Internal Short Circuit Research Articles

Quantification of Lithium Battery Fires in Internal Short Circuit

Quantification of Lithium Battery Fires in Internal Short Circuit

Early Internal Short Circuit Diagnosis for Lithium-Ion Battery Packs Based on Dynamic Time Warping of Incremental Capacity

Timely identification of early internal short circuit faults, commonly referred to as micro short circuits (MSCs), is essential yet poses significant challenges for the safe and reliable operation of lithium-ion battery (LIB) energy storage systems. This paper introduces an innovative diagnostic method for early internal short circuits in LIB packs, utilizing dynamic time warping (DTW) applied to incremental capacity (IC). Initially, the terminal voltages of all cells within the LIB pack are ordered at any moment to determine the median terminal voltage, which is then used to generate the median IC curve. This curve acts as a reference benchmark that represents the condition of healthy cells in the pack. Subsequently, the DTW algorithm is utilized to measure the similarity between each cell’s IC curve and the median IC curve. Cells exhibiting similarity scores that exceed a specified threshold are identified as having MSC faults. Lastly, for the cells diagnosed with MSC conditions, a method for estimating short-circuit resistance (SR) based on variations in maximum charging voltage is devised to quantitatively evaluate the severity and evolution of the MSC. Experimental findings reveal that the proposed method effectively identifies MSC cells in the LIB pack and estimates their SRs without the necessity of a battery model, thereby affirming the method’s validity.

Impact of external heating and state of charge on discharge performance and thermal runaway risk in 21700 Li-ion batteries

This study investigates the combined effects of external heating and State of Charge (SOC) on the discharge performance and thermal runaway risk of 21700 Li-ion batteries. Experiments subject commercially available 21700 cylindrical cells to various external heating conditions at different SOC levels (20, 40, 60, 80, and 100 %) while measuring discharge performance and thermal behavior at different discharge rates (0.2, 0.5, 1, and 1.5C). The study emphasizes the significance of Li-ions' spatial arrangement and maintaining electrical charge in the electrolyte to evaluate battery performance. Numerical simulations are then conducted to complement the experimental data and provide deeper insights. The results reveal a significant degradation in discharge performance with increasing external heat, characterized by voltage drops and reduced capacity. Cells with higher SOC levels exhibit more severe exothermic reactions during external heating, leading to a higher likelihood of thermal runaway. Cells operated at a moderate SOC of 40 % demonstrate a significantly lower risk of thermal runaway under similar heating conditions. The rapid rise in temperature at 100 % SOC of batteries showed a sharp increase of over 20 °C per second. Temperature spikes were noted at specific time intervals corresponding to different SOC levels: 100, 80, 60, 40, and 20. At this critical point, temperatures ranged from 135 to 182 °C, indicating potential thermal issues from internal short circuits causing separator melting. These findings highlight the critical role of SOC management in ensuring the safe and reliable operation of 21700 Li-ion batteries, particularly in applications involving elevated temperatures.

Enhancing multi-type fault diagnosis in lithium-ion battery systems: Vision transformer-based transfer learning approach

Ensuring the accurate diagnosis of internal short circuit (ISC) faults and consistency anomalies is crucial for maintaining the high safety and longevity of battery systems. The challenge lies in the high similarity between the features of ISC faults and consistency anomalies, which can complicate accurate fault diagnosis. This study introduces a multi-fault diagnostic model that leverages the Vision Transformer (ViT) and employs simulated data to accurately pinpoint ISC faults and intricate consistency anomalies, such as capacity and state of charge anomalies, achieving an impressive accuracy rate of up to 100 %. The process begins with an in-depth analysis of fault mechanisms to extract and differentiate multi-fault features using a mean difference model. Subsequently, the ViT's exceptional ability to capture temporal information, which aids in the accurate identification of fault features. The integration of transfer learning with experimental data further refines the real-world diagnosis accuracy. The results confirm the robustness of the proposed method, highlighting its potential to substantially mitigate safety hazards in battery systems and enhance operational reliability.

