H_2在K~0-MWCNTs上储存和吸附/脱附特性研究

利用高压容积法辅以卸压升温脱附排水法,测定金属K修饰多壁碳纳米管对H2的吸附储存容量.结果表明,在室温(25℃),7.25MPa实验条件下,x%K0-MWCNTs(x%=30%～35%,质量百分数)对H2的吸附储存容量可达3.80wt%(质量百分数),是相同条件下单纯MWCNTs氢吸附储量的2.5倍;室温下卸至常压的脱附氢量为3.36wt%(占总吸附氢量的～88%),后续升温至673K的脱附氢量为0.41wt%(占总吸附氢量的～11%).利用LRS和H2-TPD-GC/MS等谱学方法对H2/K0-MWCNTs吸附体系的表征研究表明,H2在K0-MWCNTs上吸附存在非解离(即分子态)和解离(即原子态)两种吸附态;在≤723K温度下,H2/K0-MWCNTs体系的脱附产物几乎全为H2气;723K以上高温脱附产物不仅含H2,也含有CH4,C2H4和C2H2等C1/C2-烃

LiCoO_2正极材料电子和离子传输特性的电化学阻抗谱研究

运用电化学阻抗谱(EIS)研究了LiCoO2正极的电子和离子传输特性,及其在电解液中贮存和充放电过程中的变化规律.发现当LiCoO2正极在电解液中贮存达到9h时,在EIS的中频区域出现一个新的半圆,随着贮存时间进一步延长,该半圆不断增大.在充放电过程中,这一中频区域半圆随电极电位的变化发生可逆的增大和减小,其变化规律与LixCoO2电子电导率随电极电位的变化规律相一致.因此,这一新的EIS特征应归属于LiCoO2正极在贮存或锂离子嵌脱过程中LixCoO2电子电导率的变化.研究结果还发现,LiCoO2正极表面SEI膜阻抗在充放电过程中可逆地增大和减小,也可归因于充放电过程中LiCoO2正极活性材料电子电导率的变化.国家重点基础研究发展计划(批准号:2002CB211804)资助项

Preparation and Capacity Fading Mechanism of Tin Thin Film as Anode of Lithium-ion Battery

以电镀的方法在铜基底上沉积薄膜锡作为锂离子电池负极材料.运用X射线衍射、扫描电镜、电化学循环伏安、电化学充放电和交流阻抗等多种方法对其结构和性能进行表征和研究.结果表明所制备的薄膜锡电极主要为四方晶系结构,其初始放电(嵌锂)容量为709mAh?g-1,充电(脱锂)容量为561mAh?g-1.电化学循环伏安研究发现在嵌/脱锂过程中薄膜锡经历了多种相变过程.电化学阻抗谱结果说明,首次嵌锂过程中当电极电位达到1.2V在电极表面形成SEI膜,而当电极电位低于0.4V表面SEI膜出现破裂,归因于体积膨胀所致.SEM研究表明30次充放电循环后薄膜锡负极出现龟裂现象.Tin thin film coated on Cu substrate as anode of lithium-ion battery was prepared by electroplating. Its structure and properties were characterized and studied by X-ray diffration, scanning electron microscopy, cyclic voltammetry, charging/discharging test and AC impedence method. XRD patterns indicate that the tin thin film exhibits a structure of tetragonal crystal. The first discharge and charge capacities of the tin thin film electrode were determined to be 709 and 561 mAh?g-1, respectively. Cyclic voltammetric results illustrated that multi-phase changes occurred during the lithiation and delithiation. Electrochemical impedance spectros- copy (EIS) results indicated that SEI film was begun to form on the surface of tin thin film electrode at 1.2 V, and then break down below 0.4 V because of large volume expansion. SEM investigations revealed that the tin thin film electrode appeared serious cracks after 30 charging and discharging cycles.国家重点基础研究和发展规划(973项目)(No.2002CB211804)资助项目

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

Electrochemical Impedance Spectroscopic Study of the First Delithiation of Spinel Lithium Manganese Oxide

研究了尖晶石锂锰氧化物电极首次脱锂过程中的电化学阻抗特征.通过选取适当的等效电路拟合实验所得的电化学阻抗谱数据,获得了首次脱锂过程中固体电解质相界面膜(SEI膜)的电阻、电容以及电荷传递电阻、双电层电容等随电极极化电位的变化规律.The first delithiation of the spinel LiMn2O4 electrode was studied using electrochemical impedance spectroscopy (EIS). Appropriate equivalent circuits were proposed to fit the experimental EIS data. Based on the fitting results, the variation of the capacitance and the resistance of SEI(solid electrolyte interphase) film, the resistance of charge transfer, and the capacitance of double layer along with the increase of polarization potential were quantitatively analyzed. The results demonstrated that the resistance and the thickness of the SEI film formed on the spinel LiMn2O4 electrode were both increased with the increase of polarization potential in the first delithiation of the spinel LiMn2O4 electrode; The charge transfer resistance decreases below 4.15 V and increases above 4.15 V, corresponding to the two-step reversible (de)intercalation of lithium between LiMn2O4 and λ-MnO2; The double layer capacitance was influenced by both the state of the spinel LiMn2O4 electrode(different polarization potential) and the two-step reversible (de)intercalation of lithium.国家重点基础研究发展规划项目(2002CB211804)资

Study of storage and adsorption/desorption characteristics of H-2 on MWCNTs modified by metal potassium

