天然气焦炭的嵌锂特性研究

锂离子电池的研究与开发具有诱人的商业前景．以金属锂为负极的锂二次电池存在着充放电循环寿命短和使用安全性能差等诸多问题，解决的途径之一是采用嵌锂化合物替代金属锂作为负极材料．其中，以具有贮锂功能的碳素材料作为负极的锂离子电池，不仅具有较高的电容量和较长...     

A simulation model of a high-capacity methane adsorptive storage system

A two-dimensional model is developed to describe the hydrodynamics, heat transfer and adsorption phenomena associated with the adsorptive storage of natural gas (NG) in cylindrical reservoirs. Intraparticle and film resistances to both heat and mass transfer are neglected. In the momentum equation, Ergun's law is considered locally valid and is extended to two dimensions. These assumptions are fully justified in the paper. Numerical results are presented concerning the pressurization and blowdown of an ultra-lightweight 50 litre cylinder, commercially available for the storage of compressed NG, if it were filled with an activated carbon having a good adsorptive storage capacity. A simple formula is also proposed to predict the filling times for fast charges. The predicted temperature changes in the packed-bed are in good agreement with those reported in the literature for an experimental charge/discharge.     

Soft carbon-coated bulk graphite for improved potassium ion storage

Potassium-ion batteries (PIBs) have attracted tremendous attention for large-scale energy storage fields based on abundant potassium resources. Graphite is a promising anode material for PIBs due to its low potassium ion intercalation voltage and mature industrialized preparation technology. However, the inability of graphitic structures to endure large volume change during charge/discharge cycles is a major limitation in their advancement for practical PIBs. Herein, a soft carbon-coated bulk graphite composite is synthesized using PTCDA as a carbon precursor. The PTCDA-derived soft carbon coating layer with large interlayer distance facilities fast potassium ion intercalation/extraction in the BG@C composite and buffers severe volume change during the charge/discharge cycles. When tested as anode for PIBs, the composite realizes enhanced rate capability (131.3 mAh/g at 2 C, 1 C = 279 mA/g) and cycling performance (capacity retention of 76.1% after 150 cycles at 0.5 C). In general, the surface modification route to engineer graphite anode could inherently improve the electrochemical performance without any structural alteration.     

巴基管嵌锂电极性能的研究

用化学气相沉积法制备的巴基管作为锂离子电池的负极活性物质可以达到７００ｍＡｈ／ｇ的容量，远超过了石墨嵌锂化合物理论容量。ＣＶＤ巴基管电极经２０次充放电循环后，放电容量保持率为６５．３％，尽管ＣＶＤ巴基管电极初次充放电效率低，但经表面镀铜修饰后，初次充放电效率可提高到５５．９％。     

纳米碳与石墨碳复合材料的电化学性能

在天然石墨(NG)中掺杂不同比例的碳纳米管(CNT)得到纳米碳与石墨碳的复合材料.电化学测试结果表明,在NG中掺杂质量分数为10%的CNT所得复合材料的电化学性能最好.经过20次充放电循环,该复合材料的放电容量比同样条件下的石墨提高15.9%.纳米碳管的中空式结构和不易塌陷的特点使复合材料的充放电容量和循环稳定性明显提高.     

Conductive-matrix-mediated alkaline Fe(III/VI) charge transfer: three-electron storage, reversible super-iron thin film cathodes

An extended conductive matrix facilitates a 100-fold enhancement in charge storage for reversible Fe(III/VI) super-iron thin films. These films were deposited, by electrochemical reduction of Na2FeO4, with an intrinsic high capacity 3 e- cathodic storage of 485 mAh g(-1). Whereas 3 nm Fe(III/VI) films exhibited a high degree of reversibility (throughout 100 charge/discharge cycles), thicker films had been increasingly passive toward the Fe(VI) charge transfer. Films were alternatively deposited on either smooth or on extended conductive matrixes composed of high-surface-area Pt, Ti, and Au and probed galvanostatically and via cyclic voltammetry. A 100 nm Fe(VI) cathode, on the extended conductive matrixes, sustained 100-200 reversible three-electrode charge/discharge cycles, and a 19 nm thin film cathode sustained 500 such cycles. With a metal hydride anode, full cell storage was probed, and a 250 nm super-iron film cathode film sustained 40 charge/discharge cycles, and a 25 nm film was reversible throughout 300 cycles. Fe(VI) salts exhibit higher cathodic capacity and environmental advantages, and the films are of relevance toward the next generation charge storage chemistry for reversible cathodes.     

