Recent progress on thermal runaway propagation of lithium-ion battery

简述了电动汽车锂离子动力电池热失控蔓延机理、建模与抑制技术的最新研究进展。为了满足汽车高能量的要求,需要动力电池进行串并联成组来提供动力。电池组成组安全问题成为电动汽车大规模应用的重要技术问题。电池组中的某一个电池单体发生热失控后产生大量热,导致周围电池单体受热产生热失控。因而,电池组成组安全问题的重要关注点是电池组内的热失控蔓延问题。本文对锂离子电池热失控蔓延问题的国内外研究进展进行了综述,分析了对于不同种类锂离子动力电池影响其热失控蔓延特性的主要因素。总结了文献中的热失控蔓延建模方法,并指出了已有方法的不足。从电池系统热安全管理的角度,阐述并分析了热失控蔓延防控技术的研究成果与方向。最后对锂离子电池热失控蔓延研究进行了展望。     

Application-derived safety strategy for secondary utilization of retired power battery

本研究以退役锂离子动力电池梯次利用的细分应用场景需求为导向,以我国新能源汽车推广应用历程为基础,结合政策、技术、产业与市场发展的实际,阐述了梯次利用关键环节的安全问题及其应对策略。介绍了退役动力电池梯次利用模式,总结了不同正极材料动力电池报废与梯次利用现状及趋势,指出了面临的挑战与机遇,分析了动力锂离子电池在生产和车用环节的安全隐患,以及退役后在四种不同应用场景下进行梯次利用的安全需求与风险,研究了与动力电池类型、车载应用安全基础等优化匹配的梯次利用安全策略框架,并提出了创新动力电池开发设计模式、发展梯次利用关键技术、加快商业模式创新、加速培育梯次利用市场等综合策略。     

Industrial progress of nonaqueous liquid electrolytes for lithium-ion batteries

电解质是锂离子电池的关键材料,作为锂离子传输的媒介,其选择直接影响锂离子电池的能量密度、循环性能、倍率性能、储存性能及安全性等特性。我国电解液产业经过十多年的快速发展,已经具备了一定的国际竞争力。本文以锂离子电池电解液产业国产化进程为切入点,梳理了该产业的发展脉络,对国内电解液企业的市场份额和竞争格局进行了重点剖析;以电解液常用添加剂的专利持有情况为例,评述了国内外主要企业在电解液专利申请方面的差别;介绍了3C电池电解液、动力电池电解液、储能电池电解液以及功能性电解液等四大类产品的性能特点,着重阐述了前两类产品的设计开发思路;对我国锂离子电池电解液行业标准亦作了简述;展望了电解液材料的技术发展方向和产业前景。     

Recent progress on evolution of safety performance of lithium-ion battery during aging process

安全性是制约锂离子电池规模应用的重要技术问题。锂离子电池的安全性能不仅仅与材料体系、电芯设计相关,还会随着使用过程而发生变化。锂离子电池安全性能在全生命周期内的演变规律需要重点展开研究,以保障电池在使用过程中的安全性。本文对锂离子电池全生命周期安全性演变问题的国内外研究进展进行了综述,分析了国内外关于电池安全性能在循环老化和储存老化两种工况下的演变规律的研究,总结了电池老化衰减机理与安全性能变化之间的关系,指出负极析锂是影响电池全生命周期安全性能的重要因素,最后对锂离子电池全生命周期安全性演变研究进行了展望。     

Research on early warning system of lithium ion battery energy storage power station

研究锂离子电池储能电站消防预警技术对于储能系统的安全运行具有重要意义。本文通过对电池热失控及热扩散特征识别展开讨论,由于锂离子电池发生热失控时会伴随着可燃气体缓慢释放,如果能够提取电池热失控早期气体参数并对其进行研究分析,可以在此基础上建立电池系统的热失控预警机制。本文采用加热方式和过充方式诱发电池热失控气体提取试验,通过采气试验进行气体成分含量分析,确定了将一氧化碳和温度作为典型的侦测依据来实现锂电池热失控的早期预警。并将这种电池热失控早期预警判断应用到了储能电站消防预警系统中,同时结合多级预警及防护机制和安全联动策略做了深入研究,确定了锂离子电池储能电站消防预警系统的设计架构,从系统部件、联动通信、人员安全3个方面对系统设计做了简要说明,在保证快速有效的检测出电池热失控状态的同时快速联动消防设施,极大提高了储能系统运行的可靠性。     

Review of lithium-ion battery state of charge estimation

The technology deployed for lithium-ion battery state of charge (SOC) estimation is an important part of the design of electric vehicle battery management systems. Accurate SOC estimation can forestall excessive charging and discharging of lithium-ion batteries, thereby improving discharge efficiency and extending cycle life. In this study, the key lithium-ion battery SOC estimation technologies are summarized. First, the research status of lithium-ion battery modeling is introduced. Second, the main technologies and difficulties in model parameter identification for lithium-ion batteries are discussed. Third, the development status and advantages and disadvantages of SOC estimation methods are summarized. Finally, the current research problems and prospects for development trends are summarized.     

