Thermal Runaway Triggered by Plated Lithium on the Anode after Fast Charging

Understanding mechanical failure behaviours and protocol optimization for fast charging applications in Co-free Ni-based cathodes for lithium-ion batteries

Currently, it is a significant challenge to achieve long-term cyclability and fast chargeability in lithium-ion batteries, especially for the Ni-based oxide cathode, due to severe chemo-mechanical degradation. Despite its importance, the fast charging long-term cycling behaviour is not well understood. Therefore, we comprehensively evaluate the feasibility of fast charging applications for Co-free layered oxide cathodes, with a focus on the extractable capacity and cyclability. The cathodes with a Ni content of over 80% attain 80% of their nominal capacity, along with superior cyclability under fast charging due to the suppression of the following two mechanical failure modes: (i) Li-ion concentration shock fracture (CSF) and (ii) H2-H3 phase shock fracture (HSF). In particular, CSF produces stronger stress than HSF and causes severe crack penetration in mid-Ni cathodes under fast charging. Meanwhile, HSF induces mild internal stress, but prolonged exposure accelerates mechanical degradation. To maximize the fast charging application of high-Ni cathodes, we evaluated a 5C constant current constant voltage protocol to deliver 180 mAh g-1 in 35 min, improving the cycle life by up to 89% over 100 cycles with LiNi0.90Mn0.10O2. This study provides insights into the fast charging applications of high-Ni cathodes, thereby advancing the understanding of their behaviour and optimization.

Mechanism and Control Strategies of Lithium-Ion Battery Safety: A Review

Lithium-ion batteries (LIBs) are extensively used everywhere today due to their prominent advantages. However, the safety issues of LIBs such as fire and explosion have been a serious concern. It is important to focus on the root causes of safety accidents in LIBs and the mechanisms of their development. This will enable the reasonable control of battery risk factors and the minimization of the probability of safety accidents. Especially, the chemical crosstalk between two electrodes and the internal short circuit (ISC) generated by various triggers are the main reasons for the abnormal rise in temperature, which eventually leads to thermal runaway (TR) and safety accidents. Herein, this review paper concentrates on the advances of the mechanism of TR in two main paths: chemical crosstalk and ISC. It analyses the origin of each type of path, illustrates the evolution of TR, and then outlines the progress of safety control strategies in recent years. Moreover, the review offers a forward-looking perspective on the evolution of safety technologies. This work aims to enhance the battery community's comprehension of TR behavior in LIBs by categorizing and examining the pathways induced by TR. This work will contribute to the effective reduction of safety accidents of LIBs.

Composite Track-Etched Membranes: Synthesis and Multifaced Applications

Composite track-etched membranes (CTeMs) emerged as a versatile and high-performance class of materials, combining the precise pore structures of traditional track-etched membranes (TeMs) with the enhanced functionalities of integrated nanomaterials. This review provides a comprehensive overview of the synthesis, functionalization, and applications of CTeMs. By incorporating functional phases such as metal nanoparticles and conductive nanostructures, CTeMs exhibit improved performance in various domains. In environmental remediation, CTeMs effectively capture and decompose pollutants, offering both separation and detoxification. In sensor technology, they have the potential to provide high sensitivity and selectivity, essential for accurate detection in medical and environmental applications. For energy storage, CTeMs may be promising in enhancing ion transport, flexibility, and mechanical stability, addressing key issues in battery and supercapacitor performance. Biomedical applications may benefit from the versality of CTeMs, potentially supporting advanced drug delivery systems and tissue engineering scaffolds. Despite their numerous advantages, challenges remain in the fabrication and scalability of CTeMs, requiring sophisticated techniques and meticulous optimization. Future research directions include the development of cost-effective production methods and the exploration of new materials to further enhance the capabilities of CTeMs. This review underscores the transformative potential of CTeMs across various applications and highlights the need for continued innovation to fully realize their benefits.

