海藻酸钠水性粘结剂对石墨负极电化学性能的影响

应用循环伏安、恒电流充放电等电化学方法以及利用扫描电镜对循环后的电极进行分析,研究海藻酸钠水性粘结剂对石墨负极电化学嵌脱锂性质行为的影响。结果表明,海藻酸钠对石墨电极的初始充放电容量、库仑效率、倍率充放电性质以及电化学循环性能均有一定的影响。水性粘结剂对改善石墨电极的嵌脱锂循环方面具有较大的发展前景。     

氰酸盐离子液体在石墨烯基超级电容器中的应用

将石墨烯电极与离子液体N-甲基-N-丙基吡咯烷氰酸盐（[C₃mpyr][OCN]）/碳酸丙烯酯（PC）混合电解液组装成超级电容器,采用循环伏安（CV）、交流阻抗（EIS）、恒电流充放电（GCD）等方法研究了其在50、60、70℃环境下的电化学性能。结果表明：该体系在较高温度下的电化学性能优异,70℃下其比容量最高可达295 F·g^-1,能量密度可达118 W·h·kg^-1,且恒电流充放电循环稳定性较好。     

锂电解过程中杂质元素的电化学行为

采用循环伏安法研究了锂电解过程中杂质元素的电化学行为。电解过程中杂质元素镁将优先于锂在阴极析出, 然后是金属锂的欠电位沉积形成镁锂合金, 最后才是金属锂的析出, Mg ²⁺的还原电极过程受扩散控制, 扩散系数为1.44×10 ^-5 cm ²/s;微量的Ca ²⁺即发生钙锂共沉积;在含少量氯化钠的熔盐体系中, 杂质元素钠被锂还原并形成合金, 随着电解质体系中氯化钠含量的增加, 金属锂中的钠含量有较大的增加;杂质元素铁优先于锂在阴极析出, 在阴极被还原成海绵铁使阴极钝化, 引起熔盐体系锂的析出电流急剧降低, Fe ³⁺的还原电极过程受扩散控制, 扩散系数为3.14×10 ^-5 cm ²/s。     

KF对Na3AlF6-Al2O3熔盐电解阴极过程的影响

采用循环伏安法、交流阻抗法和方波伏安法等电化学测量技术,考察了KF对Na₃AlF₆-Al₂O₃熔盐电解体系的阴极过程的影响。研究结果表明：在Na₃AlF₆-Al₂O₃和Na₃AlF₆-Al₂O₃-KF电解质体系的循环伏安曲线中,还原峰随着扫描速率的增大而负移,氧化峰随着扫描速率的增大而正移,在扫描速率较低（25～100 mV·s^-1）的情况下,反应过程不可逆,反应过程相对平缓稳定;随着扫描速率的提高,电极可逆性相对提高。由于电极附近铝离子的聚合现象,使得在无KF的熔盐体系下,交流阻抗的高频区出现了感抗现象;在含KF的体系下,反应是由电化学反应过程和扩散过程共同控制的,且随着KF含量的增加,Warburg阻抗系数减小,电化学反应过程控制逐步取代扩散过程控制;反应电流也随之增大,氧化速率加快,还原和氧化过程可逆性降低。同时KF的加入抑制了铝的沉积,合金化作用比较明显,通过对阴极前波进行高斯拟合,得到不同KF含量（0、3%、5%）体系下的铝离子的电子转移数分别为1.19、1.02、0.75。     

锂离子电池Si薄膜负极材料的制备及性能

采用直流磁控溅射法成功制备了钾离子电池用Si薄膜负极材料.通过SEM、恒电流充放电对薄膜材料的形貌及电化学性能进行了表征.结果表明,样品表面颗粒呈球状,表面较粗糙.电化学性能测试表明,Si电极存在较大的初期不可逆容量损失,其首次库仑效率为53%,首次嵌钾容量为1300 mAh/g,10次循环后,嵌锂容量维持在530 mAh/g,容量保持率为41%.     

