CoO AS ADDITIVE IN POSITIVE ELECTRODE OF NICKEL-METAL HYDRIDE BATTERY

A series of positive electrodes for Ni/MH battery were fabricated by addition of CoO.The morphology and microstructure of the electrodes were examined by SEM and EDS, and electrochemical behavior was investigated in three-compartment appliances at room temperature.The electrochemical performance of the positive electrodes with CoO was improved. Under the same charge-discharge cycle, the electrodes with CoO showed higher specific capacity, lower charge mean voltage and higher discharge mean voltage. But further increasing the content of CoO in the electrodes contributed negative effect on the overall performance. Addition of 8% (mass) CoO was suggested to be a suitable content for the positive electrode.     

Preparation and Application of Nano-composite Poly(vinyl alcohol) Gel Electrolyte in Electrochemical Capacitor

A nano-composite polymer gel electrolyte was prepared using titanium oxide nanowire, poly(vinyl alcohol) (PVA), lithium salt and organic solvent N-methyl-2-pyrrolidone (NMP). The obtained electrolyte has the potential for application in electrochemical capacitor, the PVA in it is in an amorphous state. The ionic conductivities of electrolytes increased after addition of the nanowire, and the electrolyte with 3%(w) of nanowire exhibited the highest ionic conductivity of 3.2 mS/cm at 20℃, as measured by electrochemical impedance spectroscopy. The temperature dependence of the conductivity was found to be in agreement with the Arrhenius equation. Functioning as separator and electrolyte, this nano-composite PVA gel electrolyte was used to assemble the electrochemical capacitor with active carbon film as electrodes. The compositing of nanowire may extend the life of electrochemical capacitors as they keep more than 90% of their capacitance after 5000 cycles of charging and discharging.     

Influence of synergistic effect of LiNi0.8Co0.15Al0.05O2@Cr2O5 composite on the electrochemical properties

LiNi_(0.8)Co_(0.15)Al_(0.05)O_2@Cr_2O_5(NCA)@Cr_2 O_5 composite electrode combines the high rate-capability characteristics of NCA with the stability of Cr_2 O_5, playing a synergistic role in improving the cyclic stability, initial discharge capacity and the security of low cut-off voltage(2.0 V). When the mass ratio of Cr_2 O_5 in NCA is 45%(mass), the capacity retention rate increases from 58.5% without Cr_2 O_5 to 69.3% in the range of 2.0–4.3 V.The initial discharge capacity of NCA@Cr_2 O_5 composite material is 211.4 m A·h·g~(-1), its first coulombic efficiency is 94.2%, and the charging capacity remains approximately constant when mixed with 15%(mass)Cr_2 O_5. The reason for the improvement of the initial charge–discharge efficiency(ICDE) was explained.Impedance and cyclic voltammetry analysis reveal more detailed reasons of the observed improvements.Compared with NCA cathode material, the NCA@Cr_2 O_5 composite material can provide not only additional stable sites and channels for Li+insertion/extraction to make up for the loss of active Li+sites and prevent the accumulation of Li+in the circulation process, but also protect the NCA electrode from the corrosion of the electrolyte decomposition by the Cr_2 O_5 nanoparticles adhering to NCA interface.     

A design of Nafion-coated bilayered quasi-solid electrolyte for lithium-O2 batteries with high performance

Lithium-air(also known as lithium-oxygen) batteries have attracted considerable global attention in recent years due to their extremely high energy density(11,140 W·h·kg~(-1)).The electrolyte is a key element in lithium-air batteries and the traditional organic electrolyte has great safety risk due to leakage.On the contrary,the polymer electrolyte has the advantages of high safety,high stability and easy processing comparing with the organic liquid electrolytes.In this paper,a new idea was proposed to coat the Nafion membrane on a layer of polymer for blocking the oxidation reduction electric(RM) and Li based on the selective permeability on lithium ion of the Nafion membrane.Self-made thicknesscontrollable Nafion membrane,polyvinylidene fluoride-hexafluoropropylene copolymer(PVDF-HFP)and 2,2,6,6-tetramethylpiperidinooxy(TEMPO) were used to prepare a quasi solid polymer electrolyte(NSPE).Electrochemical workstation and LAND battery testing system were used to perform a galvanostatic charge/discharge test on Li-O_2.The ionic conductivity of NSPE was 4.3 × 10~(-4) S·cm~(-1) at room temperature and the discharge platform was 2.6 V and the charging voltage was 3.7 V after 50 cycles with the cut-off capacity of 500 mA·h·g~(-1).     

