金属锂电池的热失控与安全性研究进展

锂离子电池在便携式储能器件及电动汽车领域得到了广泛应用,然而频繁发生的电池起火爆炸事故,使热失控和热安全问题备受人们关注,目前已有多篇综述报道了缓解锂离子电池热失控的措施。相比于已经接近理论比能极限的锂离子电池,金属锂负极具有更高的比容量、更低的电势和高反应活性,但是不可控的锂枝晶生长,使得金属锂电池的热失控问题更为复杂和严重。针对金属锂电池的热失控问题,本文首先介绍了热失控的诱因及基本过程和阶段,其次从材料层面综述了提高电池热安全性的多种策略,包括使用阻燃性电解质、离子液体电解质、高浓电解质和局域高浓电解质等不易燃液态电解质体系,开发高热稳定性隔膜、热响应隔膜、阻燃性隔膜和具有枝晶检测预警与枝晶消除功能的新型智能隔膜,以及研究热响应聚合物电解质,最后对金属锂电池热失控在未来的进一步研究进行了展望。     

锂离子电池释热机理与模型及安全改性技术研究综述

锂离子电池具有能量功率密度高、寿命长、无记忆效应等优点，被广泛应用于移动电子产品、电动汽车、储能系统、航空航天等领域。然而近年来以电池热失控相关的电动汽车和储能系统安全事故频发，引起高度关注。高能量密度电池的高安全性是推动电池大规模应用的首要保障，以电池产热特性、热失控机理、防护和抑制方法为核心的研究成为近几年电池热安全领域的热点。因此，本文对电池热安全领域的核心问题进行了全面的综述。首先讨论电池在常规工况下的产热特性、热失控链式放热反应以及三种滥用条件下的电池失效机理；其次，阐述电池电化学-热耦合模型以及热失控模型的机理方程、构建、应用及演化；再次，介绍电池正负极材料、隔膜、电解液以及集流体安全改性技术的研究进展；最后本文对该领域的研究趋势做出展望，为提升锂离子电池的本征安全性，防止热失控提供思路和方向。     

阴极限制型Li／SOCl2电池过放电产物的热分析

Li/SOCl_2电池体系以其高比能量和优异的放电性能引起了电源界的重视。有关该体系的不安全行为曾有一些研究。本文用DSC、EDAX、XPS等方法分析了电池的反应产物和热敏性,和模拟组分对比,以图找出引起电池热失控爆炸的原因。     

高安全锂离子电池复合集流体的界面强化

面向高能量密度电池的高比容量三元正极材料的应用，使锂离子电池更容易发生热失控，这不仅降低了其安全性,也限制了锂离子电池的进一步发展。如何在提高能量密度的同时保证电池的安全性是亟待解决的问题。以绝缘高分子薄膜为支撑基材，两侧沉积金属层得到了具有夹芯结构的铝复合集流体能有效保证电池在针刺条件下的安全性，且更轻的复合集流体的使用能进一步提高电池能量密度。但高分子基材与铝金属层之间界面结合力较差，这会导致复合集流体在高温电解液浸泡中发生脱层现象，从而影响其在电池中的使用。本研究采用聚对苯二甲酸乙二醇酯(PET)作为支撑基材，通过在铝金属镀层与高分子基材之间引入氧化物中间层，有效地增强了金属与高分子基材之间的界面结合力，提升复合集流体的电解液兼容性。此外，复合集流体良好的机械性能使其能很好地兼容现有的电池制备技术，利用其制备的软包电池表现出与使用传统铝箔为集流体的电池相当的电化学性能。进一步的针刺测试表明，复合集流体能有效阻止锂电池在针刺过程中的热失控，显著改善了电池的安全性能。     

一维棒状ZnO的制备及电化学嵌锂性能研究

目前,商业化锂离子电池一般采用石墨作为负极材料,因其电位与金属锂电极的电位很接近,所以当电池反复循环和过充时,石墨表面易析出金属锂,会因形成枝晶而短路。在温度过高时还容易引起热失控。同时,锂离子电池的容量在很大程度上取决于负极的锂嵌入量,而且石墨材料容量相对较低     

锂离子电池安全性保护措施研究进展

锂离子电池最常见的安全性问题主要出现在电解液和隔膜.热失控是导致锂离子电池产生安全事故的主要原因.改变电解液组分、增加电解液组分、引入阻燃添加剂等措施,能够有效缓解并抑制热效应,降低可燃性.改性聚烯烃隔膜是提高隔膜热稳定性的简单方法,使用高熔点的聚合物或无机材料对隔膜进行修饰,其本质类似于给隔膜穿上一层“外骨骼”,用来抵御热冲击和机械冲击.隔膜在保证具备基本功能的同时,还要更加环保,逐步转向可持续的生物质材料.本文针对近年来锂离子电池的安全保护措施进行了综述,主要包括近几年内部保护措施和外部保护措施的相关研究和探索方面的成果.详细介绍了最近报道的不易燃电解液、阻燃添加剂、隔膜、正极材料、限流设备和电池管理系统的作用机理和研究进展,并展望了未来锂离子电池安全性研究的发展方向.     