熔盐电解法制备Cu-Er合金及其机理研究

本文采用熔盐电解的方法,以等质量比的LiCl-KCl为电解质,电解制备Cu-Er合金。利用循环伏安法、方波伏安法、计时电位法和开路计时电位法,研究Cu(Ⅱ)、Er(Ⅲ)在钨电极和铜电极的电化学行为,得到熔盐电解制备Cu-Er合金的电化学机理。最后以铜为工作电极,在-2.20V条件下恒电位电解3h,制备了含有CuEr和Cu_2Er_5相的Cu-Er合金。     

活性炭在室温熔盐电解质中的电容特性

制备了热稳定性高、电化学性能良好的室温熔盐高氯酸锂(LiClO4)-1,3-氮氧杂环戊-2-酮(OZO),对其作为电解质材料在活性炭电化学电容器中的应用进行了研究.恒流充放电和循环伏安测试表明,活性炭电极与该类室温熔盐电解质表现出良好的电化学兼容性,比电容达到55.2 F/g,并具有良好的循环性能,循环充放电760次后容量损失小于5%.结合室温熔盐不宜燃、不挥发等特性,表明其是超级电容器非常有前景的新型电解液.     

高比表面活活性炭电级的电化学性能研究

选用比表面积为2590m^2/g的石油焦基活性炭作为双电层电容器的炭电极材料,用直流恒流循环实验考察双电层电容器在不同允放电条件下的电化学性能。实验发现,活性炭电极具有良好的循环充放电性能,充放电效率高达97％,远高于普通电池。不同充放电电流有不同的充放电容量,恒流1mA充放电容量大于2mA和5mA时的充放电容量。活性炭的比电容为60F／g,且电化学性能稳定,有良好的应用前景。     

LiF对Na3AlF6-Al2O3熔盐电解阴极过程的影响

电解铝工业中铝在阴极上析出,铝析出反应的机理对电解铝生产具有理论指导意义。在运用循环伏安法研究的基础上,通过理论计算,对Na₃AlF₆-Al₂O₃和Na₃AlF₆-Al₂O₃-LiF体系中金属铝在钨电极上的电化学沉积行为以及铝钨金属间化合物的形成机理进行了研究。结果表明：两体系中铝钨金属间化合物在50 mV·s^-1≤ν≤150 mV·s^-1扫描速率下的形成过程是受扩散控制的准可逆过程。在化合物形成的过程中,两体系中Al³⁺的扩散系数从4.54×10^-9 cm²·s^-1增长到5.71×10^-9 cm²·s^-1,Al³⁺反应的活化能分别为11.14 kJ·mol^-1和10.47 kJ·mol^-1。在Na₃AlF₆-Al₂O₃-LiF体系的还原过程中,Li并没有还原析出,而在氧化过程中Al在金属间化合物中的氧化电流增大;在恒电流电解时,Al-W金属间化合物并不溶于熔盐中,会附着在工作电极表面,LiF的加入会使电极表面的WAl₄量变小,取而代之的是Al₂O₃的增加,说明LiF的加入使电解更加稳定,抑制了电极表面WAl₄的生长。     

三维柱阵列型纳米多孔硫化亚锡负极的电化学合成与储锂性能研究

本研究在铜箔基底上通过无模板恒流电沉积技术成功制备出三维柱阵列型纳米多孔铜镍集流体。采用恒压电沉积方式在该集流体表层沉积SnS纳米颗粒,形成了具有三维柱状结构的纳米多孔硫化亚锡电极。利用恒流充放电测试与XRD、SEM、EDS技术,综合评估了该负极的电化学特性、微观结构、化学元素分布及其物相成分。结果表明,所制备的纳米柱表面存在孔隙,阵列间隙均匀。在0.1 mA/cm²电流密度下,该电极首次放/充电过程中分别提供了0.77/0.48 mAh/cm²的面积比容量,首次库仑效率为62%。经过50周循环后,电极可逆比容量仍达0.30 mAh/cm²,容量保持率为62.5%。     