Real-Time Detection of Internal Short Circuits in Lithium-Ion Batteries using an Extend Kalman Filter

Concerns over fuel scarcity and environmental degradation largely drive the increasing popularity of electric vehicles (EVs). Lithium-ion batteries (LIBs), known for their high energy and power densities, are the favored power source for EVs. Over the past few decades, research has been concentrated on ensuring these batteries operate efficiently, safely, and reliably. A key issue impacting the safety of Li-ion batteries is thermal runaway (TR), which can lead to hazardous battery fires. Internal short circuits (ISCs) are often the primary cause of these TR incidents, making the early detection of spontaneous ISC formation a pivotal diagnostic task. This research introduces an innovative ISC detection technique for cylindrical Li-ion battery cells. This technique is based on the augmentation of the model state vector in an extended Kalman filter (EKF), combining both classical voltage measurements to surface temperature observations. This framework enables real-time estimation of the internal ISC state while maintaining computational efficiency. The proposed method is tested numerically considering a high-fidelity numerical plant cycled using charge-depleting tests that mimic a practical battery cell working cycle at various C rates and at different ambient temperatures to account for both load and environmental uncertainties. The results demonstrate the robustness and effectiveness of the method. In addition, the method has been proven to be computationally efficient, demonstrating the feasibility of its real-time implementation.

Study on the Commercial Metalized Plastic Current Collector PET-Cu and PP-Cu Toward High-Energy Lithium-Ion Battery.

Commercial metalized plastic current collector (MPCC) is receiving widespread attention from the business and academic communities, due to its properties of excellent electrical conductivity and low mass density. However, the application of MPCC on the side of copper is rarely studied. Herein, sandwich-like polyethylene terephthalate-based (PET) and polypropylene-based (PP) copper (Cu) current collectors via magnetron sputtering and electroplating are fabricated. Most importantly, the electrical performance, mechanical safety quality, and revealed the corresponding failure mechanism for the MPCC cells are first systematically evaluated. First, during the 45°C electrical cycling tests, PET-Cu CC (82.67%) and PP-Cu CC (82.32%) cells both have comparable capacity retention with the traditional Cu CC (Tra-Cu CC) cell (84.55%) after 500 cycles. The slight reduction in the cycling performance is induced by the crack of the Cu layer around the embedded SiO2 particle for PET-Cu CC cell and the detachment of Cu layer for PP-Cu CC cell. Second, during the nail-penetration test, MPCC cells maintain no fire and explosion for more than 5min, since the heat-shrinkable function of polymeric film can interrupt the continuous Joule heat released by internal short-circuit. This work provides important guidance for the large-scale application of MPCC in the field of lithium-ion batteries.

Lithium p-toluenesulfinate-coated poly(imide) separators for enhanced safety and electrochemical performances of lithium-ion batteries

Increasing the energy density of lithium-ion batteries enhances their applicability; however, ensuring their safety remains a critical issue in the energy society. Herein, we report the development of a lithium p-toluenesulfinate (PTSL)-coated polyimide (PI) separator with improved safety and electrochemical performance during cycling. It is anticipated that integrating PTSL particles into the PI separator will mitigate the risk of internal short circuits by clogging the porous structure of the PI separator and enhance the interfacial stability of the electrode materials. The PTSL is expected to act as an effective component of protective layers, physically separating the cathode from direct contact with electrolytes. The PTSL-embedded PI separator regulated the porous structure inherent to the PI separator, thereby enhancing its physical and thermal properties, such as improved wetting characteristics (evidenced by higher ionic conductivities and lithium-ion transference numbers) and thermal behaviors (reduced shrinkage and more stable thermal decomposition behaviors). During cycling, the cells with the PTSL-coated PI separator demonstrated increased cycling retention compared to the cells with graphite/NCM811 electrodes because the additional PTSL-based protective layers mitigated the electrolyte decomposition upon cycling.