利用启普发生器原理解决金属空气电池的停机腐蚀问题

金属空气电池的负极与电解液在停机期间一直接触发生腐蚀反应,这严重影响了金属空气电池的保质期。 通过对常规金属空气电池结构简单改进,利用启普发生器原理解决金属空气电池的停机腐蚀问题。 以铝箔为负极搭建结构改进前后的金属空气电池单池进行间断性恒流放电来测试电池停机寿命,并通过失重实验、析氢损耗测试实验对电池负极的停机腐蚀情况进行定量研究。 结果显示,当负极为0.25 mm厚铝箔时,金属空气电池结构改进前后的停机寿命分别为4和21 d;改进结构后的金属空气电池负极在相同时间内的停机腐蚀量远小于常规金属空气电池负极;对单池而言,产生固液分离所需的氢气只需要消耗约0.0380 g的铝,约为一般商用铝负极的0.038%。     

非水溶剂Li-O_2电池锂负极研究进展（英文）

非水溶剂Li-O_2电池因其高的理论能量密度,近年来备受关注。非水溶剂Li-O_2电池的典型结构为金属锂负极、含Li+的非水溶剂电解液和多孔氧气正极。目前,多数Li-O_2电池研究集中在正极的氧气电极反应;金属锂负极极强的还原性导致的副反应使Li-O_2电池中的化学和电化学反应变得更为复杂。因为,电解液和从正极扩散来的O_2都会与金属锂发生反应;锂负极上生成的副反应产物同样会扩散到正极一侧,干扰正极的O_2反应。此外,锂负极上可能生成锂枝晶,降低电池的安全性能,进而阻碍Li-O_2电池的实用化。因此,研究并解决锂负极的电化学稳定性和安全问题迫在眉睫。本文综述了近年来国内外在非水溶剂Li-O_2电池锂负极保护和修饰方面的最新研究进展,包括:可替代的对/参比电极的选择、电解液和添加剂、复合保护层与隔膜的研究、先进实验技术的开发与应用、并针对未来非水溶剂Li-O_2电池的发展进行了展望。     

静电纺丝技术在锂-空气电池上的应用

近年来,锂-空气电池由于具有极高的理论容量和对环境友好等优势,作为“终极电池”引起了广大科研工作者和电动汽车公司的极大兴趣和广泛关注. 但目前锂-空气电池还存在着充放电过电位大、循环性能差等局限性,寻找高效的锂-空气电池催化剂成为该领域发展的研究热点之一. 锂-空气电池阴极催化剂主要有贵金属、非贵金属、碳材料以及金属氧化物等,可通过多种方法合成制备,如水热(溶剂热)法、溶胶-凝胶法、共沉淀法、静电纺丝法等等. 其中,静电纺丝技术由于具有制备方法简易、高效且产量高等优点,近年来得到了长足的发展,可以用来大量制备锂-空气电池阴极催化剂,甚至制备自支撑结构的锂-空气电池阴极催化剂材料. 本文综述了静电纺丝技术在锂-空气电池上的应用,主要包括利用静电纺丝技术制备非贵金属催化剂、碳材料催化剂、金属氧化物催化剂和复合催化剂等,以及将制备的催化剂组装成锂-空气电池后表现出的优异的电池性能.     

钠基固体电解质及其在能源上的应用

由于以钠基固体电解质为核心的新型钠电池体系具有低成本和高安全性,在能源领域应用潜力巨大。高离子电导率和稳定性是钠基固体电解质应用于新型钠电池体系的前提。近年来,人们通过对制备方法改进和掺杂改性等方面的研究显著提高了钠基固体电解质的离子电导率和稳定性。此外,新型钠电池体系亟需解决固体电解质与电极间的界面接触性差和界面稳定性差等问题。本文首先总结了β″-Al₂O₃、NASICON型、硫化物类和聚合物类钠基固体电解质的研究进展,然后介绍了钠基固体电解质在以钠-硫电池,有机/水混合系钠-空气电池和全固态钠离子电池为代表的新型钠电池体系中的应用情况,并对界面问题和采取的解决策略进行系统论述。基于固体电解质的新型钠电池体系在能源上的大规模应用还需要电池材料、界面和电池设计等多方面的研究同时突破。     

Thermal runaway and fire behavior investigation of lithium ion batteries using modified cone calorimeter

