丙酸乙酯对LiFePO4锂离子电池低温性能的影响

以丙酸乙酯(EP)作为碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)和碳酸二甲酯(DMC)的共溶剂,研究其对LiFePO4锂离子电池低温电化学性能的影响.利用循环伏安曲线、交流阻抗图谱和恒电流充放电曲线等方法测试电池电化学性能.结果表明,添加一定量EP,可提高碳酸酯电解液的离子电导率,改善电解液与正极LiFePO4材料和负极石墨材料的相容性,从而提高LiFePO4锂离子电池的低温性能.使用1 mol·L-1LiPF6/(EC:EMC:DMC:EP=1:1:1:3,by mass)电解液的石墨/LiFePO4锂离子电池在10oC(1C)、-10oC(0.2C)、-20oC(0.2C)、-30oC(0.2C)和-40oC(0.2C)下的相对放电容量(以25oC时的放电容量为基准)分别为82.9%、75.6%、59.0%、46.4%和37.6%.     

一种新型锂离子电池用聚合物电解质复合膜的制备和性能表征

阐述了一种新型锂离子电池用PVDF-HFP(聚偏氟乙烯-六氟丙烯聚合物树脂)基聚合物电解质复合膜的制备过程. 对复合膜中使用的无机TiO2纳米颗粒进行固体超强酸化处理, 并进行颗粒表面酸强度H0测试、XRD晶体结构分析以及复合膜的电解液吸附率测试和电化学阻抗谱测试. 采用PE无纺布支撑体作为增强材料, 以浸涂方法制备复合膜,并进一步组装为锂离子电池, 性能测试表明该电池具有良好的电化学性能.     

锂离子电池高电压和耐燃电解液研究进展

电解液作为锂离子电池的重要组成部分,起着传输离子的作用,电解液的性质对电池的容量、循环性能及安全性能等影响巨大.近年来,随着高电压、高能量密度锂离子电池的开发应用,现有常规碳酸酯电解液存在正极稳定性差、闪点低、易燃烧等问题.因此,发展高电压耐燃电解液是应用高电压高容量正极材料、发展高电压高容量高安全性锂离子电池的迫切需要.主要综述了高电压电解液、耐燃性电解液及兼具抗氧化性和耐燃性的高浓度电解液的研究进展和现状.在此基础上,对锂离子电池新型电解液的发展方向进行了展望.     

锂离子电池电解液成膜添加剂乙烯基亚硫酸乙烯酯的电化学行为

研究了具有不饱和双键和亚硫酸酯双官能团的乙烯基亚硫酸乙烯酯(VES)作为锂离子电池电解液成膜添加剂对中间相碳微球(CMS)和LiFePO4电极电化学性能的影响. 结果表明: 在1 mol/L LiClO4/PC电解液体系中, 少量的VES (5%)能够在电化学过程中先于PC在CMS表面还原, 形成稳定的SEI膜, 明显抑制PC和溶剂化锂离子共嵌入石墨层间, 改善了电池的循环性能. 此外, 电解液1 mol/L LiClO4/PC＋5%VES (V∶V)在LiFePO4电极中展现出良好的电化学稳定性.     

4-溴苯甲醚用作锂离子电池过充保护添加剂的研究

通过在锂离子电池电解液中添加4-溴苯甲醚(4-Bromoanisole, 简称4BA)来提高锂离子电池的过充保护能力. 对电池分别进行了过充实验、循环伏安扫描、红外光谱分析、交流阻抗和容量特性测试, 实验结果表明, 在1 mol•L－1 LiPF6/EC＋DEC＋DMC(质量比1/1/1)中添加5% 的4BA(质量分数)时, 当外加电压为4.4 V(相对于Li/Li＋)时, 4BA开始发生电聚合反应且生成高分子聚合物膜, 使电池内阻增大而阻止电压的升高, 从而使电池处于比较安全的状态. 该体系正常充放电过程中, 添加5%的4BA对电池容量特性基本没有影响, 4BA 的防过充机理为阻断机理.     

