Overview of research on thermal safety of lithium-ion batteries

随着锂离子电池在生活和工作中的普及,锂离子电池的安全事故逐年增加,锂离子电池的安全研究逐渐引起学术界的关注。研究锂离子电池的热安全性,可以有效分析锂离子电池发生起火和爆炸的内在原因,指导锂离子电池安全性研究的开展。本文介绍了锂离子电池工作过程中产热的来源和影响因素,以及锂离子电池热失控发生时的内部反应和反应对应的温度,并对电池热失控时的热特性参数进行了总结。     

Thermal management of lithium-ion batteries using phase change materials

良好的热管理系统是电池安全及高效使用的保证,电池的热管理需要确保电池温度在安全温度范围以及电池组内最大温差不超过5 ℃.传统的热管理方式,如空气冷却,不仅需要额外的动力输入,而且越来越不能满足高能量密度的新型锂离子电池的热管理需要.使用相变材料的电池热管理系统,利用相变材料的相变潜热吸收电池产生的热量,在不使用外界功耗的条件下,可以长时间保持电池的温度在适宜的范围内.通过与膨胀石墨,金属泡沫复合,相变材料的热导率可以大大提高,电池组内体系温度均匀性可以满足工作要求.而且,相变材料的形状不固定,可以使用在任意形状的电池上.被动式热管理是应用于电池热管理系统中最具前景的技术.     

Challenges in data-based degradation models for lithium-ion batteries

This work summarizes the findings resulting from applying an aging modeling approach to four different capacity loss experimental datasets of lithium-ion batteries (LIBs). This approach assumes that the degradation trajectory of the capacity is a function of three variables: time, kinetic constant, and time-dependent factor. The analysis shows that the time-dependent factor α is cell-chemistry dependent and cannot be averaged for calendar and cycling modes and combined modes. This factor was also found to be a function of the stress factors. A quadratic model was used to obtain the kinetic constants per test, and statistical metrics were provided to evaluate the quality of the fitting, which was significantly affected when using averaged values of α and refitted kinetic constants. A set of test matrices is proposed for calendar, cycling, and mixed aging modes to overcome the challenges of data-based models developed from accelerated test approaches for modeling aging in LIBs. This work also proposes a methodology to develop these data-based aging models.     

Thermal safety studies of high energy density lithium-ion batteries under different states of charge

The popularity of lithium-ion batteries in electric vehicles has promoted the increase of its energy density, and battery cathode and anode materials have developed rapidly in recent years. As the next generation of material systems, high-nickel-content Li-Ni-Co-Mn oxide cathode and high-silicon-content Si-C anode material systems have a high potential for further application. However, safety is a key indicator for their use in traction batteries. We thus conducted a thermal safety analysis of the pouch cells of such a system for different states of charge and revealed the key factors for the thermal safety evolution of batteries by analyzing the morphology and thermal stability of cathodes and anodes.     

Applications of carbon nanotubes in the lithium-ion batteries

碳纳米管因具有优异的电导率、热导率、力学性能以及独特的结构形貌,被用于改进锂离子电池性能。该文总结了近年来碳纳米管作为锂离子电池的添加剂、电极材料复合基体以及集流体的最新研究进展,重点介绍了最新的碳纳米管作为电极材料添加剂的使用方法、碳纳米管与电极材料的不同复合方法及其对锂离子电池容量性能、倍率性能以及循环寿命的影响。同时指出了碳纳米管在锂离子电池中大规模应用时需要克服的问题,如降低碳纳米管的制备成本、开发适用于工业生产的复合技术、改善碳纳米管的分散性能等。     

Experimental study on fire extinguishing of large-capacity lithium-ion batteries by various fire extinguishing agents