Nitrogen doped porous carbon as excellent dual anodes for Li- and Na-ion batteries

Biomass-derived carbon materials have obtained great attention due to their sustainability,easy availability,low cost and environmentally benign.In this work,bamboo leaves derived nitrogen doped hierarchically porous carbon have been efficiently synthesized via an annealing approach,followed by an etching process in HF solution.Electrochemical measurements demonstrate that the unique porous structure,together with the inherent high nitrogen content,endow the as-derived carbon with excellent lithium/sodium storage performance.The porous carbon annealed at 700℃presents outstanding rate capability and remarkable long-term stability as anodes for both lithium-ion batteries and sodium-ion batteries.The optimized carbon delivers a high discharge capacity of 450 mAh/g after 500 cycles at the current density of 0.2 A/g for LIBs,and a discharge capacity of 180 mAh/g after 300 cycles at the current density of 0.1 A/g for SIBs.     

Cathode Materials for Hybrid Supercapacitors Based on Ozonated Reduced Graphene Oxide

A carbon material capable of reversible electrochemical oxidation and reduction with relatively high electrical conductivity was prepared by ozonation of thermally reduced graphene oxide. The specific discharge energy for such materials used in lithium ion electrochemical cell cathodes with non-aqueous electrolytes (LP-71) can reach 540 W h/kg at 40 mA/g current, while the average specific discharge power is 11.5 kW/kg at 5 A/g current. The specific charge after 2500 charge/discharge cycles at 5 A/g current was at a level of 93% of the initial value. The obtained materials appear promising for the design of new electricity storage systems.     

High‐Power Electrochemical Energy Storage System Employing Stable Radical Pseudocapacitors

The development of electrical energy storage devices that can operate at high charge and discharge rates is fundamentally important, however although electrochemical capacitors (ECs) can charge and discharge at high rates, their electrochemical storage capacity remains an order of magnitude lower than that of conventional lithium‐ion batteries. Novel pseudocapasitors are developed, based on the stable persilyl‐susbtituted free radicals of the heavy group 14 elements, (tBu₂MeSi)₃E^. [E=Si ( 1 ), Ge ( 2 ), and Sn ( 3 )], as anode materials for energy storage system. Such systems showed a remarkable cycle stability without significant loss of power density, in comparison with similar characteristics of the known organic radical batteries, the dual carbon cell, and the electrochemical capacitor. Particularly important is that these novel electrochemical energy storage systems employing stable heavy group 14 element radicals are lithium‐free. The electrochemical properties and structures of the reduced and oxidized species were studied by the cyclic voltammetry (CV), electron paramagnetic resonance (EPR) spectroscopy, and X‐ray diffraction (XRD).     

锂离子电池负极碳材料的表面改性与修饰Ⅱ.具有“核壳”结构的碳及其对电池性能的影响

以具有气相碳化形式的精制煤焦油沉积碳为壳层材料、人造石墨（ＡＧ）及中间相石墨微球（２８００℃）为核材料制备了核壳结构的碳及碳电极．核壳结构碳及核壳结构碳电极的充放电研究表明碳负极的稳定充放电容量及首次充放电效率都得到了较大的改善,循环伏安研究表明在０．７Ｖ（ｖｓＬｉ＋／Ｌｉ）左右用于形成碳电极表面钝化膜的溶剂的还原分解峰显著减小,显示了核壳结构碳材料电极对电极表面钝化膜的影响作用,Ｘ射线衍射研究揭示了石墨及石墨电极上的无定形碳壳层的存在     

Bismuth chloride@mesocellular carbon foam nanocomposite cathode materials for rechargeable chloride ion batteries

Chloride ion batteries(CIB) are considered to be one of the most promising energy storage devices. As cathode materials for CIBs, metal chlorides have many advantages, such as high theoretical energy density, abundant elemental resources and ideal discharge voltage plateau. However, the dissolution and huge volume change of metal chlorides during cycling lead to considerable short lifespan, which limits their potential application for CIBs. Herein, the bismuth chloride nanocrystal is confined in...     

