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Abstract

The safety concern is the main obstacle that hinders the large-scale applications of lithium ion batteries in electric vehicles. With continuous improvement of lithium ion batteries in energy density, enhancing their safety is becoming increasingly urgent for the electric vehicle development. Thermal runaway is the key scientific problem in battery safety research. Therefore, this paper provides a comprehensive review on the thermal runaway mechanism of the commercial lithium ion battery for electric vehicles. Learning from typical accidents, the abuse conditions that may lead to thermal runaway have been summarized. The abuse conditions include mechanical abuse, electrical abuse, and thermal abuse. Internal short circuit is the most common feature for all the abuse conditions. The thermal runaway follows a mechanism of chain reactions, during which the decomposition reaction of the battery component materials occurs one after another. A novel energy release diagram, which can quantify the reaction kinetics for all the battery component materials, is proposed to interpret the mechanisms of the chain reactions during thermal runaway. The relationship between the internal short circuit and the thermal runaway is further clarified using the energy release diagram with two cases. Finally, a three-level protection concept is proposed to help reduce the thermal runaway hazard. The three-level protection can be fulfilled by providing passive defense and early warning before the occurrence of thermal runaway, by enhancing the intrinsic thermal stability of the materials, and by reducing the secondary hazard like thermal runaway propagation.

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... Furthermore, it is worth mentioning an extreme condition called battery thermal runaway (TR), which is a potential risk in the battery pack [4,5]. In addition, battery TR propagation has become one of the greatest challenges for battery safety and often aggravates the thermal hazards through the domino effect during TR propagation [6]. Fig. 1.1 shows a series of chain reactions corresponding to the battery TR process, and the three-stage profile was presented by Wu et al. [7]. ...
... Due to the typical explosive components of a battery, such as plastic packing, separator and electrolyte, LIB accidents happen in various applications, from mobile telephones to EVs and even aeroplanes. Based on these reviews, the various abusive conditions, such as over-heating, over-charged, short circuit and mechanical shock, have been studied, and it is easy to conclude that thermal abuse is the root cause of battery TR [6]. Moreover, the abuse conditions can be categorized into three sections: mechanical abuse, electrical abuse and thermal abuse, whose common features are smoke, fire and explosion, as shown in Fig. 4.1 (a). ...
... (a) Accidents related to LIB failure and correlated abuse conditions[6]; (b) Thermal digraph of a reaction and heat loss from a vessel at three ambient temperatures, where B is at the critical temperature[97]. ...
Article
With an increasingly wider application of the lithium-ion battery (LIB), specifically the drastic increase of electric vehicles in cosmopolitan cities, improving the thermal and fire resilience of LIB systems is inevitable. Thus, in-depth analysis and performance-based study on battery thermal management system (BTMs) design have arisen as a popular research topic in energy storage systems. Among the LIB system parameters, such as battery temperature distribution, battery heat generation rate, cooling medium properties, electrical properties, physical dimension design, etc., multi-factor design optimisation is one of the most difficult experimental tasks. Computational simulations deliver a holistic solution to the BTMs design, yet it demands an immense amount of computational power and time, which is often not practical for the design optimisation process. Therefore, machine learning (ML) models play a non-substitute role in the safety management of battery systems. ML models aid in temperature prediction and safety diagnosis, thereby assisting in the early warning of battery fire and its mitigation. In this review article, we summarise extensive lists of literature on BTMs employing ML models and identify the current state-of-the-art research, which is expected to serve as a much-needed guideline and reference for future design optimisation. Following that, the application of various ML models in battery fire diagnosis and early warning is illustrated. Finally, the authors propose improved approaches to advanced battery safety management with ML. This review paper aims to bring new insights into the application of ML in the LIB thermal safety issue and BTMs design and anticipate boosting further advanced battery system design not limited to the thermal management system, as well as proposing potential digital twin modelling for BTMs.
... Facts show that some lithium-ion batteries can catch fire while others can catch fire in accidents leading to death. Battery packs are designed for safety-related challenges such as mechanical, electrical, and thermal abuse [90], [91], [94]- [97]. According to the author's knowledge, the application of the cellular structure to the design of battery packs has not been carried out by many researchers. ...
... The Brinkman-Forchheimer equation approximates fluid flow through a lattice structure. A review of the thermal runaway mechanism of lithium-ion battery for electric vehicles has been carried out by Feng et al. [94]. Various possible battery failures due to accidents include mechanical abuse, electrical abuse, thermal abuse, and internal short circuits. ...
Article
Cellular structures can be classified into foams, honeycombs, and lattice structures. Each type of structure has its characteristics. Various applications of cellular structures can be found in aviation, bioengineering, automotive, and other fields. In the automotive sector, cellular structures have been used for structural applications and impact- absorbing modules, for example, for protecting the electric vehicle battery pack against impact loading. The challenges that limit the application of cellular structures today include systematically designing pseudo-random cellular structures, assessing which cellular patterns are most suitable for a particular application, and mastery of manufacturing technology for efficient mass production of cellular structures. In this paper, the authors examine the state-of-the-art technology in geometry, applications, and manufacturing of various cellular structures carried out by researchers to obtain an overview of the current conditions for further development of these cellular structures. Limited manufacturing capabilities encourage researchers to design an optimal cellular structure to be applied to a particular function but have high manufacturability. The development of additive manufacturing technology has provided opportunities for researchers to produce an optimal cellular structure commercially soon.
... Numerous experimental pieces of evidence confirm that TR can be easily triggered for the LIB when it is exposed to abnormal operating circumstances, such as mechanical abuse, electric abuse, and thermal abuse (Feng et al., 2018;Wang et al., 2019). In an electrochemical energy storage station, to satisfy the demand for capacity and voltage, a large number of single cells are connected in series and parallel to form a battery module. ...
... In TR evaluation and early warning about large-format batteries, the surface temperature and voltage are the essential data (Jin et al., 2020;Li et al., 2019). The process of safety vent opening can eject a large amount of electrolyte (Feng et al., 2018;Zhao et al., 2021). When an internal short circuit occurs in the battery, the chemicals inside the cell may undergo a variety of chemical reactions to produce gases (Mathieu et al., 2022). ...
... The onset of a safety-critical condition can be triggered by mechanical, electrical or thermal failures [11,12]. With the addition of passive protection devices [13], a battery management system (BMS) with intelligent fault detection [14,15], a robust mechanical design [16] or with appropriate cooling solutions [17] on system level, the risk of many faults can be reduced to a lower and acceptable level. ...
... Understanding the development, fault behaviour and consequences of an ISC is a significant aspect of battery safety [19,35,65]. Due to its rare and stochastic [23] behaviour, ISC research requires methods for the intentional creation of such field failures [12,66]. Thus, a wide variety of trigger methods are discussed for investigating ISC behaviour [22,35,67]. ...
Article
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A possible contamination with impurities or material weak points generated in cell production of lithium-ion batteries increases the risk of spontaneous internal short circuits (ISC). An ISC can lead to a sudden thermal runaway (TR) of the cell, thereby making these faults especially dangerous. Evaluation regarding the criticality of an ISC, the development of detection methods for timely fault warning and possible protection concepts require a realistic failure replication for general validation. Various trigger methods are currently discussed to reproduce these ISC failure cases, but without considering a valid basis for the practice-relevant particle properties. In order to provide such a basis for the evaluation and further development of trigger methods, in this paper, the possibilities of detecting impurity particles in production were reviewed and real particles from pouch cells of an established cell manufacturer were analysed. The results indicate that several metallic particles with a significant size up to 1 mm × 1.7 mm could be found between the cell layers. This evidence shows that contamination with impurity particles cannot be completely prevented in cell production, as a result of which particle-induced ISC must be expected and the need for an application-oriented triggering method currently exists. The cause of TR events in the field often cannot be identified. However, it is noticeable that such faults often occur during the charging process. A new interesting hypothesis for this so-far unexplained phenomenon is presented here. Based on all findings, the current trigger methods for replicating an external particle-induced ISC were evaluated in significant detail and specific improvements are identified. Here, it is shown that all current trigger methods for ISC replication exhibit weaknesses regarding reproducibility, which results mainly from the scattering random ISC contact resistance.