Initial stages of the electrocrystallization of Co-Cu alloys on GCE from the Co rich electrolytes

The electrocrystallization of cobalt-copper alloy on the glass carbon electrode from Co rich sulfate solutions was studied by utilizing electrochemical techniques of cyclic voltammetry (CV) and chronoamperometry (CA), coupled with the scanning electronic microscopy (SEM) and the energy dispersive X-ray (EDX) analysis. EDX results indicated that the nuclei formed were Co-rich Co-Cu alloy. Analysis of the current-time transients by the chronoamperometry and SEM images indicated that the nucleation mechanism of Co-Cu alloy from the sulfate solution occurred by the instantaneous nucleation with the three-dimensional growth under the diffusion control. Furthermore, with the increase of the copper ion concentration in the bath, the nucleation and growth rate improved.     

柠檬酸钠体系中Ni・Fe合金的电沉积行为

采用循环伏安曲线、电化学阻抗谱、计时电流曲线等方法对柠檬酸钠体系中Ni-Fe合金的电沉积行为进行了研究。结果表明:柠檬酸钠体系中Ni-Fe合金电沉积是一个受扩散控制的不可逆过程。随着电位的增大,电沉积依次经历了电化学活化阶段、电结晶成核阶段、动力学-扩散混合控制阶段和扩散控制阶段。阴极附近未被及时消耗的FeOH+会覆盖在电极表面,阻碍金属离子扩散到电极表面放电,使电化学阻抗谱低频端存在阻挡层扩散阻抗特征。随着电位的增大,Ni-Fe合金的成核速率逐渐加快。Ni-Fe合金的成核机制在低电位下表现为连续成核,在高电位下表现为瞬时成核。     

High-performance Sn–Ni alloy nanorod electrodes prepared by electrodeposition for lithium ion rechargeable batteries

To reduce irreversible capacity and improve cycle performance of tin used in lithium ion batteries, Sn–Ni alloy nanorod electrodes with different Sn/Ni ratios were prepared by an anodic aluminum oxide template-assisted electrodeposition method. The structural and electrochemical performance of the electrode were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, cyclic voltammetry, and galvanostatic charge–discharge cycling measurement. The results showed that the copper substrate is covered with uniformly distributed Sn–Ni alloy nanorods with an average diameter of 250 nm. Different phases (Sn, Ni₃Sn₄ and metastable phases) of alloy nanorod formed in the electrodeposition baths with different compositions of Sn²⁺ and Ni²⁺ ions. Sn–Ni alloy nanorod electrode delivered excellent capacity retention and rate performance.     

Application of pulse methods to the determination of the electrochemical characteristics of lithium intercalates

The transfer processes proceeding in insertion electrodes with surface control on the application of a potential or current step are considered theoretically. The theoretical relationships have been verified by the determination of the kinetic and diffusion parameters of electrochemical lithium intercalation into thin carbon films. The overall electrode polarization is divided, both theoretically and experimentally, into the kinetic component, related to hindered ion transfer in the passive surface layer, and the diffusion one, related to decelerated lithium diffusion in the carbon matrix. The polarization dependence of kinetic current is shown to obey the same regularities that the current-potential function of the lithium electrode. The concentration dependences of the surface layer parameters and the diffusion coefficient of lithium in carbon have been determined.     

Fabrication and characterization of LATP/PAN composite fiber-based lithium-ion battery separators

Lithium aluminum titanium phosphate (LATP)/polyacrylonitrile (PAN) composite fiber-based membranes were prepared by electrospinning dispersions of LATP particles in PAN solutions. The electrolyte uptakes of the electrospun LATP/PAN composite fiber-based membranes were measured and the results showed that the electrolyte uptake increased as the LATP content increased. The lithium ion conductivity, the electrochemical oxidation limit and the interface resistance of liquid electrolyte-soaked electrospun LATP/PAN composite fiber-based membranes were also measured and it was found that as the LATP content increased, the electrospun LATP/PAN composite fiber-based membranes had higher lithium ion conductivity, better electrochemical stability, and lower interfacial resistance with lithium electrode. Additionally, lithium//1 M LiPF₆/EC/EMC//lithium iron phosphate cells using LATP/PAN composite fiber-based membranes as the separator demonstrated high charge/discharge capacity and good cycle performance.     