为研究不同灭火介质对大容量动力锂离子电池火灾的有效性,搭建了适用于多种灭火介质的灭火测试平台。在灭火测试平台上以功率为300 W的电热管作为外热源引发单电池热失控,通过改变灭火介质,研究了不同灭火介质的灭火行为及灭火效率。研究结果表明,对于38 A·h单体动力电池火灾,ABC干粉、七氟丙烷（HFC）、水、全氟己酮和CO₂灭火剂均能快速熄灭电池明火,但CO₂灭火剂灭火后电池出现了复燃;电池灭火过程中,不同的灭火剂在抑制电池温度上升表现出明显差异,其中,抑制温升效果优劣依次为水、全氟己酮、HFC、ABC干粉和CO₂。本研究的结果可为工程应用及电池灭火规范制定提供实验支撑。     

Patent application of silicon-based anode for lithium-ion batteries

本文通过对锂离子电池硅基负极技术领域的专利申请态势进行分析,揭示该技术领域当前的专利活动特点,为我国在该领域的科技创新和产业化提供参考。本文从国际专利申请数量年度分布、主要竞争国家/地区、专利技术来源国和目标国、主要专利申请人等方面,对硅基负极技术领域的专利申请态势进行分析,在此基础上,对世界范围内的主要竞争国家及重要申请人的专利申请特点进行重点分析。分析结果表明,硅基负极专利申请主要集中在中国、美国、日本和韩国。国外申请人注重同时在上述四国进行专利布局,并且已经在我国进行大量专利布局,而我国申请人主要在国内进行专利布局,在国外申请较少。最后,就我国未来的锂离子电池硅基负极技术的研发和专利申请与保护工作提出一些建议。     

The progress in fault diagnosis techniques for lithium-ion batteries

实施精准、可靠的故障诊断,是确保电池系统安全、稳定、可靠运行的关键,并为电池系统的精准运营维护提供理论、方法与技术支撑。本文首先在总结电池系统故障类型与表现形式的基础上,重点分析了在电池制造、成组筛选和使用各个阶段的本体故障引发机制。其次,对现有研究发展的电池系统故障诊断方法进行了分类,大致分为基于电池模型的故障诊断方法和无模型的故障诊断方法。之后,针对不一致故障诊断、短路故障诊断、热故障诊断、传感器故障诊断、连接组件故障诊断和多故障联合诊断,对现有文献提出的解决策略及应用案例进行了全面综述。最后,以全面文献调研为基础,提出了电池系统故障诊断研究面临的主要挑战和未来的研究方向。     

Research progress on electrolyte additives for high voltage lithium-ion batteries

普通锂离子电池在高电压下的氧化分解限制了高压锂离子电池的发展,为了解决这一问题,可以设计、合成新型的耐高压电解液;寻找合适的电解液添加剂,然而从经济效益考虑,发展合适的电解液添加剂来稳定电极/电解液界面更加受到研究者们的青睐。本文综述了最近几年在高压锂离子电池电解液添加剂方面的研究进展,并按照添加剂的种类将其分为6部分进行探讨：含硼类添加剂、有机磷类添加剂、碳酸酯类添加剂、含硫添加剂、离子液体添加剂及其它类型添加剂。分别对这些添加剂的作用机理、作用效果进行了阐述,展望了添加剂在高压锂离子电池中的发展前景及未来研究方向。     

Research progress of high safety flame retardant electrolytes for lithium-ion batteries

商品锂离子电池在机械冲击、热冲击和过充短路等滥用条件下易发生起火燃烧甚至爆炸。为了解决这一安全性问题,需要开发高安全性阻燃电解液取代传统易燃烧的碳酸酯电解液。本文综述了高安全性阻燃电解液的研究进展,首先介绍了燃烧机理、阻燃机理和阻燃测试方法,再阐述锂离子电池对阻燃电解液的性质要求,并对阻燃电解液进行分类探讨,包括阻燃添加剂、阻燃溶剂（共溶剂）、高浓度阻燃电解液、离子液体和阻燃型凝胶聚合物电解质。重点对这些高安全性阻燃电解液的配方、阻燃效果、适用的电池体系进行详细阐述。最后对高安全性阻燃电解液未来的研究方向进行展望。     