... accidents or LIBs with manufacturing defects. 2,3 Energy released from a cell TR may damage adjacent cells or even cause the adjacent cells to TR, known as TR propagation. [4][5][6][7][8][9][10][11][12][13][14][15] Many kinds of battery abuse conditions, categorised as electrical, mechanical, thermal, and environmental can lead to cell TR. ...
... 16 The outcome of cell TR ranges from the release of toxic and non-toxic gases, smoke, spark, fire, rupture or explosion. 2,3 Rupture is one of the most severe scenarios of battery failure and it happens when stresses generated by internal pressure and thermal strain exceed the strength of the battery casing itself. Once one or more cells have sidewall rupture, sparks, hot gases, and flames coming out from the opening of the cell side can promote cascading failure of adjacent cells. ...
Article
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To understand the relationship of the sidewall rupture at different state of charge (SOC) of cylindrical cells with high specific energy, this work presents the results of radial nail penetration tests of 21700 cylindrical cells at different SOC. The thermal runaway and sidewall rupture behaviours were characterised by key performance indicators such as temperature, mass, fire behaviour, and voltage change. In addition, released gases from a subset of tests were measured using the Fourier transform infrared spectroscopy. The change in the internal structure of another subset of cells after the test was observed by X-ray computed tomography. The results show that the sidewall rupture still exists for tests at low SOC (< 30% SOC), but the outcome of thermal runaway and sidewall rupture is milder than those at high SOC (≥ 50% SOC). The average mass loss of cells increases with the increment of SOC. The cell casing thickness is reduced by 12.7% ± 0.3% of the fresh cell, which in combination with the reduction in the strength of the casing material at high temperatures could contribute to sidewall rupture
... Separators should be equipped with thermal shutdown to prevent safety issues caused by the elevating temperature during operation. This feature can promptly cut off the current and prevent the electrodes from contacting [87,91,92]. ...
Article
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Lithium is a vital raw material used for a wide range of applications, such as the fabrication of glass, ceramics, pharmaceuticals, and batteries for electric cars. The accelerating electrification transition and the global commitment to decarbonization have caused an increasing demand for lithium. The current supply derived from brines and hard rock ores is not enough to meet the global demand unless alternate resources and efficient techniques to recover this valuable metal are implemented. In the past few decades, several approaches have been studied to extract lithium from aqueous resources. Among those studied, chemical precipitation is considered the most efficient technology for the extraction of metals from wastewater. This paper outlines the current technology, its challenges, and its environmental impacts. Moreover, it reviews alternative approaches to recover lithium via chemical precipitation, and systematically studies the effects of different operating conditions on the lithium precipitation rate. In addition, the biggest challenges of the most recent studies are discussed, along with implications for future innovation.
... Improving the safety of the energy sources used in electric vehicles requires major and constant attention from manufacturers [13,14]. Currently, there is much research that is focused on the safe integration of energy sources in electric vehicles to solve problems that can result in various safety incidents (which can lead to ignition and fire hazards), which are a pressing priority already in the design phase [13,[15][16][17][18][19][20]. It is considered that the stresses that may appear in the exploitation of EV energy sources ( Figure 1) are multiple from the point of view of physical phenomena. ...
Article
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The exponential development and successful application of systems-related technologies that can put electric vehicles on a level playing field in direct competition with vehicles powered by internal combustion engines mean that the foreseeable future of the automobile (at least) will be dominated by vehicles that have electric current stored in batteries as a source of energy. The problem at the European level related to the dependence on battery suppliers from Asia directly correlates with the need to use batteries as energy storage media for energy from renewable sources (photovoltaic and wind), and leads to the need for research into the possibilities for their reuse, remanufacturing or recycling (at the end of their life or purpose of use), and reintroduction, either fully or partially, back into the economy. This article presents possibilities for increasing the protection of the integrity of the cells that form a battery in the event of an impact/road accident, by the numerical analysis of a topographically optimized battery module case. The proposed solution/method is innovative and offers a cell protection efficiency of between 16.6–60% (19.7% to 40.7% if the mean values for all three impact velocities are considered). The efficiency of a cell’s protection decreases with the increase in impact velocity and provides the premise for a greater part of the saved cells to be reintegrated into other energy storage systems (photovoltaic and/or wind), avoiding future problems relating to environmental pollution.
... Li-ion batteries (LiBs) are widely used in energy storage applications, such as power grids, electric vehicles, and electric locomotives, due to their high energy density, power density, long cycle life, and extended calendar life. Feng et al. [1], however, list several recent accidents due to the failure of LiBs, often due to thermal runaway. Thermal runaway is often preceded by an internal short circuit caused by thermal, mechanical, and electrical abuse. ...
Article
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The early detection and tracing of anomalous operations in battery packs are critical to improving performance and ensuring safety. This paper presents a data-driven approach for online anomaly detection in battery packs that uses real-time voltage and temperature data from multiple Li-ion battery cells. Mean-based residuals are generated for cell groups and evaluated using Principal Component Analysis. The evaluated residuals are then thresholded using a cumulative sum control chart to detect anomalies. The mild external short circuits associated with cell balancing are detected in the voltage signals and necessitate voltage retraining after balancing. Temperature residuals prove to be critical, enabling anomaly detection of module balancing events within 14 min that are unobservable from the voltage residuals. Statistical testing of the proposed approach is performed on the experimental data from a battery electric locomotive injected with model-based anomalies. The proposed anomaly detection approach has a low false-positive rate and accurately detects and traces the synthetic voltage and temperature anomalies. The performance of the proposed approach compared with direct thresholding of mean-based residuals shows a 56% faster detection time, 42% fewer false negatives, and 60% fewer missed anomalies while maintaining a comparable false-positive rate.
... Because the working principles of sodium-ion battery (SIB) and LIB are similar, SIB is considered as a very promising alternative to LIB, abundant and uniform global distribution of sodium, as well as low cost, good safety and low-temperature performance, and other advantages of SIB [1][2][3]. Because of the similar working principles, some cathode materials that perform well in Li-ion batteries also perform well in Na-ion batteries, such as layered transition metal oxides (LTMO), polyanionic compounds, Prussian blue and its analogs [4][5][6][7]. However, since the atomic radius of Na (1.06 Å) is larger than that of Li (0.76 Å), when graphite, a typical negative electrode material for lithium-ion batteries, is used as a negative electrode material for sodium-ion batteries, not only the capacity is much smaller than that of the negative electrode of lithium-ion batteries, but it is also accompanied by volume expansion, poor cycle life, and other issues [8]. ...
Article
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Currently, MXenes have been identified as promising candidate electrode materials for Na-ion batteries because of their excellent energy storage and electrical conductivity. Among them, dual transition metal MXenes have attracted attention due to their excellent properties as anode materials for Na-ion batteries. In order to explore the reason why dual transition metal MXenes outperform single transition metal MXenes, we systemically investigated and compared the performance of TiNbC-based dual transition metal MXenes (TiNbC, TiNbCF2, and TiNbCO2) with that of Nb2C-based single transition metal MXenes (Nb2C, Nb2CF2, and Nb2CO2) as anode materials for Na-ion batteries based density functional theory calculations. The results showed that TiNbC, TiNbCO2, Nb2C, and Nb2CO2 are promising anode materials for Na-ion batteries due to the low diffusion barrier and high capacity of Na on their surfaces. Compared with the Nb2C-based single transition metal MXenes, the TiNbC-based dual transition metal MXenes have better adsorption performance, diffusion rate, and theoretical storage of Na atoms. The higher adsorption ability of TiNbC and TiNbCO2 to Na atoms was attributed to the synergistic effect of Ti and Nb which increases the interaction between the substrate and Na. This conclusion provides a new insight for the development of other high-performance MXenes-based anode materials for Na-ion batteries.
... 1 and C Na, K, or H 2 (62) As shown in Figure 92b, the PBA(Na + )−H 2 battery shows outstanding rate performance, where the discharge capacities reach ∼52, 47, 41, 34, and 30 mAh g −1 at current rates of 5, 10, 20, 40, and 60 C, respectively. Even at a high rate of 100 C, the battery capacity is still 26 mAh g −1 . ...