Intrinsically Safe Lithium Metal Batteries Enabled by Thermo-Electrochemical Compatible In Situ Polymerized Solid-State Electrolytes

In situ polymerized solid-state electrolytes have attracted much attention due to high Li-ion conductivity, conformal interface contact, and low interface resistance, but are plagued by lithium dendrite, interface degradation, and inferior thermal stability, which thereby leads to limited lifespan and severe safety hazards for high-energy lithium metal batteries (LMBs). Herein, an in situ polymerized electrolyte is proposed by copolymerization of 1,3-dioxolane with 1,3,5-tri glycidyl isocyanurate (TGIC) as a cross-linking agent, which realizes a synergy of battery thermal safety and interface compatibility with Li anode. Functional TGIC enhances the electrolyte polymeric level. The unique carbon-formation mechanism facilitates flame retardancy and eliminates the battery fire risk. In the meantime, TGIC-derived inorganic-rich interphase inhibits interface side reactions and promotes uniform Li plating. Intrinsically safe LMBs with nonflammability and outstanding electrochemical performances under extreme temperatures (130 °C) are achieved. This functional polymer design shows a promising prospect for the development of safe LMBs.

Inorganic Composition Modulation of Solid Electrolyte Interphase for Fast Charging Lithium Metal Batteries

The solid electrolyte interphase (SEI) with lithium fluoride (LiF) is critical to the performance of lithium metal batteries (LMBs) due to its high stability and mechanical properties. However, the low Li ion conductivity of LiF impedes the rapid diffusion of Li ions in the SEI, which leads to localized Li ion oversaturation dendritic deposition and hinders the practical applications of LMBs at high-current regions (>3 C). To address this issue, a fluorophosphated SEI rich with fast ion-diffusing inorganic grain boundaries (LiF/Li3P) is introduced. By utilizing a sol electrolyte that contains highly dispersed porous LiF nanoparticles modified with phosphorus-containing functional groups, a fluorophosphated SEI is constructed and the presence of electrochemically active Li within these fast ion-diffusing grain boundaries (GBs-Li) that are non-nucleated is demonstrated, ensuring the stability of the Li || NCM811 cell for over 1000 cycles at fast-charging rates of 5 C (11 mA cm-2). Additionally, a practical, long cycling, and intrinsically safe LMB pouch cell with high energy density (400 Wh kg-1) is fabricated. The work reveals how SEI components and structure design can enable fast-charging LMBs.

Side Reactions/Changes in Lithium-Ion Batteries: Mechanisms and Strategies for Creating Safer and Better Batteries

Lithium-ion batteries (LIBs), in which lithium ions function as charge carriers, are considered the most competitive energy storage devices due to their high energy and power density. However, battery materials, especially with high capacity undergo side reactions and changes that result in capacity decay and safety issues. A deep understanding of the reactions that cause changes in the battery's internal components and the mechanisms of those reactions is needed to build safer and better batteries. This review focuses on the processes of battery failures, with voltage and temperature as the underlying factors. Voltage-induced failures result from anode interfacial reactions, current collector corrosion, cathode interfacial reactions, overcharge, and over-discharge, while temperature-induced failure mechanisms include SEI decomposition, separator damage, and interfacial reactions between electrodes and electrolytes. The review also presents protective strategies for controlling these reactions. As a result, the reader is offered a comprehensive overview of the safety features and failure mechanisms of various LIB components.

Structural Design and Energy and Environmental Applications of Hydrogen-Bonded Organic Frameworks: A Systematic Review

Hydrogen-bonded organic frameworks (HOFs) are emerging porous materials that show high structural flexibility, mild synthetic conditions, good solution processability, easy healing and regeneration, and good recyclability. Although these properties give them many potential multifunctional applications, their frameworks are unstable due to the presence of only weak and reversible hydrogen bonds. In this work, the development history and synthesis methods of HOFs are reviewed, and categorize their structural design concepts and strategies to improve their stability. More importantly, due to the significant potential of the latest HOF-related research for addressing energy and environmental issues, this work discusses the latest advances in the methods of energy storage and conversion, energy substance generation and isolation, environmental detection and isolation, degradation and transformation, and biological applications. Furthermore, a discussion of the coupling orientation of HOF in the cross-cutting fields of energy and environment is presented for the first time. Finally, current challenges, opportunities, and strategies for the development of HOFs to advance their energy and environmental applications are discussed.

