Effect of safety valve types on the gas venting behavior and thermal runaway hazard severity of large-format prismatic lithium iron phosphate batteries

The safety valve is an important component to ensure the safe operation of lithium-ion batteries(LIBs).However,the effect of safety valve type on the thermal runaway(TR)and gas venting behavior of LIBs,as well as the TR hazard severity of LIBs,are not known.In this paper,the TR and gas venting behavior of three 100 A h lithium iron phosphate(LFP)batteries with different safety valves are investigated under overheating.Compared to previous studies,the main contribution of this work is in studying and evaluating the effect of gas venting behavior and TR hazard severity of LFP batteries with three safety valve types.Two significant results are obtained:(Ⅰ)the safety valve type dominates over gas venting pressure of battery during safety venting,the maximum gas venting pressure of LFP batteries with a round safety valve is 3320 Pa,which is one order of magnitude higher than other batteries with oval or cavity safety valve;(Ⅱ)the LFP battery with oval safety valve has the lowest TR hazard as shown by the TR hazard assessment model based on gray-fuzzy analytic hierarchy process.This study reveals the effect of safety valve type on TR and gas venting,providing a clear direction for the safety valve design.

Self-actuating protection mechanisms for safer lithium-ion batteries

Safety issue is still a problem nowadays for the large-scale application of lithium-ion batteries(LIBs)in electric vehicles and energy storage stations.The unsafe behaviors of LIBs arise from the thermal run-away,which is intrinsically triggered by the overcharging and overheating.To improve the safety of LIBs,various protection strategies based on self-actuating reaction control mechanisms(SRCMs)have been proposed,including redox shuttle,polymerizable monomer additive,potential-sensitive separator,thermal shutdown separator,positive-temperature-coefficient electrode,thermally polymerizable addi-tive,and reversible thermal phase transition electrolyte.As build-in protection mechanisms,these meth-ods can sensitively detect either the temperature change inside battery or the potential change of the electrode,and spontaneously shut down the electrode reaction at risky conditions,thus preventing the battery from going into thermal runaway.Given their advantages in enhancing the intrinsic safety of LIBs,this paper overviews the research progresses of SRCMs after a brief introduction of thermal runaway mechanism and limitations of conventional thermal runaway mitigating measures.More importantly,the current states and issues,key challenges,and future developing trends of SRCTs are also discussed and outlined from the viewpoint of practical application,aiming at providing insights and guidance for developing more effective SRCMs for LIBs.

A holistic approach to improving safety for battery energy storage systems

The integration of battery energy storage systems(BESS)throughout our energy chain poses concerns regarding safety,especially since batteries have high energy density and numerous BESS failure events have occurred.Wider spread adoption will only increase the prevalence of these failure events unless there is a step change in the management and design of BESS.To understand the causes of failure,the main challenges of BESS safety are summarised.BESS consequences and failure events are discussed,including specific focus on the chain of events causing thermal runaway,and a case study of a BESS explosion in Surprise Arizona is analysed.Based on the technology and past events,a paradigm shift is required to improve BESS safety.In this review,a holistic approach is proposed.This combines currently adopted approaches including battery cell testing,lumped cell mathematical modelling,and calorimetry,alongside additional measures taken to ensure BESS safety including the requirement for computational fluid dynamics and kinetic modelling,assessment of installation level testing of the full BESS system and not simply a single cell battery test,hazard and layers of protection analysis,gas chromatography,and composition testing.The holistic approach proposed in this study aims to address challenges of BESS safety and form the basis of a paradigm shift in the safety management and design of these systems.