6.0mol•L－1KOH溶液中锌单晶（002）和（100）晶面的电化学行为

In this article, the electrochemical performance of the electrodes of zinc polycrystal, Zn（002） and Zn（100） single crystals were studied by the Tafel line extrapolation of the potentio-dynamic polarization curves, the cyclic voltammetry and the charge/discharge experiment. The results shows that in 6.0 mol·L^-1 KOH solution the corrosion rate of Zn polycrystal, Zn（100） and Zn（002） single crystals decreases in turn; and the reversibility and the charge/discharge performance of Zn single crystal was superior to Zn polycrystal. The dendrite growth of the surface of Zn polycrvstal was easier than Zn single crystal during the stages of charge/discharge.     

Electrocatalytic Activity of Ti/TiO2 Electrodes in H2SO4 Solution

Ti/TiO2 electrodes were prepared with the polymeric precursor method (PPM). The structure and morphology of Ti/TiO2 electrodes were examined with XRD and ESEM. The voltammetric charge (q*) of Ti/TiO2 electrodes as cathode in 0.5 mol/L H2SO4 solution was investigated with cyclic voltammetry. It was found that the electrocatalytic activity of the Ti/TiO2 electrodes was affected by the structure and morphology of the Ti/TiO2 electrodes, in other words, was affected by the calcination conditions of preparing the electrodes. The value of q*in was considerably larger than that of q*out, which means that the ‘inner’ active surface area was much larger than the ‘outer’ active surface area, and ‘inner’ active surface played a main role in the electrocatalytic activity of the Ti/TiO2 electrodes.     

碳毡基体电活性铁氰化镍电极电控离子交换连续分离Cs~+(英文)

Nickel hexacyanoferrate (NiHCF) film was synthesized on porous three-dimensional carbon felt (PTCF) substrate by repetitious batch chemical depositions, and the NiHCF/PTCF electrode was used as electrochemically switched ion exchange (ESIX) electrode in a packed bed for continuous separation for cesium ions. The morphologies of the prepared electrodes were characterized by scanning electron microscopy and the effects of solution concentration on the ion-exchange capacity of the electrodes were investigated by cyclic voltammetry technique. Cycling stability and long-term storage stability of NiHCF/PTCF electrodes were also studied. The NiHCF/PTCF electrodes with excellent ion-exchange ability were used to assemble a diaphragm-isolated ESIX reactor for cesium separation. Continuous separation of cesium and regeneration of NiHCF/PTCF electrode based on the diaphragm-isolated reactor were performed in a laboratory-scale two-electrode system.     

Structural evolution of plasma sprayed amorphous Li4Ti5O12 electrode and ceramic/polymer composite electrolyte during electrochemical cycle of quasi-solid-state lithium battery

A quasi-solid-state lithium battery is assembled by plasma sprayed amorphous Li₄Ti₅O₁₂ to provide the outstanding electrochemical stability and better normal interface contact.Scanning Electron Microscope(SEM),Scanning Transmission Electron Microscopy(STEM),Transmission Electron Microscopy(TEM),and Energy Dispersive Spectrometer(EDS)were used to analyze the structural evolution and performance of plasma sprayed amorphous LTO electrode and ceramic/polymer composite electrolyte before and after electrochemical experiments.By comparing the electrochemical performance of the amorphous LTO electrode and the traditional LTO electrode,the electrochemical behavior of different electrodes is studied.The results show that plasma spraying can prepare an amorphous LTO electrode coating of about 8μm.After 200 electrochemical cycles,the structure of the electrode evolved,and the inside of the electrode fractured and cracks expanded,because of recrystallization at the interface between the rich fluorine compounds and the amorphous LTO electrode.Similarly,the ceramic/polymer composite electrolyte has undergone structural evolution after 200 test cycles.The electrochemical cycle results show that the cycle stability,capacity retention rate,coulomb efficiency,and internal impedance of amorphous LTO electrode are better than traditional LTO electrode.This innovative and facile quasi-solid-state strategy is aimed to promote the intrinsic safety and stability of working lithium battery,shedding light on the development of next-generation high-performance solid-state lithium batteries.     