... have proven themselves as an enabling technology for various applications, including electric cars, electric aircraft, smart grid, and space systems [1][2][3][4]. Despite their high energy density and long cycle life, lithium-ion batteries suffer from safety risks, which trace to the high reactivity of lithium and flammability of the commonly used electrolyte solutions and are exacerbated by side reactions, aging, and degradation [5]. Hence, it is imperative to ensure their safe and reliable arXiv:2301.05168v1 ...
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This paper presents a novel modular, reconfigurable battery energy storage system. The proposed design is characterized by a tight integration of reconfigurable power switches and DC/DC converters. This characteristic enables isolation of faulty cells from the system and allows fine power control for individual cells toward optimal system-level performance. An optimal power management approach is developed to extensively exploit the merits of the proposed design. Based on receding-horizon convex optimization, this approach aims to minimize the total power losses in charging/discharging while allocating the power in line with each cell's condition to achieve state-of-charge (SoC) and temperature balancing. By appropriate design, the approach manages to regulate the power of a cell across its full SoC range and guarantees the feasibility of the optimization problem. We perform extensive simulations and further develop a lab-scale prototype to validate the proposed system design and power management approach.
... In LIBs, charged NRL materials undergo exothermic reactions with organic electrolytes. 11 The heat generated by interactions between the delithiated cathode and electrolytes can be quite dangerous. These reactions generate a large amount of gas (e.g., O 2 , CO 2 ) and heat, resulting in a rapid rise in internal temperature, increased pressure, and finally battery explosion. ...
Article
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Ni‐rich layered (NRL) cathodes have been widely considered to undergo a degeneration from layered to spinel‐like phases and finally to a rock−salt phase, which jeopardizes the battery's performance and safety. However, this process does not sufficiently explain the drastic structure collapse that occurs during thermal runaway, as the lattice constants of these structures are similar. Herein, an intermediate β‐Li2NiO3 phase is identified during the thermally driven structural evolution via in situ heating scanning transmission electron microscopy imaging. The antihoneycomb‐ordered structure leads to a larger lattice mismatch of up to ∼15% with the layered structure. The resulting strain triggers huge bulk stress and the labile oxygen of the β‐Li2NiO3 phase aggravates the oxygen release, severely reducing the thermal stability of NRL materials. Finally, based on the screening for 3d transition metals, doping elements are chosen to suppress the β‐Li2TMO3 phase and enhance thermal stability. The findings provide comprehensive insights into the structural degradation process of NRL materials and pave the way to design high‐performance and safe battery systems. In thermal degradation of Ni‐rich layered (NRL) cathodes, we first find the intermediate β‐Li2NiO3 phase causes the large lattice mismatch and bulk stress, accounting for the poor thermal stability of NRL materials. Then, the thermodynamic stability of the β‐Li2NiO3 phase is discussed for pointing out the future design of high‐performance and safe NRL cathodes.
... To date, many scholars have dedicated a lot of effort towards studying EV fires, which mainly comprise three stages: (i) the mechanism of the EV fires, (ii) the fire onset stage and (iii) the fire investigation stage. In particular, in the first stage, efforts were taken to conduct thermal runaway tests on batteries to investigate the internal mechanism of the EV fires and develop the corresponding protection strategies [1]. In the second stage, studies on the impacts of the EV fires were analyzed to support pedestrian evacuation and fire safety system design [2][3][4]. ...
Article
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Electric vehicle (EV) fire accidents are caused by multiple factors, including the traffic conditions, parking environment and firefighting facilities, and are a typical public safety issue in cities. Owing to the lack of accurate and quick estimation methods for the EV fire analysis in roadside parking scenarios and their impacts, this study applied the solid flame model to simplify the determination of the dynamic turbulence characteristics of the EV fire flames and proposed a thermal radiation model of an EV thermal runaway combustion flame based on the peak heat release rate. Subsequently, the radiation accuracy of the model near the flame was verified by a simulation and a comparison with the point source flame model, where the safety threshold of the fire accident propagation was determined. Finally, the evacuation strategy for pedestrians in an EV fire was investigated based on the proposed model. From the results, the safe distance of adjacent vehicles and the cumulative value of the pedestrians affected by the thermal radiation of EV fires can be obtained under the influence of the environmental factors. The proposed model can be used to optimize the design of roadside parking lots and guide the formulation of pedestrian emergency plans during an EV fire.
... However, the application of lithium metal electrodes has been facing many challenges. For example, during the charging and discharging process, lithium metal expands and reacts with air and water easily, and the growth of dendritic crystals on the surface of the cathode is difficult to control during electrodeposition, and even "dead lithium" occurs [1][2][3][4][5][6]. These problems have seriously affected the cycle life and safety performance of lithium-ion batteries. ...
Article
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The lithium metal anode has attracted much attention from researchers because of its extremely high theoretical capacity and most negative potential, but some problems caused by lithium dendrites grown on the lithium metal anode have seriously hindered its practical application. With the development of computer technology and the improvement of quantum chemical theory, theoretical calculations have become an effective tool to assist in the study of lithium dendrite growth. Firstly, this paper introduces computational simulation methods such as DFT-based first-principles calculations, molecular dynamics, and machine learning. Secondly, strategies to inhibit lithium dendrite formation are summarized for liquid and solid-state batteries, including the construction of stable SEI membranes, electrolyte modification, solid-state electrolyte development, etc. Finally, the research progress and applications of computational simulations for the inhibition of lithium dendrite growth in different battery systems in recent years are summarized.
... Since thermal runaway leads to fire in battery packs [37], regulating the battery temperature within a safe range of 25 • C to 40 • C during charging and discharging cycles in EVs is essential for the battery's longevity and safety [38]. A 10 Ah pouch Li-ion cell has been tested at various C-rates to measure the time-dependent temperature behaviour constant current charge/discharge. ...
Article
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With the large-scale commercialization and growing market share of electric vehicles (EVs), many studies have been dedicated to battery systems design and development. Their focus has been on higher energy efficiency, improved thermal performance and optimized multi-material battery enclosure designs. The integration of simulation-based design optimization of the battery pack and Battery Management System (BMS) is evolving and has expanded to include novelties such as artificial intelligence/machine learning (AI/ML) to improve efficiencies in design, manufacturing, and operations for their application in electric vehicles and energy storage systems. Specific to BMS, these advanced concepts enable a more accurate prediction of battery performance such as its State of Health (SOH), State of Charge (SOC), and State of Power (SOP). This study presents a comprehensive review of the latest developments and technologies in battery design, thermal management, and the application of AI in Battery Management Systems (BMS) for Electric Vehicles (EV).
... The working temperature of the battery or the temperature consistency between the cells in the battery module are very demanding [4][5]. Local overheating may cause safety problems of the battery pack [6] . It is generally believed that the maximum operating temperature of the lithium iron phosphate battery pack should not exceed 55℃, and the internal temperature difference of the battery pack should not exceed 5℃ [7]. ...
Chapter
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With the new energy vehicles’ rapid rising, fast charging and fast discharging of power battery is gradually becoming the mainstream working mode. The heat transfer characteristics of power battery pack at different rates of charge/discharge during fast charge/discharge are studied by numerical simulation. The heat dissipation effects of pure phase change material (PCM) cooling and liquid coupled with PCM cooling on the battery module are compared, and the control effects of the above two heat transfer methods on the temperature difference and maximum temperature are analyzed. The simulation results show that when 5C fast charging and 5C fast releasing, the optimal velocity of flow is 0.05m/s, the maximum temperature of the battery module is kept within 47.33 ∘C, and the temperature difference is 3.39 ∘C. Compared with the pure phase change cooling mode, the maximum temperature of the battery module is reduced by 34.57∘ C, and the temperature difference is reduced by 1.14 ∘C. Therefore, the coupled system of liquid cooling and PCM has a good temperature control effect under the condition of fast charging and fast discharging.
