Microporous activated carbon fibers (ACF) having huge specific surface areas are characterized as a three-dimensional network of nano-sized graphite domains. We investigate ACF-hosting host-guest systems aiming at novel phenomena produced by the host-guest interface interactions. An extraordinarily large amount of helium is condensed in the ACF micropores, suggesting the presence of ultra-micropores and the enhancement in the helium- nano-graphite interaction. Chemisorbed oxygen molecules are stabilized in the singlet states caused by the interaction with nano-graphite and it makes the micorpore volume swell. Iodine forms an intercalation system with nano-graphites through charge transfer process, in contrast with the behavior of bulk graphite that does not accept iodine as an acceptor-type intercalate. Fluorine reacting with nano-graphite generates dangling bond spins by breaking graphite π- bonds, where the fluorine-induced defect is found to have a widely extended electronic structure.

The structure of the polymer polyparaphenylene (PPP), heat-treated at temperatures (THT) between 650°C≤ THT ≤750°C and prepared according to either the Kovacic or the Yamamoto methods, is studied by the resonant Raman technique using five laser excitation energies Elaer in the range 1.92–3.05 eV. The resonant Raman analysis allows identification of the benzenoid and quinoid forms of PPP as well as the amorphous material associated with the onset of the carbonization process. The results enable us to follow the evolution of the PPP polymer with heat-treatment temperature and to determine the differences between the materials prepared using the two different methods.

Carbon powders prepared by the RF thermal plasma treatment of phenolic resin were examined for the anode materials of lithium secondary battery. Modification of these carbon powders in chemical composition, crystal structure and surface morphology was characteristics of the thermal plasma treatment The treated powders showed the unique microstructure. TEM observation showed the non-uniform distribution of graphitized and amorphous areas in the particles. The electrochemical measurements as an anode for lithium secondary battery were examined in IM LiClO4 in a 50:50 mixture of ethylene carbonate and diethyl carbonate. While the electrochemical extraction of lithium ion from plasma-prepared carbon powders proceeded in three stages, the electrochemical insertion looked to proceed in two stages. These electrochemical features can be associated with the uncommon microstructure characteristics.

Carbonaceous anodes are the most practical elecrode for application in lithium-ion battery, mainly due to their low cost, flexibility for modification to achieve high energy capacity and high rate capability, abundance and environmentally uniquencess. Despite superior advantages of carbonaceous anodes vs other alternative anode and metallic lithium, there is considerable reactivity of lithiated graphite with organic electrolytes, which is a major safety concern. In this work, we report the nature of gaceous species generated on various carbonaceous anodes during initial charge-discharge cycling. The correlation between structural parameters of carbonaceous materials and their irreversible capacity loss have been investigated. Structural parameters have been studied using x-ray diffraction, Raman spectroscopy, and scanning and transmission electron microscopy. We have found a direct correlation between crystal morphology, degree of disorder, degree of graphitisation and the irreversible capacity loss. There is also a direct correlation between the irrversible capacity loss and the volume of gas generated during initial charge- disharge cycling. Results also show the importance of removing adsorbed and trapped gases in addition to removal of bonded impurities, such as functional groups from carbonaceous electrode before fabrication of batteries.

Particular attention is given on thermal analysis for different graphite compounds and the influence of different parameters and conditions: nature of graphite in term of specific surface area, degree of graphitization and the length of microcristallites, degree of intercalation, nature of electrolytes on irreversible capacity loss and volume of gases generated during the initial charge-discharge cycles.

The microstructures of lithiated synthetic graphite and carbon black were studied by high- resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) analysis. Information about the crystal structure of carbon containing various Li compositions can provide useful insights to our understanding of the Li storage mechanism in carbonaceous materials. Samples with compositions of Li0.93C6or Li0.45C6 were found to contain both stage-one and stage-two compounds. These observations are consistent with XRD data. The changes in sample microstructure as the results of lithiation and exposure to electron irradiation were observed by TEM and recorded over several minutes in the microscope environment. Selected area electron diffraction patterns indicated that the lithiated samples quickly changed composition to LiC 24, which appeared to dominate during the brief analysis period. The layer planes in the lattice image of a disordered carbon black after Li insertion are poorly defined, and changes in the microstructure of these lithiated carbons was not readily apparent. Observations on these lithium intercalation compounds as well as the limitation of the experimental procedure will be presented.

The intercalation, at room temperature, of the sodium-potassium eutectic into graphite is performed, in a glove box under purified argon. It leads to a high alkali metal content powder. The annealing under vacuum, at 200°C for two days leads to a pure first stage compound whose formula is NaK2C12 with a color and a structure close to that of KC8. This phase is unstable and decomposes slowly in a mixture of KC8 and free alloy. However, this free alloy, which is liquid at room temperature, remains as inclusions between the graphene layers and the compound remains as a powder which can be useful for some applications when one needs large quantities of an alkali metal “solid” at room temperature, e.g. for gas purification (it reacts with oxygen and with moisture), for rapid and intense heat provider (it burns in air and the carbon is also participating to the heating), for ionic polymerization catalyst…

Two tin-graphite composite electrodes (27.8 % and 44.4 % tin) were evaluated for their use as high capacity anodes in rechargeable lithium ion cells. The initial charge capacities of these two electrodes were 520 mAh/g and 590 mAh/g, respectively. Cyclic voltammetry and charge-discharge cycling studies point to the alloy formation reaction between tin and lithium being the main contributing factor to the increased capacity. The capacity of these electrodes decreases with cycling but maintains considerably higher capacity than graphite electrode with same number of cycles. The development of optimized tin-graphite composite electrodes with much higher capacity than graphite electrodes looks promising.