碳纳米管在室温熔盐中的电容特性

研究了碳纳米管在室温熔盐二(三氟甲基磺酸酰)亚胺锂(LiTFSI)-乙酰胺中的电容特性. 将碳纳米管制成薄膜电极, 以LiTFSI-乙酰胺为电解液, 装配成模拟电容器, 用循环伏安和恒流充放电法研究其电化学性能. 结果表明, 碳纳米管在室温熔盐中表现出典型的电容特性, 其比电容为22 F•g^-1, 模拟电容器的工作电压可达2.0 V, 具有非常好的循环性能, 循环充放电1000次后容量损失仅10%, 表明室温熔盐是超级电容器非常有前景的新型电解液.     

Catalytically Active CoSe2 Supported on Nitrogen-Doped Three Dimensional Porous Carbon as a Cathode for Highly Stable Lithium-Sulfur Battery

Lithium-sulfur batteries are promising secondary energy storage devices that are mainly limited by its unsatisfactory cyclability owing to inefficient reversible conversion of sulfur and lithium sulfide on the cathode during the discharge/charging process. In this study, nitrogen-doped three-dimensional porous carbon material loaded with CoSe₂ nanoparticles (CoSe₂-PNC) is developed as a cathode for lithium-sulfur battery. A combination of CoSe₂ and nitrogen-doped porous carbon can efficiently improve the cathode activity and its conductivity, resulting in enhanced redox kinetics of the charge/discharge process. The obtained electrode exhibits a high discharge specific capacity of 1139.6 mAh g⁻¹ at a current density of 0.2 C. After 100 cycles, its capacity remained at 865.7 mAh g⁻¹ thus corresponding to a capacity retention of 75.97 %. In a long-term cycling test, discharge specific capacity of 546.7 mAh g⁻¹ was observed after 300 cycles performed at a current density of 1 C.     

Gas chromatographic analysis of trace gas impurities in tungsten hexafluoride

Highly reactive fluorinated gaseous matrices require special equipment and techniques for the gas chromatographic analysis of trace impurities in these gases. The impurities that were analysed at the low-microg/l levels included oxygen, nitrogen, carbon dioxide, carbon monoxide, sulfur hexafluoride and hydrogen. This paper describes the use of a system utilising backflush column switching to protect the columns and detectors in the analysis of trace gas impurities in tungsten hexafluoride. Two separate channels were used for the analysis of H2, O2, N2, CO, CO2 and SF6 impurities with pulsed discharge helium ionisation detection.     

Nanostructured Carbon/Antimony Composites as Anode Materials for Lithium‐Ion Batteries with Long Life

A series of nanostructured carbon/antimony composites have been successfully synthesized by a simple sol–gel, high‐temperature carbon thermal reduction process. In the carbon/antimony composites, antimony nanoparticles are homogeneously dispersed in the pyrolyzed nanoporous carbon matrix. As an anode material for lithium‐ion batteries, the C/Sb10 composite displays a high initial discharge capacity of 1214.6 mAh g^?1 and a reversible charge capacity of 595.5 mAh g^?1 with a corresponding coulombic efficiency of 49 % in the first cycle. In addition, it exhibits a high reversible discharge capacity of 466.2 mAh g^?1 at a current density of 100 mA g^?1 after 200 cycles and a high rate discharge capacity of 354.4 mAh g^?1 at a current density of 1000 mA g^?1. The excellent cycling stability and rate discharge performance of the C/Sb10 composite could be due to the uniform dispersion of antimony nanoparticles in the porous carbon matrix, which can buffer the volume expansion and maintain the integrity of the electrode during the charge–discharge cycles.     

Optimisation of a gas chromatographic method for trace gaseous impurities in nitrogen trifluoride by column sequence reversal

Highly reactive fluorinated gaseous matrices require special equipment and techniques for the gas chromatographic analysis of trace impurities in these gases. The impurities that were analysed at the low mg/L levels included dioxygen (O2), dinitrogen (N2), carbon dioxide (CO2), carbon monoxide (CO), sulfur hexafluoride (SF6), methane (CH4) and nitrous oxide (N2O). Carbon tetrafluoride (CF4) is also present in the product at levels of 20-400mg/L and had to be analysed as well. This paper compares the use of a custom-built dual-channel gas chromatograph utilising single column back flush switching on one channel for the determination of O2, N2, CH4 and CO with column sequence reversal on a second channel for the determination of CO2, N2O, SF6 and CF4 to a similar system using a combination of dual-column back flush and heart-cut configurations. Pulsed discharge helium ionisation detectors were used on both channels in both configurations.     