Quantitative Diagnosis of Internal Short Circuit for Lithium-Ion Batteries Using Relaxation Voltage

Quantitative Diagnosis of Internal Short Circuit for Lithium-Ion Batteries Using Relaxation Voltage

Thermal runaway prevention through scalable fabrication of safety reinforced layer in practical Li-ion batteries

Integrating safety features to cut off excessive current during accidental internal short circuits in Li-ion batteries (LIBs) can reduce the risk of thermal runaway. However, making this concept practical requires overcoming challenges in both material development and scalable manufacturing. Here, we demonstrate the roll-to-roll production of a safety reinforced layer (SRL) on current collectors at a rate of 5 km per day. The SRL, made of molecularly engineered polythiophene (PTh) and carbon additives, interrupts current flow during voltage drops or overheating without adversely affecting battery performance. Impact testing on 3.4-Ah pouch cells shows that the SRL reduces battery explosions from 63% to 10%. This work underscores the potential of integrating material science with manufacturing technology to enhance battery safety.

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

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

Tracing Root Causes of Electric Vehicle Fires

As electric vehicles (EVs) emerge as the backbone of modern transportation, the concurrent uptick in battery fire incidents presents a disconcerting challenge. To tackle this issue effectively, it is imperative to pierce beyond the superficial causes of lithium‐ion battery (LIB) failures—such as equipment malfunctions or physical damage—and to excavate the underlying triggers. This nuanced approach is pivotal to refining EV quality, diminishing fire incidents, and bolstering consumer trust. While issues that are readily apparent to consumers, like spontaneous battery degradation, vehicular collisions, or submersion, may seem like the primary culprits, they merely scratch the surface of a more complex problem. The true mechanisms behind these fires involve internal and external short circuits, yet these explanations fall short in providing actionable guidance for manufacturers or end‐users to enhance LIB safety. The heart of the issue is identifying the root causes that bridge failure triggers and resulting fires. A total of 20 root causes are identified, linking them to real‐world scenarios like overcharging causing internal shorts or wire harness issues leading to external shorts. With this insight, stakeholders can more effectively investigate and understand EV LIB fire incidents, bolstering EV safety and reliability, and promoting consumer confidence.

Unveiling Cu Nanoparticles Formed During Li Deposition in Anode-Free Batteries.

Developing high-energy-density Li metal batteries is essential for sustainable progress, necessitating in-depth studies of complex battery reactions. The presence of metallic Cu impurities detrimentally impacts battery performance, leading to issues such as self-discharging and internal soft short-circuit. Nevertheless, their formation mechanism and structural characteristics have not been revealed clearly. Here the formation of single-crystalline Cu nanoparticles during the Li deposition process in anode-free cells was identified by transmission electron microscopy. Through investigation of the chemical state of Cu before and after Li deposition, the formation of Cu NPs was attributed to the reduction of the oxide layers formed on the surface of Cu current collectors. Additionally, it was observed that Cu nanoparticles can be formed inside of deposited Li metal. This work reveals the formation pathway and microstructural characteristics of Cu nanoparticles appearing during Li deposition, underscoring the importance of nanoscale investigations into the underlying battery reactions.

Phase-field modeling of lithium dendrite deposition process: When an internal short circuit occurs

Lithium dendrite growth is the main trigger for internal short circuits (ISC) of lithium-ion batteries. This paper investigates the lithium dendrite growth during the whole short circuit evolution process. In this paper, the lithium dendrite growth is divided into the initial deposition of the initial operation and the secondary deposition due to the internal short circuit. Firstly, a two-dimensional model based on the phase-field theory is developed and the growth in static electrolyte is investigated. Secondly, we summarize the whole evolution process and analyze the internal structural changes as well as the external features due to the internal short circuit. Based on this analysis, a model of secondary deposition in a flowing electrolyte is proposed. The model takes into account the effect of the flowing electrolyte on the dendrites. Finally, we investigate the growth of dendrites during secondary deposition. Due to an internal short circuit that damages the separator, a flowing electrolyte appears around the damaged region. This flowing electrolyte leads to uneven growth of dendrites, with “splitting” and “branch inhibition”. This phenomenon will accelerate the continued deposition of dendrites and induce a secondary internal short circuit. This work provides a quantitative simulation model for dendrite growth when an ISC occurs. Moreover, it also provides a reference for designing the structure of liquid batteries with high cycle times and safety.