Research progress of high rate Li-ion battery materials

电动汽车行业迅速发展,高倍率的锂离子电池是其关键,因此需要不断开发适用高倍率充放电的电池材料。本文简要综述了高倍率锂离子电池正极材料、负极材料、隔膜和电解液方面的研究进展,并对高倍率锂离子电池材料发展进行了展望。     

基于加速寿命试验的锂离子电池可靠性分析方法

为了有效地提高锂离子电池寿命评估的准确性,延长储能系统在配电网中运行年限,文章提出了基于加速寿命试验的锂离子电池可靠性分析方法。综合考虑不同放电深度对锂离子电池寿命影响,建立了锂离子电池的寿命衰退模型;确定了荷电状态(SOC)与健康度(SOH)的关联特性关系;提出了基于逆幂率方程的储能系统加速寿命试验方法;基于情景分析法对锂离子电池的可靠性进行了分析。研究结果表明,文章所提出的试验方法能够准确地对不同运行状态下的锂离子电池储能系统进行可靠性评估,保证储能系统并网运行过程中的调控准确性。     

Solar photovoltaic charging of lithium-ion batteries

Solar photovoltaic (PV) charging of batteries was tested by using high efficiency crystalline and amorphous silicon PV modules to recharge lithium-ion battery modules. This testing was performed as a proof of concept for solar PV charging of batteries for electrically powered vehicles. The iron phosphate type lithium-ion batteries were safely charged to their maximum capacity and the thermal hazards associated with overcharging were avoided by the self-regulating design of the solar charging system. The solar energy to battery charge conversion efficiency reached 14.5%, including a PV system efficiency of nearly 15%, and a battery charging efficiency of approximately 100%. This high system efficiency was achieved by directly charging the battery from the PV system with no intervening electronics, and matching the PV maximum power point voltage to the battery charging voltage at the desired maximum state of charge for the battery. It is envisioned that individual homeowners could charge electric and extended-range electric vehicles from residential, roof-mounted solar arrays, and thus power their daily commuting with clean, renewable solar energy.     

Research progress on capacitive lithium-ion battery

锂离子电池具有高的能量密度,而超级电容器则以高功率密度和长循环寿命为突出优势。电容型锂离子电池是在锂离子电池的正极中加入部分电容炭材料,在不显著降低能量密度的情况下,大幅度改善锂离子电池的功率特性和循环寿命,从而实现电容与电池技术的融合。本文综述了国内外近年来在电容型锂离子电池领域的最新研究进展,介绍了主要的电容型锂离子电池体系及其性能特点,并对其未来发展方向进行了展望。     

Recycling and reusing batteries: A significant way for effective sustainability of FCEVs and EVs

In the last 20 years, the transportation sector has enabled the technology to evolve in its direction with both environmental and energy efficiency in the use of electric and fuel cell vehicles. The two important components of these vehicles are the batteries and electric motors. The batteries are produced within a certain life cycle, and unfortunately it is not possible to use them without conversion/recycling. In this study, the crucial importance of battery recycling/reusing is underliying and last researches will be given about battery recycling, above next ten years. Recommendations and future forseen advices will be presented about the current state of battery recycling technology, how recycling systems exist in different batteries, and the future of battery recycling standart. As a result, battery recycling and reusing for fuel cell and electric vehicles is considered to be an important keypoint in terms of both envirenmontial, economical and technologial menner for the transportation sector in the next decades.     

Effectiveness analysis of energy reclamation from partially depleted batteries

This paper presents the study of energy reclamation from partially depleted primary batteries using secondary battery cells as temporary energy repositories. A DC/DC power converter is interposed between the two types of batteries to control the discharging of the primary battery as well as the charging of the secondary battery. The energy reclamation process is simulated and verified in the virtual test bed (VTB) computational environment using pre-validated battery models. Energy transferring and power losses among components are quantificationally studied. For an example system including a lithium sulfur dioxide primary battery with an initial state-of-charge of 0.3 at 296 K, an aggregated total of 216 kJ of energy is reclaimed and 82.87% of the energy (179 kJ) is stored in a 10-cell lithium-ion battery pack. A simple application scenario is used to show the potentially significant benefit of performing this energy reclamation technology. The study results demonstrate that 8.3% of weight and 10% of cost are saved. The main factors affecting the system performance are varied and the effects are analyzed. The results show that battery energy reclamation can be improved by: (1) appropriately increasing the battery operating temperature, (2) using relatively low discharging current, and (3) improving the power converter efficiency at the user-specified discharging current level.     