Review on state of health estimation of retired lithium-ion batteries

由于电池组中电池单体之间存在性能差异,退役锂离子电池在投入梯次利用前需要借助健康状态（SOH）评估技术进行电池单体的分类与配组。健康状态评估系统的构建涉及电池建模、电池测试、数据处理、算法开发等各种技术问题。目前通过基于模型的参数识别与直接提取健康因子是构建SOH评估体系的两种主要思路。在电池模型的简化、测试工况的设计、健康因子的选择和算法的应用与优化等方面已经有了很多研究。如何在缩短电池测试时间的同时提高评估系统的泛化能力是目前该研究领域的主要问题,这些问题的解决对于SOH评估系统真正在梯次利用锂离子电池的产业化中发挥作用至关重要。在未来的研究中通过优化测试工况和数据融合等技术,有望开发出性能更好的SOH评估系统。     

Application of biphenyl additive in electrolyte for liquid state Al-plastic film lithium-ion batteries

In order to investigate the influence of the biphenyl (BH) as a polymerizable electrolyte additive on the properties of Al-plastic film lithium-ion batteries, we examined the electrochemical properties of batteries which containing different amounts of BH. The main analysis tools were overcharge tests, linear sweep voltammetry, cycling tests, rate capability, thermal stability, AC impedance, etc. The results showed that the BH can electrochemically polymerize at the overcharge potential of 4.5–5.5 V to form a layer on the cathode surface, the internal resistance was increased rapidly after the electrode covered with the black electro-polymerization production, and the internal short-circuit was occurred with enough polymerization product, all of these caused to low overcharge current and good overcharge performance, meanwhile, the overcharge performance was increased with the increasing of BH content. However, the cycling performance was deteriorated with an increase in BH content, but not seriously, so the content of additive is ought to be adjusted to practical need in production.     

Thermal runaway-preventing technologies for lithium-ion batteries

安全性是制约高比能、大容量锂离子电池规模应用的重要技术问题,热失控是导致电池发生爆炸、燃烧等不安全行为的根本原因。从电化学角度来看,在锂离子电池内部建立一种自激发热保护机制,切断危险温度下电池内部的离子或电子传输,关闭电池反应,是解决这一问题的有效途径。基于这一考虑,近年来人们提出了一系列新型热失控防范技术,包括正温度系数电极（即PTC电极）、热敏性微球修饰隔膜（或电极）、热聚合添加剂等。本文在简要介绍这些安全性技术的实现方式和工作原理之后,重点介绍了这一领域的最新研究进展。在此基础上,从实际应用需求出发,对其存在的问题及发展趋势进行了探讨。     

Thermal behavior of lithium batteries used in electric vehicles using phase change materials

Electric vehicles equipped with lithium-ion batteries face a huge challenge, and the fact that battery life is very much affected by the temperature conditions of their operating environment, the heat reduces battery life cycle and time and increases the likelihood of thermal degradation and explosion. This problem has forced engineers to cool the battery. The methods used to cool the battery includes a cool water method (passing water or a dielectric fluid from the battery pack), cooling air (blowing air into the battery compartment by the fan), using a refrigeration system (such as cooling screens), and the use of phase-change material (PCM). In this research after reviewing and referring to valid authorities, it was found that PCMs are superior to all three other cooling systems because the air-conditioning system is not very desirable due to the high-temperature gradient between the battery cells. Also, cooling and refrigeration systems with refrigerant gases will also cost a very high cost on the electric car. The results of the studies showed that the cooling the battery using the PCM creates a similar temperature profile between the batteries in the battery pack, the temperature gradient is much smaller than the air cooler and cool water, and the final cost will be much lower. Also, it performs more efficiently in high-speed road dynamics and increases the battery life of an electric car or electric hybrid.     

Research on thermal runaway test platform design for energy-storage lithium-ion batteries

介绍了锂离子储能电池热失控研究的目的和意义,探讨了储能电池与动力电池在热失控检测实验研究关注上的异同,从理论分析和实验研究两方面归纳了影响储能电池热失控的促发条件及对应的关键阈值.在此基础上,完成了模拟热失控促发条件和满足阈值要求的检测实验平台设计及功能验证,并对此平台的应用前景进行了展望.     