Internal Short Circuit and Dynamic Response of Large-Format Prismatic Lithium-Ion Battery Under Mechanical Abuse

Abstract Prismatic lithium-ion batteries (LIBs) are becoming the most prevalent battery type in electric vehicles, and their mechanical safety is garnering increased attention. Understanding the mechanical response and internal short circuit (ISC) of prismatic LIBs during dynamic impact is important for enhancing the safety and reliability of electric vehicles. Thanks to the pioneer's works on the cylindrical and pouch LIB, prismatic LIB can draw on relevant experimental and numerical modeling methods. However, there is still a lack of research on the dynamic effects of prismatic LIB in various loading directions. To address this disparity, the current research utilizes quasi-static and dynamic impact experiments on prismatic LIBs as a foundation. First, the mechanical response of a sizable prismatic LIB under quasi-static conditions and the dynamic effects are examined when subjected to mechanical abuse from various loading directions. Second, an anisotropic finite element model that considers dynamic strain rates are developed, enabling it to accurately represent the mechanical response to both quasi-static and dynamic impact loads. At last, we performed an analysis of ISC occurring under dynamic loading conditions combining the experimental and simulated results. The experimental results as well as the established model can provide reference for the safe design, application, and analysis of prismatic LIBs.

External short circuit of lithium-ion battery after high temperature aging

The microscopic and macroscopic changes of lithium-ion batteries after high temperature cycling and their effect on external short circuit (ESC) are studied in this study. The results indicate that solid electrolyte interphase and cathode electrolyte interphase cover the surface of anode and cathode. Transition metal, Mn is dissolved from the cathode. Capacity and resistance decreases and increases after cycling at high temperature. The safety of batteries after ESC is ranked as: 70 % state of health (SOH) > 100 % SOH > 80 % SOH > 90 % SOH. Thermal runaway only occurs to battery with 90 % SOH after ESC. Increase of resistance after cycling affects heat generation during ESC less. Onset temperature and thermal runaway temperature increases and decreases owing to solid electrolyte interphase growth and Mn dissolution. Compared to fresh battery, safety of battery with 70 % SOH after ESC increases. Fast discharging causes side reactions for aged batteries, which also generate heat. The heat generation effect of fast discharging decreases with the decrease of SOH after 90 % SOH. Local micro internal short circuit causes more heat generation for aged batteries. The results are important for safety control of lithium-ion battery.

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

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

Fault diagnosis of early internal short circuit for power battery systems based on the evolution of the cell charging voltage slope in variable voltage window

Internal short circuit (ISC) is one of the main causes of thermal runaway (TR) accident in power battery systems, to effectively avoid the development of early stage ISC towards TR, this paper innovatively proposes an ISC fault diagnosis method based on the evolution of the cell charging voltage slope (CCVS) in variable voltage window (VVW). Firstly, the ISC characterisation parameter, i.e. CCVS, is extracted through battery cell aging and equivalent ISC experimental studies. This parameter has two advantages: on the one hand, the charging voltage slopes of different cycles of one cell in different voltage windows keep the same evolution law, so that the mechanism of VVW can be established, and the generalisation ability of the algorithm is improved. On the other hand, the charging voltage data of one cell as the research object effectively avoids the interference of inconsistent factors between battery cells. Then, the battery data are preprocessed using wavelet denoising, and a sliding window strategy is introduced to calculate the positional ranking of the CCVS in the historical data, which represents the capacity ranking level of the cell in this charging segment, defined as the capacity rating factor (CRF). Further, a double-layer diagnostic strategy based on the 3 σ criterion and distance factor assessment is used to localise the fault, which can effectively avoid the occurrence of false alarms. Finally, experimental and real-world vehicle data validate the effectiveness of the method, different types of battery data verify the applicability of the method, and the comparison results of the same type of model show that the proposed method is significantly superior in terms of robustness, accuracy and computational efficiency.

