In situ detection of lithium dendrite in the failure of lithium-ion batteries

锂离子电池在应用过程中常出现一些失效现象如循环寿命缩短、自放电率变大、功率特性劣化等,甚至发生安全问题。负极析锂是导致这些失效甚至安全问题的主要因素之一,因此了解析锂的原因与过程就显得格外重要。探明析锂原因的关键是表征锂的存在和锂枝晶的生长过程。本文综述了锂离子电池负极析锂现象常用的原位检测技术,包括物理检测法和电化学法。物理检测法主要介绍：光学原位技术、原位X射线技术、原位核磁技术以及原位中子技术,电化学方法包含：充放电电压曲线法、Arrhenius法、内阻容量曲线分析法和容量衰减率法。本文针对物理检测法的原理、优缺点以及对应的特殊检测装置实例,电化学检测法的原理及分析方法等进行简要概述,并对目前析锂原位检测存在的问题进行总结及其研究方向进行展望。     

Rechargeable lithium sulfide electrode for a polymer tin/sulfur lithium-ion battery

In this work we investigate the electrochemical behavior of a new type of carbon-lithium sulfide composite electrode. Results based on cyclic voltammetry, charge (lithium removal)-discharge (lithium acceptance) demonstrate that this electrode has a good performance in terms of reversibility, cycle life and coulombic efficiency. XRD analysis performed in situ in a lithium cell shows that lithium sulfide can be converted into sulfur during charge and re-converted back into sulfide during the following discharge process. We also show that this electrochemical process can be efficiently carried out in polymer electrolyte lithium cells and thus, that the Li₂S-C composite can be successfully used as cathode for the development of novel types of rechargeable lithium-ion sulfur batteries where the reactive and unsafe lithium metal anode is replaced by a reliable, high capacity tin-carbon composite and the unstable organic electrolyte solution is replaced by a composite gel polymer membrane that is safe, highly conductive and able to control dendrite growth across the cell. This new Sn-C/Li₂S polymer battery operates with a capacity of 600 mAh g⁻¹ and with an average voltage of 2 V, this leading to a value of energy density amounting to 1200 Wh kg⁻¹.     

High safety electrolyte for lithium-ion battery

锂离子电池安全性问题的本质是电池内部发生了热失控,热量不断的累积,造成电池内部温度持续上升,其外在的表现是燃烧、爆炸等。因此,锂离子电池的安全性与比能量、使用温度和倍率性能等存在一定的矛盾。电池能量密度越高、倍率性能越快和使用环境越恶劣,其能量剧烈释放时对电池体系的影响就越大,安全问题也越突出。当前锂离子电池电解液一般由低闪点的碳酸酯、对痕量水和温度敏感的LiPF₆和其它添加剂组成,本身具有高度可燃性。同时,电解液与正负极材料之间形成界面膜被认为是电池热失控的起点。因此,电解液改性是提升电池安全性的重要措施。本文分析了离子液体和氟代溶剂等溶剂对电解液安全性的提升效果,对比了多种锂盐对电解液安全性的影响,介绍了阻燃剂、过充保护剂、锂枝晶抑制剂和成膜稳定剂等电解液添加剂对锂电池安全性的改善。最后,从电池整体应用性能的角度出发,讨论了今后高安全性锂离子电池电解液的研发方向。     

Interpretation of the electrode binder standard for lithium ion battery

电极黏结剂是锂离子电池的重要辅助功能材料之一,虽然本身没有容量,但却是维持电极完整性的关键,决定了电极涂层的附着力和电极的柔韧性,并会影响到电极浆料的流变特性等工艺性能。本文主要分析了与电极黏结剂相关的国内标准,对锂离子电池电极黏结剂的相关特性和测试方法进行了介绍,并对未来电极黏结剂标准的制定提出了建议。     

Low temperature thermal safety performance of soft packaged lithium iron phosphate battery

本文以剩余容量接近80%的软包磷酸铁锂电池为研究对象,研究其在-10 ℃低温充放电循环后的安全性能.对低温和常温循环后的电池进行热失控实验分析,同时解剖电池并测试电池材料的锂元素含量和热稳定性能.测试结果表明,电池低温循环过程中容量急剧衰减,低温循环后电池热失控温度明显降低,低温循环过程中电池负极析出了锂单质,电池材料的热稳定性也发生了变化.另外,还对低温循环后的电池进行了满电状态下的常温搁置实验,实验过程中电池全部产生胀气现象,通过进一步测试分析发现,气体以CO和H₂为主.与新电池对比发现,剩余容量接近80%的软包磷酸铁锂电池低温下充放电循环更容易产生锂枝晶,造成其电化学性能发生严重的不可逆衰退,热失控温度明显提前,因此剩余容量接近80%的磷酸铁锂电池应避免在低温下运行.     

