Preparation of conductive fire retardant and its application in Li-ion battery

锂离子电池内短路是诱发电池热失控的主要原因,适当的安全性添加剂可以阻止电池热失控的发生。本文通过界面聚合法在聚乙烯蜡表面生成适量的导电聚苯胺,制备了一种具有良好导电性能的PTC材料（PANI-PEW）,并对PANI-PEW的微观形貌、电导率以及添加至LiFePO₄正极中的电化学性能进行了对比分析。测试结果表明,PANI-PEW在常温下的电导率为1.08×10^-3 S/m,在90~120℃时,其电阻值急剧增大。在0.5 C和1 C倍率下,PANI-PEW的加入对LiFePO₄电池的阻抗和循环性能影响较小,而经过120℃热处理后的含15%（质量分数） PANI-PEW的极片,其电池的阻抗大幅增加且首次放电比容量只有35.3 mA·h/g,在第12次循环后,放电比容量接近于0。以上结果表明,PANI-PEW是一种性能优异的PTC材料且能在120℃时阻止电池热失控的发生。     

Solvothermal synthesis and electrochemical performances of nanosized CoSb3 as anode materials for Li-ion batteries

In the present study, the CoSb₃ powder was prepared by solvothermal route for the first time and the particle size of the as-prepared powder is in nanoscale. The electrochemical performances of the nanosized CoSb₃ were characterized by galvanostatic charge and discharge cycling, cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical lithiation and delithiation mechanism of CoSb₃ compound was investigated by ex situ XRD (X-ray diffraction) technique. The large reversible capacity and good cycling stability of nanosized CoSb₃ suggest that it stands as a promising anode material for secondary Li-ion batteries.     

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。     

一种基于PTVE正极的高电压钾-有机自由基电池

钾/钾离子电化学储能系统具有诸多优势,如钾资源丰富、K⁺/K标准电位低及K⁺ 导电性高等。钾离子电池/超级电容器、K//O₂电池和K//S电池正受到越来越多的关注,同时也在实际应用中面临许多挑战,如缺乏高电压储钾材料等。因此,构建新型钾/钾离子电化学储能体系具有重要意义。本文成功组装了钾-有机自由基（K//PTVE）电池,并对其电化学性能进行了研究。结果显示,该电池表现出较高的放电电压（3.63 V）,具有良好的倍率性能和循环稳定性。     

钛酸锂基锂离子电池及其健康状态研究进展

锂离子电池的高功率密度和高能量密度等特性使其成为电动汽车能源和新能源电网储能的重要载体。功率性能和安全特性是锂离子电池发展的两个主要挑战。钛酸锂Li₄Ti₅O₁₂材料因具有良好的结构稳定性、安全性能、长循环寿命、高功率特性和高低温放电性能,被认为是锂电池负极材料的良好备选。综述了以钛酸锂材料为负极的锂离子电池的相关工作,介绍了钛酸锂材料的结构、电化学特性、制备方法和作为电池负极材料面临的主要问题,重点介绍了钛酸锂负极电池的全电池性能和健康状态研究等方面。     

电活性双酚A的合成及其锂离子电池防过充性能研究

对双酚A进行结构修饰,经甲醚化、氰基取代,设计合成了2,2-双-(4-(β-氰基乙氧基)苯基)丙烷（DBDCN）、2-(4-(β-氰基乙氧基)苯基)-2'-(4-甲氧基苯基)丙烷（DBMCN）和2,2-双-(4-甲氧基苯基)丙烷（DBMB）,将三种化合物作为锂离子电池的防过充添加剂开展研究。在锂离子电池电解液1 mol/L LiPF₆/[碳酸乙烯酯（EC）+ 碳酸二乙酯（DEC） + 碳酸甲乙酯（EMC） （1∶1∶1,体积比）]中分别添加0.1 mol/L的DBDCN、DBMB和DBMCN,采用循环伏安、过充测试、电化学阻抗、恒流充放电和扫描电子显微镜等手段研究DBDCN、DBMB和DBMCN的防过充性能,并探讨添加剂与正极材料LiFePO₄的相容性。这些化合物的氧化还原电位均为4.1 V,显著提高了电池的过充保护。100%过充测试和5 V截止电压测试结果表明,DBMB的防过充性能明显优于DBDCN和DBMCN。以0.5 C倍率电流循环100圈,基础电解液和分别添加0.1 M DBDCN、DBMB、DBMCN的电池放电比容量分别为134.5 mA∙h/g、135.3 mA∙h/g、132.8 mA∙h/g和127.0 mA∙h/g,容量保持率分别为87.7%、87.0%、89.5%和84.3%。结果表明,DBMB对电池防过充作用最明显。     