Storage capacity of H-2 in a kind of potassium-modified multiwalled carbon nanotubes, K-0-MWCNTs, was measured by using high-pressure volumetric method combined with desorption water-displacement method. It was experimentally shown that appropriate incorporation of a certain amount of metallic potassium into the MWCNTs could significantly increase the storage capacity of hydrogen. Under conditions of 7.25 MPa and ambient temperature, H-2 uptake of 3.8 wt% could be achieved by the x%K-0-MWCNTs (x%=30%-35%, mass percentage), which was 2.5 times as high as that by the KO-free MWCNTs under the same conditions. It was also indicated that adsorption of 99% of the H2 was reversible, and that 88% of the stored hydrogen (equalling storage capacities of 3.36 wt%) could be desorbed while the pressure was relieved to atmospheric pressure and similar to 11% of the stored hydrogen (equalling storage capacities of 0.41 wt%) was desorbed in the following process of elevating temperature from room temperature to 673 K. The Raman-spectroscopic and TPD-MS/GC investigations of the H-2/K-0-MWCNTs adsorption systems showed that adsorption of H-2 on the MWCNTs could occur in associative and dissociative forms, with the observed v(s)(C-H) for CH2, v(C-H) for CH and v(H-H) for H-2 (a) at 2856, 3228 and 3946 cm(-1), respectively, and that H-2 Was the predominant products desorbed at temperatures lower than 723 K, whereas in addition to H-2, light hydrocarbons such as CH4, C2H4, C2H2, etc. were also involved in the products desorbed at temperatures higher than 723 K

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

Electrochemical impedance spectroscopic study of the first delithiation of spinel lithium manganese oxide

The first delithiation of the spinel LiMn2O4 electrode was studied using electrochemical impedance spectroscopy (EIS). Appropriate equivalent circuits were proposed to fit the experimental EIS data. Based on the fitting results, the variation of the capacitance and the resistance of SEI (solid electrolyte interphase) film, the resistance of charge transfer, and the capacitance of double layer along with the increase of polarization potential were quantitatively analyzed. The results demonstrated that the resistance and the thickness of the SEI film formed on the spinel LiMn2O4 electrode were both increased with the increase of polarization potential in the first delithiation of the spinel LiMn2O4 electrode; The charge transfer resistance decreases below 4.15 V and increases above 4.15 V, corresponding to the two-step reversible (de)intercalation of lithium between LiMn2O4 and lambda-MnO2; The double layer capacitance was influenced by both the state of the spinel LiMn2O4 electrode (different polarization potential) and the two-step reversible (de)intercalation of lithium

Preparation and capacity fading mechanism of tin thin film as anode of lithium-ion battery

Tin thin film coated on Cu substrate as anode of lithium-ion battery was prepared by electroplating. Its structure and properties were characterized and studied by X-ray diffration, scanning electron microscopy, cyclic voltammetry, charging/discharging test and AC impedence method. XRD patterns indicate that the tin thin film exhibits a structure of tetragonal crystal. The first discharge and charge capacities of the tin thin film electrode were determined to be 709 and 561 mAh(.)g(-1), respectively. Cyclic voltammetric results illustrated that multi-phase changes occurred during the lithiation and delithiation. Electrochemical impedance spectroscopy (EIS) results indicated that SEI film was begun to form on the surface of tin thin film electrode at 1.2 V, and then break down below 0.4 V because of large volume expansion. SEM investigations revealed that the tin thin film electrode appeared serious cracks after 30 charging and discharging cycles

Organizing Software System of CSR Operation Running Data

CSR运行数据组织软件系统是CSR工程控制系统的重要组成部分，它是CSR同步控制系统的最上层，是CSR调束中统领整个CSR运行的核心系统，负责对CSR运行设备的数据进行组织和管理、对同步事例进行组织和调度，从而实现对其同步控制。本系统是建立在各个子系统硬件同步基础之上的，通过使用数据组织软件来使这些具有同步功能的各个子系统的硬件按照调速研究人员的思路同步协调地运行。本文主要解决了CSR控制工程中CSR运行数据组织软件系统的设计和实现问题，软件实现方案有两种：第一种是运行在本机的文件数据库和Windows客户；第二种是运行在网络上的Oracle数据库和Web客户。这两种解决方案都是建立在数据库和网络技术上的。同时，数据库的实时性与可靠性也是建立在网络技术基础之上的。文本的创新点：通过数据预先计算、分发技术、同步事例组织技术，降低了实时性对CSR控制系统，特别是对高速以太网的要求，并实现了具有精确定时的控制和监测硬件的同步触发，使得CSR控制系统完全能够满足控制和监测的实时性要求。CSR运行数据组织软件的可靠性是通过TCP/IP网络协议技术以及控制硬件的内置软件的可靠性来保证的CSR运行数据组织软件系统是CSR工程控制系统的重要组成部分，它是CSR同步控制系统的最上层，是CSR调束中统领整个CSR运行的核心系统，负责对CSR运行设备的数据进行组织和管理、对同步事例进行组织和调度，从而实现对其同步控制。本系统是建立在各个子系统硬件同步基础之上的，通过使用数据组织软件来使这些具有同步功能的各个子系统的硬件按照调速研究人员的思路同步协调地运行。本文主要解决了CSR控制工程中CSR运行数据组织软件系统的设计和实现问题，软件实现方案有两种：第一种是运行在本机的文件数据库和Windows客户；第二种是运行在网络上的Oracle数据库和Web客户。这两种解决方案都是建立在数据库和网络技术上的。同时，数据库的实时性与可靠性也是建立在网络技术基础之上的。文本的创新点：通过数据预先计算、分发技术、同步事例组织技术，降低了实时性对CSR控制系统，特别是对高速以太网的要求，并实现了具有精确定时的控制和监测硬件的同步触发，使得CSR控制系统完全能够满足控制和监测的实时性要求。CSR运行数据组织软件的可靠性是通过TCP/IP网络协议技术以及控制硬件的内置软件的可靠性来保证