In this work we have examined different types of synthetic graphites (SFG and KS types) that have different morphology and particle sizes. In our analysis we examined the incremental capacity (dC/dV), which shows a series of peaks that correspond to potential plateaus. This approach enable us to identify the processes involved (formation of SEI, Li+ intercalation or de-intercalation, etc.). Our analysis was mainly concentrated on the first lithiation, in an attempt to specify the origin of the capacity loss related to each type of synthetic graphite.

The open framework material, CaFe204 and the isostructural solid solution phases, LiyCa1−(x+y)/2SnxFe2−xO4, where 0<y<x and O<x<0.6 have been evaluated as promising anodic materials in Li-ion batteries. These materials can be discharged to low potential, the end member CaFe2O4 attaining a discharge capacity of 800 mAh/g at a cutoff voltage of 50 mV. The capacity is enhanced on substitution of Fe3+, for Sn4+ in the framework (920 mAh/g for the composition, Li0.6Ca0.4Sn0.6Fe1.404). On introducing Sn into the structure the reversible capacity is also substantially increased compared with the parent material. Although there is a large irreversible component to the redox process during first discharge-charge, the materials can sustain a stable reversible capacity of >600 mAh/g within the voltage window of 3.0-0.005 V. The profile of the electronic density plots suggest there is no phase separation to Li/Sn alloy phases on reduction, but rather a lithium-rich, oxygen deficient Sn/Fe/oxide matrix is formed.

We report the vibrational spectra of various layered transition-metal oxides, which are potential cathode materials for advanced Li-ion batteries. They provide high specific energy density, high voltage, and remarkable reversibility for lithium intercalation-deintercalation process. Studies were carried out by Raman and FTIR spectroscopies. Oxides such as LiMO2 (M=Co, Ni, Cr) layered compounds and their mixed compounds have been investigated. The local environment of cations against oxygen neighboring atoms has been determined by considering polyhedral units building the lattice. Structural modifications induced by intercalation-deintercalation process, by cation substitution, or by low-temperature preparation route are examined.

Intercalation compounds of CdPS3 with 4-[4-(dimethylamino)-α-styryl]- 1-methylpyridine cation (DAMS+) exhibit high-efficiency optical second harmonic generation (SHG). This is unexpected since the native CdPS3 host crystallizes in a centrosymmetric lattice. It is believed that the SHG results from the aggregation of the intercalate within the interlamellar spaces of the host lattice. For efficient SHG the spatial organization must have a characteristic length scale on the order of the second harmonic wavelength, or about 1 micron. We have studied the temperature dependence of the fluorescence of CdPS3:DAMS intercalation compounds and have demonstrated the presence of DAMS aggregates.

We report on the growth of molybdenum and vanadium oxide films, i.e., MOO3, V205, and V6013, and their application as positive electrodes in lithium microbatteries. We have characterized various polycrystalline samples and studied how their structural and electrical properties are affected by the different preparation conditions. The highest quality films were grown on silicon substrate maintained at 250°C and annealed at 300°C. It is shown that the growth conditions play an important role in the electrochemical properties of the film. Both thermodynamic and kinetic parameters are strongly dependent on film morphology and stoichiometry. Microbatteries fabricated with cathodes formed at moderate temperature have shown a volumetric capacity about 80 μAh/μm/cm2. The cells exhibit a monotonous discharge profile indicating that the cathode materials remain single phase even for a large degree of intercalation.

We have synthesized novel nickel and manganese vanadium oxides using the hydrothermal reactions of vanadium(V) pentoxide, Ni(CH3COO)2, and MnSO4 with an organic templating cation at 165°C. The [NH2(CH2)2NH2]2NiV6O14 has a monoclinic structure. It has some disordered V and 0 atoms in the V6014 layer, which appear to be very close to each other with occupation factor around 0.5. The disordered model was decomposed for two ordered configurations, which differ in the stacking of the layers. The (Mn+2)6(Mn+3)l−2/3z(OH)3(1−Z)(VO4)3[(VO4)l−2z(v207)z] (Z≈0. 1) phase has a hexagonal pipe morphology. These compounds were also characterized by electron microprobe, FTIR and TGA. They reacted readily with lithium, and their electrochemical behavior in lithium cells was determined.

