boundary of this methodology. A non-contact ultrasonic scanning system with multi-channel was built to scan the battery sample with aluminum foil, copper foil and copper powder defects. The position and shape of those defects were clearly shown by using tomography methodology. It was found that the acoustic properties difference between metal defects and battery active materials has a strong influence on detection sensitivity. Compared with aluminum foil, copper foil and copper powder are easier to be detected and change the ultrasonic signal greatly, they will produce an obvious shadowing artifacts and speed displacement phenomena in tomography images. Ultrasonic tomography technology is an effective method for non-destructive testing of lithium-ion batteries.

Surface Stabilization of O3-type Layered Oxide Cathode to Protect the Anode of Sodium Ion Batteries for Superior Lifespan.