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This study aims to reveal and analyze the landscape of China’s scientific publications in 2018–2020 on the subject “Energy Engineering and Power Technology” using bibliometric data from the Lens platform. Bibliometric data of 26,623 scholarly works that satisfy the query: “Filters: Year Published = (2018–); Publication Type = (journal article); Subject = (Energy Engineering and Power Technology); Institution Country/Region = (China)” were used to analyze their main topics disclosed by Fields of Study and Subject; the leading contributors to these R&D activities were also detected. Chinese Academy of Sciences, China University of Petroleum, Tsinghua University, Xi’an Jiaotong University, China University of Mining and Technology are the leading institutions in the subject. Most research works were funded by National Natural Science Foundation of China. China carries out its research not only in conjunction with the leading economies: United States, United Kingdom, Australia and Canada, but also with the developing countries: Pakistan, Iran, Saudi Arabia and Viet Nam. Materials science, Chemical engineering, Computer science, Chemistry, Catalysis, Environmental science are the top Fields of Study. Analysis of co-occurrence of Fields of Study allowed to identify 5 thematic clusters: 1. Thermal efficiency and environmental science; 2. Materials science for energy storage and hydrogen production; 3. Catalysis and pyrolysis for better fossil fuels; 4. Computer science and control theory for renewable energy; 5. Petroleum engineering for new fossil fuel resources and composite materials. The results of the work can serve as a reference material for scientists, developers and investors, so that they can understand the research landscape of the “Energy Engineering and Power Technology” subject.
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Solid-state lithium batteries (SSLBs) have been broadly accepted as a promising candidate for the next generation lithium-ion batteries (LIBs) with high energy density, long duration, and high safety. The intrinsic non-flammable nature and electrochemical/thermal/mechanical stability of solid electrolytes are expected to fundamentally solve the safety problems of conventional LIBs. However, thermal degradation and thermal runaway could also happen in SSLBs. For example, the large interfacial resistance between solid electrolytes and electrodes could aggravate the joule heat generation; the anisotropic thermal diffusion could trigger the uneven temperature distribution and formation of hotspots further leading to lithium dendrite growth. Considerable research efforts have been devoted to exploring solid electrolytes with outstanding performance and harmonizing interfacial incompatibility in the past decades. There have been fewer comprehensive reports investigating the thermal reaction process, thermal degradation, and thermal runaway of SSLBs. This review seeks to highlight advanced thermal-related analysis techniques for SSLBs, by focusing particularly on multiscale and multidimensional thermal-related characterization, thermal monitoring techniques such as sensors, thermal experimental techniques imitating the abuse operating condition, and thermal-related advanced simulations. Insightful perspectives are proposed to bridge fundamental studies to technological relevance for better understanding and performance optimization of SSLBs.
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Hundreds of thermal-runaway-induced battery fire accidents have been occurring to real-world electric vehicles (EVs) recent years, exposing life to danger and causing property losses. Timely and fast battery thermal runaway prognosis is essential but restricted by limited parameters and complex influencing factors during real-world operation of EVs, i.e., environment, driving behavior, and weather. To cope with the issue, several data-driven methods are combined and thermal runaway prognosis is realized by two steps, i.e., temperature prediction by the modified extreme gradient boosting (XGBoost) then abnormality detection by principal components analysis (PCA) and density-based spatial clustering of applications with noise (DBSCAN). The XGBoost is modified and trained by data of real-world EVs to couple the influencing factors during real-world operation of EVs. For parameter optimization, the ‘pre-training and adjacent grid optimizing method’(P-AGOM) and ’adjacent grid optimizing method’ (AGOM) are proposed to achieve locally optimal hyperparameters for XGBoost and DBSCAN. Verified results showcase the XGBoost-PCA-DBSCAN achieves accurate 5-minute-forward temperature prediction and the mean-square-errors (MSEs) of four seasons are only 0.0729, 0.0594, 0.0747, 0.0523 respectively. By modification of XGBoost, the MSE of temperature prediction is reduced by 31.2%. In addition, 35-minute-forward thermal runaway prognosis by the XGBoost-PCA-DBSCAN will provide driver sufficient response time to minimize the loss of life and property.
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Electric vehicle sharing is necessary for achieving carbon neutrality. The self-service electric vehicle mode offers unique advantages in terms of freedom of movement and privacy protection. Meanwhile, this mode requires a high-quality service guarantee because of the separation of management and use. The purpose of this study is to propose a framework for the risk control and service optimization of self-service electric vehicles, which includes service life cycle analysis, risk assessment by using a newly integrated fuzzy failure mode and effect analysis, and a consumer satisfaction survey based on the Kano model. Sixteen services were extracted through the service life cycle analysis and online review study, and their corresponding service failures were then ranked through risk assessment. The risk assessment showed that the reliability of vehicle-related services has the greatest impact on safety, followed by financial-related and driving-safety-related services. A Kano model-based survey showed that all kinds of service failures brought significant customer non-satisfaction, while different service improvements brought differentiated satisfaction. To deeply improve service satisfaction, a Risk-Satisfaction analysis was conducted, indicating that services with high risk and high satisfaction deserve further investment.
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The low ionic conductivity of poly(ethylene oxide) (PEO)‐based polymer electrolytes at room temperature and the undesired lithium‐dendrite growth at Li|PEO interface impede their further application. Herein, a PEO polymer is regulated at the molecular level through a copper ion (Cu2+) coordination effect with both PEO and Li salts to achieve a high Li+ conductivity of 0.2 mS cm−1 and a transference number of 0.42 at 30 °C. Moreover, the Cu‐coordinated PEO electrolyte is neither sticky nor hygroscopic because the hydrophilic oxygen groups in PEO are terminated by Cu ions. Furthermore, the in situ formed F/Li‐rich inorganic layer induced by CuF2 additive accelerates Li+ transport kinetics and enables uniform Li+ deposition during Li plating/stripping. As a result, the Cu2+‐coordinated PEO electrolytes deliver a high critical current density of 1.5 mA cm−2 at 30 °C. An all‐solid‐state Li‐LiNi0.83Co0.12Mn0.05O2 (NCM83) battery with such a copper coordinated PEO electrolyte exhibits a long cycle life over 500 cycles with a capacity retention of 71% under 0.6 C at 30 °C. When the mass loading increases to a record high of 7 mg cm−2, the Li‐NCM83 cell delivers a high areal capacity of 1.07 mAh cm−2 under 0.1 C at 30 °C. A molecular regulation poly(ethylene oxide) (PEO) electrolyte is prepared through a Cu2+‐coordination effect with both PEO and LiTFSI, which is stable in moist air and presents high ionic conductivity, transference number, and mechanical strength due to the coordinated 3D structure. Moreover, the coordinated PEO electrolyte shows superb cycling stability when employed in high‐voltage lithium‐metal batteries.
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Fighting lithium ion battery (LIB) fire has always been a hard work, due to the uncontrollable internal thermal runaway (TR) reactions of LIBs. In this work, a kind of inorganic phase change material composited commercial dry power extinguishant was studied for LIB fire. Different with the traditional dry powder extinguishants, the composite dry powers exhibited large heat absorbing capacities below the TR temperatures of LIBs. The results of LIB TR propagation suppression experiment show that the composite dry powers not only can extinguish LIB fire, but also can suppress LIB TR propagation. Moreover, the composite dry powers still keep the advantages of low cost, insulation and environment friendliness. This work delivers a novel method for designing more practical dry power extinguishants to suppress LIB fires.
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The risk of thermal runaway in lithium-ion battery (LIB) attracts significant attention from domains of society, industry, and academia. However, the thermal runaway prediction in the framework of system safety requires further efforts. In this paper, we propose a methodology for dynamic risk prediction by integrating fault tree (FT), dynamic Bayesian network (DBN) and support vector regression (SVR). FT graphically describes the logic of mechanism of thermal runaway. DBN allows considering multiple states and uncertain inference for providing quantitative results of the risk evolution. SVR is subsequently utilized for predicting the risk from the DBN estimation. The proposed methodology can be applied for risk early warning of LIB thermal runaway.
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Lithium-ion batteries are widely used in electric vehicles because of their high energy density and long cycle life. However, the spontaneous combustion accident of electric vehicles caused by thermal runaway of lithium-ion batteries seriously threatens passengers' personal and property safety. This paper expounds on the internal mechanism of lithium-ion battery thermal runaway through many previous studies and summarizes the proposed lithium-ion battery thermal runaway prediction and early warning methods. These methods can be classified into battery electrochemistry-based, battery big data analysis, and artificial intelligence methods. In this paper, various lithium-ion thermal runaway prediction and early warning methods are analyzed in detail, including the advantages and disadvantages of each method, and the challenges and future development directions of the intelligent lithium-ion battery thermal runaway prediction and early warning methods are discussed.