Effect of binders on performances of ceramic coated separators for lithium-ion batteries

为优化陶瓷涂敷隔膜热稳定性,提高锂离子电池的安全性和电化学性能,本工作选用热稳定性优异的聚酰亚胺和电化学稳定的聚偏氟乙烯六氟丙烯作为复合黏结剂,将Al₂O₃无机颗粒涂敷于商品级聚烯烃隔膜两侧。通过调控两种黏结剂组分含量,测试隔膜性能发现,增加聚酰亚胺的含量可以明显提高涂覆隔膜的热稳定性,但隔膜的电化学性能不理想;在黏结剂中引入适量的聚偏氟乙烯六氟丙烯组分,涂覆隔膜可在保持其热稳定性的同时,获得良好的离子电导率、电化学稳定性和金属锂电极兼容性等性能。最后选用电化学性能表现最为优异且热稳定性良好的黏结剂组分制备陶瓷涂敷隔膜,在Li|LiCoO₂电池中,比聚烯烃隔膜表现出更优异的电化学性能,在8 C倍率下的放电比容量为109.3 mA/g,容量保持率为66.1%,而使用PE隔膜的电池的放电比容量和容量保持率仅为88.7 mA/g和54.7%。     

Thermal analysis of lithium-ion batteries

A detailed three-dimensional thermal model has been developed to examine the thermal behaviour of a lithium-ion battery. This model precisely considers the layered-structure of the cell stacks, the case of a battery pack, and the gap between both elements to achieve a comprehensive analysis. Both location-dependent convection and radiation are adopted at boundaries to reflect different heat dissipation performances on all surfaces. Furthermore, a simplified thermal model is proposed according to the examination of various simplification strategies and validation from the detailed thermal model. Based on the examination, the calculation speed of the simplified model is comparable with that of a one-dimensional model with a maximum error less than 0.54 K. These models successfully describe asymmetric temperature distribution inside a battery, and they predict an anomaly of temperature distribution on the surface if a metal case is used. Based on the simulation results from the detailed thermal model, radiation could contribute 43–63% at most to the overall heat dissipation under natural convection. Forced convection is effective in depressing the maximum temperature, and the temperature uniformity does not necessarily decrease infinitely when the extent of forced convection is enhanced. The metal battery case serves as a heat spreader, and the contact layer provides extra thermal resistance and heat capacity for the system. These factors are important and should be considered seriously in the design of battery systems.     

Applications of ultrasound technique in characterization of lithium-ion batteries

锂离子电池由于其在能量密度、循环寿命、能量效率、安全性等方面的综合优势,成为了应用最广泛的电化学储能器件,然而其性能仍有进一步提升的必要。大量的先进表征技术应用在锂电池研究中,有力推动了锂离子电池基础理论的进步。超声作为一种无损表征手段,具有灵敏度高、成本低、使用方便、速度快等优点,在电池特性表征领域具有巨大的应用潜力。本文总结概述了现有超声检测技术在电池表征领域的应用,包括内部气体检测、电解液浸润测试、电池析锂检测、电池荷电状态测量、电池寿命预测等,对其发展前景进行了展望。     

Recent progress in electrode materials for aqueous lithium-ion batteries

水系锂离子电池是以水溶液为电解质的二次电池,它克服了传统有机体系电池电解液昂贵,有毒,易燃,离子电导率低,制作成本高等缺点,成为继风能,太阳能后最具发展潜力的绿色能源之一.本文归纳了近年来国内外水系锂离子电池正负极材料的研究进展,介绍了各种电极材料存在的主要问题(如电极材料在电解液中的溶解,电解液中质子活性大导致电极材料发生副反应等)以及改性方法,并提出对电极材料进行修饰是水系锂离子电池未来的发展趋势.