Thermal runaway of Li-ion batteries caused by hemispherical indentation under different temperatures: Battery deformation and fracture

Thermal runaway (TR) of Li-ion batteries (LIBs) presents a disastrous safety hazard and a significant barrier to the wider adoption of electric vehicles (EVs). Internal short circuit (ISC) induced by mechanical abuse is one of the causes of battery TR. This paper uses hemispherical indentation tests to trigger ISC in the battery at different temperatures and studies the battery deformation and fracture mode. Results show as the initial temperature increases, the battery hardness and strength decrease, and the fracture mode of the laminar structure changes from shear fracture to localized rupture. In the shear fracture mode, the ISC homogeneously heats the battery, and it does not directly trigger TR. In the localized rupture mode, the ISC is only induced at the layers close to the indenter and generates a hot spot exceeding 200 °C, leading to the initiation of TR. Therefore, the mechanical properties of batteries under different conditions need to be studied in more detail to develop batteries that are safer under mechanical abuse.

Investigating the safety of solid/liquid hybrid electrolyte lithium-ion battery: A comparative study with traditional LIBs under abuse condition

Lithium-ion battery (LIB) with solid‒liquid hybrid electrolyte is an important milestone in the development of all-solid-state battery (ASSB) to achieve higher energy density. In-depth understanding of the safety of solid‒liquid hybrid electrolyte battery (HS-LIB) is investigated for the first time: a detailed analysis and comparison of the possibility and severity of thermal runaway (TR) of HS-LIB and LIB are performed under typical abuse conditions to further explain the practical safety of HS-LIB in multiple dimensions. Poor thermal safety is identified by the lower self-heating onset temperature Tonset (78 °C) and thermal runaway triggering temperature Ttr (138 °C) of HS-LIB with 100 % state of charge (SOC), as well as higher maximum temperature Tmax (>1200 °C) and 2–3 times maximum temperature rise rate dT/dtmax (349.3 °C/s) higher than LIBs. The significant volume changes of SiOx as an anode material contribute to uneven SEI formation, while the resultant cracks and voids accelerate SEI decomposition prematurely. The lower thermodynamic parameter-apparent activation energy Ea also indicates that the test battery has lower thermal stability, and the comparative results of the TNT-equivalent corroborated the greater thermal hazards. External overheating conditions also results in a lower Ttr (168 °C) and shorter time to thermal runaway ttr (177 s) due to faster heat absorption with dT/dtmax (933.8 °C/s). Self-generation of heat by SE in the temperature range that triggers the main response to TR and the high energy release in a short period of time exacerbate the TR hazard. Worse electrical behavior is proven through lower state of charge (114 %) and higher dT/dtmax (>420 °C/s). Encouragingly, HS-LIB exhibits excellent mechanical safety, due to the double roles of solid-state electrolytes: as an electrolyte and a separator, which avoids internal short-circuits caused by melting of the separator at hot spots. Lower thermal stability with greater hazards is explained by a correlation mechanism analysis and these experimental results can provide some reference for the safe design of ASSB.

On the strain rate-dependent mechanical behavior of PE separator for lithium-ion batteries

The separator is a critical component for ensuring electrochemical cycling performance and preventing internal short circuits in lithium-ion batteries. For the collision safety of lithium-ion batteries, understanding the rate-dependent mechanical behavior of the separator is essential for battery impact modeling and safety prediction. This study conducts a comprehensive experimental investigation into the strain rate–dependent tensile/compressive behavior and failure mechanism of the polyethylene (PE) separator under quasi-static and dynamic conditions. The combination of deformation images recorded by cameras and post-mortem characterization using SEM was employed to clarify the rate-dependent deformation and fracture mechanism of the separator under both tensile and compressive loading. The experimental results demonstrate a significant strain rate effect on the tensile/compressive mechanical properties and damage/failure behavior of the separator. Furthermore, the effect of the strain rate on the mechanical properties, including the tensile strength, tensile fracture strain, tensile elastic modulus, compressive modulus, yield stress and yield strain of separator, was analyzed and discussed. A significant strain rate-dependent tensile damage and fracture behavior of the separator was observed, where the fracture site exhibited an obvious phase transition and skeletal lamella fracture under extremely high strain rate tensile loading. The separator underwent severe damage under dynamic compressive conditions. The results of this study provide an important basis for the establishment of rate-dependent safety criterion and short circuit prediction of lithium-ion batteries under impact loading, and shed light on understanding separator failure-induced short circuit issues in battery collision safety scenarios.