Advances in All-Solid-State Lithium-Sulfur Batteries for Commercialization

Solid-state batteries are commonly acknowledged as the forthcoming evolution in energy storage technologies. Recent development progress for these rechargeable batteries has notably accelerated their trajectory toward achieving commercial feasibility. In particular, all-solid-state lithium-sulfur batteries (ASSLSBs) that rely on lithium-sulfur reversible redox processes exhibit immense potential as an energy storage system, surpassing conventional lithium-ion batteries. This can be attributed predominantly to their exceptional energy density, extended operational lifespan, and heightened safety attributes. Despite these advantages, the adoption of ASSLSBs in the commercial sector has been sluggish. To expedite research and development in this particular area, this article provides a thorough review of the current state of ASSLSBs. We delve into an in-depth analysis of the rationale behind transitioning to ASSLSBs, explore the fundamental scientific principles involved, and provide a comprehensive evaluation of the main challenges faced by ASSLSBs. We suggest that future research in this field should prioritize plummeting the presence of inactive substances, adopting electrodes with optimum performance, minimizing interfacial resistance, and designing a scalable fabrication approach to facilitate the commercialization of ASSLSBs.

Battery deactivation with redox shuttles for safe and efficient recycling

To safely recycle spent lithium-ion batteries (LIBs), their deactivation as a pretreatment is essential. However, the conventional deactivation methods, mainly inducing an external short circuit, cannot be applied to LIBs with disconnected electrical circuits or Li deposited, despite their safety risk. Here, we propose a deactivation method using redox shuttles (RSs). The addition of an RS with redox potentials located between the two electrode potentials into a LIB electrochemically induces an internal short circuit with or without disconnected electrical circuits. A fully charged LIB discharges to approximately 0 V when a deactivation agent containing ferrocene or phenothiazine as an RS is added. Moreover, we demonstrate that RSs introduced into LIB can simultaneously dissolve Li deposited on the negative electrode surface and return it to the positive electrode as mobile ions. These characteristics of our method contribute to the improvement in safety and collection rate of Li in the recycling processes, promoting the sustainability of LIBs.

Operando Li metal plating diagnostics via MHz band electromagnetics

A nondestructive detection method for internal Li-metal plating in lithium-ion batteries is essential to improve their lifetime. Here, we demonstrate a direct Li-metal detection technology that focuses on electromagnetic behaviour. Through an interdisciplinary approach combining the ionic behaviour of electrochemical reactions at the negative electrode and the electromagnetic behaviour of electrons based on Maxwell's equations, we find that internal Li-metal plating can be detected by the decrease in real part of the impedance at high-frequency. This finding enables simpler diagnostics when compared to data-driven analysis because we can correlate a direct response from the electronic behaviour to the metallic material property rather changes in the ionic behaviour. We test this response using commercial Li-ion batteries subject to extremely fast charging conditions to induce Li-metal plating. From this, we develop a battery sensor that detects and monitors the cycle-by-cycle growth of Li-metal plating. This work not only contributes to advancing future Li-ion battery development but may also serve as a tool for Li-metal plating monitoring in real-field applications to increase the useable lifetime of Li-ion batteries and to prevent detrimental Li-metal plating.

In Situ Li-Plating Diagnosis for Fast-Charging Li-Ion Batteries Enabled by Relaxation-Time Detection

The Li-plating behavior of Li-ion batteries under fast-charging conditions is elusive due to a lack of reliable indicators of the Li-plating onset. In this work, the relaxation time constant of the charge-transfer process (τCT ) is proposed to be promising for the determination of Li-plating onset. A novel pulse/relaxation test method enables rapid access to the τCT of the graphite anode during battery operation, applicable to both half and full batteries. The diagnosis of Li plating at varying temperatures and charging rates enriches the cognition of Li-plating behaviors. Li plating at low temperatures and high charging rates can be avoided because of the battery voltage limitations. Nevertheless, after the onset, severe Li plating evolves rapidly under harsh charging conditions, while the Li-plating process under benign charging conditions is accompanied by a simultaneous Li-intercalation process. The quantitative estimates indicate that Li plating at high temperatures/high charging rates leads to more irreversible capacity losses. This facile method with rational scientific principles can provide inspiration for exploring the safe boundaries of Li-ion batteries.