Analysis of equalization technology of series lithium-ion battery pack based on power frequency modulation

近年来,锂离子电池在储能电站调频领域得到了飞速发展。为满足调频电站的电压和功率要求,需将大量电池单体进行串联,如此产生的电池组串联不一致性问题,以及调频过程中高倍率和频繁切换充放电状态对不一致性程度的加剧,严重影响电池组的使用寿命和安全性能。针对上述问题,本文基于调频储能串联锂离子电池模组不一致性问题的形成原因,归纳分析用于改善电池组串联不一致性问题的均衡技术和均衡策略。其中,均衡拓扑结构按能量流向角度进行分类梳理,均衡控制策略则基于均衡的不同目标进行优劣分析。在此基础上对锂离子调频电池模组均衡技术的发展趋势进行展望。     

废旧锂离子动力电池的性能和梯次利用的可能性研究

近年来随着电动汽车产业的发展,大量锂离子动力电池达到使用寿命,进入报废退役阶段,报废动力电池的处置成为人们关注的热点。综述了废旧锂离子动力电池的性能和梯次利用方面的技术进展,指出做好筛选分类与重新组合的工作,以确保二次利用电池组内部电池单元性能的同质性将是梯次利用的关键。     

State of health prediction model based on internal resistance

The state of health (SOH) is a crucial indicator of lithium-ion batteries. A battery cycle and calendar life are critical for electric vehicle batteries. Complex interactions occur between the SOH and internal resistance of a battery. In this study, several ternary lithium-ion battery charge discharge experiments were performed to investigate the effects of the ambient temperature, discharge rate, and depth of discharge on a battery's internal resistance. An SOH prediction model was then constructed and used to evaluate the remaining capacity of the electric vehicle battery. The model was verified through various experiments, and a comparison of experimental and model-derived data revealed a favorable agreement. Thus, the model accurately predicted the SOH of a ternary lithium-ion battery.     

The patent road of power battery unicorn——Analysis of CATL patent application and layout

本文从专利申请与布局角度出发,分析了宁德时代新能源科技股份有限公司的历年申请趋势、申请地域布局、申请技术布局、重点技术分支及研发路径等方面的基本情况,并将上述专利信息与企业自身发展及行业特点综合分析,总结出其成长为动力电池独角兽企业的深层原因,主要为专利申请与企业发展并行、兼顾海内外专利布局、工艺流程的持续改善、在优势领域提升研发专注度、在核心领域坚持自主创新,上述成功经验值得国内外同行或初创企业学习借鉴。     

循环充放电条件下锂离子电池的温度模拟

锂离子电池在充放电过程中产生的热量主要为两部分,即因电化学反应而产生的可逆热和由极化产生的不可逆热。若电池内部温度达到82℃以上时,钴酸锂电池材料将发生热分解,引发一系列不可控化学反应,释放出大量的反应热。本论文在可逆热和不可逆热的基础上,耦合电池材料分解热,采用有限元技术,模拟锂离子电池在充放电过程中不同对流条件以及不同外界温度下电池内部温度的变化,为揭示锂离子电池热失控机制提供理论依据。     

Progress in lithium ion battery simulation model

基于锂离子电池的仿真对新能源汽车动力电池的生产与应用的重要性,本文对锂离子电池模型的分类以及近年来的发展进行了分析,包括对集中质量模型、一维模型、二维模型、三维模型的研究,以及包含多个维度子模型的多物理场耦合模型的研究,并总结了当前模型的不足之处和未来需要发展的方向。     

基于深度神经网络的梯次利用电池健康状态评估

随着大量退役电池梯次利用,对退役动力电池健康状态的准确估计是保障电池梯次利用安全高效运行的前提。针对上述问题,提出基于深度神经网络学习的梯次利用电池健康状态评估方法。根据不同循环次数下梯次利用电池充放电性能的差异性,从梯次利用电池物理特性角度挖掘影响梯次利用电池老化特征的主要参数,利用皮尔逊法计算电池老化特征与梯次利用电池健康状态的相关系数,选取较高相关度特征作为深度神经网络的输入,建立基于深度神经网络学习的梯次利用电池健康状态评估模型。通过美国国家航空航天局Ames卓越预测中心的锂离子电池测试数据仿真实例验证了该文方法的有效性。仿真结果表明,与传统神经网络相比,深度神经网络学习可明显提高梯次利用电池健康状态的预测精度,为退役动力电池健康状态评估提供理论依据。     

A comprehensive study on thermal conductivity of the lithium-ion battery

The reliable thermal conductivity of lithium-ion battery is significant for the accurate prediction of battery thermal characteristics during the charging/discharging process. Both isotropic and anisotropic thermal conductivities are commonly employed while exploring battery thermal characteristics. However, the study on the difference between the use of two thermal conductivities is relatively scarce. In this study, the isotropic and anisotropic thermal conductivities of the four commercially available lithium-ion batteries, ie, LiCoO₂, LiMn₂O₄, LiFePO₄, and Li (NiCoMn)O₂, were reviewed and evaluated numerically through the heat conduction characteristics inside the battery. The results showed that there are significant differences in the temperature distribution in the battery caused by the isotropic and anisotropic thermal conductivities, which could affect the layout and cooling effectiveness of battery thermal management system. Furthermore, the effective thermal conductivities of porous electrodes and separator were determined to establish thermal conductivity bounds of lithium-ion batteries combined with the thicknesses of battery components. The thermal conductivity bounds could be applied to evaluate the rationality of the thermal conductivity data used in battery thermal models.