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Lithium-sulfur (Li-S) batteries are considered as promising candidates for novel energy storage technology that achieves energy density of 500 Wh·kg−1. However, poor cycle stability resulting from notorious shuttle effect and the safety concerns deriving from flammability of ether-based electrolyte hinder the practical application of Li-S batteries. Because of low solubility to polysulfide, high ionic conductivity, and safety property, sulfide-based electrolytes can fundamentally address above issues. It is widely known that the effective transports of both electrons and ions are basic requirement for redox reaction of active materials in cathode. Thereby, construction of fast and stable ionic and electronic transport paths in cathode is especially pivotal for cycle stability of solid-state Li-S batteries (SSLSBs). In this review, we provide research progresses on facilitating transport of charge carriers in composite cathode of SSLSBs. From perspective of materials, intrinsically conductivity of electrolyte and carbon shows dramatic effect on migration of charge carriers in cathode of SSLSBs, thereby the conductive additives are summarized in the manuscript. Additionally, the charge transport in cathode of SSLSBs fully depends on the physical contact between active materials and conductive additives, therefore we summarized the strategies optimizing interfacial contact and reducing interfacial resistance. Finally, potential future research directions and prospects for SSLSBs with improved energy density and cycle performance are also proposed.
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Thermal performance has long been recognized as a critical attribute for space systems. Thermal control surface coating is a common method in passive thermal protection. Unfortunately, limited analyzing models and data on the influence of thermal control coatings’ α/ε (absorptivity/emissivity) on the space power system have been published to date. To fill this gap, we proposed a multiphysics model that combined environmental temperature calculating and electrical performance analysis together for the satellite power system. In this paper, different coating materials are applied to the radiator surface and thermal insulation surface, respectively. Additionally, a new concept of energy storage, named energy storage voltage, is introduced. The results are analyzed and parametric fits with different formulas using ordinary least squares are conducted. Finally, the change rules are presented, which will prove particularly useful to the space industry, for example, in thermal designs and on-orbit battery studies.
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Although Li‐ion superconducting sulfides have been developed as solid electrolytes (SEs) in all‐solid‐state batteries, their high deformability, which is inherently beneficial for room‐temperature compaction, is overlooked and sacrificed. To solve this dilemmatic task, herein, highly deformable Li‐ion superconductors are reported using an annealing‐free process. The target thioantimonate, Li5.2Si0.2Sb0.8S4Br0.25I1.75, comprising bimetallic tetrahedra and bi‐halogen anions is synthesized by two‐step milling tuned for in situ crystallization, and exhibits excellent Li‐ion conductivity (σion) of 13.23 mS cm⁻¹ (averaged) and a low elastic modulus (E) of 12.51 GPa (averaged). It has a cubic argyrodite phase of ≈57.39% crystallinity with a halogen occupancy of ≈90.67% at the 4c Wyckoff site. These increased halogen occupancy drives the Li‐ion redistribution and the formation of more Li vacancies, thus facilitating Li‐ion transport through inter‐cage pathway. Also, the facile annealing‐free process provides a unique glass‐ceramic structure advantageous for high deformability. These results represent a record‐breaking milestone from the combined viewpoint of σion and E among promising SEs. Electrochemical characterization, including galvanostatic cycling tests for 400 h, reveals that this material displays reasonable electrochemical stability and cell performance (150.82 mAh g⁻¹ at 0.1C). These achievements shed light on the synthesis of practical SEs suffice both σion and E requirements.
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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 indication for early detection of approaching battery safety problems.
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A separator plays a crucial role in ensuring the safety in lithium-ion batteries (LIBs). However, commercial separators are mainly based on microporous polyolefin membranes, which possess serious safety risks, such as their thermal stabilities. Although many efforts have been made to solve these problems, they cannot yet fully ensure the safety of the batteries, especially in large-scale applications. Herein, we report a rational design of separator with substantially enhanced thermal features. We report how, by a simple dip-coating process, polydopamine (PDA) formed an overall-covered self-supporting film, both on the ceramic layer and on the pristine polyolefin separator, which made the ceramic layer and polyolefin separator appear as a single aspect and furthermore, this layer amended the film-forming properties of the separator. Combining the function of the ceramic and PDA, the developed composite-modified separator displays substantially enhanced thermal and mechanical stability, with no visual thermal shrink and can maintain its mechanical strength up to 230 °C when the polyethylene separator acts as the pristine separator.
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Lithium-ion batteries connected in series are prone to be overdischarged. Overdischarge results in various side effects, such as capacity degradation and internal short circuit (ISCr). However, most of previous research on the overdischarge of a cell was terminated when the cell voltage dropped to 0 V, leaving the further impacts of overdischarge unclear. This paper investigates the entire overdischarge process of large-format lithium-ion batteries by discharging the cell to −100% state of charge (SOC). A significant voltage platform is observed at approximately −12% SOC, and ISCr is detected after the cell is overdischarged when passing the platform. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) results indicate that the overdischarge-induced ISCr is caused by Cu deposition on electrodes, suggesting possible Cu collector dissolution at the voltage platform near −12% SOC. A prognostic/mechanistic model considering ISCr is used to evaluate the resistance of ISCr (RISCr), the value of which decreases sharply at the beginning of ISCr formation. Inducing the ISCr by overdischarge is effective and well controlled without any mechanical deformation or the use of a foreign substance.
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The need for lighter, thinner, and smaller products makes lithium-ion batteries a popular power source for applications such as mobile phones, laptop computers, digital cameras, electrical vehicles, and hybrid electrical vehicles. For high power applications, the development of high capacity and high voltage electrode materials is in progress. Battery performance and safety issues are also related to the properties of the electrolytes used. To improve the properties of the electrolytes, small amounts of other components, known as electrolyte additives, are incorporated. This paper reviews the recent progress of electrolyte additives used to improve performance and other properties, such as safety. This review classifies the additives based on their functions and their effects on specific electrode materials focusing on electrodes under current development. From anodes: carbonaceous electrodes, silicon, tin and Li4Ti5O12; from layered cathodes: LiCoO2, Li-rich and LiNiyMnyCo1−2yO2 (NMC); from spinel: LiM2O4, from olivine: LiFePO4 are selected. We believe that this approach will help readers easily identify and understand the additives suitable for their target materials.
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Safety issues concerning the use of large lithium-ion (Li-ion) batteries in electrified vehicles are discussed based on the abuse test results of Li-ion cells together with safety devices for cells. The presented abuse tests are: overcharge, short circuit, propane fire test and external heating test (oven). It was found that in a fire, cells with higher state of charge (SOC) gave a higher heat release rate (HRR), while the total heat release (THR) had a lower correlation with SOC. One fire test resulted in a hazardous projectile from a cylindrical cell. In the fire tests, toxic gas emissions of hydrogen fluoride (HF) were measured for 100%, 50% and 0% SOC.
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The thermal stability of electrochemically delithiated Li0.1Ni0.8Co0.15Al0.05O2 (NCA), FePO4 (FP), Mn0.8Fe0.2PO4 (MFP), hydrothermally synthesized VOPO4, LiVOPO4 and electrochemically lithiated Li2VOPO4 is investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis, coupled with mass spectrometry (TGA-MS). The thermal stability of the delithiated materials is found to be in the order: NCA< VOPO4< MFP< FP. Unlike the layered oxides and MFP, VOPO4 does not evolve O2 on heating. Thus VOPO4 is less likely to cause a thermal runaway in batteries at elevated temperature, and so is inherently safer. The lithiated materials LiVOPO4, Li2VOPO4 and LiNi0.8Co0.15Al0.05O2 are found to be stable in the presence of electrolyte, but sealed capsule high-pressure experiments show a phase transformation of VOPO4 → HVOPO4 → H2VOPO4 when VOPO4 reacts with electrolyte (1 M LiPF6 in EC: DMC=1:1) between 200 and 300 °C. Using first principles calculations, we confirm that the charged VOPO4 cathode is indeed predicted to be marginally less stable than FP, but significantly more stable than NCA in the absence of electrolyte. An analysis of the reaction equilibria between VOPO4 and EC using a multi-component phase diagram approach yields products and reaction enthalpies that are highly consistent with the experiment results.