Coupled Effect of Low Temperature and Electrolyte Immersion on the Tensile Properties of Separators in Lithium-Ion Batteries

The performance degradation at low temperatures and frequent safety accidents have aggravated security risks and inhibited the long-term service of lithium-ion batteries (LIBs). As a key component of LIBs, the separator has a great impact on the performance and safety of the battery. In this study, tensile tests of two commercial polyolefin separators (Celgard 2325 and Celgard PE) are performed under low-temperature and immersion conditions. Four representative temperature points and dimethyl carbonate [(DMC), the common solvent in electrolytes] are selected to investigate the coupling effect on the mechanical properties of the separators. The results show that both the separators have anisotropy, but the performance of Celgard 2325 varies more significantly than that of Celgard PE along different directions. Additionally, it is found that with a decrease in the temperature, the tensile strength of the two separators increases, while the elongation decreases. Electrolyte immersion induces a softening tendency in Celgard 2325. Due to the special effect of the residual electrolyte on polyethylene fibers, Celgard PE shows the opposite result. Furthermore, the effect of low temperature is revealed by the analysis of the crystallinity and molecular structure, which can be obtained by X-ray diffraction and Raman spectroscopy, respectively. In addition, the contact angle is measured to describe the wettability variation related to low temperature. The present work provides a theoretical basis and experimental data for the application and development of separators.

Direct Observation of the Anisotropic Transport Behavior of Li+ in Graphite Anodes and Thermal Runaway Induced by the Interlayer Polarization

Graphite is one of the major anode materials for commercial lithium-ion batteries. Li+ transport in a single graphite granule along intra and interlayer modes is a crucial factor for the battery performance. However, direct evidence and visualized details of the Li+ transports are hardly provided. Here, we report the direct observation of the anisotropic transport behavior of Li+ and investigate the electro-chemo-structure evolution during the lithiation of graphite through both the intra and interlayer pathways via in situ transmission electron microscopy. The in situ experiments of nano batteries give two extreme conditions, in which thermal runaway induced by polarization only occurs along the interlayer, not along the intralayer. The high diffusion energy barrier induced large polarization when the interlayer Li+ transport became dominant. The energy of the polarization electric field would be instantaneously released like a short electric pulse, which generated a substantial amount of joule heat and created an extremely high temperature, causing the melting of the tungsten tip. We provide another possible fundamental mechanism of thermal failure in graphite-based Li-ion batteries and hope this insightful work would help the safety management of graphite-based lithium-ion batteries.

Quantifying the Influence of Li Plating on a Graphite Anode by Mass Spectrometry

The prominent problem with graphite anodes in practical applications is the detrimental Li plating, resulting in rapid capacity fade and safety hazards. Herein, secondary gas evolution behavior during the Li-plating process was monitored by online electrochemical mass spectrometry (OEMS), and the onset of local microscale Li plating on the graphite anode was precisely/explicitly detected in situ/operando for early safety warnings. The distribution of irreversible capacity loss (e.g., primary and secondary solid electrolyte interface (SEI), dead Li, etc.) under Li-plating conditions was accurately quantified by titration mass spectroscopy (TMS). Based on OEMS/TMS results, the effect of typical VC/FEC additives was recognized at the level of Li plating. The nature of vinylene carbonate (VC)/fluoroethylene carbonate (FEC) additive modification is to enhance the elasticity of primary and secondary SEI by adjusting organic carbonates and/or LiF components, leading to less "dead Li" capacity loss. Though VC-containing electrolyte greatly suppresses the H₂/C₂H₄ (flammable/explosive) evolution during Li plating, more H₂ is released from the reductive decomposition of FEC.

