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The polyoxovanadate K7MnV13O38 (KMV) has been studied as cathode material of lithium ion batteries. The nanosize particles show initial discharge capacities over 308 and 225 mAh g− 1 at current densities of 17 and 167 mA g− 1, respectively. However, the capacity fading of nanosize particles is notably high with increasing cycle number, particularly when cycling at high rate. An effective approach to reduce the capacity fading is to use a composite cathode consisting of a mixture of nanosize particles and microsize particles in the weight ratio of 1:1. This composite cathode exhibits excellent cycle performance with capacity retention over 97% after 50 cycles at both low rate and high rate.

Nano-porous graphitized carbons were successfully prepared by using mono-dispersed SiO2 colloidal crystal as a template and mesophase pitch as a carbon source with final heat treatment temperatures (HTT) of 1000?2500 °C. Rate capability of lithium intercalation/de-intercalation of the nano-porous graphitized carbons was investigated. 35?60% of capacities were retained when the current density was increased from 37.2 mA g? 1 to 372 mA g? 1. Electrochemical impedance spectra indicated that formation of SEI layers caused increased polarization., Solid State Ionics, 179(27-32), pp.1706-1709; 2008

We report on the microstructural changes of amorphous V 2 O 5 films with lithium intercalation. The Raman spectra of as-deposited films show two broad peaks around at 520 and 650 cm −1 , due to the stretching modes of the V 3 –O and V 2 –O bonds, respectively, and a relatively sharp peak at 1027 cm −1 due to the V 5+ O stretching mode of terminal oxygen atoms. In addition, there is a peak at 932 cm −1 that we attribute to the V 4+ O bonds. Comparison of the Raman spectra of V 2 O 5 films with different oxygen deficiencies confirms this assignment. This Raman peak due to the stretching mode of the V 4+ O bonds develops and shifts toward lower frequencies with increasing lithium concentration. Comparison to results from gasochromic hydrogen insertion indicates that the 932 cm −1 Raman peak is not a result of vibrations which involve Li or H atoms. We propose that the V 4+ O bonds are created by two different mechanisms: a direct conversion from V 5+ O bonds and the breaking of the single oxygen bonds involving V 4+ ions.

Hexagonal tungsten trioxide (h-WO3) (ideally P6/mmm) has three kinds of lithium intercalation sites which are the hexagonal-window (1a), hexagonal-cavity (1b) and trigonal-cavity (2d). Calculation by the DV-Xα method using a LixW36O138(60-x)− cluster showed that inserted lithium ions were more stable at the trigonal-cavity site than at the other sites. When lithium intercalation in h-WO3 was performed electrochemically, OCV (open circuit voltage) traces exhibited large hysteresis between insertion and the extraction process. On the basis of DV-Xα calculation results and changes in lattice parameters, we concluded that lithium ions started occupying hexagonal-window and/or hexagonal-cavity sites before the trigonal-cavity site was completely filled in the insertion process, and that lithium ions at the trigonal-cavity site were extracted after the hexagonal-window and hexagonal-cavity sites were almost empty during the extraction process.

Li intercalation in AFeMP3O12 (A=Ca, Sr, Ba; M=Ti, Zr) is achieved using n-BuLi. The lattice parameters indicate the presence of Li in the type II sites. The amount of Li intercalated and the results of ac and dc conductivity measurements proves that the steric factors rather than electronic factors play a crucial role in such intercalation reactions.

The lithium intercalation into the layered dichalcogenide 3R-WS2 has been investigated by electrochemical reduction and by chemical reaction in n-butyl lithium solution. Essential results are (a) a charge transfer of nearly 0.6e−/W in LixWS2, (b) a small increase of the c-axis parameter of about 0.6%, and (c) a high mobility of the Li+-ions. The chemical diffusion coefficient of Li+-ions is estimated to be 8 × 10−9 cm2 s−1 in the composition range 0 ≤ x ≤ 0.25. The appearance of a structural transformation from 3R-WS2 to 2H-LixWS2 is interpreted on grounds of instabilities in the interlayer structure.

Chemical lithium insertion into five different types of V2O13-based intercalation hosts have been performed in this study. Four phases were identified: Li0.5V6O13, Li1.5V6O13, Li3V6O13 and Li6V6O13; the latter phase representing the highest degree of intercalation. These phases are crystallographically and magnetically different not only from the phase-pure V6O13 host, but also from one another. The presence of other VOy-phases (10 mol% VO2 or V2O5) caused slower lithium intercalation into V6O13, different final phases and poor stability in the presence of water.

Polycrystalline V 2 O 5 films (0.15 microm thick) have been electrochemically intercalated with Li + at constant current, so that to obtain a set of different cation concentrations. The open circuit potential and the optical transmittance of the Li x V 2 O 5 films were followed as a function of the lithium charge. The electrochemical measurements show a reversible Li + intercalation for x ≦1, in agreement with previous observations on pellettized V 2 O 5 powder electrodes. Some compositions ( x ∼0, 0.3, 1) have been also characterized by both absorption and micro-Raman spectroscopy, which appear to be very sensitive to the Li + content. Raman and absorption spectra seem to indicate a non complete recovery of the original electronic configuration and of the structure in the material after the inserted Li + has been fully extracted via a reverse electrochemical reaction.