Invited Review Reduction,reuse and recycle of spent Li-ion batteries for automobiles:A review

The demand for Li-ion batteries (LIBs) for vehicles is increasing. However, LIBs use valuable rare metals, such as Co and Li, aswell as environmentally toxic reagents. LIBs are also necessary to utilize for a long period and to recycle useful materials. The reduction, reuse,and recycle (3R) of spent LIBs is an important consideration in constructing a circular economy. In this paper, a flowsheet of the 3R of LIBs isproposed and methods to reduce the utilization of valuable rare metals and the amount of spent LIBs by remanufacturing used parts and designingnew batteries considering the concept of 3R are described. Next, several technological processes for the reuse and recycling of LIBs are introduced.These technologies include discharge, sorting, crushing, binder removal, physical separation, and pyrometallurgical and hydrometallurgicalprocessing. Each process, as well as the related physical, chemical, and biological treatments, are discussed. Finally, the problem of developedtechnologies and future subjects for 3R of LIBs are described.

Influence of calendering process on the structural mechanics and heat transfer characteristics of lithium-ion battery electrodes via DEM simulations

Elucidating the intricate correlation between calendering,structure,and performance is crucial to comprehending the relationship between performance parameters and process steps of lithium-ion batteries(LIBs).Discrete element method(DEM)simulations were adopted in this work to calculate the interparticle force and stress tensor under incremental calendering process conditions,which revealed the effect of the anisotropy of complex contact force network on the anisotropy of heat transfer within porous electrode.The thermal conductivity of electrode was predicted using porosity to characterize the process-structure-performance correlation.The comprehensive influence of contact number and con-tact area between particles and current collector determines the magnitude of interfacial thermal resistance and interfacial heat transfer coefficient.For the first time,this work quantitatively analyzed the structural mechanics and heat transfer mechanism during calendering process of porous electrodes,and the results indicate a promising way to optimize and design battery electrode structures.

A facile path from fast synthesis of Li-argyrodite conductor to dry forming ultrathin electrolyte membrane for high-energy-density allsolid-state lithium batteries

All-solid-state lithium batteries(ASSLBs),utilizing sulfide solid electrolyte,are considered as the promising design on account of their superior safety and high energy density,whereas the time-consuming preparation process of sulfide electrolyte powders and the thickness of electrolyte layer hinder their practical application.Herein,an innovative ultimate-energy mechanical alloying plus rapid thermal processing approach is employed to rapidly synthesize the crystalline Argyrodite-type conductor Li_(5.3)PS_(4.3)ClBr_(0.7)(LPSCIBr)with superior ionic conductivity(11.7 mS cm^(-1)).Furthermore,to realize the higher energy density of the battery,an ultrathin LPSCIBr sulfide electrolyte membrane with superior ionic conductivity of 6.5 mS cm^(-1)is fabricated with the aid of polytetrafluoroethylene(PTFE)binder and the reinforced cellulose mesh.Moreover,a simple solid electrolyte interphase(SEI)is constructed on the surface of lithium metal to enhance anodic stability.Benefiting from the joint efforts of these merits,the modified ASSLBs with a high cell-level energy density of 311 Wh kg^(-1) show an excellent cyclic stability.The assembled all-solid-state Li_(2) S/Li pouch cell can operate even under the severe conditions of bending and cutting,demonstrating the enormous potential of the sulfide electrolyte membrane for ASSLBs application.

Optimization of Synthesis Conditions of LiMn_2–xFe_xO₄Cathode Materials Based on Thermal Characterizations

We have synthesized LiMn2–xFexO4 (x = 0, 0.25, and 0.50) cathode materials for applications in Li ion rechargeable batteries via sol-gel method. We studied thermal characteristics of as synthesized materials using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). In order to optimize the synthesis conditions, we studied X-ray diffraction (XRD) of synthesized cathode materials at various temperatures, based on the transitions obtained from DSC/TGA. The XRD results can be co-related to the thermal behavior of the synthesized cathode materials and the synthesis conditions optimized.