Toward Improving the Thermal Stability of Negative Electrode Materials: Differential Scanning Calorimetry and In Situ High-Temperature X-ray Diffraction/X-ray Absorption Spectroscopy Studies of Li2ZnTi3O8 and Related Compounds

Negative electrode materials with high thermal stability are a key strategy for improving the safety of lithium-ion batteries for electric vehicles without requiring built-in safety devices. To search for crucial clues into increasing the thermal stability of these materials, we performed differential scanning calorimetry (DSC) and in situ high-temperature (HT)-X-ray diffraction (XRD)/X-ray absorption (XAS) up to 450 °C with respect to a solid-solution compound of Li_4/3-2x/3Zn_xTi_5/3-x/3O₄ with 0 ≤ x ≤ 0.5. The DSC profile of fully discharged x = 0.5 (Li₂ZnTi₃O₈) with a LiPF₆-based electrolyte could be divided into three temperature (T) regions: (i) T ≤ 250 °C for ΔH_accumⁱ, (ii) 250 °C < T ≤ 350 °C for ΔH_accumⁱⁱ, and (iii) T > 350 °C for ΔH_accumⁱⁱⁱ, where ΔH_accumⁿ is the accumulated change in enthalpy in region n. The HT-XRD/XAS analyses clarified that ΔH_accumⁱ and ΔH_accumⁱⁱ originated from the decomposition of solid electrolyte interphase (SEI) films and the formation of a LiF phase, respectively. Comparison of the DSC profiles with x = 0 (Li[Li_1/3Ti_5/3]O₄) and graphite revealed the operating voltage, i.e., amount of SEI films, and stability of the crystal lattice play significant roles in the thermal stability of negative electrode materials. Indeed, the highest thermal stability was attained at x = 0.25 using this approach.

Highly Stable Iron- and Carbon-Based Electrodes for Li-Ion Batteries: Negative Fading and Fast Charging within 12 Min

Lithium-ion batteries (LIBs) with high energy density and safety under fast-charging conditions are highly desirable for electric vehicles. However, owing to the growth of Li dendrites, increased temperature at high charging rates, and low specific capacity in commercially available anodes, they cannot meet the market demand. In this study, a facile one-pot electrochemical self-assembly approach has been developed for constructing hybrid electrodes composed of ultrafine Fe₃ O₄ particles on reduced graphene oxide (Fe₃ O₄ @rGO) as anodes for LIBs. The rationally designed Fe₃ O₄ @rGO electrode containing 36 wt % rGO exhibits an increase in specific capacity as cycling progresses, owing to improvements in the active sites, electrochemical kinetics, and catalytic behavior, leading to a high specific capacity of 833 mAh g^-1 and outstanding cycling stability over 2000 cycles with a capacity loss of only 0.127 % per cycle at 5 A g^-1 , enabling the full charging of batteries within 12 min. Furthermore, the origin of this abnormal improvement in the specific capacity (called negative fading), which exceeds the theoretical capacity, is investigated. This study opens up new possibilities for the commercial feasibility of Fe₃ O₄ @rGO anodes in fast-charging LIBs.

Interface Engineering to Boost Thermal Safety of Microsized Silicon Anodes in Lithium-Ion Batteries

Battery safety is vital to the application of lithium-ion batteries (LIBs), especially for high energy density cells applied in electric vehicles. As an anode material with high theoretical capacity and natural abundance, Si has received extensive attention for LIBs. However, it suffers from severe electrode pulverization during cycling due to large volume changes and an unstable solid electrolyte interphase (SEI), resulting in accelerated capacity fading and even safety hazards. Therefore, safe and long-term cycling of Si-based anodes, especially under high-temperature cycling, is highly challenging for state-of-the-art high-energy LIBs. The thermal behavior of SEI is crucial for a high safety battery as the decomposition of SEI is the first step in thermal runaway. Here, highly reversible and thermotolerant microsized Si anodes for safe LIBs are demonstrated. Comprehensive electrochemical/mechanical/thermochemical behaviors of the SEI are systematically investigated. The rational design of robust SEI endows the Si-based cells with long-term durability at elevated temperatures and superior thermal safety. This work paves the way for designing industrial-scale, low-cost, microsized Si anodes with applications in next-generation LIBs with high energy densities and high safety.

