Impact of selected supramolecular additives on the initial electrochemical lithium intercalation into graphite in propylene carbonate

Impact of silicon tripodand-type electrolyte additives and graphite pre-treatment agents on the electrochemical intercalation of lithium cations into graphite was investigated. Addition of Si-tripodand-type silanes to propylene carbonate-based electrolytes was found to suppress detrimental solvent co-intercalation and graphite exfoliation. Similar effects were observed for graphite pre-treated with the reported silane agents. It was observed that the presented supramolecular additives allow for the formation of effective passive layers on graphite during first charging, and thus can be considered as novel low-cost film-forming components for rechargeable lithium batteries.      

The lithium intercalation into graphite from electrolyte and from solid lithium

The values of diffusion coefficient (D) of lithium in thermoexpanded graphite during cathodic intercalation from aprotic electrolyte, and upon direct contact with lithium metal, are measured. In the first case galvanostatic switch-on curves were registered, in the second case the method of x-ray diffraction was used. In the both cases D was close to 10^-10 cm²/s.Presented at the 3rd International Meeting "Advanced Batteries and Accumulators," June 16th–20th 2002, Brno, Czech Republic     

Electrochemical investigation of lithium intercalation into graphite from molten lithium chloride

Lithium reduction at a graphite electrode in molten lithium chloride was studied at temperatures from 650 to 900 °C using cyclic voltammetry and chronoamperometry. It was found that, during cathodic polarization, lithium intercalation into graphite occurred before deposition of metallic lithium started. This process was confirmed to be rate-controlled by the diffusion of lithium in the graphite. When the cathodic polarization potential was more negative than that for metallic lithium deposition, exfoliation of graphite particles from the electrode surface was observed. This was caused by fast and excessive accumulation of lithium intercalated into the graphite, which produced mechanical stress too high for the graphite matrix to accommodate. The erosion process was abated once the graphite surface was covered by a continuous layer of liquid lithium. These results are of relevance to the mechanism of carbon nanotube and nanoparticle formation by electrochemical synthesis in molten lithium chloride.     

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.

     

Preparation and characterization of modified graphite oxide/poly(propylene carbonate) composites by solution intercalation

Modified graphite oxide (MGO)/Poly (propylene carbonate) (PPC) composites with excellent thermal and mechanical properties have been prepared via a facile solution intercalation method. An intercalated structure of MGO/PPC composites was confirmed by X-ray diffraction and scanning electron microscope. The thermal and mechanical properties of MGO/PPC composites were investigated by thermal gravimetric analysis, differential scanning calorimetric, dynamic mechanical analysis, and electronic tensile tester. Due to the nanometer-sized dispersion of layered graphite in PPC matrix and the strong interfacial interaction between MGO and PPC, the prepared MGO/PPC composites exhibit improved thermal and mechanical properties in comparison with pure PPC. Compared with pure PPC, the MGO/PPC composites show the highest thermal stability and the T_g is 13.8 °C higher than that of pure PPC, while the tensile strength (29.51 MPa) shows about 2 times higher than that of pure PPC when only 3.0 wt.% MGO is incorporated. These results indicate that this approach is an efficient method to improve the properties of PPC.     

锂在共轭双键高分子中的电化学嵌入反应3: 锂在聚萘中的电 化学嵌入反应

研究了锂在导电高聚物---聚萘中的嵌入反应。聚萘样品经650℃处理,作为锂电池的正极,组装成Li/(C~1~0H~6)~n电池。X射线衍射分析、ESR实验、X射线光电子能谱分析等一系列实验证实上述电池的正板反应是锂在聚萘中的电化学嵌入反应。通过XPS实验对嵌入聚萘的锂进行了价态分析,认为嵌进去的锂是以原子态及离子态两种状态存在,其结合能分别为55.7eV和57.4eV。采用电化学暂态测量技术研究了锂在导电高聚物---聚萘中的扩散,计算了锂在嵌合物中的离子电导率及淌度。用Hebb-Wagner直流极化法测量了嵌合物的电子电导。     

Facile preparation of graphite intercalation compounds in alkali solution

Graphite intercalation compounds are often prepared by flake graphite, oxidants, inorganic acids, organic acids and intercalated ions which are usually hydrogen protons between the graphene planes. They are also known as the acid-treated graphite intercalation compounds. In this work, alkaline graphite intercalation compounds were prepared by flake graphite, K₂Cr₂O₇, concentrated H₂SO₄ and NaOH, and the morphology and structure were characterized by Electron microscopy and X-ray techniques. The results display that the combination of neutralisation heat and oxidation capability produced by K₂Cr₂O₇ can break the bonds to produce the spaces between the graphene planes and hydroxyl ions also intercalate into the graphene planes to form alkaline graphite intercalation compounds in alkali solution. The morphology and structure of alkaline graphite intercalation compounds are analogous to the ones of the acid-treated graphite intercalation compounds, but the intercalated ions and the expansion volume are different. The results show that the method is an innovation.     

Adsorption characteristics of nanoporous carbon-silica composites synthesized from graphite oxide by a mechanochemical intercalation method

Nanoporous carbon-silica composites were synthesized from graphite oxide (GO) precursor by a mechanochemical intercalation (MCI) method at different conditions, and their structural property, thermal decomposition behaviors, and adsorption characteristics were examined. MCI method yields regular tetraethoxysilane (TEOS)-intercalated GO layer structures with controllable silicon content depending on the TEOS addition. Adsorption behaviors of water and hexane indicate the amphiphilic properties of the composites. The detailed porosities of the composites and their changes upon water adsorption were analyzed on the basis of alpha(s)-plot method of N(2) adsorption isotherms using a weight-averaged standard data from non-porous silica and non-porous carbon, which plausibly divides microporosity and mesoporosity.     