Lithium metal rechargeable cells using Li2MnO3 as the positive electrode

Rechargeable lithium cells have been fabricated using Li₂MnO₃ as the positive electrode, lithium metal as the negative electrode and 1 M LiAsF₆ in DMC/EC (1:1 v/v) as the electrolyte. Charge/discharge behaviour was evaluated and the cells showed improved performance after the first five cycles. The cells could be cycled at least 15 times without loss in capacity. Similar electrochemical trends were observed with LiPF₆ in a EC/DEC mixture.     

锂离子电池电-热耦合模型分析及其温度场仿真研究

锂离子电池由于放电过程产生大量的热,不可避免的使得电池温度升高。研究大倍率放电时的电池温升,忽略电化学反应热,进一步简化原有的生热模型。为了得到电池温度分布,从电池内部结构出发,根据电流密度在集流板上的分布以及极耳处的收缩/扩散效应,分析集流板上电流密度的分布规律,从而建立电池的电-热耦合模型。通过生热模型模拟电池放电过程的温升现象,并与实验结果对比,发现模拟结果与实验结果能够很好地吻合。文章给出了电池在不同放电倍率条件下放电终了时的温度分布图,并解释了造成这种分布现象的原因。     

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.     

Effect and mechanism study on buffer layer in secondary Li metal battery

锂金属是已知的理论比容量（3860 mA·h/g）最高的材料,且锂金属具有最低的对氢电位（-3.040 V）和极小的密度（0.53 g/cm³）。所以锂金属是一种极具潜力的电池负极材料。但是锂金属电池存在着很严重的安全问题且循环效率低,所以直到现在还没有正式商用。锂离子电池的发展日趋成熟,但是其容量已经无法满足科技的发展,所以发展下一代电池刻不容缓,而锂金属电池是一个良好的选择。为了克服锂金属负极在应用中存在的问题,本文提出了一种缓冲层结构插入锂金属电池的隔膜与负极之间,并分别将碳纳米管和聚苯胺/碳纳米管复合材料作为缓冲层插入锂电池中。倍率性能测试、循环性能测试和形貌测试均指出,缓冲层结构对锂金属负极的枝晶生长具有抑制作用,从而改善了锂金属电池的安全问题,并对其循环效率具有很大的提升作用。     

Characterization of MnO2 positive electrode for Fuel Cell/Battery (FCB)

The use of manganese dioxide (MnO₂) as a positive electrode material in Fuel Cell/Battery (FCB) systems is described. A positive electrode containing MnO₂ was fabricated and its performance was evaluated for charge/discharge behavior in three different systems: (i) secondary battery positive electrode, (ii) positive electrode in an alkaline fuel cell, and (iii) positive electrode performance in an FCB system by performing half cell tests. MnO₂ was observed to possess redox capabilities as the positive electrode of a secondary battery when it was subject to charge/discharge cycles. It was found that Mn₃O₄, which inhibits the discharge reaction, was produced during charge/discharge cycles. The I–V characteristics of MnO₂ material were measured to check the feasibility of the fuel cell system by supplying H₂ into the negative electrode and O₂ into the MnO₂ positive electrode, respectively. The MnO₂ electrode showed similar performance to Ni electrode, which was fabricated by using a similar method to the MnO₂ electrode. The MnO₂ electrode also showed that it functioned as an FCB positive electrode, which was confirmed by continued production of current when the O₂ supply was terminated. These results suggest that MnO₂ is a good candidate for an FCB positive electrode material.     