羟基氧化镍的电解制备，结构表征和电化学性能研究

NiOOH was prepared by one-step electrolysis of spherical Ni（OH）2 and the effects of electrolysis parameters were examined. The highly pure NiOOH was obtained after electrolysis at a current density of 60mA.g^-1 and 30℃ with anodic potential controlled in the range of 1.73-1.85V （vs. Zn/ZnO） for 360min. The NiOOH samriles were characterized bv X-ray oowder diffraction （XRD） and scanning electron microscope （SEM） analysis.Resuits indicate that the electrolysis product is spherical NiOOH doped with graphite. Charge and discharge tests show that the prepared NiOOH offers a discharge capacity of over 270mAh·g^-1 at current density of 30mA·g^-1 and can be directly used as cathode material of alkaline Zn/NiOOH batteries. Galvanostatic charge/discharge and cyclic voltammetry （CV） tests reveal good cycling reversibility, of the NiOOH electrode.     

高比容量镍氢电池的制备及电化学性能

Cylindrical nickel metal hydride （Ni-MH） battery with high specific volume capacity was prepared by using the oxyhydroxide Ni（OH）2 and AB5 type hydrogen storage alloy and adjusting the designing parameters of positive and negative electrodes. The oxyhydroxide Ni（OH）2 was synthesized by oxidizing spherical β-Ni（OH）2 with chemical method. The X-ray diffraction （XRD） patterns and the Fourier transform infrared （PT-IR） spectra indicated that 7-NiOOH was formed on the oxyhydroxide Ni（OH）2 powders, and some H2O molecules were inserted into their crystal lattice spacing. The battery capacity could not be improved when the oxyhydroxide Ni（OH）2 sample was directly used as the positive active materials. However, based on the conductance and residual capacity of the oxyhydroxide Ni（OH）2 powders, AA size Ni-MH battery with 2560 mA.h capacity and 407 W·h·L^-1 specific volume energy at 0.2C was obtained by using the commercial spherical β-Ni（OH）2 and AB5-type hydrogen-storage alloy powders as the active materials when 10% mass amount of the oxyhydroxide Ni（OH）2 with 2.50 valence was added to the positive active materials and subsequently the battery designing parameters were adjusted as well. The as-prepared battery showed 70% initial capacity after 80 cycles at 0.5C. The possibility for adjusting the capacity ratio of positive and negative electrodes from 1 ： 1.35 to 1 ： 1.22 was demonstrated preliminarily. It is considered the as-prepared battery can meet the requirement of some special portable electrical instruments.     

Performance improvement of pasted nickel electrodes with multi-wall carbon nanotubes for rechargeable nickel batteries

Carbon nanotubes (CNTs) were employed as a functional additive to improve the electrochemical performance of pasted nickel-foam electrodes for rechargeable nickel-based batteries. The nickel electrodes were prepared with spherical β-Ni(OH)₂ powder as the active material and various amounts of CNTs as additives. Galvanostatic charge/discharge cycling tests showed that in comparison with the electrode without CNTs, the pasted nickel electrode with added CNTs exhibited better electrochemical properties in the chargeability, specific discharge capacity, active material utilization, discharge voltage, high-rate capability and cycling stability. Meanwhile, the CNT addition also lowered the packing density of Ni(OH)₂ particles in the three-dimensional porous nickel-foam substrate, which could lead to the decrease in the active material loading and discharge capacity of the electrode. Hence, the amount of CNTs added to Ni(OH)₂ should be optimized to obtain a high-performance nickel electrode, and an optimum amount of CNT addition was found to be 3 wt.%. The superior electrochemical performance of the nickel electrode with CNTs could be attributed to lower electrochemical impedance and less γ-NiOOH formed during charge/discharge cycling, as indicated by electrochemical impedance spectroscopy and X-ray diffraction analyses. Thus, it was an effective method to improve the electrochemical properties of pasted nickel electrodes by adding an appropriate amount of CNTs to spherical Ni(OH)₂ as the active material.     

氧化镍/碳纳米管构筑准固态不对称超级电容器及电化学性能

以Ni(NO₃)₂为原料、NaOH为沉淀剂和羟基化碳纳米管（CNT）为基质首先制备了Ni(OH)₂/CNT复合材料, 然后将其于一定温度下煅烧,使其转变为NiO/CNT复合材料。用X射线粉末衍射仪（XRD）、场发射电子显微镜（FESEM）和透射电子显微镜（TEM）表征了样品的晶相与形貌,结果表明NiO纳米粒子紧密锚附在碳纳米管表面。复合材料可能的形成机理被提出。采用循环伏安法（CV）、单电极充放电和电化学阻抗研究了反应条件对其电化学性能的影响,确定最佳制备条件。将复合材料正极、活性炭负极和PVA-KOH电解质膜组装成准固态不对称超级电容器,电化学性能测试结果表明,在充放电电流密度11.2mA/cm²下,其比电容达到868.0F/g并保持稳定循环3700圈。7500次循环后,其比电容值仍有564.2F/g,显示出高的比电容和长的循环稳定性。     