动力汽车用锂电池热管理系统仿真分析

为了研究动力汽车用锂电池温度场分布,建立了单体电池及电池组仿真模型,通过实验与FLUENT软件模拟验证的方式分析单体电池温度场。通过仿真分析讨论电池组温度场,采用三种不同的进出风方式进行空气强制冷却电池组,分析了进出风口有倾角与无倾角的不同温度控制效果,结果表明带有倾角的进出风方式有利于降低电池组最高温度。采用电池组壳体侧面开孔方式进行电池组热管理,可有效改善电池组放电过程的温度分布均匀性。     

锂离子电池高温化成工艺研究

为缩短锂电池生产工艺时间、节约成本,高温压力化成受到工艺人员的关注,本文以钴酸锂-石墨体系的软包装锂离子电池为研究对象,研究了高温压力化成工艺中温度对化成效果的影响。在某一压力作用下,采用不同化成温度,分析了不同化成温度对应的实际化成时间、化成电压、电压降以及电池倍率放电与高温处理的性能,结果显示化成温度越高,化成时间越长;在不同的温度下化成,对电池的循环性能及倍率性能影响不同。     

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。     

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。     

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.     

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.     

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。     

Review on heat generation theory model of lithium-ion battery

本文根据近年来锂离子电池产热特性方面的研究,详细阐述了锂离子电池产热的基本原理,并总结了国内外锂离子电池产热模型的研究现状。重点针对电化学-热耦合模型、电-热耦合模型以及热滥用模型进行了详细综述,并在此基础上对锂离子电池热效应的研究和产热模型的建立进行了展望。     

Cobalt-doped layered lithium nickel oxide as a three-in-one electrode for lithium-ion and sodium-ion batteries and supercapacitor applications

Layered LiNi_0.94Co_0.06O₂ (LNCO) was prepared and explored as an energy-storage material for Li-ion (LIBs), Na-ion (SIBs) batteries as well as supercapacitor application for the first time. All the physical and morphological characterizations were studied for the sample LNCO. The result displays good thermal stability, phase purity in the crystal structure, appreciable Brunauer-Emmett-Teller (BET) surface area (5.53 m² g⁻¹) and possesses cubic morphology. The cobalt was identified in lithium nickel oxide with binding energies at 794.02, 779.04 and 784.30 eV, respectively. In the case of LIBs, LNCO exists with a minimal difference of 5 mAh g⁻¹, even when cycled from 2C to 0.1C. After 200 cycles, the specific capacity, 247 mAh g⁻¹, is obtained for the cell with retention of 97.8% (efficiency 99.8%) at 0.1C. In SIBs, at 0.1C, the discharge capacity of 182 mAh g⁻¹ was restored even when cycled after 2C. After 200 cycles, a discharge capacity of 204 mAh g⁻¹ is ensured with retention of 96.6% (efficiency of 99.4% at 0.1C). In supercapacitor, the electrode, LNCO, delivered a specific capacity of 300 F g⁻¹ at 0.5 A g⁻¹. Therefore, LNCO is highly recommended as a suitable electrode material for fulfilling the requirement of energy-storage applications.     

A review of the patents of lithium-ion battery polyolefin multilayer separator

从专利角度梳理了聚烯烃多层锂电池隔膜的技术输出国和申请人分布,并总结归纳了聚烯烃多层锂电池隔膜的技术手段和技术功效分布。结果表明,日本、中国、韩国和美国是目前全球聚烯烃多层锂电池隔膜的主要技术来源国,日本的东丽、旭化成、住友,韩国的LG公司以及中国的深圳星源材质和中国科学院是主要申请人。采用特定的层组分、改性层的设计以及拉伸和造孔工艺的调控,以改进锂电池隔膜的透气性、孔隙率、孔隙均匀性,耐热性、热收缩性,热关闭性能,机械强度和离子渗透性是主要的研究方向。     