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The safety behavior of lithium-ion batteries under external mechanical crush is a critical concern, especially during large-scale deployment. We previously presented a sequentially coupled mechanical-electrical-thermal modeling approach for studying mechanical-abuse-induced short circuit. In this work, we study different mechanical test conditions and examine the interaction between mechanical failure and electrical-thermal responses, by developing a simultaneously coupled mechanical-electrical-thermal model. The present work utilizes a single representative-sandwich (RS) to model the full pouch cell with explicit representations for each individual component such as the active material, current collector, separator, etc. Anisotropic constitutive material models are presented to describe the mechanical properties of active materials and separator. The model predicts accurately the force-strain response and fracture of battery structure, simulates the local failure of separator layer, and captures the onset of short circuit for lithium-ion battery cells under sphere indentation tests with three different diameters. Electrical-thermal responses to the three different indentation tests are elaborated and discussed. Numerical studies are presented to show the potential impact of test conditions on the electrical-thermal behavior of the cell after the occurrence of short circuit.
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After an introduction to lithium insertion compounds and the principles of Li-ion cells, we present a comparative study of the physical and electrochemical properties of positive electrodes used in lithium-ion batteries (LIBs). Electrode materials include three different classes of lattices according to the dimensionality of the Li+ ion motion in them: olivine, layered transition-metal oxides and spinel frameworks. Their advantages and disadvantages are compared with emphasis on synthesis difficulties, electrochemical stability, faradaic performance and security issues.
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Thermal runaway characteristics of two types of commercially available 18650 cells, based on LixFePO4 and Lix(Ni0.80Co0.15Al0.05)O2 were investigated in detail. The cells were preconditioned to state of charge (SOC) values in the range of 0% to 143%; this ensured that the working SOC window as well as overcharge conditions were covered in the experiments. Subsequently a series of temperature-ramp tests was performed with the preconditioned cells. Charged cells went into a thermal runaway, when heated above a critical temperature. The following thermal runaway parameters are provided for each experiment with the two cell types: temperature of a first detected exothermic reaction, maximum cell temperature, amount of produced ventgas and the composition of the ventgas. The dependence of those parameters with respect to the SOC is presented and a model of the major reactions during the thermal runaway is made.
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In order to better understand the behavior of lithium-ion batteries under mechanical abuse, a coupled modeling methodology encompassing the mechanical, electrical and thermal response is presented for predicting short-circuit under external crush. The combined mechanical-electrical-thermal response is simulated in a commercial finite element software LS-DYNA® using a representative-sandwich finite-element model, where electrical-thermal modeling is conducted after an instantaneous mechanical crush. The model includes an explicit representation of each individual component such as the active material, current collector, separator, etc., and predicts their mechanical deformation under quasi-static indentation. Model predictions show good agreement with experiments: the fracture of the battery structure under an indentation test is accurately predicted. The electrical-thermal simulation predicts the current density and temperature distribution in a reasonable manner. Whereas previously reported models consider the mechanical response exclusively, we use the electrical contact between active materials following the failure of the separator as a criterion for short-circuit. These results are used to build a lumped representative sandwich model that is computationally efficient and captures behavior at the cell level without resolving the individual layers.
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State-of-energy (SoE) is a very important index for battery management system (BMS) used in electric vehicles (EVs), it is indispensable for ensuring safety and reliable operation of batteries. For achieving battery SoE accurately, the main work can be summarized in three aspects. (1) In considering that different kinds of batteries show different open circuit voltage behaviors, the Gaussian model is employed to construct the battery model. What is more, the genetic algorithm is employed to locate the optimal parameter for the selecting battery model. (2) To determine an optimal tradeoff between battery model complexity and prediction precision, the Akaike information criterion (AIC) is used to determine the best hysteresis order of the combined battery model. Results from a comparative analysis show that the first-order hysteresis battery model is thought of being the best based on the AIC values. (3) The central difference Kalman filter (CDKF) is used to estimate the real-time SoE and an erroneous initial SoE is considered to evaluate the robustness of the SoE estimator. Lastly, two kinds of lithium-ion batteries are used to verify the proposed SoE estimation approach. The results show that the maximum SoE estimation error is within 1% for both LiFePO4 and LiMn2O4 battery datasets.
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The failure mechanism of LiFePO4 cells during overcharge conditions has been systematically studied using commercial A123 18650 cells at a 1C rate and different conditions - from 5% to 20% overcharge (SOC = 105% to 120%). SEM/EDX, high-energy synchrotron XRD (HESXRD), and cyclic voltammetry (CV) were used to characterize the morphology, structure, and electrode potentials of cell components both in situ and ex situ. The failure behaviors for A123 18650 cells experiencing different degrees of overcharges were found to be similar, and the 10% overcharge process was analyzed as the representative example. The Fe redox potentials in the 1.2 M LiPF6 EC/EMC electrolyte were measured during the overcharge/discharge process using CV, proving that Fe oxidation and reduction in the cell during the overcharge/discharge cycle is theoretically possible. A possible failure mechanism is proposed: during the overcharging process, metallic Fe oxidized first to Fe2+, then to Fe3+ cations; next, these Fe2+ and Fe3+ cations diffused to the anode side from the cathode side; and finally, these Fe3+ cations reduced first to Fe2+ cations, and then reduced further, back to metallic Fe. During overcharge/discharge cycling, Fe dendrites continued growing from both the anode and the cathode sides simultaneously, penetrating through the separator and forming an iron bridge between the anode and cathode. The iron bridge caused micro-shorting and eventually led to the failure of the cell. During the overcharge/discharge cycles, the continued cell temperature increase at the end of overcharge is evidence of the micro-shorting.
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The safety issues of lithium ion batteries pose ongoing challenges as the market for Li-ion technology continues to grow in personal electronics, electric mobility, and stationary energy storage. The severe risks posed by battery thermal runaway necessitate safeguards at every design level – from materials, to cell construction, to module and pack assembly. One promising approach to pack thermal management is the use of phase change composite materials (PCC™), which offer passive protection at low weight and cost while minimizing system complexity. We present experimental nail penetration studies on a Li-ion pack for small electric vehicles, designed with and without PCC, to investigate the effectiveness of PCC thermal management for preventing propagation when a single cell enters thermal runaway. The results show that when parallel cells short-circuit through the penetrated cell, the packs without PCC propagate fully while those equipped with PCC show no propagation. In cases where no external short circuits occur, packs without PCC sometimes propagate, but not consistently. In all test conditions, the use of PCC lowers the maximum temperature experienced by neighboring cells by 60 °C or more. We also elucidate the propagation sequence and aspects of pack failure based on cell temperature, voltage, and post-mortem data.
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This paper presents a fault detection method for short circuits based on the correlation coefficient of voltage curves. The proposed method utilizes the direct voltage measurements from the battery cells, and does not require any additional hardware or effort in modeling during fault detection. Moreover, the inherent mathematical properties of the correlation coefficient ensure the robustness of this method as the battery pack ages or is imbalanced in real applications. In order to apply this method online, the recursive moving window correlation coefficient calculation is adopted to maintain the detection sensitivity to faults during operation. An additive square wave is designed to prevent false positive detections when the batteries are at rest. The fault isolation can be achieved by identifying the overlapped cell in the correlation coefficients with fault flags. Simulation and experimental results validated the feasibility and demonstrated the advantages of this method.
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This study investigates the external short circuit (ESC) fault characteristics of lithium-ion battery experimentally. An experiment platform is established and the ESC tests are implemented on ten 18650-type lithium cells considering different state-of-charges (SOCs). Based on the experiment results, several efforts have been made. (1) The ESC process can be divided into two periods and the electrical and thermal behaviors within these two periods are analyzed. (2) A modified first-order RC model is employed to simulate the electrical behavior of the lithium cell in the ESC fault process. The model parameters are re-identified by a dynamic-neighborhood particle swarm optimization algorithm. (3) A two-layer model-based ESC fault diagnosis algorithm is proposed. The first layer conducts preliminary fault detection and the second layer gives a precise model-based diagnosis. Four new cells are short-circuited to evaluate the proposed algorithm. It shows that the ESC fault can be diagnosed within 5 s, the error between the model and measured data is less than 0.36 V. The effectiveness of the fault diagnosis algorithm is not sensitive to the precision of battery SOC. The proposed algorithm can still make the correct diagnosis even if there is 10% error in SOC estimation.
