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

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

Fabrication and Performance of Cu_6Sn_5 Alloy Anode Using Porous Cu as Current Collector

以氢气泡为动力学模板电沉积获得多孔铜,并通过热处理增强其结构稳定性.进一步将多孔铜作为基底通过电沉积制备Cu-Sn合金负极.Xrd结果给出其组成为Cu6Sn5合金,扫描电子显微镜(SEM)观察到Cu6Sn5合金电极为三维(3d)多孔结构.充放电结果指出,Cu6Sn5合金电极具有较好的充放电性能,其首次放电(嵌锂)和充电(脱锂)容量分别为735和571MAH·g-1,并且具有较好的容量保持率.运用电化学阻抗谱研究了Cu6Sn5合金电极在商业电解液中的界面特性.Porous Cu was fabricated by electrodeposition through a kinetic template of hydrogen bubbles.The product was subsequently annealed to increase its structural stability.The Cu-Sn alloy was then electrodeposited onto porous Cu which served as a current collector.X-ray diffraction (XRD) studies ascertained that the composition of the Cu-Sn alloy was Cu6Sn5 and scanning electron microscopy (SEM) investigations showed a three-dimensional (3D) porous structure of the electrode.The first charge/discharge capacities of the Cu6Sn5 alloy electrode were measured respectively at 735 and 571 mAh·g-1,and a good retention of the capacities has been determined.Interfacial properties of the Cu6Sn5 alloy electrode in a commercial electrolyte were also studied by electrochemical impedance spectroscopy (EIS).国家重点基础研究发展规划(973)项目(2009CB220102)资

Electrochemical Impedance Spectroscopy Study on Phase Transformation of Cu_6Sn_5 Alloy Anode

以粗糙铜箔为基底,采用一步电沉积法获得Cu-Sn合金,X射线衍射(Xrd)测试结果显示其主要为Cu6Sn5合金相.扫描电子显微镜(SEM)测试结果表明该合金表面由大量“小岛“组成,且每个“小岛“上存在大量纳米合金粒子.充放电测试结果表明,以该合金为锂离子电池负极,其初始放电(嵌锂)和充电(脱锂)容量分别为461和405MAH·g-1.电化学阻抗谱测试结果显示,Cu6Sn5合金电极在阴极极化过程中分别出现了代表固体电解质界面膜(SEI膜)阻抗、电荷传递阻抗和相变阻抗的圆弧,并详细分析了它们的变化规律.The Cu-Sn alloy electrode was prepared by a one-step electrodepositing method using rough Cu foil as the substrate,and was determined as the intermetallic composite of Cu6Sn5 using an X-ray diffraction(XRD) method.The electrode surface morphology was analyzed by scanning electron microscopy(SEM) which displayed "small islands" structure with many nano-particles on it.The first discharge and charge capacities were determined as 461 and 405 mAh·g-1,respectively.Electrochemical impedance spectra(EIS) indicated that there appeared three arcs in the Nyquist plots respectively representing the impedance of solid electrolyte interphase film,charge transfer and phase transformation in the first lithiation,and their evolutive principles were also investigated.国家重点基础研究和发展规划(973)(No.2009CB220102);国家自然科学基金(No.20773102)资助项

LiCoO_2电极/电解液界面特性的电化学阻抗谱研究

运用电化学阻抗谱研究了LiCoO2电极在电解液中的贮存和首次脱锂过程.发现LiCoO2电极在电解液中,随浸泡时间延长其表面SEI膜不断增厚,归结为LiCoO2电极与电解液之间的自发反应导致生成一些高介电常数的有机碳酸锂化合物.研究结果指出LiCoO2电极首次脱锂过程中,SEI膜在3.8~3.95V电位区间发生可逆坍塌,对应其可逆溶解;由于过充反应,当电位大于4.2VSEI膜迅速增厚.研究结果同时表明,Li/LiCoO2电池体系的感抗来源于充放电过程中LiCoO2电极中存在LiCoO2/Li1?xCoO2局域浓差电池.发现锂离子在LiCoO2电极中的嵌脱过程可较好地用Langmuir嵌入等温式和Frumkin嵌入等温式描述,测得LiCoO2电极中锂离子嵌脱过程中电荷传递反应的对称因子α=0.5.国家重点基础研究发展计划资助项目(批准号:2002CB211804

Influence of Temperature on the Performance of a Graphite Electrode

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 degrees C, and in 1 mol . L-1 LiPF6-EC:DEC:DMC+5%VC (vinylene carbonate) electrolyte at 60 degrees C 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 degrees C. 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

Electrochemical Impedance Spectroscopy Study on Phase Transformation of Cu6Sn5 Alloy Anode

The Cu-Sn alloy electrode was prepared by a one-step electrodepositing method using rough Cu foil as the substrate, and was determined as the intermetallic composite Of Cu6Sn5 using an X-ray diffraction (XRD) method. The electrode surface morphology was analyzed by scanning electron microscopy (SEM) which displayed "small islands" structure with many nano-particles on it. The first discharge and charge capacities were determined as 461 and 405 mAh.g(-1), respectively. Electrochemical impedance spectra (EIS) indicated that there appeared three arcs in the Nyquist plots respectively representing the impedance of solid electrolyte interphase film, charge transfer and phase transformation in the first lithiation, and their evolutive principles were also investigated

Effects of temperature on the intercalation-deintercalation process of lithium ion in LiCOO2

The temperature dependent properties of the impedance spectral characters, the electronic resistance, the resistances of the SEI (solid electrolyte interphase) film as well as the charge transfer reaction of the LiCoO2 electrode in 1 mol/L LiPF6-EC (ethylene carbonate); DEC (diethyl carbonate):DMC (dimethyl carbonate) and I mol/L LiPF6-PC (propylene carbonate):DMC+5% VC (vinylene carbonate) electrolyte solutions were studied and reported. The temperature was varied from 0 to 30 degrees C. The studies of electrochemical impedance spectroscopy (EIS) revealed that, the common EIS features' of the LiCoO2 electrode in the I mol/L LiPF6-EC:DEC:DMC and I mol/L LiPF6-PC:DMC+5% VC electrolyte solutions were related to the temperature, and a straight line reflecting solid state Li ion diffusion in the bulk of active mass appeared at 10 and 20 V, respectively. In I mol/L LiPF6-EC:DEC:DMC and I mol/L LiPF6-PC:DMC+5% VC electrolyte solutions, the energy barriers for the ion jump relating to migration of lithium ions through the SEI film of the LiCoO2 electrode were determined to be 37.74 and 26.55 kJ/mol, the thermal active energy of the electronic conductivities to be 39.08 and 53.81 kJ/mol, and the intercalation-deintercalation reaction active energies to be 68.97 and 73.73 kJ/mol, respectively