Properties of electrode/electrolyte interfaces in lithium-ion batteries

摘要锂离子电池中电极表面SEI膜对电池的电化学性能有重要影响，是锂离子电池研究的热点之一。本文系统、深入地研究了石墨负极，LiCoO2正极，尖晶石LiMn2O4及其Ni、Fe、Ti掺杂产物正极表面SEI膜在首次充放电中的形成过程和性质、嵌锂电极动力学和热力学以及嵌锂过程物理机制。重点探讨了温度、充放电过程、电极电位和电解液种类等对SEI膜成膜机制、材料电子电导率、电荷传递过程和感抗产生机制的影响规律。主要研究结果如下：（1）石墨负极表面SEI膜的成膜机制。研究发现，对于扣式电池体系，石墨负极首次阴极极化过程中电化学阻抗谱（Nyquist图）的高频区域半圆除了与SEI膜的形成有关外，还与集流体与...Abstract The passive layer, which is generally called the solid electrolyte interface layer (SEI layer), covered on both anode and cathode of a Li-ion battery plays a key role in the electrochemical property of the lithium ion battery, and has attracted extensive attentions in past years. The formation mechanisms of SEI film in the first charge-discharge process, the thermodynamics and kinetics ...学位：理学博士院系专业：化学化工学院化学系_物理化学(含化学物理)学号：B20032502

Influence of Temperature on the Performance of a Graphite Electrode

运用电化学阻抗谱(EIS)并结合循环伏安法(CV)研究了石墨电极25和60℃时在1 MOl.l-1 lIPf6-EC(碳酸乙烯酯)∶dEC(碳酸二乙酯)∶dMC(碳酸二甲酯)电解液中,以及60℃时在1 MOl.l-1 lIPf6-EC∶dEC:dMC+5%VC(碳酸亚乙烯酯)电解液中的首次阴极极化过程.发现高温下(60℃)石墨电极在1 MOl.l-1 lIPf6-EC∶dEC∶dMC电解液中可逆循环容量衰减的主要原因在于其表面无法形成稳定的固体电解质相界面(SEI)膜.实验结果显示,VC添加剂能够增进高温下石墨电极表面SEI膜的稳定性,进而改进石墨电极的循环性能.The first lithiation of a graphite electrode in 1 mol.L-1 LiPF6-EC(ethylene carbonate)∶DEC(diethyl carbonate)∶DMC(dimethyl carbonate) electrolyte at 25 and 60 ℃,and in 1 mol.L-1 LiPF6-EC∶DEC:DMC+5%VC(vinylene carbonate) electrolyte at 60 ℃ were investigated by electrochemical impedance spectroscopy(EIS) combined with cyclic voltammetry(CV).It was found that deterioration of the graphite electrode′s electrochemical performance was mainly caused by the unstable solid electrolyte interphase(SEI) film on the electrode′s surface in 1 mol.L-1 LiPF6-EC:DEC:DMC electrolyte at 60 ℃.However,the use of VC as an additive to the above electrolyte significantly improved the electrochemical performance of the graphite electrode,which was attributed to an improvement in the stability of the SEI film that formed on the graphite electrode′s surface.国家重点基础研究发展规划(973)项目(2009CB220102)资

Influence of binder on the performance of graphite anode

研究了水溶性粘结剂f-103和油性粘结剂P(Vdf-HfP)对锂离子电池石墨负极电化学性能和表面SEI膜成膜机理的影响。循环伏安的结果表明:在1 MOl/l lIPf6/EC+dEC+dMC电解液中,油性粘结剂石墨负极的电化学性能较好。电化学阻抗谱的结果表明:水溶性粘结剂石墨负极和油性粘结剂石墨负极表面SEI膜的成膜电位分别为1.00--0.60 V和0.80--0.55 V。油性粘结剂石墨负极表面SEI膜的稳定性较好。The influences of water-soluble binder F-103 and oiliness binder P(VDF-HFP)on the electrochemical performance and the surface SEI film formation mechanisms of graphite anode for Li-ion battery were researched.The results of cyclic voltammetry showed that the graphite anode with oiliness binder had better electrochemical performance in 1 mol/L LiPF6/EC+DEC+DMC.The results of electrochemical impedance spectroscopy showed that the SEI film formation potential on graphite anode with oiliness binder and with water-soluble binder were between 1.00～0.60 V and 0.80～0.55 V,respectively.The stability of surface SEI film on the graphite anode with oiliness binder was better.国家重点基础研究发展规划(973)项目(2009CB220102);中国矿业大学青年科技基金(ON080282

Electrochemical Impedance Spectroscopic Studies of Insertion and Deinsertion of Lithium Ion in Spinel LiMn_2O_4

运用电化学阻抗谱(EIS)研究了尖晶石lIMn2O4电极的首次充放电过程.发现EIS谱高频区域拉长压扁的半圆是由两个半圆相互重叠而成的,分别归属于与锂离子通过固体电解质相界面膜(SEI膜)的迁移和与尖晶石lIMn2O4材料的电子电导率相关的特征.通过选取适当的等效电路,对实验所得的电化学阻抗谱数据进行拟合,获得尖晶石lIMn2O4电极首次充放电过程中SEI膜电阻、电子电阻和电荷传递电阻等随电极极化电位变化的规律.根据研究结果提出了嵌锂物理机制模型.The processes of insertion and deinsertion of lithium ion in a spinel LiMn2O4 electrode during the first charge-discharge cycle were investigated by electrochemical impedance spectroscopy (EIS).The results illustrate that the depressed semicircle in the high frequency region consists of two semicircles that are overlapped each other, and were assigned respectively to lithium-ion migration through solid electrolyte interphase (SEI) film as well as the electronic properties of the material.An appropriate equivalent circuit was proposed to fit the experimental EIS data and variations of the resistance of SEI film, the electronic resistance of the material and the resistance of charge transfer along with the increase and decrease of electrode polarization potential were quantitatively analyzed.Based on the EIS results and analysis, a physical mechanism of lithium insertion and deinsertion was suggested.国家重点基础研究和发展规划“973”项目(No.2009CB220102);中国矿业大学青年科技基金(No.ON080282)资助项