Parallel battery pack charging strategy under various ambient temperatures based on minimum lithium plating overpotential control

With the aggravation of environmental pollution and energy crisis, lithium-ion batteries are widely regarded as promising. However, the current distribution in the parallel battery pack branches is highly heterogeneous. Charging strategies based on the models can be adopted to prevent side reactions that may lead to severe degradation or even thermal runaway under various ambient temperatures. In this study, a battery model for a single cell is established by coupling a single particle model with electrolyte, degradation model, and thermal model. Besides, considering the contact resistance and wire resistance, the circuit model of a battery pack is established. A charging strategy based on minimum Li plating overpotential control is then adopted, and the effectiveness under high C-rate and low temperature to reduce capacity loss is verified by simulation. This study provides a low-loss charging strategy that can reduce the safety risk of battery packs with better performance under various ambient temperatures.

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A cell model is established accurately under various C-rates and temperatures

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The contact and wire resistances are considered into the battery pack circuit model

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Side reactions like Li plating are accurately described in the model during cycling

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Charging strategy for parallel battery pack is adopted to prevent side reactions

Data-driven prediction of battery failure for electric vehicles

Despite great progress in battery safety modeling, accurately predicting the evolution of multiphysics systems is extremely challenging. The question on how to ensure safety of billions of automotive batteries during their lifetime remains unanswered. In this study, we overcome the challenge by developing machine learning techniques based on the recorded data that are uploaded to the cloud. Using charging voltage and temperature curves from early cycles that are yet to exhibit symptoms of battery failure, we apply data-driven models to both predict and classify the sample data by health condition based on the observational, empirical, physical, and statistical understanding of the multiscale systems. The best well-integrated machine learning models achieve a verified classification accuracy of 96.3% (exhibiting an increase of 20.4% from initial model) and an average misclassification test error of 7.7%. Our findings highlight the need for cloud-based artificial intelligence technology tailored to robustly and accurately predict battery failure in real-world applications.

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A well-integrated machine learning technique is applied to failure prediction

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A cloud-based closed-loop framework is established for real-world EV applications

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Cloud-based AI solution is based on an in-depth analysis of the field data

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Both electrochemical and statistical feature engineering are established

Uncovering LiH Triggered Thermal Runaway Mechanism of a High-Energy LiNi0.5 Co0.2 Mn0.3 O2 /Graphite Pouch Cell

The continuous energy density increase of lithium ion batteries (LIBs) inevitably accompanies with the rising of safety concerns. Here, the thermal runaway characteristics of a high-energy 5 Ah LiNi0.5 Co0.2 Mn0.3 O2 /graphite pouch cell using a thermally stable dual-salt electrolyte are analyzed. The existence of LiH in the graphite anode side is innovatively identified in this study, and the LiH/electrolyte exothermic reactions and H2 migration from anode to cathode side are proved to contribute on triggering the thermal runaway of the pouch cell, while the phase transformation of lithiated graphite anode and the O2 -releasing from cathode are just accelerating factors for thermal runaway. In addition, heat determination during cycling at two boundary scenarios of adiabatic and isothermal environment clearly states the necessity of designing an efficient and smart battery thermal management system for avoiding heat accumulation. These findings will shed promising lights on thermal runaway route map depiction and thermal runaway prevention, as well as formulation of electrolyte for high energy safer LIBs.