基于热成像面积变化率的锂电池热失控研究

锂电池在生活中的使用越来越普及,但锂电池热失控造成的损失是不可估量的。使用红外热成像监测锂电池表面高温区域面积的扩散,从电池过充、内部隔膜刺穿和外部短路3个方面获取电池热成像的表面高温区域分布。通过MATLAB对电池升温过程中的热成像进行红外图像处理,使用最大类间方差法分割电池表面的高温区域。最后采用高斯逼近函数拟合高温区域面积的变化,分析出3种锂电池热失控的原因。

热电池激活过程倒灌电流影响因素研究

热电池因具有能量密度高、使用温度范围宽、耐瞬间大脉冲能力强、激活时间短、储存寿命长等优点被广泛用于各种战术武器中。热电池输出端作为与导弹对接的电气接口,其激活过程中倒灌电流的大小将直接影响弹上电子设备工作的可靠性。为了解热电池激活过程中倒灌电流变化规律,对其影响因素进行了研究。通过研究表明,倒灌电流大小与电池堆并联数量、引燃条燃速、加热片燃速、极片面积大小、电解质熔融速度、电池堆单体电池串联数量、电发火头激活方式、线阻大小及弹上负载功率大小有关。该结论为导弹电气系统的安全、可靠供电电路设计提供了有力支撑。

热等离子法制备锂离子电池硅碳负极材料

采用直流电弧热等离子法一步制备硅/碳球形纳米复合材料。以中值粒径分别为2.6、6.5和15.0μm的硅碳混合粉末为原料,制得了中值粒径为49.9、56.3和68.9 nm的纳米硅碳复合材料;在200 mA/g的电流密度下3种不同粒径的纳米硅碳负极材料的首次放电比容量分别达到1718、1651和1343 mAh/g,50次循环后其容量保持在1005、761和663 mAh/g;而未处理的硅碳混合粉末首次放电容量约为2321 mAh/g,但50次循环后,容量仅为274 mAh/g。由此可见,利用直流电弧热等离子法制备的硅/碳球形纳米复合材料的电化学性能得到了极大的提升。

面向动力电池热安全的准被动式热移出系统

发展非主动式动力电池热失控传播抑制技术对解决电动汽车在静置状态下的自燃事故具有重要意义。现有的非主动式技术是基于热阻隔机制,但由此形成的大热阻将严重影响日常的电池热管理性能。本文提出基于泵驱冷却与热电转换的准被动式动力电池热移出系统,将电池系统部分产热量转换为电能以实现准被动式的热移出,在此基础上与热阻隔相结合以减小阻断热失控蔓延所需的热阻。本文研制试验样机,通过实验分析不同电池系统发热功率工况下的热移出过程,探究发热功率分布的影响。当发热功率减少33%时,泵驱冷却过程散热量、热电转换过程吸热量及产生电能的稳态值分别降低30%、27%和15%。本文研究有助于显著提升电动汽车安全性能。

Experimental Study on Thermal Management of Cylindrical Li-ion Battery with Flexible Microchannel Plates

A novel thermal management system of cylindrical Li-ion battery with the liquid cooling in flexible microchannel plate was established in the study. The experiments were conducted with R141 b in flexible microchannel plates. The cooling system with the flexible aluminum microchannels can effectively transfer heat from battery to the cooling refrigerant R141 b based on flow boiling. A battery module with five cells along flow channel was chosen to study the effects of contact surface area and mass flux on the thermal performance and electrochemical characteristics in the experiments. Three types of structure with different contact areas were studied and their performances were compared with the experiments without cooling structures. The experiments were carried out at the same discharge rate with the inlet mass flow rates of 0–10 kg/h. For the inlet mass flow rate of 5.98 kg/h, the surface temperature and temperature uniformity of battery were the best, and the output voltage and capacity of batteries were higher than those under other mass flow rates. With given inlet mass flow rates, the five series cells exhibited different electrochemical performances, including output voltage and discharge capacity, due to the different refrigerant flow states in the microchannels. Finally, an optimal design was presented with thermal performances, macroscopic electrochemical characteristics, inlet mass flow rates and cooling performance taken into consideration.