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In this paper, a 3D thermal runaway (TR) propagation model is built for a large format lithium ion battery module. The 3D TR propagation model is built based on the energy balance equation. Empirical equations are utilized to simplify the calculation of the chemical kinetics for TR, whereas equivalent thermal resistant layer is employed to simplify the heat transfer through the thin thermal layer. The 3D TR propagation model is validated by experiment and can provide beneficial discussions on the mechanisms of TR propagation. According to the modeling analysis of the 3D model, the TR propagation can be delayed or prevented through: 1) increasing the TR triggering temperature; 2) reducing the total electric energy released during TR; 3) enhancing the heat dissipation level; 4) adding extra thermal resistant layer between adjacent batteries. The TR propagation is successfully prevented in the model and validated by experiment. The model with 3D temperature distribution provides a beneficial tool for researchers to study the TR propagation mechanisms and for engineers to design a safer battery pack.
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Lithium ion batteries have now been used as a power source for electric vehicles; however, their safety still remains a serious concern as the accidents reported increase with the rapid increase of electric vehicles in transportation markets. To address this issue, we describe herein a novel temperature-responsive cathode by coating an ultra-thin layer of poly(3-octylthiophene) (P3OT) with a thickness less than 1 μm in between the Al substrate and cathode-active LiCoO2 layer to form a sandwiched Al/P3OT/LiCoO2 cathode (LCO-PTC). This LCO-PTC cathode demonstrates almost the same electrochemical performance as the conventional LiCoO2 cathode at ambient temperature but a strong PTC behavior to switch off the cell reaction in a high temperature range of 90-100 °C, thus protecting the cell from thermal runaway. Because of its easy fabrication, cost effectiveness and particularly good compatibility with the current battery technology, this new type of PTC electrode can be conveniently extended to other Li-insertion cathodes for building safer Li-ion batteries.
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As lithium ion batteries are adopted in electric vehicles and stationary storage applications, the higher number of cells and greater energy densities increases the risks of possible catastrophic events. This paper shows a definition and method to calculate the state of safety of an energy storage system based on the concept that safety is inversely proportional to the concept of abuse. As the latter increases, the former decreases to zero.
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In this study, manganese orthophosphate (Mn3(PO4)2) is investigated as a new coating material for the Ni-rich LiNi0.6Co0.2Mn0.2O2 cathode with the aim of improving its thermal properties. A sol–gel process is employed to achieve a uniform coating of nano–sized crystalline Mn3(PO4)2. The coated electrode is found to exhibit an improved rate capability at high current drain, and cycle performance is enhanced at a high temperature of 60 °C. The effect of the Mn3(PO4)2 coating thus formed is further investigated by AC impedance spectroscopy, the results of which confirm that interfacial impedance is significantly decreased even in the initial cycles, and the growth of impedance is successfully suppressed during progressive cycles. The thermal stability of LiNi0.6Co0.2Mn0.2O2 is also improved by the Mn3(PO4)2 coating, because of the high structural stability attributed to strong PO4 covalent bonds. On the basis of these results, the Mn3(PO4)2 coating is proposed as a viable surface modification method for the enhancement of the electrochemical and thermal properties of LiNi0.6Co0.2Mn0.2O2.
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Four kinds of commercialized separator film product for lithium-ion battery are selected, the composition and structural features of separator film materials are characterized by means of FT-IR spectrometer, XRD and SEM, and their thermal performances are analyzed by TGA and DSC. In addition, the mechanical and heat-resistant performances, as well as liquid absorbency of separator film material are also tested. The results show that non polyolefin separator film has better heat-resistant performance, but poorer mechanical performance.
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The test scheme was established according to the V-t characteristic of oil-filled transformer insulation. The long-term insulation property under the 10-hour and 1.5Um/√3 power frequency voltage was proposed as the test condition to evaluate the insulation margin of UHV lead exit. The insulation margin test system was designed and manufactured, which allows the lead exit to be tested independently from the transformer or reactor. The partial discharge (PD) level was taken as the characteristic parameter to study the electrical performance of the lead exit under long duration voltage. The two connection mode of PD test circuit was adopted. Based on the analysis of PD circuit, a method of distinguishing the PD position was presented to exclude the interference of bushing PD so as to accurately evaluate the test result. The test result shows that the self-developed UHV AC lead exit in China has good insulation performance without any partial discharge under the long duration power frequency withstand voltage.
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To improve the safety of Li-ion battery, the specific flame-retardant electrolytes and their properties were studied. Triphenyl phosphate(TPP) and dimethyl methyl phosphonate (DMMP) were used as the cosolvent in 1M LiPF6/EC:DEC (1:1 in weight) to reformulate the nonflammable electrolyte. The flame-retarded ability, thermal and electrochemical performances with these electrolytes were studied. The results show that the optimal mass fractions are 55% TPP and 35% DMMP by controlling the flame-retardant efficiency (η≥0.9) of the electrolytes. Furthermore, the modified electrolyte matches the electrode materials well in both physical and electrochemical stability. © 2015, Editorial Department of Transactions of Beijing Institute of Technology. All right reserved.
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The thermal stability of a layered transition metal oxide with complete Al-substitution, Li 1-xNi 1/3CO 1/3Al 1/3O 2 (NCA 1/3), is studied in comparison to its better understood analogue, Li 1-xNi 1/3Co 1/3Mn 1/3O 2 (NCM), to elucidate information critical to the safety of lithium-ion battery materials. NCA 1/3 and NCM have crystalline structures with the R-3m space group by synthesis at high temperature from coprecipitate precursors. The specific capacities for NCA 1/3 and NCM are 115 mAh/g and 180 mAh/g when cycled within 2.5-4.5 V. The delithiated compounds maintained their R-3m structure, although this structure is lost after annealing to 750°C Thermogravimetric analysis coupled with mass spectrometry data confirms the loss of oxygen at 271°C and 292°C for NCM and NCA 1/3 delithiated to 4.4 V, respectively. The heat generation reaction of delithiated NCM is 91.7 J/g compared to just 10.5 J/g for NCA 1/3. The improved thermal stability offered by NCA 1/3 is attributed to its low Li + capacity due to the substitution of Al 3+ for Mn 4+ and its low heat of reaction due to the stability of the intermediate crystalline phases during delithiation and annealing.
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To understand the cooling effect of power battery system within electric vehicle, this paper experimentally studied a phase change material/oscillating heat pipe (PCM/OHP)-based battery thermal management (BTM) system. The influencing factors, including temperature variations under different heating powers, battery surrogate terminal direction and OHP placement, were discussed. In this study, the cooling effects of OHP-cooled and PCM/OHP-based BTM system were also compared. The results showed that: (1) in order to obtain evenly distributed temperature, the start-up temperature of OHP, which was decided by the target temperature and maximum temperature difference (ΔT), should be below the phase change temperature of PCM; (2) the battery surrogate terminals should be away from the adiabatic section of OHP; (3) the PCM/OHP-based BTM system designed in this study was more efficient in cooling than the OHP-cooled system. The results of this experiment may contribute to designing of the PCM/OHP coupled battery cooling system.
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Lithium ion capacitors (LICs) show great promise for electricity storage. However, cycle degradation and unbalanced electrode kinetics of LICs are troublesome. Meanwhile, safety has become a stringent requirement for lithium devices. Finding methods to tackle these problems is rather challenging. Here, we develop a smart lithium ion supercapacitor (SLIC) by implanting a lithium electrode into a two-electrode pouch cell. The proof-of-concept SLIC has three smart functions: (1) energy boosting: it supports an on-line electrochemical charge injection protocol that boosts the energy of symmetrical all-carbon supercapacitors. A SLIC with single-wall carbon nanotubes (SWCNTs) as both electrodes has a gravimetric energy 5 times higher than conventional supercapacitors using SWCNTs and excellent durability with no measurable degradation during 10,000 cycles; (2) safety monitoring: it allows real-time diagnosis of cell decay and warns of dangers by a built-in feedback mechanism; (3) self-regeneration: it enables regeneration of a degraded SLIC by a voltage modulator. From a practical point of view, this SLIC concept offers a general solution for extending the life of sealed power sources.