锂离子电池电解液的研究进展(英文)

综述现今锂离子电池电解液的研究进展 .评估了电解液中锂盐、溶剂、填加剂以及杂质等对电解液的电导、固体电解质相界面 (SEI)的形成、电池循环寿命等的影响     

锂离子电池阻燃剂磷酸三(β-氯乙基)酯

将磷酸三(β-氯乙基)酯(TCEP)作为锂离子电池阻燃剂以提高电池的安全性。本文采用循环伏安、差热分析(DTA)和电子扫描电镜(SEM)研究了电解液1mol/L LiPF6 EC DMC(质量比1/1)中添加7.5(wt)%TCEP时TCEP的分解电位、分解温度和电池100次循环后的负极表面形貌,用高温测试和电化学测试手段考察了电解液中添加3(wt)%和7.5(wt)%TCEP对电池安全性和电化学性能的影响。结果表明,当TCEP含量为7.5(wt)%时,电解液的分解电压为4.7V,电解液差热分析(DTA)曲线分别在250、280和320℃出现TCEP的三个分解吸热峰,电池循环100次后表面形貌良好。在150℃环境温度下对电池进行的耐高温测试表明,电池温度在147~155℃上下波动,且TCEP对电池循环性能的影响极小,是一种较为理想的阻燃剂。     

甲基丙烯酸类聚合物修饰的聚乙烯隔膜在锂离子电池中的应用

将环状碳酸酯基团引入到聚甲基丙烯酸甲酯(PMMA)侧链上, 制备了聚(2,3-环碳酸甘油酯)甲基丙烯酸酯(PDOMMA), 并用其修饰锂离子电池聚乙烯隔膜. 通过热重分析、 差示扫描量热分析及接触角和吸液率测试等研究了PDOMMA的热稳定性及其修饰的聚乙烯隔膜对电解液的浸润性和吸液率的影响, 并通过恒流充放电、 交流阻抗、 倍率性能测试及扫描电子显微镜观测等研究了修饰隔膜对锂离子电池性能的影响. 结果表明, 与未修饰隔膜相比, 修饰隔膜对电解液浸润性更优异(20 s内便完全浸润), 吸液率更高(440%), 电池循环性能更好(放电比容量提高了12.3%).     

新型锂离子电池电解液添加剂的合成与应用

设计并合成了一系列基于苯环和环状碳酸酯的有机分子双(2,3-环碳酸甘油酯)对苯二甲酸酯、三(2,3-环碳酸甘油酯)均苯三甲酸酯和四(2,3-环碳酸甘油酯)均苯四甲酸酯,采用倍率测试、恒流充放电测试、交流阻抗测试和扫描电子显微镜测试等手段研究了这些添加剂对锂离子电池性能的影响.通过对循环20周前后球化石墨电极形貌的对比,发现含均苯四甲酸酯和均苯三甲酸酯的电解液球化石墨电极表面相对于空白电解液可形成一层致密而稳定的固体电解质中间相膜(SEI),从而优化电极-电解液的界面性能,且电池电阻增加较小;在测试电池的倍率性能时发现,均苯四甲酸酯的加入可以改善电池的倍率性能,而对苯二甲酸酯的加入则未能改善电池的循环性能.     

金属有机框架(MOFs)材料在锂离子电池及锂金属电池电解液中的应用

总结了金属有机框架(MOFs)材料在锂离子电池电解液中的研究进展.通过归纳锂离子电池长期存在的一些缺陷,随后将MOFs材料作为离子筛、人造负极保护层、准固态电解质以及用来调节电解液构型,使得锂离子电池的性能得到显著提升.最后,基于MOFs材料本身的特性,还对MOFs材料在电化学储能领域中的后续应用进行了合理地前瞻性展望...     

丁磺酸内酯对锂离子电池性能及负极界面的影响

用循环伏安(CV)、电化学阻抗谱(EIS)、扫描电镜(SEM)、能谱分析(EDS)及理论计算等方法研究了添加剂丁磺酸内酯(BS)对锂离子电池负极界面性质的影响. 研究表明, 在初次循环过程中, BS具有较低的最低空轨道能量, 优先于溶剂在石墨电极上还原分解, 并形成固体电解质相界面膜(SEI膜). 在含BS的电解液中形成的SEI膜的热稳定性高, 在70 ℃下储存24 h后, 膜电阻和电荷迁移电阻大小基本保持不变, 而在不含BS的电解液中形成的SEI膜的热稳定性较差, 在70 ℃下储存24 h后, 膜电阻和电荷迁移电阻大小有明显的增加. 从BS对锂离子电池电化学性能影响的研究表明, 加入少量的BS能够显著提高锂离子电池的室温放电容量、低温及高温储存放电性能.     

