The possibility of electrochemical lithium intercalation into a nanodiamond

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Role of solution structure in the electrochemical intercalation of Ca2+ into graphite layers

In this study, we investigated the electrochemical intercalation of Ca²⁺ into graphite as an anode material for calcium-ion batteries (CIBs). The electrochemical intercalation of Ca²⁺ into a graphite electrode is possible when γ-butyrolactone (GBL) is utilized as a solvent, resulting in a reversible charge/discharge capacity. The GBL-based electrolyte allows a reversible redox reaction, thereby resulting in the intercalation and deintercalation of Ca²⁺ within the graphite electrode. Conversely, Ca²⁺ cannot be intercalated between the graphite layers in the ethylene carbonate–diethyl carbonate (EC–DEC)–based electrolyte. Analyses of the solution structures of both cases indicated that the interaction between the GBL solvent and Ca²⁺ was weak whereas that between the EC–DEC solvent and Ca²⁺ was strong. As a result of analyzing the surface of the negative electrode after charging and discharging from XPS, it was confirmed that a component that seems to be a solid electrolyte interphase (SEI) was confirmed in the graphite electrode using the GBL-based electrolyte.

     

A comparison of negative and positive ion mass spectrometry

Negative ion mass spectrometry using a conventional mass spectrometer with a special ion source and a sample pressure of approximately 2 × 10^?5 Torr is shown to be an excellent method for the qualitative analysis of lower mass alcohols, mercaptans, ketones, aldehydes, aliphatic carboxylic acids and esters, the spectra of which are characterized by intense [M – H] ^? ions. The method may be termed a ‘selective’ low energy ionization technique, being suitable for the above organic compounds, but not for nitriles, nitro compounds, hydrocarbons, ethers, amines, amides, nitrogen heterocycles and chlorinated compounds. This method can be looked upon as a complementary method, to positive ion mass spectrometry.     

锂在共轭双键高分子中的电化学嵌入反应Ⅱ:锂在聚吡咯中嵌入反应的量子化学研究

本文用量子化学CNDO/2方案计算,取文献中吡咯骨架原子的结构参数,再优化锂嵌入聚吡咯的几何参数.结果表明不管是Li+离子还是中性Li原子,嵌入单个吡咯上还是嵌入两个吡咯之间,它与吡咯环四个碳原子平面的距离都为0.210到0.216nm.且锂与碳原子键合,形成多中心键,锂嵌入聚吡咯后,固有的Ca=Cs双键的键级和键能明显减弱.这与前一报中发现IR谱的1560cm-1吸收峰消失相一致.锂正离子嵌入聚吡咯后,使吡咯的前沿π*空轨道的能量由正变为负值,而成为电子接受体(正极).遍及全部聚吡咯的π*LUMO和HOMO使得聚吡咯呈现导电性能.     

Electron capture negative ion and positive ion chemical ionization mass spectrometry of polychlorinated phenoxyanisoles

Several polychlorinated phenoxyphenols with three to nine chlorine atoms were examined as their methyl ethers by electron capture negative ion and positive ion chemical ionization and electron impact mass spectrometry. In chemical ionization studies methane, hydrogen, nitrogen, helium and argon were used as reagent gases. Selected compounds were also examined with deuteriomethane, ammonia and deuterioammonia as reagent gases. Utilization of chemical ionization spectra in conjuction with electron impact spectra provides substantial structural information about these compounds. Chemical ionization spectra provide information about chlorine atom substitution. The position of phenoxy substitution can be established from electron capture negative ion and positive ion spectra.     

Enhanced electrochemical performance of Li-ion batteries with nanoporous titania as negative electrodes