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The effects of vinylethylene carbonate (VEC) as electrolyte additive and the content of VEC in ethylene carbonate (EC)-based electrolyte on the formation mechanisms of solid electrolyte interphase (SEI) film and the electrochemical properties of the graphite electrodes in lithium-ion batteries are investigated by cyclic voltammetry (CV) measurement and charge-discharge test. Enhanced electrochemical performance is observed for graphite electrodes in VEC-containing electrolytes with low content. Scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy are used to investigate the morphology and the surface chemistry of graphite electrodes cycled in VEC-free and VEC-containing electrolytes. Finally, electrochemical impedance spectroscopy (EIS) is used in order to better understand the formation mechanisms of SEI film in VEC-containing electrolyte. The results reveal that the main reduction products of the SEI film formed in VEC-containing electrolyte are VEC polymerizes, Li2CO3 and ROCO2Li. The SEI film covering graphite electrodes in VEC-containing electrolyte can be more stable during lithium ions insertion, and be flexible to accommodate the volume changes of graphite material, resulting in a better reversibility of lithium ions insertion and extraction.
Article
Small lightweight electric vehicle (SLEV) is an approach for compensating low energy density of the current battery. However, small lightweight vehicle presents technical challenges to crash safety design. One issue is that mass of battery pack and occupants is a significant portion of vehicle's total weight, and therefore, the mass distribution has great influence on crash response. This paper presents a parametric analysis using finite element modeling. We first build LS-DYNA model of a two-seater SLEV with curb weight of 600 kg. The model has no complex components and can provide reasonable crash pulses under full frontal rigid barrier crash loading and offset deformable barrier (ODB) crash loading. For given mass of battery pack and one occupant (the driver), different battery layouts, representing different combinations of center of gravity and moment of inertia of the whole vehicle, are analyzed for their influences on the crash responses under the two frontal crash loadings. Then the mass of a second occupant is added to the passenger side for analysis. It has been found that these changes of mass distribution have significant impact on the crash pulse shape and peak, through the pitch in the full frontal crash loading and the yaw in the ODB loading. Therefore, mass distribution is critical in crash safety design of SLEV.
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Storage of electrical energy generated by variable and diffuse wind and solar energy at an acceptable cost would liberate modern society from its dependence for energy on the combustion of fossil fuels. This perspective attempts to project the extent to which electrochemical technologies can achieve this liberation. Realization of a reversible plating of a Lithium or Sodium anode through a solid Li+ or Na+ electrolyte would offer the best solution for a rechargeable battery that powers electric vehicles, thereby replacing the internal combustion engines that are creating a distributed emission of polluting gases from an increasing fleet of automobiles. Removal from the cathode to an external store of the product of the chemical reaction on discharge of a rechargeable battery can increase the capacity and lower the cost of stationary electrical energy storage in a battery. The ability to store electrical energy from wind and/or solar energy in rechargeable batteries at distributed sites can lower the cost and enhance the security of energy availability. The contributions from electrochemical capacitors and reversible fuel cells are also considered.
Article
In this paper, a composite membrane with nonwoven polyimide (PI) membrane as structural support and polyethylene (PE) particles coating layer as a thermal shutdown layer, is fabricated as the separator for lithium-ion battery. Different from PI nonwoven membrane, the PE coating PI nonwoven composite membrane (PE-PI-S) not only shows excellent thermal shutdown function, similar to traditional multilayer PP/PE/PP separator, but also exhibits much higher thermal stability, better wettability to the polar electrolyte and lower internal resistance than the PP/PE/PP separator. The electrolyte uptake and ionic conductivity of PEePIeS increase from 58%, 0.84 mS cm�1 to 400%, 1.34 mS cm�1, respectively. Furthermore, the thermal shutdown function of PE-PI-S can be controlled widely in the temperature range from 120 oC to more than 200 �C while the multilayer PP/PE/PP separator only with a shutdown temperature range from 130 oC to 160 oC. Lithium ion battery with PE-PI-S nonwoven separator also shows excellent stable cycling and good rate performance.
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The life cycle cost and environmental impacts of electric vehicles are very uncertain, but extremely important for making policy decisions. This study presents a new model, called the Electric Vehicles Regional Optimizer, to model this uncertainty and predict the optimal combination of drivetrains in different U.S. regions for the year 2030. First, the life cycle cost and life cycle environmental emissions of internal combustion engine vehicles, gasoline hybrid electric vehicles, and three different Electric Vehicle types (gasoline plug-in hybrid electric vehicles, gasoline extended range electric vehicle, and all-electric vehicle) are evaluated considering their inherent uncertainties. Then, the environmental damage costs and the water footprint of the studied drivetrains are estimated. Additionally, using an Exploratory Modeling and Analysis method, the uncertainties in the life cycle cost, environmental damage cost, and water footprint of studied vehicle types are modeled for different U.S. electricity grid regions. Finally, an optimization model is coupled with Exploratory Modeling and Analysis to find the ideal combination of different vehicle types in each U.S. region for the year 2030. The findings of this research will help policy makers and transportation planners to prepare our nation's transportation system for the influx of electric vehicles.
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Chemical reactions taking place at elevated temperatures in a polymer-bonded lithiated carbon anode were studied by differential scanning calorimetry. The influences of parameters such as degree of intercalation, number of cycles, specific surface area, and chemical nature of the binder were elucidated. It was clearly established that the first reaction taking place at ca. 120-140 degrees C was the transformation of the passivation layer products into lithium carbonate, and that lithiated carbon reacted with the molten binder via dehydrofluorination only at T > 300 degrees C. Both reactions strongly depend on the specific surface area of the electrodes and the degree of lithiation.
Article
The LiCoO2/mesocarbon microbeads (MCMB) batteries are over-discharged to 102% DOD, 105% DOD and 115% DOD, respectively, then are fully charged and cycled 1000 times at 0.6 C with 30% DOD. The capacity fading mechanism during long-term cycling of over-discharged batteries is analyzed by electrochemical and physical characterization. No remarkable difference is found on the morphology of LiCoO2 material from SEM. However, copper is detected on anode over-discharged to 115% DOD by EDS and XRD. The structures of LiCoO2 and MCMB materials have almost no change according to the result of XRD test. The performance of MCMB material can be degraded by over-discharge, however the LiCoO2 material still keeps good performance. The capacity of MCMB electrode is improved after being washed with water to remove the SEI film, indicating that the capacity loss of MCMB electrode is mainly attributed to the increase of SEI film. The capacity deterioration of over-discharged battery is mainly caused by the dissolution of copper current collector and the deposition of Cu on the surface of anode during the following charging process. The copper deposited on the surface of anode can hinder the lithium intercalation into/de-intercalation from the anode and promote the increase of SEI film.
Article
Lithium-ion batteries are becoming increasingly important for electrifying the modern transportation system and, thus, hold the promise to enable sustainable mobility in the future. However, their large-scale application is hindered by severe safety concerns when the cells are exposed to mechanical, thermal, or electrical abuse conditions. These safety issues are intrinsically related to their superior energy density, combined with the (present) utilization of highly volatile and flammable organic-solvent-based electrolytes. Herein, state-of-the-art electrolyte systems and potential alternatives are briefly surveyed, with a particular focus on their (inherent) safety characteristics. The challenges, which so far prevent the widespread replacement of organic carbonate-based electrolytes with LiPF6 as the conducting salt, are also reviewed herein. Starting from rather "facile" electrolyte modifications by (partially) replacing the organic solvent or lithium salt and/or the addition of functional electrolyte additives, conceptually new electrolyte systems, including ionic liquids, solvent-free, and/or gelled polymer-based electrolytes, as well as solid-state electrolytes, are also considered. Indeed, the opportunities for designing new electrolytes appear to be almost infinite, which certainly complicates strict classification of such systems and a fundamental understanding of their properties. Nevertheless, these innumerable opportunities also provide a great chance of developing highly functionalized, new electrolyte systems, which may overcome the afore-mentioned safety concerns, while also offering enhanced mechanical, thermal, physicochemical, and electrochemical performance. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.