Study progress of non-flammable and fire-retardant organic solvents for lithium-ion batteries

分析了锂离子电池中安全性问题产生的原因,讨论了相应的解决办法。论述了不燃和阻燃有机溶剂的作用原理,并总结了它们用于改善锂离子电池安全性时存在的主要问题,同时综述了这一领域的当前研究现状。Safety concern of lithium-ion batteries were analyzed, and several techniques devised to improve safety were also discussed. The functional mechanisms of non-flammable and fire-retardant organic solvents as cosolvents or additives for organic electrolyte solutions for lithium-ion batteries were introduced, issues and challenges facing non-flammable and fire-retardant organic solvents when they are applied to lithium-ion batteries were summarized, and finally progresses in studies of this field in recent years were reviewed.国家重点基础研究和发展规划项目(2002CB211804);; 中国矿业大学青年科技基金项目(ON080282

Application of IR spectroscopy in Li-ion batteries studies

综述了傅立叶变换红外光谱在锂离子电池基础研究中应用的进展,主要包括负极表面SEI膜的组成和结构、电解液稳定性、电极材料的结构表征以及聚合物电解质的表征等。Progress in applications of FTIRS in studies of Li-ion batteries was reviewed. It included composition and structure of SEI film on anode, stability of electrolyte, structure characterization of electrode materials and characterization of polymer electrolyte.国家"973"项目(2002CB211804);; 国家自然科学基金项目(20173045

石墨电极首次阴极极化过程的两电极和三电极电化学阻抗谱研究

运用电化学阻抗谱(EIS)并结合扫描电子显微镜(SEM)研究了石墨电极在两电极扣式电池和三电极玻璃电解池中的首次阴极极化过程.研究指出,两电极扣式电池体系中石墨电极首次阴极极化过程的EIS谱特征及其变化不能解释固体电解质相界面膜(SEI膜)的形成过程,但是可以用三电极玻璃电解池中获得的石墨电极首次阴极极化的EIS谱特征及其变化加以说明.结果表明,在石墨负极首次阴极极化过程中SEI膜主要在1.0~0.6V电位区间形成.国家重点基础研究发展计划(编号:2009CB220102)资助项

Fe@Fe2O3/石墨烯复合材料的制备与电化学性能研究

采用水热反应和高温固相反应方法合成了Fe@Fe2O3/石墨烯复合材料。运用扫描电子显微镜（SEM）、X射线衍射（XRD）、光电子能谱仪（XPS）和透射电镜（TEM）对复合材料进行了物理表征。结果表明,..

Three-dimensional Porous Cu_6Sn_5 Alloy Anodes for Lithium-ion Batteries

以三维多孔泡沫铜为基底,通过直接电沉积的方法制备锂离子电池Cu6Sn5合金负极材料.发现合金表面大量的微孔和“小岛”不仅增大电极的表面积,而且显著缓解充放电过程中的体积变化.测得三维多孔Cu6Sn5合金的初始放电(嵌锂)容量为620mAh·g-1,充电(脱锂)容量为560mAh·g-1,库仑效率达到90.3%,具有较好的循环性能.扫描电子显微镜(SEM)结果显示,在泡沫铜基底上制备的Cu6Sn5合金电极具有比通常的铜片基底更好的结构稳定性,经过50周充放电循环后无明显的脱落现象.Three-dimensional porous Cu6Sn5 alloy electrodes were prepared by electroplating using copper foam as current collector.The micro-holes and small islands on surface of the Cu6Sn5 alloy increased largely the surface area of the electrode,and improved significantly the ability of the electrode in buffering the volume change in process of charge/discharge when the Cu6Sn5 alloy was employed as anode in a lithium-ion battery.Galvonostatic charging/discharging results demonstrated that the initial discharge(lithiation)and charge(delithiation)specific capacities of the Cu6Sn5 alloy electrode were 620 mAh·g-1 and 560 mAh·g-1,respectively.It demonstrated that the Cu6Sn5 alloy electrode exhibited a large initial coulomb efficiency(90.3%)and good capacity retention.SEM(scanning electron microscope)results illustrated that the Cu6Sn5 alloy deposited on copper foam substrate was more stable than that on a conventional copper substrate,and displayed no obvious exfoliation after 50 charge/discharge cycles.国家重点基础研究发展规划项目(973)(2002CB211804)资

一种新型微孔聚合物电解质的制备与表征

以介孔分子筛SBA-15为填料,探索出一种无需使用增塑剂制备微孔型聚合物电解质的新方法.当SBA-15︰PVdF-HFP(偏氟乙烯-六氟丙烯共聚物)=3︰8时,所制备的复合固体聚合物电解质(CSPE)室温电导率达0.30mS·cm~(-1).红外透射光谱显示,成膜液中溶剂分子和SBA-15分子筛之间的相互作用所引发的相分离导致微孔的形成.X射线衍射(XRD)结果表明,SBA-15分子筛的加入,降低了聚合物电解质的结晶度,而SBA-15分子筛仍保持原有的骨架结构.所组装的Li/CSPE/MCF电池具有较为平稳的充放电平台,首次循环的库仑效率约为85.0%,经过20次循环后,容量保持率为94.0%