Wadsley-Roth Crystallographic Shear Structure Niobium-Based Oxides: Promising Anode Materials for High-Safety Lithium-Ion Batteries

Wadsley-Roth crystallographic shear structure niobium-based oxides are of great interest in fast Li+ storage due to their unique 3D open tunnel structures that offer facile Li+ diffusion paths. Their moderate lithiation potential and reversible redox couples hold the great promise in the development of next-generation lithium-ion batteries (LIBs) that are characterized by high power density, long lifespan, and high safety. Despite these outstanding merits, there is still extensive advancement space for further enhancing their electrochemical kinetics. And the industrial feasibility of Wadsley-Roth crystallographic shear structure niobium-based oxides as anode materials for LIBs requires more systematic research. In this review, recent progress in this field is summarized with the aim of realizing the practical applications of Wadsley-Roth phase anode materials in commercial LIBs. The review focuses on research toward the crystalline structure analyses, electrochemical reaction mechanisms, modification strategies, and full cell performance. In addition to highlighting the current research advances, the outlook and perspective on Wadsley-Roth anode materials is also concisely provided.

Influence of Aging on the Failing Behavior of Automotive Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are a dominant state-of-the-art energy storage system and have importance in the automotive sector. Still, LIBs suffer from aging effects and serious hazards from failing batteries are possible. These failures can lead to exothermic chemical reactions inside the cell, ending up in thermal runaway (TR). TR has caused most electric vehicle (EV) fires. Since statistically most accidents with EVs happen after about one year of vehicle usage, in particular, the failing behavior of aged cells needs to be investigated. Little information is available in open literature about the influence of aging paths on the failing behavior and especially on the degassing behavior of large automotive LIBs. Therefore, this study investigates the influence of three different aging paths (cyclic at −10 °C and at 45 °C and calendric at 60 °C) on the thermal behavior, the vent gas emission, and the vent gas composition. The results show a clear effect of aging on the failing behavior. The aged cells showed a less violent failing reaction, reduced maximal temperatures, lower amount of produced gas, significantly lower amount of CO in the vent gas, and lower mass loss than fresh cells in the same overtemperature experiments. The results are valuable for the scientific and industrial community dealing with LIBs.

Drive circuitry of an electric vehicle enabling rapid heating of the battery pack at low temperatures

Heating battery at low temperatures is fundamental to avoiding the range anxiety and the time-consuming charging associated with electric vehicles (EVs). One method for achieving fast and uniform battery heating is to polarize the cell under pulse currents. However, the on-board implementation of this method leads to an increase in the cost and size. Therefore, in this study, an adapted EV circuitry compatible with the existing one and an optimized operating condition are proposed to enable rapid battery heating. With this circuit, electricity transfer between the cells can be realized through a motor, leading to remarkably higher battery currents than those of the conventional circuit. The increase in the maximum heating currents (from 1.41C to 4C) resulted in a battery temperature rise of 8.6°C/min at low temperatures. This heating method exhibits low cost, high efficiency, and negligible effects on battery degradation, practical and promising on battery heating of EVs.

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Rapid temperature rise, high efficiency, and low cost for battery heating are obtained

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The batteries are divided into two modules and connected to the inverter individually

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The electricity transferred between battery modules is motivated by a static motor

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The pulse currents for battery heating are improved significantly at any frequency

Thermal runaway of Lithium-ion batteries employing LiN(SO2F)2-based concentrated electrolytes

Concentrated electrolytes usually demonstrate good electrochemical performance and thermal stability, and are also supposed to be promising when it comes to improving the safety of lithium-ion batteries due to their low flammability. Here, we show that LiN(SO₂F)₂-based concentrated electrolytes are incapable of solving the safety issues of lithium-ion batteries. To illustrate, a mechanism based on battery material and characterizations reveals that the tremendous heat in lithium-ion batteries is released due to the reaction between the lithiated graphite and LiN(SO₂F)₂ triggered thermal runaway of batteries, even if the concentrated electrolyte is non-flammable or low-flammable. Generally, the flammability of an electrolyte represents its behaviors when oxidized by oxygen, while it is the electrolyte reduction that triggers the chain of exothermic reactions in a battery. Thus, this study lights the way to a deeper understanding of the thermal runaway mechanism in batteries as well as the design philosophy of electrolytes for safer lithium-ion batteries.