Interdispersed silicon–carbon nanocomposites and their application as anode materials for lithium-ion batteries

As an anode material for lithium-ion batteries (LIBs), silicon offers among the highest theoretical storage capacity, but is known to suffer from large structural changes and capacity fading during electrochemical cycling. Nanocomposites of silicon with carbon provide a potential material platform for resolving this problem. We report a spray-pyrolysis approach for synthesizing amorphous silicon–carbon nanocomposites from organic silane precursors. Elemental mapping shows that the amorphous silicon is uniformly dispersed in the carbon matrix. When evaluated as anode materials in LIBs, the materials exhibit highly, stable performance and excellent Coulombic efficiency for more than 150 charge discharge cycles at a charging rate of 1 A/g. Post-mortem analysis indicates that the structure of the Si–C composite is retained after extended electrochemical cycling, confirming the hypothesis that better mechanical buffering is obtained when amorphous Si is embedded in a carbon matrix.     

Enhancement of intensities in glow discharge mass spectrometry by using mixtures of argon and helium as plasma gases

Glow discharge mass spectrometry (GD-MS) is an excellent technique for fast multi-element analysis of pure metals. In addition to metallic impurities, non-metals also can be determined. However, the sensitivity for these elements can be limited due to their high first ionization potentials. Elements with a first ionization potential close to or higher than that of argon, which is commonly used as discharge gas in GD-MS analysis, are ionized with small efficiency only. To improve the sensitivity of GD-MS for such elements, the influence of different glow-discharge parameters on the peak intensity of carbon, chlorine, fluorine, nitrogen, phosphorus, oxygen, and sulfur in pure copper samples was investigated with an Element GD (Thermo Fisher Scientific) GD-MS. Discharge current, discharge gas flow, and discharge gas composition, the last of which turned out to have the greatest effect on the measured intensities, were varied. Argon–helium mixtures were used because of the very high potential of He to ionize other elements, especially in terms of the high energy level of its metastable states. The effect of different Ar–He compositions on the peak intensity of various impurities in pure copper was studied. With Ar–He mixtures, excellent signal enhancements were achieved in comparison with use of pure Ar as discharge gas. In this way, traceable linear calibration curves for phosphorus and sulfur down to the μg kg⁻¹ range could be established with high sensitivity and very good linearity using pressed powder samples for calibration. This was not possible when pure argon alone was used as discharge gas. This contribution is based on a presentation given at the Colloquium for Analytical Atomic Spectroscopy (CANAS ’07) held March 18–21, 2007 in Constance, Germany.     

纳米碳管的电化学贮锂性能

用透射电镜、高分辩透射电镜、X射线衍射和拉曼光谱表征了用催化热解法制备的纳米碳管的结构,研究了纳米碳管的电化学嵌脱锂性能.以纳米级铁粉为催化剂热解乙炔气得到的纳米碳管石墨化程度较低,结构中存在褶皱的石墨层、乱层石墨和微孔等缺陷,具有较高的贮锂容量,初始容量为640mAh/g,但循环稳定性较差.而以纳米级氧化铁粉为催化剂热解乙烯得到的纳米碳管结构比较规则,循环稳定性较好,但贮锂容量较低,初始容量为282 mAh/g.讨论了纳米碳管的结构对其温度特性和不同电流密度下的充放电容量的影响.     

Multilayer Porous Vanadium Nitride Microsheets Anodes for Highly Stable Na-ion Batteries

Sodiumion batteries(SIBs)have attracted intensive attention as promising alternative to lithium-ionbatteries(LIBs)for large scale energy storage systems because of low cost of sodium,similar energy storage mechanism and the reasonable performance.However,it is still a great challenge to search and design a robust structure of anode materials with excellent cycling stability and high rate capability for SIBs.Herein,multilayer porous vanadium nitride(VN)microsheets are synthesized through a facile and scalable hydrothermal synthesis-nitrogenization strategy as an effective anode material for SIBs.The multilayer porous VN microsheets not only offer more active sites for fast Na+insertion/extraction process and short diffusion pathway,but also effectively buffer the volume change of anode due to more space in the multilayer porous structure.The large proportions of capacitive behavior imply that the Na+charge storage depends on the intercalation pseudocapacitive mechanism.The multilayer porous VN microsheets electrodes manifest excellent cycling stability and rate capability,delivering a discharge capacity of 156.1 mA·h/g at 200 mA/g after 100 cycles,and a discharge capacity of 111.9 mA·h/g at 1.0 A/g even after 2300 cycles with the Coulombic efficiency of nearly 100%.