Various forms of vanadium pentoxide, including xerogel, aerogel, and aerogel-like forms, were prepared by sol-gel synthesis and processed by novel procedures following synthesis. It was demonstrated that the intrinsic thermodynamics of lithium intercalation of the ARG and ARG-like materials prepared by solvent exchange processes involving methyl formate (MF/ARG and MF/ARG-xslike) are identical, while they are drastically different from those of the parent XRG, which gives rise to significantly increased specific energies for the MF/ARG or MF/ARG-like as lithium intercalation hosts. All three forms are capable of reversibly intercalating up to four moles of Li+ ions per mole of V205 electrochemically and can be cathode candidates for rechargeable lithium batteries. Various processing methods for fabricating composite electrodes with the XRG led to specific capacity in the range of 300 to 350 mAh/g at C4Li/ 20 rate, and good cyclability.

Sol-gel derived amorphous manganese dioxide (a-MnO2) showed extremely high reversible lithium intercalation capacity. The composition and structure of the material were modified by heating at different temperatures. Cycling performance of the modified samples suggests that lowering the water content in the material is beneficial, while introducing crystallinity is detrimental, to its cyclability. A novel double-solvent-exchange process was tried for the processing of the material. Preliminary results indicated significant improvement in the reversibility of the insertion/release cycles.

KxMnO2 exhibits a layered structure that provides attractive properties as a cathode material for secondary Li batteries. Therefore, in the present study, our attention was paid to the hydrothermal preparation of highly homogenous KxMnO2 in presence of citric acid. Out X-ray diffraction and SEM studies indicated that the final product markedly change the phase and morphology on vary the concentration of citric acid. The prepared products have also studied with the help of TGA and DTA. EDS and DCP made the chemical analysis of the compounds. The impedance data of the materials were explained in terms of the compounds formed.

Polycrystalline thin films of lithium cobalt oxide (nominally LiCo02) have been deposited by a process which we have named, ion beam directed assembly (IBDA). It is similar to ion assisted deposition (IAD) or ion beam assisted deposition (IBAD), but the major difference is that in IBDA the ion beam directs, via the vector momenta of the ions, rather than merely assists, the growth. Hence, we also term the process directed assembly to distinguish it from self assembly. Also, in directed assembly the ions may or may not become an integral part of the film's composition.

In this paper we wish to show that the IBDA process may be capable of controlling microstructure, e.g., in the case of polycrystalline films, control the orientations of the crystallites. For LiCoO2 we have observed this in two ways - by X-ray analysis, and electrochemically, by lithium diffusivity measurements. In particular, we have observed increased lithium diffusivities (≥ 10−8 cm 2/s) in IBDA deposited films as compared to that found for rf sputter deposited films (z 10−10 cm2/s). In addition, the coulometric titration characteristics of an IBDA deposited Lil−yCoO2 are very similar to those of sputtered deposited films (for lithium extraction/insertion, y ≤0.5, and for quasi-equilibrium voltages up to 4.2 volts).

First principles calculations within the local-spin-density-functional theory (LSDFT) framework are presented of densities of electronic states for MnO, LiMnO2 in the monoclinic and orthorhombic structures, cubic LiMn204 spinel and λ-MnO2 (delithiated spinel), all in antiferromagnetic spin configurations. The changes in energy spectra as the Mn oxidation state varies between 2+ and 4+ are illustrated. Preliminary calculations for Co-doped LiMnO2 are presented, and the destabilization of a monoclinic relative to a rhombohedral structure is discussed.

Lithium transition metal oxides used as intercalation electrodes for rechargeable lithium batteries are widely studied in search of structural stability and improved electrochemical performance. Recent studies showed that the orthorhombic and monoclinic LiMnO2 compounds, unlike LiMn204 spinels, could be cycled on both the 4 V and 2.9 V plateaus with high and stable discharge capacity. In this study, we have performed direct high resolution observations of electrochemically cycled LiMnO2 particles in the fully discharged state. Extensive damage including local strain variation, nanodomain formation, and changes in cation ordering, has been observed. Individual particles retain overall single crystallinity despite having differing structures at the nanodomain level. While cycling causes a macroscopic transformation to spinel cation ordering, the formation of nanodomains differing in cation ordering and/or composition appears to accommodate or prevent the destructive Jahn-Teller distortion that normally occurs at high lithium concentration, thereby resulting in cycling stability.

Partial substitution of Mn in lithium manganese oxide spinel materials by Cu and Ni greatly affects the electrochemistry and the cycle life characteristics of the cathode. Substitution with either metal or a combination of both shortens the 4.2 V plateau associated with the conversion of Mn3+ to Mn4+. A higher voltage plateau associated with oxidation of the substituted transition element is also observed. These substituent also significantly alter the onset of Jahn Teller distortions in the 3 V plateau. Synchrotron based in situ x-ray absorption (XAS) is used to determine the exact nature of the oxidation state changes in order to explain the overall capacities at the different voltage plateaus. Synchrotron based in situ x-ray diffraction (XRD) studies on LiCu0.5Mn1.504 shows single phase behavior in the 4-5 V region and a good cycle life. Lower cycle life characteristics for LiNi0.5Mn1.504 and LiNi0.25Cu0.25Mn1.504 are accounted for on the basis of several phase coexistence in this potential region. In the 3 V plateau however, the LiCu0.5Mn1.504 shows onset of the Jahn Teller distortions, in contrast to the LiNi0.5Mn1.504 and LNi0.25Cu0.25WMn1.504.