A novel CuO-nanotube/SnO2 composite as the anode material for lithium ion batteries

A novel CuO-nanotubes/SnO₂ composite was prepared by a facile solution method and its electrochemical properties were investigated as the anode material for Li-ion battery. The as-prepared composite consisted of monoclinic-phase CuO-nanotubes and cassiterite structure SnO₂ nanoparticles, in which SnO₂ nanoparticles were dramatically decorated on the CuO-nanotubes. The composite showed higher reversible capacity, better durability and high rate performance than the pure SnO₂. The better electrochemical performance could be attributed to the introducing of the CuO-nanotubes. It was found that the CuO-nanotubes were reduced to metallic Cu in the first discharge cycle, which can retain tube structure of the CuO-nanotubes as a tube buffer to alleviate the volume expansion of SnO₂ during cycling and act as a good conductor to improve the electrical conductivity of the electrodes.     

Achieving high performance lithium-O2 battery by introducing a novel urea electrolyte

在锂空气电池中,电解液对电池的充放电过程、放电产物的稳定性以及循环性能有着至关重要的影响。本文利用脲类溶剂1,3-二甲基-2-咪唑啉酮（DMI）作为新型的锂空气电池电解液,有效地增加了放电产物过氧化锂（Li₂O₂）的溶解度,促进其溶剂化,并改善Li₂O₂与正极之间的接触,使得电池性能得到有效提高。通过研究表明,相比较传统的醚类电解液四乙二醇二甲醚（TEGDME）,DMI能将电池放电容量提升1.5倍,而充电过电位则降低了0.6 V,减少了高电位导致的副反应。同时,通过加入氧抑制剂,稳定溶剂中的氧自由基,减少放电中间产物对DMI的攻击,使得电池循环性能得到显著提高。     

Effect of conductive additives on electrochemical performance of Li4Ti5O12 in hybrid capacitor

将添加不同导电剂的钛酸锂负极与活性炭正极组装成混合电容器,研究了不同导电剂对混合电容器性能的影响。利用扫描电子显微镜表征了钛酸锂负极的表面形貌,采用LAND测试仪、电化学工作站对混合电容器的电化学性能进行测试分析,最终确定最佳的导电剂类型。实验表明,以super-P/VGCF为导电剂的混合电容器具有最佳的电化学特性,在0.1 A/g条件下,电容器的比容量达到45.4 F/g,在2 A/g时容量保持率为91.5%;在0.5 A/g条件下,经过10000次循环后,容量保持率为93.2%。     

Graphite modified LiNi1/3Co1/3Mn1/3O2 cathodes with improved performance for lithium-ion battery

通过丝网印刷方法用石墨改性LiNi_1/3Co_1/3Mn_1/3O₂（NCM）电极片的表面。采用X射线衍射（XRD）和扫描电子显微镜（SEM）表征未改性和改性电极片的晶体结构和形貌特征,恒流充放电测试评估两种样品的电池性能,CV和EIS测试比较两种样品的电化学极化程度。结果表明,改性NCM电极的晶体结构没有明显变化;在改性电极片的表面上检测到了片状石墨;在截止电压为4.3 V的条件下改性样品比未改性样品具有更好的循环性能和倍率性能;石墨印刷的样品可以减缓电化学极化的增加。     

Review of doping and surface coating of cathode materials for lithium ion batteries

随着国家政策对电动汽车的支持力度不断加大,锂离子电池的电化学性能瓶颈愈发凸显。本文综述了锂离子电池正极材料钴酸锂、锰酸锂、磷酸铁锂及三元材料在掺杂和表面包覆两种工艺对电池电化学方面的影响,并展望了掺杂和表面包覆两种工艺未来的研究方向。     

The degradation analysis of lithium-ion storage battery with Li4Ti5O12 anode

钛酸锂作为储能电池负极材料,在长循环和安全性上有突出的表现。通过对室温1C和2C倍率下循环的三元+钴酸锂/钛酸锂储能电池拆解,结合SEM、FTIR、XRD和EIS等分析手段,发现造成容量衰减和阻抗增大的原因出现在正极,由于正极与电解液发生反应,在表面生成界面膜,并且循环过程中界面膜不稳定,进一步消耗活性锂离子导致。另外,对这款电池的产气分析发现,所产生气体的主要成分为CO2和C2H6,原因可能是在制备电池过程中严格控制水分以及在电解液添加剂方面做了改进。     