The lithium ion battery has been widely used, but it has high fire risk due to its flammable materials. In this study, a series of combustion tests are conducted on the 18650-type lithium ion batteries using the modified cone calorimeter. The temperature and voltage variation of the battery, heat release rate and gas generation during combustion are measured in this study. The battery is heated evenly by the self-made heater, and the reliable trigger temperatures of thermal runaway are obtained for different states of charge (SOCs) batteries in this study. The fire behavior of the 100% SOC batteries is shown in this paper. The net heat absorption by the battery before thermal runaway is calculated based on the heat transfer theory. It ranges from 56.81 to 64.05 kJ for 0 to 100% SOC batteries, which shows a decreasing trend as SOC increases. The peak combustion heat release rate of 100% SOC batteries is 3.747?±?0.858 kW. CH₄ and CO gases are detected before and after thermal runaway. The generation of CO shows an increasing trend as SOC increases. Some suggestions on the early warning system of battery thermal runaway are proposed based on this study.

     

Evaluation of thermal hazard for commercial 14500 lithium-ion batteries

Commercial lithium-ion batteries ranged from different sizes, shapes, capacities, electrolytes, anode and cathode materials, etc. have recently caused many incidents under abusive or normal operating conditions worldwide. Inherently safer designs with active or passive protections have became the captious issues that need more attentions paid to. In this study, the worst scenarios on thermal runaway of four commercial batteries were conducted and compared. A customized-made closed testing instrument was utilized to measure and track thermal behaviors of four brands of cylindrical lithium-ion batteries under maximum open circuit voltage condition. Characteristics on thermal hazards of lithium-ion batteries such as onset temperature, maximum temperature, maximum self-heat rate, maximum pressures, battery mass loss, etc. were measured and evaluated. Results point out that one brand of cells reached the maximum temperature and maximum self-heat rate of 590.9 K and 1,130.4 K min^?1, respectively. In conclusion, in case of thermal runaway all the lithium-ion batteries will rupture the cell and catch fire automatically owing to the maximum temperatures over the auto-ignition temperature of electrolytes and the maximum pressure higher than four times of maximum allowable working pressure, respectively. In addition, Lithium-ion battery with cathode material of LiFePO₄ was verified to be more stable than the lithium-ion battery with cathode material of LiMn₂O₄ or LiCoO₂.     

Thermal hazard evaluations of 18650 lithium-ion batteries by an adiabatic calorimeter

In this study, the thermal hazard features of various lithium-ion batteries, such as LiCoO₂ and LiFePO₄, were assessed properly by calorimetric techniques. Vent sizing package 2 (VSP2), an adiabatic calorimeter, was used to measure the thermal hazards and runaway characteristics of the 18650 lithium-ion batteries under an adiabatic condition. The thermal behaviors of the lithium-ion batteries were obtained at normal and abnormal conditions in this study. The critical parameters for thermal hazardous behavior of lithium-ion batteries were obtained including the exothermic onset temperature (T ₀), heat of decomposition (ΔH), maximum temperature (T _max), maximum pressure (P _max), self-heating rate (dT/dt), and pressure rise rate (dP/dt). Therefore, the result indicates the thermal runaway situation of the lithium-ion battery with different materials and voltages in view the of TNT-equivalent method by VSP2. The hazard gets greater with higher voltage. Without the consideration of other anti-pressure measurements, different voltages involving 3.3, 3.6, 3.7, and 4.2 V are evaluated to 0.11, 0.23, 0.88, and 1.77 g of TNT. Further estimation of thermal runaway reaction and decomposition reaction of lithium-ion battery can also be confirmed by VSP2. It shows that the battery of a fully charged state is more dangerous than that of a storage state. The technique results showed that VSP2 can be used to strictly evaluate thermal runaway reaction and thermal decomposition behaviors of lithium-ion batteries. The loss prevention and thermal hazard assessment are very important for development of electric vehicles as well as other appliances in the future. Therefore, our results could be applied to define important safety indices of lithium-ion batteries for safety concerns.     

Study about thermal runaway behavior of high specific energy density Li-ion batteries in a low state of charge

Lithium-ion batteries are widely used in electric vehicles and electronics, and their thermal safety receives widespread attention from consumers. In our study, thermal runaway testing was conducted on the thermal stability of commercial lithium-ion batteries, and the internal structure of the battery was analyzed with an in-depth focus on the key factors of the thermal runaway. Through the study of the structure and thermal stability of the cathode, anode, and separator, the results showed that the phase transition reaction of the separator was the key factor affecting the thermal runaway of the battery for the condition of a low state of charge.     

Thermal management of modern electric vehicle battery systems (MEVBS)

Journal of Thermal Analysis and Calorimetry - The operating temperature of Li-ion batteries used in modern electric vehicles should be maintained within an allowable range to avoid thermal runaway...     