Nanoporous anatase TiO2(np-TiO2) electrodes have been developed via the anodization of titanium foils in fluoride containing electrolytes,and its application in rechargeable lithium-ion batteries(LIBs) was investigated. Four different types of np-TiO2 electrodes with different pore diameters of 14.7±8.2 nm, 12.8±6.8 nm, 11.0±5.5, and 26.7±13.6 nm were fabricated for evaluating the effect of nanoporous characteristics on the LIB performance. The discharge capacity of the four battery types 1, 2, 3, and 4 were 132.7 m Ah g-1, 316.7 m Ah g-1, 154.3 m Ah g-1,and 228.4 m Ah g-1, respectively. In addition, these electrodes 1, 2, 3, and 4 exhibited reversible capacity of 106.9 m Ah g-1after 295 th,180.9 m Ahg-1 after 220 th, 126.1 m Ah g-1after 150 th, and 206.7 m Ahg-1after 85 th cycle at a rate of 1 C, respectively. It was noted that the cyclic life of the batteries had an inverse relationship, and the capacity had a proportional relationship to the pore diameter. The enhanced electrochemical performance of the nanoporous electrodes can be attributed to the improved conductivity and the enhanced kinetics of lithium insertion/extraction at electrode/electrolyte interfaces because of the large specific surface area of np-TiO2 electrodes.     

Alkali halides based on nano-alumina as positive and negative ion source for ion mobility and mass spectrometry

In this work, a new long-life alkali ion source is proposed that is based on alkali halide salts doped in nano-γ-alumina (Al₂O₃). Depending on the polarity, the ion source produces both alkali and halide ions. The source was characterized using different techniques such as scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), fourier transform infrared (FT-IR), and ion mobility spectrometry (IMS). SEM images confirm a strong interaction between the alkali halide (MX) and nano-γ-alumina. The average particle size of the doped nanoparticles was calculated to be 44 nm by TEM. Formation of new phases (KAlCl₂O and K₃AlF₆) was confirmed by XRD and that of Al–O–K group in the synthesized particles by FT-IR. Alkali and halide ion peaks were observed by IMS in the positive and negative modes, respectively. The lifetime of the ion source for different alkali halides was measured to range from 216 to 960 h. The total ion current emitted from the source was about 2 µA, while it was 12 nA at the collector plate of the IMS. Finally, application of the new source in ion mobility spectrometry was demonstrated by observing ion mobility spectra of compounds ionized via cation and anion attachment reaction.     

Composite electrodes of electrochemical capacitors based on carbon materials with different structure

For composite electrodes based on active carbon DCL Supra 30, ordered mesoporous carbon, and synthetic carbon material Sibunit, the electrical double layer capacitance is studied. The original carbon samples are characterized by the methods of gas adsorption, X-ray diffraction, and transmission electron microscopy. The mesoporous structure of the material synthesized by the template method provides the maximum rate of ion transport in pores and demonstrates an insignificant decrease in the specific capacitance (9.5% in an aqueous electrolyte and 1.1% in an nonaqueous electrolyte) with an increase in the polarizing current.     

Atomic scale understanding of aluminum intercalation into layered TiS_2 and its electrochemical properties

正Aluminum-ion batteries (AIBs) are attracting great attentions recently because of the high volumetric capacity,natural abundance of Al and operational safety.Using metallic A1 as anode,the development of suitable cathode materials is a key issue to build an advanced AIBs system [1,2].Up to now,various materials have been studied as cathode materials for AIBs,including graphite [3,4],metal oxides [5-7],and metal sulfides [8,9].However,few of them can meet the application requirements,and the theoretical understanding of their electrochemical mechanism is limited.     

金衬底上阴、阳离子型硫醇分子的量子化学计算

采用量子化学程序Gaussian98从头计算方法，对用做金衬底离子化的2—巯基乙基—二甲基氯化铵和3—巯基丙磺酸钠两种硫醇分子进行了全优化计算，得到了这两种化合物的平衡几何构型、基态能量、分子轨道组成和电荷分布等，并分析讨论了其分子轨道作用性质以及自由硫醇分子和金表面的相互作用．研究发现，表面分子基团带有大部分的净电荷，说明利用金与硫醇分子的自组装可实现金衬底的离子化。     

Electrochemical performance of lithium ion capacitors with different types of negative electrodes

The electrochemical properties of various commercial carbon materials (activated carbon (AC), graphite (GP) and hard carbon (HC)) have been investigated for use as negative electrode for lithium ion capacitors. The rate capabilities and cycle durabilities are tested up to 20 C and 1000 cycles using full cell configurations. It is found that the lithium ion could not efficiently intercalate into the activated carbon materials. The symmetrical AC/AC capacitor shows good cycle durabilities at 10 C with capacity of 17 mA h g^?1. The asymmetrical capacitors AC/GP and AC/HC with intercalated negative electrodes show higher capacities than that of AC/AC capacitor. Moreover, the AC/HC has better rate capabilities than AC/GP.     