Preparation,electrochemical performance and phase transition of high voltage LiNi0.5Mn1.5O4 cathode material

尖晶石LiNi_0.5Mn_1.5O₄因其可在4.7 V高电位下工作并有良好的循环特性,已成为最具潜力的高能量密度锂离子电池正极材料。本文首先采用喷雾干燥辅助烧结法制备了LiNi_0.5Mn_1.5O₄正极材料,考察了热处理条件对材料结构与性能的影响。用XRD、SEM和FT-IR等技术对所制备的LiNi_0.5Mn_1.5O₄材料的结构和表面形貌进行表征,利用原位XRD技术研究了LiNi_0.5Mn_1.5O₄正极材料在充放电过程中结构相变规律。结果表明,所制备的LiNi_0.5Mn_1.5O₄材料均具有Fd-3m空间群的立方相尖晶石型结构,并具有优异的电化学性能,其0.1 C时首次放电容量为132 mA·h/g,首轮库仑效率93.48%,高倍率下该材料的电化学性能优越。原位XRD测量结果分析表明,尖晶石型LiNi_0.5Mn_1.5O₄材料在充电过程中存在4个显著的相变过程,在嵌脱锂过程中,从四面体相向立方相结构相变过程是可逆的。     

Influence of cycling on the heat-release and thermal runaway of the lithium ion battery under adiabatic condition

随着锂离子电池能量、寿命的提升,对安全性需求也越来越高,温度对电池的寿命和安全有着重要影响。以钴酸锂/中间相碳微球体系电池为研究对象,采用加速量热仪研究了不同工作电流、不同循环老化周期电池的产热特性和热失控行为,电池的发热量随着充放电倍率的增加而增大。通过比较不同循环老化周期电池的产热速率,发现容量衰减速度与直流内阻、产热量之间存在很强的关联性。从热失控行为研究发现,自放热起始温度为105.4℃,随后发生连续自放热,直到温度达到149.7℃热失控起始温度,发生内短路,最终导致电池热失控。循环后电池的热失控过程中自放热和热失控起始温度稍有变化,热失控时间大大缩短。     

Improved electrolytes for Li-ion batteries: Mixtures of ionic liquid and organic electrolyte with enhanced safety and electrochemical performance

Physical and electrochemical characteristics of Li-ion battery systems based on LiFePO₄ cathodes and graphite anodes with mixture electrolytes were investigated. The mixed electrolytes are based on an ionic liquid (IL), and organic solvents used in commercial batteries. We investigated a range of compositions to determine an optimum conductivity and non-flammability of the mixed electrolyte. This led us to examine mixtures of ILs with the organic electrolyte usually employed in commercial Li-ion batteries, i.e., ethylene carbonate (EC) and diethylene carbonate (DEC). The IL electrolyte consisted of (trifluoromethyl sulfonylimide) (TFSI) as anion and 1-ethyl-3-methyleimidazolium (EMI) as the cation. The physical and electrochemical properties of some of these mixtures showed an improvement characteristics compared to the constituents alone. The safety was improved with electrolyte mixtures; when IL content in the mixture is ≥40%, no flammability is observed. A stable SEI layer was obtained on the MCMB graphite anode in these mixed electrolytes, which is not obtained with IL containing the TFSI-anion. The high-rate capability of LiFePO₄ is similar in the organic electrolyte and the mixture with a composition of 1:1. The interface resistance of the LiFePO₄ cathode is stabilized when the IL is added to the electrolyte. A reversible capacity of 155 mAh g⁻¹ at C/12 is obtained with cells having at least some organic electrolyte compared to only 124 mAh g⁻¹ with pure IL. With increasing discharge rate, the capacity is maintained close to that in the organic solvent up to 2 C rate. At higher rates, the results with mixture electrolytes start to deviate from the pure organic electrolyte cell. The evaluation of the Li-ion cells; LiFePO₄//Li₄Ti₅O₁₂ with organic and, 40% mixture electrolytes showed good 1st CE at 98.7 and 93.0%, respectively. The power performance of both cell configurations is comparable up to 2 C rate. This study indicates that safety and electrochemical performance of the Li-ion battery can be improved by using mixed IL and organic solvents.