Thermal runaway features of 18650 lithium-ion batteries for LiFePO4 cathode material by DSC and VSP2

In view of availability, accountability, and applicability, LiFePO₄ cathode material has been confirmed to be better than LiCoO₂ cathode material. Nevertheless, few related researches were conducted for thermal runaway reaction of the LiFePO₄ batteries. In this study, vent sizing package 2 (VSP2) and differential scanning calorimetry were employed to observe the thermal hazard of 18650 lithium-ion batteries and their content??LiFePO₄ cathode material, which were manufactured by Commercial Battery, Inc. Two states of the batteries were investigated, which was charged to 3.6?V (fully charged) and 4.2?V (overcharged), respectively, and important parameters were obtained, such as self-heating rate (dT?dt ^?1), pressure-rise rate (dP?dt ^?1), and exothermic onset temperature (T ₀). The results showed that T ₀ for fully charged is about 199.94?°C and T _max is about 243.23?°C. The entire battery for LiFePO₄ cathode material is more stable than other lithium-ion batteries, and an entire battery is more dangerous than a single cathode material. For process loss prevention, the data of battery of VSP2 test were applied as reference for design of safer devices.     

Synthesis and characterization of reversible thermosensitive methylated chitin and its application in zinc-ion battery thermal runaway

Novel water-soluble methylated chitins (MCHs) were synthesized homogeneously in aqueous alkaline solution. The relatively mild reaction conditions resulted in the MCH with high degree of acetylation (DA >0.76). The chemical structure of the obtained MCHs was analyzed and the degree of methylation substitution (DS) and DA were determined by proton NMR in both D₂O and 20% DCl/D₂O. The MCH aqueous solutions (DS = 0.46 ~ 0.71) showed a reversible thermosensitive sol–gel–sol transition upon heating and cooling. The gel transition temperature of these MCHs (in the range of 15–85 °C) increased with increasing DS and decreasing polymer concentration. Thermal runaway has been an important safety issue impeding the development of high-energy-density zinc-ion batteries. A smart thermosensitive reversible electrolyte was prepared based on this MCH for the aqueous zinc-ion battery to prevent thermal runaway. When the temperature of zinc-ion battery rises or even gets out of control, the thermosensitive electrolyte can quickly gel and inhibit the migration of zinc ions, resulting in increase of the internal resistance and realizing intelligent and efficient thermal self-protection. Thus the novel thermosensitive methylated chitin shows promise for safe aqueous zinc-ion batteries.     

Fire behaviors study on 18650 batteries pack using a cone-calorimeter

To investigate the effects of different state of charges (SOCs), external heating powers and charging/discharging treatment on the fire behaviors of 18650 batteries pack, three groups of abuse experiments were conducted with the help of a cone-calorimeter. The fire hazards of batteries pack were characterized by measuring the flame photographs, battery surface temperature, ignition time, thermal runaway time, heat release rate and radiative heat flux. According to the results, it is found that the fire behaviors of batteries pack will appear in advance and behave more violent with the increase in SOC. Additionally, the higher heating power will exacerbate the fire hazards of batteries pack by increasing the surface temperature rise rate, the total heat released and the total heat flux of pack leading to an earlier thermal runaway and more rigorous consequence. Finally, the pack with discharging/charging treatment has a much lower heat released compared to the pack without any treatment due to the incomplete burning and incomplete release of energy. Besides, their fire behaviors also exhibit earlier and severer.

     

A multifunctional separator with Mg(OH)_2 nanoflake coatings for safe lithium-metal batteries

Dendrite growth and thermal runaway induce serious safety hazards,impeding the practical applications of lithium metal batteries(LMBs).Although extensive advances have been attained in terms of LMB safety,most work only focus on a single aspect at a time.This paper reports a multifunctional separator coated by Mg(OH)2 nanoflakes with various excellent properties including electrolyte wettability,ionic conductivity,Li+ transference number,puncture strength,thermal stability and flame retardance.When used in LMBs,the Mg(OH)2 nanoflake coatings enable uniform Li+ distributing,which makes it homogeneous to deposit lithium,realizing effective dendrite suppression and less volume expansion.Meanwhile,Mg(OH)2 coatings can ensure LMBs are in normal conditions without thermal runaway until 140 ℃.A part of lithium can be converted into Li+ ions by Mg(OH)2 during repeated charge/discharge cycles,not only reducing the risk of separator damage and consequent short circuit,but also replenishing the capacity loss of LMBs.The Mg(OH)2 nanoflakes can coat on all kinds of commercial separators to improve their performances,which offers a facile but effective strategy for fabricating multifunctional separators and a comprehensive insight into enhancing LMB safety.