Kinetics of electrochemical lithium intercalation into thin tungsten (VI) oxide layers

The methods of galvanostatic intermittent titration, cyclic voltammetry, and electrode impedance spectroscopy are used to study the behavior of tungsten (VI) oxide film electrodes free of binding and conducting additives in the course of reversible lithium intercalation from nonaqueous electrolyte at 25°C. The studies are performed for electrodes with different degrees of crystallinity at the variation of the lithium concentration in intercalate from zero to 0.017 mol/cm³. Lithium diffusion coefficient is in the range of 10^?11–10^?16 cm²/s. The concentration dependences of the intercalation-layer transport parameters are analyzed, the equivalent circuit versions are discussed, and results obtained by different methods are compared.     

Formation and characterization of ethyl 2-oxocyclo-pentanecarboxylate/graphitic oxide intercalation compounds

A study by X-ray diffraction, gravimetric adsorption, gravimetric and differential thermal analysis and Fourier transform infrared spectroscopy was made of the intercalation compounds which ethyl 2-oxocyclopentanecarboxylate (CBCP) forms with graphitic oxide. The interlamellar disposition of the organic molecule as well as the CBCP/graphitic oxide interaction is also discussed.     

Influence of carbon shell structure on electrochemical performance of multi-walled carbon nanotube electrodes

Core/shell nanostructures have received considerable attention due to the synergistic effect of their combination of materials. In this work, core/shell carbon/multi walled carbon nanotubes (MWNTs) (C-MWNTs) composed of core MWNTs and carbon shells were prepared to obtain a new type of carbon electrode materials. Carbon shells containing nitrogen groups were prepared by coating polyaniline (PANI) onto the MWNTs by in situ polymerization and subsequent carbonization at 850 °C. After carbonization, the C-MWNTs contained 5.84% nitrogen and showed a hollow structure and crystallinity like that of pristine MWNTs. In addition, the C-MWNTs exhibited electrochemical performance superior to that of pristine MWNTs, and the highest specific capacitance (231 F g⁻¹) of the C-MWNTs was obtained at a scan rate of 0.1 A g⁻¹, as compared to 152 F g⁻¹ for pristine MWNTs. This superior performance is attributed to the maintenance of high electrical conductivity by the π–π interaction between the carbon layer and the MWNTs, increased specific surface area of C-MWNTs, and the presence of nitrogen groups formed on the carbon electrode after the carbonization of the shell PANI.     

High-voltage materials for positive electrodes of lithium ion batteries (review)

The main publications of recent years devoted to functional materials for positive electrodes of rechargeable lithium-ion batteries destined to work at the potential more positive than that of conventional lithiated oxides of cobalt and manganese are considered. The problem of electrolytes stable at these potentials is discussed briefly.     

Effect of reaction temperature on intercalation of octyltrimethylammonium chloride into kaolinite

The structural property, thermal behavior, and morphology of octyltrimethylammonium chloride–kaolinite complexes prepared at different reaction temperatures were studied by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry–differential scanning calorimetry, and scanning electron microscope. The present study demonstrated that the arrangement model of octyltrimethylammonium cations (OTAC⁺) within the kaolinite interlayer space was independent of reaction temperature. The alkyl chains adopted a similar rigid paraffin-bilayer arrangement with different tilted angles. Although the intercalation led to an increased number of gauche conformers, the number of nonlinear conformers remained constant with increasing temperature. With increasing temperature, the number of trans conformers continuously augmented and resulted in decreased gauche/trans ratio. Therefore, the molecular environment remained solid like. Simultaneously, the surfactant packing density gradually increased, along with the decreasing water content in the organoclays. This effect improved thermal stability and hydrophobicity. The thermal decomposition processes of the kaolinite–OTAC⁺ complex can be divided into four steps. Furthermore, SEM images showed that the morphology of these complexes was strongly dependent on the given temperature. In general, increasing the temperature within the limited given temperature (≤70 °C) promoted the transformation from platy layers to nanoscrolls. Most of the transformed nanoscrolls were acquired in the products prepared at 70 °C, and further increasing in temperature decreased the nanoscrolls yield. Nevertheless, the packing density increased in the process, thereby demonstrating that the packing density not only promoted nanoscrolls transformation but also prevented the progress.