Enabling the thermal stability of solid electrolyte interphase in Li-ion battery

Lithium-ion batteries(LIBs)provide power for a variety of applications from the portable electronics to electric vehicles,and now they are supporting the smart grid.Safety of LIBs is of paramount importance in these scenarios.Specifically,thermal safety arouses increasing attention with the piling-up of LIBs.Heat generation can be significant.Hazardous incidents happen when thermal runaway occurs in a single cell level and drives the battery pack failure.Moreover,thermal runaway of LIBs is believed to originate from the exothermic reactions starting from the breakdown of the solid/cathode electrolyte interphase(SEI/CEI).To mitigate this challenge for a safe operation of LIBs,one straightforward and low-cost method is to build thermally stable SEI/CEI.This review gives an overview on the thermal behaviors of SEI/CEI as the first step in thermal runaway.We analyzed the electrolyte composition and the formation process of SEI/CEI that enable SEI/CEI of high thermal stability.It is identified that the stable lithium salts coupled with solvents of high boiling point is one way to enhance thermal stability of the battery system.In addition,the unsaturated bonds,halogen,phosphorus,sulfur,phenol,organic borate,borane,and silane are functional components to facilitate the formation of a thermally stable SEI/CEI,which is the immediate solution to boost thermal stability of high capacity electrodes.Moreover,in-situ polymerization/solidification is effective in enhancing simultaneously the electrochemical,chemical,and thermal stability.Finally,we revealed that only by constructing a stable SEI/CEI simultaneously could we harvest a battery system of high thermal stability.

Cost-efficient Thermal Management for a 48V Li-ion Battery in a Mild Hybrid Electric Vehicle

The 48V mild hybrid system is a cost-efficient solution for original equipment manufacturers to meet increasingly stringent fuel consumption requirements.However,hybrid functions such as auto-stop/start and brake regeneration are unavailablewhen a 48V battery is at very low temperature because of its limited charge and discharge capability.Therefore,it is important to develop cost-efficient thermal management to warm-up the battery of a 48V mild hybrid electric vehicle(HEV)to recover hybrid functions quickly in cold climate.Following the model-based“V”process,we first define the requirements and then design different mechanisms to heat a 48V battery.Afterward,we build a 48V battery model in LMS AMESim and conduct co-simulation with simplified battery management system and hybrid control unit algorithms in MATLAB Simulink for analysis.Finally,we carry out a series of vehicle experiments at low temperature and observe the effect of heating to validate the design.Both simulation results and experimental data show that a cold 48V battery placed in a cabin with hot air can be heated effectively in the developed“Enhanced Generator Mode with 48V Battery”mode.The entire design is in a newly developed software that cyclically charges and discharges a 48V battery for quick warm-up in cold temperature without needing any additional hardware such as a heater,making it a cost-efficient solution for HEVs.

原纤化PBO纤维耐高温复合隔膜的制备

隔膜对锂离子电池安全性能有着重要影响。为了提高隔膜的耐热性能,采用湿法成型技术,使用聚对苯撑苯并二噁唑(PBO)原纤化纤维和聚对苯二甲酸乙二醇酯(PET)无纺布作为原料,制备了一种耐高温的双层复合隔膜(PET/PBO)。差示扫描量热法(DSC)和热尺寸收缩实验证明,PET/PBO复合膜与商用PP隔膜Celgard 2500相比具有更出色的热稳定性,225℃下尺寸收缩仅2.5%;湿法成型工艺又赋予隔膜更高的孔隙率,可达70%;PBO面与电解液接触角仅为14°,具有良好的电解液浸润性;充放电实验证明,PET/PBO隔膜组装的电池有着良好的循坏和倍率性能。表明该复合膜是高性能锂离子电池隔膜的理想候选者。

LIV_3O_8的溶胶-凝胶法合成及500℃阴极放电性能

用柠檬酸溶胶－凝胶工艺制备出了ＬｉＶ３Ｏ８化合物，并检测了其作为热电池阴极材料时的放电性能。干凝胶２１０℃熔烧所得的粉末颗粒疏松多孔，３００℃时可变成结晶岩状，低温焙烧时出现了Ｌｉ0．3Ｖ2Ｏ５和ＬｉＶ２Ｏ５相经６５０℃长时间保温后可转交为 ＬｉＶ３Ｏ８。模拟 Ｌｉ－Ｂ／ＬｉＣｌ－ＫＣｌ／ＬｉＶ３Ｏ８（或 Ｖ２Ｏ５）热电池５００℃放电试验表明，ＬｉＶ３Ｏ８因具有良好的电子导电体和较低的Ｌｉ＋扩散极化，其放电较 Ｖ２Ｏ５平稳，虽峰值电压略有降低，但可利用的比容量（电压降至峰值电压的７５％或２．０Ｖ）均不低于Ｖ２Ｏ５；ＬｉＶ３Ｏ８中掺入８％的Ｐ２Ｏ５时可提高小电流放电时的电压。