锂在共轭双键高分子中的电化学嵌入反应I.锂在聚吡咯中嵌入过程的电子能谱研究

通过电子能谱(AES 和ESCA)研究了锂-聚吡咯电池的放电反应,认为该电池的放电是锂在聚吡咯的嵌入过程,嵌入的锂主要是以Li[+]存在,其1s电子的结合能为56.0eV.Li[+]在嵌合物中的扩散系数D为10[-12]一10[-13]cm[2].s[-1]数量级。     

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.     

Modeling a solid-phase electrochemical reaction of lithium intercalation in aluminum during a noninstantaneous nucleation of Β-LiAl

The interfacial surface area and the electrode surface coverage by a product during the nucleation and growth of a new phase are modeled numerically and calculated analytically for electrochemical intercalation of lithium in aluminum in the course of which intermetallic compound Β-LiAl forms. As opposed to the theoretical calculation, the model accounts for mutual influence of the new-phase nuclei on their distribution over the cathode surface under conditions of noninstantaneous nucleation. The ordering of such a distribution varies extremally (passes through a maximum) with increasing size of zones where the nucleation probability is low and which surround the nuclei. This makes the dependence of a maximum specific interfacial area on the zone radius extremal as well. The model may be applied for analyzing potentiostatic current transients during cathodic intercalation of lithium in aluminum from a LiClO₄ solution in propylene carbonate.     

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.     

Preparation and characterization of poly(propylene carbonate)/montmorillonite nanocomposites by solution intercalation

Poly(propylene carbonate) (PPC) is a new biodegradable aliphatic polycarbonate. However, the poor thermal stability and low glass transition temperatures (T_g) have limited its applications. To improve the thermal properties of PPC, organophilic montmorillonite (OMMT) was mixed with PPC by a solution intercalation method to produce nanocomposites. An intercalated-and-flocculated structure of PPC/OMMT nanocomposites was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The thermal and mechanical properties of PPC/OMMT nanocomposites were investigated by thermal gravimetric analysis (TGA), differential scanning calorimetric (DSC), and electronic tensile tester. Due to the nanometer-sized dispersion of layered silicate in polymer matrix, PPC/OMMT nanocomposites exhibit improved thermal and mechanical properties than pure PPC. When the OMMT content is 4 wt%, the PPC/OMMT nanocomposite shows the best thermal and mechanical properties. These results indicate that nanocomposition is an efficient and convenient method to improve the properties of PPC.     

Chronovoltammetry of electrolytic molybdenum oxides at the electrochemical intercalation/deintercalation of lithium ions

Chemical diffusion coefficients of lithium ions in processes of electrochemical intercalation/deintercalation in electrolytic molybdenum oxides and the parameter of interaction between the intercalated particles (g) have been obtained by the following methods: the galvanostatic intermittent titration technique (GITT), the potential relaxation technique after current interruption (PRT), and the potential intermittent titration technique (PITT). In the potential range 2.40–1.40 V the values of of the order of 10^–11–10^–13 cm²/s have been obtained for Mo₄O₁₁ oxide. Intercalation/deintercalation was realized in one phase when g>4.Presented at the 3rd International Meeting on Advanced Batteries and Accumulators, 16–20 June 2002, Brno, Czech Republic     

Carbamates from alcohol diversity: a simple solution phase library method

A simple one-pot, solution phase method for the parallel synthesis of carbamates from amines and alcohols is described. The high-yielding method does not require support-bound reagents, extractions or resin washing steps and should be broadly applicable to the manual or automated generation of carbamate libraries.     

Mathematical simulation of the electrochemical intercalation of graphite in concentrated sulfuric and dilute nitric acids

A mathematical model of the process of electrochemical intercalation of a granular graphite bed in nitric and sulfuric acids that takes into account the varying physicochemical properties of the graphite matrix is proposed. The numerical solution of the problem by the finite element method shows that, in agreement with the literature data, the current distribution is nonuniform even for a granular bed of a small height (∼2 × 10⁻² m), which results in the synthesis of a nonuniform product. The methods of assessing the nonuniformity of intercalation and its elimination by passing to a multistage process are proposed. The results of numerical methods can be used in predicting the technological characteristics of the final product.     

A simple method for local resolved electrochemical surface characterisation

A transportable mini-cell has been developed to perform non-destructive electrochemical measurements on solid samples, even those with a complicated shape. The characterisation of dental and medical alloys is given as an example.     

A simple facet-based method for single crystal electrochemical study

In this paper, we demonstrate a simple facet-based method for single crystal electrochemical study. Based on the design of a simple and proper electrochemical cell using a cone-shaped pipette tip, one of the natural (1 1 1) facets of a Au single crystal bead has been directly used for electrochemical measurements. Since the processes of orientating, cutting and mechanical polishing are avoided, misorientation and mechanical damage to single crystal surface can be eliminated and reliable data are expected. The advantages of the method have been proved by the nice cyclic voltammogram of Ag underpotential deposition (UPD), a system that has shown large discrepancy in cyclic voltammograms reported by different laboratories due to the dissimilarity of the surface state. The sharp and reversible UPD peaks from the facet-based measurements resemble the best of the reported data in the literature. The method can be extended to (1 1 1) surfaces of some other metals.     

Preparation and characterization of a tetrabutylammonium graphite intercalation compound

The intercalation of tetrabutylammonium (TBA) cations into graphite by cation exchange from a sodium-ethylenediamine graphite intercalation compound yields a single-phase first-stage product, C(44)TBA, with a gallery expansion of 0.47 nm. The gallery dimension requires an anisotropic "flattened" cation conformation.