     

Enhanced energy density of asymmetric supercapacitors via optimizing negative electrode material and mass ratio of negative/positive electrodes

An asymmetric supercapacitor based on manganese dioxide/Au/nickel foam (MANF) electrode as positive electrode and graphene or commercial activated carbons (AC) as negative electrode was fabricated. The effect of different negative electrode materials and mass ratios of negative/positive electrodes on the electrochemical properties of the asymmetric supercapacitor was carefully investigated. The results suggest that the mass ratio of negative/positive electrode has a significant impact on the specific capacitance of the asymmetric supercapacitor. Especially, it is found that the optimal mass ratio of the negative/positive electrode is slightly lower than that calculated according to charge balance. On the other hand, the asymmetric supercapacitor with commercialized AC as negative electrode possesses higher specific capacitance and better rate capability than that of the asymmetric supercapacitor with graphene as negative electrode. The negative material has slight impact on the cycle stability of the asymmetric supercapacitor. In addition, the optimized asymmetric supercapacitor with MANF composite as positive electrode and AC as negative electrode can obtain an energy density as high as 65.9 Wh?kg^?1 at a power density of 180 W?kg^?1 and a cell voltage of 1.8 V in the neutral Na₂SO₄ aqueous solution.     

石墨-五氯化锑层间化合物在有机电介质溶液中的电化学行为和结构研究

通过测定循环伏安曲线研究了石墨-SbCl5在1MLiClO4-PC(碳酸丙二醇酯)溶液中的电化学行为.I.II级石墨-SbCl5的还原电流峰出现在2.75～2.35V,氧化电流峰在2.85～3.05V(相对于Li/Li[+]).III级和IV级的相应电位区间与上相同,但其峰值较小,且曲线较为平缓,III级石墨-SbCl5的方波恒电流充放电表明,在500μA/cm[2]下,Li的插入量x(x=Li/C36SbCl5)在0.3以内,电极具有良好的可逆性,根据库仑滴定数据,放电前后X射线衍射图谱与电镜衍射花样的变化,初步认为I.II混合级石墨-SbCl5放电时的阴极反应是锂插入和形成新的层间化合物LiC24SbCl5的两个过程。     

Anion intercalation into highly oriented pyrolytic graphite studied by electrochemical atomic force microscopy

Knowledge of the dimensional changes occurring during electrochemical processes is fundamental for understanding of the electrochemical intercalation/insertion mechanism and for evaluation of potential application in electrochemical devices. We studied a highly oriented pyrolitic graphite (HOPG) electrode in perchloric acid, as a model to elucidate the mechanism of electrochemical anion intercalation in graphite. The aim of the work is the local and time dependent investigation of dimensional changes of the host material during electrochemical intercalation processes on the nanometer scale. We used atomic force microscopy (AFM), combined with cyclic voltammetry, as the in situ tool of analysis during intercalation and deintercalation of perchlorate anions. According to the AFM measurements, the HOPG interlayer spacing increases by 32% in agreement with the formation of stage IV of graphite intercalation compounds, when perchlorate anions intercalate. In addition, the local aspect of the process has been demonstrated by revealing coexisting regions with different kinetics for intercalation and deintercalation processes.     

Large-scale synthesis of single-crystal hexagonal tungsten trioxide nanowires and electrochemical lithium intercalation into the nanocrystals

Single-crystal nanowires of hexagonal tungsten trioxide in a large scale have been successfully prepared by a simple hydrothermal method without any templates and catalysts. Uniform h-WO₃ nanowires with diameter of 25-50 nm and length of up to several micrometers are obtained. It is found that the morphology and crystal form of the final products are strongly dependent on the amount of the sulfate and pH value of the reaction system. The electrochemical performances of the as-prepared h-WO₃ nanowires as anodic materials of Li-ion batteries have also been investigated. It deliveres a discharge capacity of 218 mAh g⁻¹ for the first cycle. In addition, the cycle ability of the nanocrystals is superior to that of bulk materials, which implies the morphology and particle size have the influence on the electrochemical performances.