二氟草酸硼酸钠作为电解液添加剂对石墨负极性能的影响

锂离子电池日益广泛的应用对其性能提出越来越高的要求,而在电解液中加入适当的添加剂能够显著提升电极材料的电化学性能. 本文首次在1 mol·L^-1 LiPF₆/EC + DMC + EMC（体积比1:1:1）的电解液中添加一定量的二氟草酸硼酸钠(NaDFOB),并通过循环伏安（CV）、电化学阻抗图谱（EIS）和扫描电子显微镜（SEM）等分析考察了其对石墨负极材料性能的具体影响. 结果显示,添加NaDFOB的电解液显著提高了石墨材料在常温下的可逆充放电容量和循环性能,同时明显改善了石墨材料的高温循环性能. 其机理在于NaDFOB的阴阳离子同时参与了石墨表面固体电解质界面膜（SEI）的形成,形成高稳定性的电解液/电极界面.     

LiCoO_2 electrode/electrolyte interface of Li-ion batteries investigated by electrochemical impedance spectroscopy

The storage behavior and the first delithiation of LiCoO2 electrode in 1 mol/L LiPF6-EC:DMC:DEC elec- trolyte were investigated by electrochemical impedance spectroscopy (EIS). It has found that, along with the increase of storage time, the thickness of SEI film increases, and some organic carbonate lithium compounds are formed due to spontaneous reactions occurring between the LiCoO2 electrode and the electrolyte. When electrode potential is changed from 3.8 to 3.95 V, the reversible breakdown of the resistive SEI film occurs, which is attributed to the reversible dissolution of the SEI film component. With the increase of electrode potential, the thickness of SEI film increases rapidly above 4.2 V, due to overcharge reactions. The inductive loop observed in impedance spectra of the LiCoO2 electrode in Li/LiCoO2 cells is attributed to the formation of a Li1-xCoO2/LiCoO2 concentration cell. Moreover, it has been demonstrated that the lithium-ion insertion-deinsertion in LiCoO2 hosts can be well described by both Langmuir and Frumkin insertion isotherms, and the symmetry factor of charge transfer has been evaluated at 0.5.     

The understanding of solid electrolyte interface (SEI) formation and mechanism as the effect of flouro-o-phenylenedimaleimaide (F-MI) additive on lithium-ion battery

Solid electrolyte interface (SEI) is a critical factor that influences battery performance. SEI layer is formed by the decomposition of organic and inorganic compounds after the first cycle. This study investigates SEI formation as a product of electrolyte decomposition by the presence of flouro-o-phenylenedimaleimaide (F-MI) additive. The presence of fluorine on the maleimide-based additive can increase storage capacity and reversible discharge capacity due to high electronegativity and high electron-withdrawing group. The electrolyte containing 0.1 wt% of F-MI-based additive can trigger the formation of SEI, which could suppress the decomposition of remaining electrolyte. The reduction potential was 2.35 to 2.21 V vs Li/Li⁺ as examined by cyclic voltammetry (CV). The mesocarbon microbeads (MCMB) cell with F-MI additive showed the lowest SEI resistance (Rsei) at 5898 Ω as evaluated by the electrochemical impedance spectroscopy (EIS). The morphology and element analysis on the negative electrode after the first charge-discharge cycle were examined by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS). XPS result showed that MCMB cell with F-MI additive provides a higher intensity of organic compounds (RCH₂OCO₂Li) and thinner SEI than MCMB cell without an additive that provides a higher intensity of inorganic compound (Li₂CO₃ and Li₂O), which leads to the performance decay. It is concluded that attaching the fluorine functional group on the maleimide-based additive forms the ideal SEI formation for lithium-ion battery.     

Impedance Studies of Spinel LiMn2O4 Electrode/electrolyte Interfaces

The formation process of solid electrolyte interphase（SEI） film on spinel LiMn2O4 electrode surface was studied by electrochemical impedance spectroscopy（EIS） during the initial storage in 1 mol/L LiPF6-EC：DMC：DEC electrolyte and in the subsequent first charge-discharge cycle. It has been demonstrated that the SEI film thickness increased with the increase of storage time and spontaneous reactions occurring between spinel LiMn2O4 electrode and electrolyte can be prevented by the SEI film. In the first charge-discharge cycle succeeding the storage, the electrolyte oxidation coupled with Li-ion insertion is evidenced as the main origin to increase the resistance of SEI film. The results also confirm that the variations of the charge transfer resistance（Rot） with the electrode potential（E） can be well described using a classical equation.     