Performance improvement of Nafion based solid state electrochemical supercapacitor

An electrochemical supercapacitor in all solid configuration using perfluorosulfonate ionomer as polymer electrolyte has been successfully realized. Electrodes of supercapacitor have been prepared using activated carbon material and Nafion ionomer. This latter had the double function of binder and electrolyte. Nafion 115 membrane has been used as electrolyte separator in the preparation of small scale supercapacitors. The capacitance performance of these devices is comparable or better than traditional systems, which use sulfuric acid as electrolyte. The electrochemical evaluation of studied supercapacitor has been carried out by cyclic voltammetry, dc charge/discharge measurements and electrochemical impedance spectroscopy. A capacitance of 90 F/g (referred to the weight of active carbon material in the electrode) has been obtained with carbon having surface area (SA) of about 1000 m²/g and, a capacitance of 130 F/g with activated carbon having SA of 1500 m²/g. These interesting results have been tentatively explained with an optimal configuration of electrodes and with the concomitant beneficial effects on the carbon pores of adsorbed water and Nafion distribution, which produce low distribute resistance in the carbon composite electrodes.     

Ni(OH)2/活性炭复合材料在超级电容器中的应用

用化学沉淀法在活性炭(AC)表面和微孔内掺杂不同量的氢氧化镍,制备了氢氧化镍-活性炭[Ni(OH)2-AC]复合材料. 用X射线衍射(XRD)和氮气吸附等温线等对活性炭和复合材料进行表征,结果表明,所制材料为b-Ni(OH)2-AC复合材料. 对不同掺杂量的b-Ni(OH)2-AC复合材料的电化学性能进行了研究,循环伏安、恒流充放电实验表明,少量氢氧化镍掺入活性炭表面和微孔中,所得材料的比电容较活性炭有所提高,并具有良好的充放电性能;当氢氧化镍的掺入量为6%(w)时,所制备的超级电容器单电极表现出优良的电化学性能. 以活性炭电极作负极,复合材料作正极制成复合型超级电容器,循环性能测试发现,掺入6%(w)氢氧化镍的复合材料制成的Ni(OH)2-AC/AC复合型超级电容器比电容高达330.7 F/g,比活性炭(AC/AC)超级电容器比电容(245.6 F/g)提高了34.6%,且Ni(OH)2-AC/AC复合型超级电容器具有更好的循环充放电性能.     

并流沉淀法合成氧化镍及其电容性能

以硝酸镍和碳酸铵为原料,采用并流沉淀法得到碱式碳酸镍前驱体,经300℃热处理后得到NiO。X射线衍射分析表明,其衍射峰位置分别为37.2°、43.2°和62.8°,与标准图谱比照,所制样品为立方相的NiO。按m(NiO):m(乙炔黑):m(聚四氟乙烯)=75:15:10制备电极材料,在电解液c(KOH)=5mol.L-1的三电极体系中,通过循环伏安、交流阻抗和恒流充放电对其超级电容性能进行了考察。不同扫速循环伏安曲线表明,该材料具有典型的超级电容特性;交流阻抗测试结果表明,溶液电阻RL为0.5Ω,电极电阻RE为0.6Ω;在电位为0～0.4V,10mA.cm-2恒流充放电条件下,测得其放电比容量可达352.7F.g-1。经12mA.cm-2恒电流循环100次,其放电效率仍达97.5%。     

秸秆基碳材料在Li2SO4电解液中的电化学性能

以生物质秸秆为碳源,利用水热结合KOH活化法制备了多孔碳材料,对其结构与形貌进行了表征。采用三电极体系,在不同浓度的Li₂SO₄电解液中,对多孔碳电极进行循环伏安、恒电流充放电和交流阻抗测试。结果表明,在0.5 mol·L^-1的Li₂SO₄电解液中,秸秆基生物质碳材料呈现出较好的电化学性能。当电流密度为0.5 A·g^-1时,比电容可达224 F·g^-1;经1500次充放电测试后,比电容保持率高达94.1%,循环性能良好。     

Performance improvement of pasted nickel electrodes with an addition of ball-milled nickel hydroxide powder