Numerical study on thermal behavior and a liquid cooling strategy for lithium-ion battery

Investigation on the thermal behavior of the lithium-ion battery which includes the temperature response, heat contribution and generation, is of vital importance for their performance and safety. In this study, an electrochemical-thermal cycling model is presented for a 4 Ah 21700 type cylindrical single cell and 3× 3 battery pack and the model is validated by experiment on a single cell. Thermal behavior on a single cell is first analyzed, the results show that the heat generated in the charge is smaller than the discharge, and the polarization heat contributes the most to total heat, especially under higher rate. It can also be concluded from the battery pack that the temperature of the cell inside the battery pack is significantly greater than the external battery, while the temperature difference exists the opposite regular due to the worst heat dissipation of the central cell. Finally, after taking the enhanced liquid cooling strategy, the maximum temperature is 320.6 K that is reduced by 9.38%, and the maximum temperature difference is 4.9 K which is reduced by 69.6% at 2C, meeting the requirements of battery thermal management system.     

Studies on the standard of lithium ion battery separator

隔膜是保障电池安全、影响电池性能发挥的重要材料。随着隔膜产业在中国的快速发展,我国的隔膜产能已经排进了世界前列。产品系列化、产品质量标准化、检测标准规范化是我国隔膜产业做大、做强的必要环节。分析了国内涉及隔膜的相关标准情况,并主要针对隔膜的检测方法及参考的标准做解读。     

Dynamic behavior and modeling of prismatic lithium-ion battery

The inevitable vehicle collision has made the safety of lithium-ion battery (LIB) carried by electric vehicles (EVs) a problem that restricts the further and large-scale promotion of EVs. Therefore, establishing the numerical mechanics model of LIBs and studying their mechanical integrity are imperative. In this study, we design indentation, compression, and drop-weight experiments for prismatic LIBs (PLIBs). Mechanical integrity and internal short circuit are analyzed in consideration of state of charge (SOC) and dynamic effects. A homogeneous PLIB model that considers anisotropic property, SOC, and dynamic effects is developed for the first time for application in different loading conditions. After its effectiveness is validated, the affecting parameters (ie, SOC and impact velocity) of the mechanical behaviors during dynamic loadings are investigated using the established model. The results show that strain rate effect and SOC state have impact on the mechanical properties of PLIB. However, the strain rate effect has much larger influence than the SOC state. Results may shed lights on the safety design of PLIBs in a mechanical aspect.     

Progress on high energy density lithium batteries by CAS battery research group

提高动力电池的能量密度将显著延长续航里程,对发展电动汽车具有重要的意义.中国科学院在2013年底部署了中国科学院战略性先导科技专项,通过合作研究,积极探索了第三代锂离子电池,固态锂电池,锂-硫电池和锂-空气电池等电池体系.其中,采用纳米硅碳负极,富锂正极的24 A·h的锂离子电池单体,质量能量密度达到374 W·h/kg,体积能量密度达到577 W·h/L.8 A·h固态聚合物锂电池60 ℃下能量密度达到240 W·h/kg,基于无机陶瓷固态电解质的固态锂电池室温下能量密度达到240 W·h/kg.37 A·h的锂硫电池单体室温能量密度达到566 W·h/kg,50 ℃达到616 W·h/kg.5 A·h锂空气电池单体能量密度达到526 W·h/kg.目前这些样品电池在综合技术指标方面离实际应用还有较大的距离,需要进一步深入细致的进行基础科学与关键技术方面的研究.从长远考虑,电池能量密度的提高必然进一步增加电池安全性风险,因此不同形式的固态锂电池将是未来长续航动力锂电池的发展方向.     

Research progress on safety of lithium ion battery electrolyte

锂离子电池的能量密度及其安全问题是限制其在电动汽车应用中的主要障碍。随着能量密度的不断提升,当务之急是有效解决锂离子电池的安全性问题。锂离子电池安全问题本质上与当前电解液中使用的高挥发性、易燃的有机溶剂有关。因此,本文主要从电解液的燃烧性角度,介绍了电解液在锂离子电池材料安全性方面的研究现状,包括阻燃添加剂、不燃性氟代有机溶剂、高浓度电解液及固液混合电解质的应用等,分析其对安全性能提升的机理,并对电解液的发展方向进行了展望。