动力锂离子电池的安全性控制策略及其试验验证

锂离子动力电池的安全性决定了它的市场生存,而控制电池热失控是锂离子电池安全性研究的最具挑战的课题。该文介绍了动力锂离子电池的现场失效安全性和滥用安全性现状,探究了动力电池发生热失控的内在演变过程,并从电池的正负极、电解液、隔膜和集流体等方面分析了材料对电池热失控安全性的影响;提出了控制大型动力电池安全性的一般策略;并通过关键材料的改性,研制了标称容量12Ah的三元材料(LiNi1/3Co1/3Mn1/3O2)体系动力锂离子电池,其比能量为160Wh/kg,比功率达1.25kW/kg。进行了该电池的0.5C倍率、20V过充电测试和150℃、4h的4.2V满电态热箱试验。结果表明:电池具有较高安全性,验证了安全性控制策略的有效性;安全性电池的自放电和化学稳定性均优于普通电池。

基于ANSYS的热电池激活过程模拟研究

基于ANSYS对电激活热电池的激活过程进行了模拟,给出了该类热电池激活时间的模拟计算方法,并简要分析了激活过程热电池内部温度分布特性。将该类热电池激活过程分解为点火头着火、引燃纸与加热片燃烧和电解质吸热熔融三个过程,点火头着火用时通过实验获得,引燃纸和加热片燃烧用时通过测试两种材料燃速来计算,电解质吸热熔融过程则通过ANSYS模拟来获取其用时及温度分布。模拟了两款热电池的激活时间,并将其与实测值进行了对比,结果表明该模拟方法能够在一定程度上表征热电池的激活过程,对预测热电池激活时间有一定指导意义。

钴酸锂正极锂离子电池的过充电安全性

分析了影响锂离子电池安全性的主要因素和关键材料。通过钴酸锂(LiCoO2)表面包覆和使用电解液阻燃添加剂,研制了具有较好耐过充安全性的原型LiCoO2正极锂离子电池。该电池经1C、20 V过充电,没有燃烧的现象。

β-M_xV_2O_5(M=Li,Na,K)的溶胶凝胶法合成及其高温阴极放电性能

用柠檬酸盐溶胶－凝胶工艺制取了三种β－ＭｘＶ２Ｏ５氧化物Ｌｉ０．３Ｖ２Ｏ５、Ｎａ０．３３Ｖ２Ｏ５和Ｋ０．２５Ｖ２Ｏ５；ＴＧ和ＤＴＡ试验显示干凝胶焙烧过程中出现两个吸热峰，中间有一个放热峰；ＸＲＤ分析表明高温处理时Ｌｉ０．３Ｖ２Ｏ５可氧化成 ＬｉＶ３Ｏ８和Ｖ２Ｏ５，而Ｎａ０．３３Ｖ２Ｏ５和Ｋ０．２５有较好的化学稳定性；模拟Ｌｉ－Ｂ合金／ＬｉＣｌ－ＫＣｌ／β－ＭｘＶ２Ｏ５（或α－Ｖ２Ｏ５）热电池５００℃放电试验表明β相阴极效电较α相平稳，但初始电压峰值略有降低，β－Ｌｉ０．３Ｖ２Ｏ５相因具有较α－Ｖ２Ｏ５相更通畅的Ｌｉ＋ 快速扩散通道，且通道内没有Ｎａ＋或Ｋ＋大离子对Ｌｉ＋扩散的阻碍，放电最为平稳，有效比容量最高。