新型锂盐LiBC2O4F2在EC＋DMC溶剂中的电化学行为

采用差热-热重(TG-DTA)、恒电流充放电和交流阻抗(EIS)分析了二氟草酸硼酸锂(LiODFB)的热稳定性,研究了LiODFB/碳酸乙烯酯(EC)+碳酸二甲酯(DMC)电解液的电化学性能及界而特征.实验结果表明,LiODFB不仅具有更高的热稳定性,而且在EC+DMC溶剂中具有较好的电化学性能.与使用LiPF6/EC+DMC的电解液相比,锂离子电池应用LiODFB基电解液在55℃的高温具有更好的容量保持能力;以0.5C、1C(1C=250 mA·g-1)倍率循环放电,两种电池间的倍率性能差别较小;LiODFB能够在1.5 V(vs Li/Li+)左右在石墨电极表面还原形成一个优异稳定的保护性固体电解质相界面膜(SEI膜);交流阻抗表明,使用LiODFB基电解液的锂离子电池仅具有稍微增加的界面阻抗.因此LiODFB是一种非常有希望替代LiPF6用作锂离子电池的新盐.     

Electrochemical SPM investigation of the solid electrolyte interphase film formed on HOPG electrodes

Solid electrolyte interphase (SEI) film formation on graphite electrodes was studied on highly oriented pyrolytic graphite (HOPG) in nonaqueous electrolyte by in situ electrochemical atomic force microscopy (AFM). For potentials negative to 0.7 V versus Li|Li⁺ a SEI film is formed on the HOPG electrode surface. After the first cycle the film is rough and covers the surface of the HOPG electrode only partially. After the second cycle the HOPG surface is fully covered by a compact film. The thickness of the SEI film was measured by increasing the pressure of the AFM tip and thus scraping a part of the electrode surface. In this way a thickness of about 25 nm was found for the SEI film formed after two scan cycles between 3 and 0.01 V versus Li|Li⁺.     

新型锂盐LiBC2O4F2在EC+DMC溶剂中的电化学行为

采用差热-热重(TG-DTA)、恒电流充放电和交流阻抗(EIS)分析了二氟草酸硼酸锂(LiODFB)的热稳定性, 研究了LiODFB/碳酸乙烯酯(EC)+碳酸二甲酯(DMC)电解液的电化学性能及界面特征. 实验结果表明, LiODFB不仅具有更高的热稳定性, 而且在EC+DMC溶剂中具有较好的电化学性能. 与使用LiPF6/EC+DMC的电解液相比, 锂离子电池应用LiODFB基电解液在55 ℃的高温具有更好的容量保持能力; 以0.5C、1C(1C=250 mA·g-1)倍率循环放电, 两种电池间的倍率性能差别较小; LiODFB能够在1.5 V(vs Li/Li+)左右在石墨电极表面还原形成一个优异稳定的保护性固体电解质相界面膜(SEI膜); 交流阻抗表明, 使用LiODFB基电解液的锂离子电池仅具有稍微增加的界面阻抗. 因此LiODFB是一种非常有希望替代LiPF6用作锂离子电池的新盐.     

添加剂氟代乙烯碳酸酯对锂离子电池低温性能影响的机制研究

本文通过磷酸铁锂/碳电池研究了电解液添加剂氟代乙烯碳酸酯（FEC）对电池低温性能的影响. 电池充放电实验证明,FEC添加剂能够在负极表面形成良好的固体电解质界面层（SEI）. 电解液中添加5% FEC后,电池-40 ^oC低温放电容量保持率可以从31.7%提高至43.7%,还提高了电池放电电压平台. 交流阻抗测试表明,FEC的加入能够有效降低电池的界面传荷阻抗（R_ct）. 参比电极测试表明,其主要是降低了碳负极的低温极化.     

LiCoO<Subscript>2</Subscript> electrode/electrolyte interface of Li-ion batteries investigated by electrochemical impedance spectroscopy

The storage behavior and the first delithiation of LiCoO₂ electrode in 1 mol/L LiPF₆-EC:DMC:DEC electrolyte were investigated by electrochemical impedance spectroscopy (EIS). It has found that, along with the increase of storage time, the thickness of SEI film increases, and some organic carbonate lithium compounds are formed due to spontaneous reactions occurring between the LiCoO₂ electrode and the electrolyte. When electrode potential is changed from 3.8 to 3.95 V, the reversible breakdown of the resistive SEI film occurs, which is attributed to the reversible dissolution of the SEI film component. With the increase of electrode potential, the thickness of SEI film increases rapidly above 4.2 V, due to overcharge reactions. The inductive loop observed in impedance spectra of the LiCoO₂ electrode in Li/LiCoO₂ cells is attributed to the formation of a Li_1−x CoO₂/LiCoO₂ concentration cell. Moreover, it has been demonstrated that the lithium-ion insertion-deinsertion in LiCoO₂ hosts can be well described by both Langmuir and Frumkin insertion isotherms, and the symmetry factor of charge transfer has been evaluated at 0.5. Supported by the Special Funds for Major State Basic Research Project of China (Grant No. 2002CB211804)