Spherical β-Ni(OH)₂ was modified by a low-cost method of normal ball milling (NBM), and the physical properties of both ball-milled and un-milled Ni(OH)₂ were characterized by transmission electron microscopy, specific surface area, particle size distribution and X-ray diffraction. It was found that NBM could obviously increase the surface area, decrease the particle and crystallite size, and reduce the crystallinity of β-Ni(OH)₂, which were advantageous to the improvement of the electrochemical activity of Ni(OH)₂. NBM also lowered the packing density and flowability of Ni(OH)₂, as revealed by the measurements of tapping density and angle of repose. Electrochemical performances of pasted nickel electrodes with an addition of ball-milled Ni(OH)₂ to spherical Ni(OH)₂ as the active material were investigated, and were compared with those of the pure spherical Ni(OH)₂ electrodes. Charge/discharge tests showed that ball-milled Ni(OH)₂ addition could enhance the charging efficiency, specific discharge capacity, discharge voltage and high-rate capability of the electrodes. This performance improvement could be attributed to a more compact electrode microstructure, better reaction reversibility and lower electrochemical impedance, as indicated by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. Thus, it was an effective method to modify the microstructure and improve the electrochemical properties of pasted nickel electrodes by adding an appropriate amount of ball-milled Ni(OH)₂ to spherical Ni(OH)₂ as the active material.     

Preparation and electrochemical properties of poly‐2,5‐dihydroxyaniline/activated carbon composite electrode in organic electrolyte

Poly‐2,5‐dimethoxyaniline coating has been fabricated on active carbon (AC) substrates by cyclic voltammetry (CV) in organic system. The resulted coating is hydrolyzed to produce poly‐2,5‐dihydroxyaniline (PDHA) to enhance the capacitance of the composite electrode. Scanning electron microscope, Fourier transform infrared spectroscopy, X‐ray diffraction, Raman spectra, CV, electrochemical impedance spectroscopy, and galvanostatic charge/discharge test are used to investigate the properties of these electrodes. In organic electrolyte, due to the introduced hydroquinone units, high value of capacitance up to 975 F g^?1 of the PDHA/AC has been obtained at a current density of 0.37 A g^?1 at a potential window of 0–1.5 V. An asymmetric capacitor has been assembled with the PDHA/AC positive and pure AC negative electrodes, which is able to obtain a specific energy as high as 178 Whkg^?1 in the potential range of 0–2.0 V at a current density of 0.93 A g^?1. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of unequal load of carbon xerogel in electrodes on the electrochemical performance of asymmetric supercapacitors

This paper investigates the electrochemical performance of asymmetric supercapacitors in an environmentally friendly aqueous electrolyte (1.0 mol L^?1 sodium sulfate solution). The asymmetric configuration is based on the use of a highly porous carbon xerogel as active material in both the positive and negative electrodes, but the carbon xerogel loading in each electrode has been substantially modified. This configuration leads to an increase in the operational voltage window up to values of 1.8 V and consequently to a higher specific capacitance (200 F g^?1) and energy density (~25 Wh kg^?1). Four different mass ratios were employed (1, 1.5, 2 and 3), and the electrochemical response of the cells was evaluated by means of cyclic voltammetry, galvanostatic charge–discharge and impedance spectroscopy. The results demonstrate that the optimal carbon mass ratio in the electrodes is about 2.0 because in these conditions the devices are able to operate with a maximum cell voltage of 1.8 V and with a high electrical efficiency.     

Preparation and electrochemical investigation of the polyaniline/activated carbon nanocomposite for supercapacitor applications

The polyaniline (PANI)/activated carbon (AC) nanocomposite electrodes were prepared by electropolymerization of aniline monomers on the surface of AC/polyvinyl alcohol (PVA) electrodes for supercapacitor studies. Fourier transforms infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses were performed to characterize the structure and morphology of the nanocomposite electrodes. The electrochemical properties of the prepared nanocomposite electrodes and the supercapacitive behavior of the PANI, AC, and AC/PANI/PVA electrodes were investigated using cyclic voltammetry (CV) and galvanostatic charge/discharge measurements, respectively. Morphological studies showed that a thin film of PANI has been uniformly deposited on the porous surface of AC electrode, and an ordered arrangement of nanostructures with interlinked porous network has been made. Electrochemical measurements showed that AC particles prevent the degradation of PANI chains during charge/discharge cycles. The specific capacitance of the AC/PANI/PVA nanocomposite electrode was 338.15 F/g which is higher than that of the pristine AC electrode (0.08 F/g). This is due to the contribution of PANI chains by their pseudocapacitance (redox reaction) properties. Although the specific capacitance of PANI electrode (378.57 F/g) was greater than that of the nanocomposite electrode, the cyclic stability of the PANI electrode was lower than that of the AC/PANI/PVA nanocomposite electrode.