Suppressing propylene carbonate decomposition by coating graphite electrode foil with silver

A method has been developed to suppress the decomposition of propylene carbonate (PC) by coating graphite electrode foil with a layer of silver. Results from electrochemical impedance measurements show that the Ag-coated graphite electrode presents lower charge transfer resistance and faster diffusion of lithium ions in comparison with the virginal one. Cyclic voltammograms and discharge-charge measurements suggest that the decomposition of propylene carbonate and co-intercalation of solvated lithium ions are prevented, and lithium ions can reversibly intercalate into and deintercalate from the Ag-coated graphite electrode. These results indicate that Ag-coating is a good way to improve the electrochemical performance of graphitic carbon in PC-based electrolyte solutions.     

Reprint of “Suppressing propylene carbonate decomposition by coating graphite electrode foil with silver”

A method has been developed to suppress the decomposition of propylene carbonate (PC) by coating graphite electrode foil with a layer of silver. Results from electrochemical impedance measurements show that the Ag-coated graphite electrode presents lower charge transfer resistance and faster diffusion of lithium ions in comparison with the virginal one. Cyclic voltammograms and discharge-charge measurements suggest that the decomposition of propylene carbonate and co-intercalation of solvated lithium ions are prevented, and lithium ions can reversibly intercalate into and deintercalate from the Ag-coated graphite electrode. These results indicate that Ag-coating is a good way to improve the electrochemical performance of graphitic carbon in PC-based electrolyte solutions.     

梯度电流密度下电沉积制备铜-镍-钼合金电极及其性能研究

采用梯度电沉积法制备铜基Cu–Ni–Mo合金电极,电流密度参数为:10 mA/cm^2×5 min+30 mA/cm^2×40 min+50 mA/cm^2×5 min。通过扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)和X射线光电子能谱仪(XPS)分析了Cu–Ni–Mo合金镀层的表面形貌、元素组成、相结构和各元素的化学价态,并通过线性扫描伏安曲线(LSV)、电化学阻抗谱(EIS)和计时电流法对比了Cu–Ni和Cu–Ni–Mo合金电极在1 mol/L KOH溶液中的析氢性能和稳定性。结果表明,所得Cu–Ni–Mo合金镀层是呈花椰菜多孔形貌的非晶态结构。与Cu–Ni合金电极相比,Cu–Ni–Mo合金电极具有更大的比表面积,可为析氢反应提供更多活性位点,表现出更好的析氢性能,稳定性也更好。     

Electrochemical performances of lithium ion battery using alkoxides of group 13 as electrolyte solvent

Tris(methoxy polyethylenglycol) borate ester (B-PEG) and aluminum tris(polyethylenglycoxide) (Al-PEG) were used as electrolyte solvent for lithium ion battery, and the electrochemical property of these electrolytes were investigated. These electrolytes, especially B-PEG, showed poor electrochemical stability, leading to insufficient discharge capacity and rapid degradation with cycling. These observations would be ascribed to the decomposition of electrolyte, causing formation of unstable passive layer on the surface of electrode in lithium ion battery at high voltage. However, significant improvement was observed by the addition of aluminum phosphate (AlPO₄) powder into electrolyte solvent. AC impedance technique revealed that the increase of interfacial resistance of electrode/electrolyte during cycling was suppressed by adding AlPO₄, and this suppression could enhance the cell capabilities. We infer that dissolved AlPO₄ components formed electrochemically stable layer on the surface of electrode.