Lithium intercalation by soft chemistry of the NASICON-derived phosphate CuII0.5Ti2(PO4)3 lead to the elaboration of a new phosphate Li3.5Cu0.5Ti2(PO4)3. In this phase also of the NASICON-type the lithium and copper atoms are located in the usually labelled M(2) site but actually in strongly distorted oxygenated tetrahedra.

Lithium intercalation reactions into “SnTiS 3 ” and “BiTi 2 S 5 ” misfit layer sulfides are studied. Chemical intercalation using n-buty llithium takes place by a monophasic mechanism inducing changes in the relative orientations of MS and TiS 2 sublattices. Extensive lithiation causes the loss of long-range ordering in the host lattice. This process occurs at a lower extent of intercalation for the 1:1:3 approximate composition. Electrochemical intercalation in lithium test batteries using “SnTiS 3 ” cathodes takes place by a biphasic mechanism in non-equilibrium conditions. The lithiated products increase the periodic length by ca. 0.5 A Amorphization takes place in an extended plateau of the discharge curves above 0.75 F mol −1 . For “BiTi 2 S 5 ”, the complexity of the structure of the starting material, with extensive twinning in the BiS sublattice, leads to a more complicated pattern below 1 F mol −1 . Three phases are involved in the process while the voltage decreases gradually: pristine “BiTi 2 S 5 ”, a Stage I 17.3 A li thiated phase and an intermediate 19.5 A phase. A sharp decrease in voltage at 1 F mol −1 implies that the final product is Li(BiS) 1.14 (TiS 2 ) 2 . Further discharge results in the amorphization of this product in an extended plateau of the discharge curve.

New vanadium bronzes have been obtained by chemical oxidative reactions. The electrochemical performance of these bronzes, used as electrode material in secondary lithium batteries, is presented. The most promising electrochemical behavior is achieved with e-Cu0.2V2O5, which intercalates 1.4 Li ions per vanadium at an average potential of 2.8 V, resulting in one of the highest theoretical specific energy ever reported (1100 Wh/Kg of cathode material).

The electrochemical intercalation of lithium was found to occur above the potential of 2.5 V in two steps, associated with lattice expansion along c -axis. The capacity for lithium intercalation depended strongly on the structure of V 2 O 5 host, which was characterized by specific surface area and broadening of 001 X-ray diffraction.

The glasses in the system Fe 2 O 3 −V 2 O 5 were prepared by rapid quenching and their electrochemical properties as a cathode of lithium cells were investigated. Both the glass-transition temperature and the crystallization temperature increased with an increase in the Fe 2 O 3 content of the glasses. The lithium cells with those glasses showed the high specific capacity in the range of 230 to 100 Ah kg −1 , when the cells discharged under a constant-current density 1 Am −2 to a cut-off voltage 2.0 V. There was a maximum in the discharge capacities at around 15 mol% Fe 2 O 3 of the glasses. A maximum in chemical diffusion coefficients is also observed at around 15 mol% Fe 2 O 3 . These results suggest that the discharge properties of the cells with the Fe 2 O 3 −V 2 O 5 glasses are primary governed by the diffusion of lithium ions into the glasses.

By assuming that the presence of a Li+ ion in the van der Waals gap between two conducting TiS2 layers induces electronic charges in the layers, a semi-atomistic model was developed to explain the expansion of the c-axis of LixTiS2 and the decrease of the open circuit voltage of a Li-LixTiS2 cell, E(x), with increasing Li+ concentration. The results suggest that (1) only the six S atoms adjacent to the Li+ ion are displaced by its intercalation, and (2) the almost linear decrease of E(x) with increasing x can be explained with a double-layer capacitance of about 260 μF/cm2 between the Li+ ion layer and the adjacent TiS2 layers. It is shown that the discreteness of the charge on the Li+ ions is important in determining the values of the double-layer capacitance.

The lithium electrochemical intercalation into two different types of graphite fluorides is investigated using PEO-based solid state cells. In the fist compound (CF) n it is showed that the electrode reaction is irreversible highly contrasting with the second one, CF 0.8 I 0.02 which exhibits a good reversibility. This difference in behaviour may be related to the contrasted electronic properties of those materials mostly due to different types of C-F bonds involved in their respective structures.

Lithium has been intercalated in LiW3O9F. This phase exhibits a peculiar packing of hexagonal tungsten bronze layers. Up to two lithium atoms can be intercalated reversibly. If the Li3W3O9F composition is overpassed the reaction becomes irreversible and an amorphization occurs. The variation of the diffusion coefficient versus the amount of lithium has been determined from the electrochemical relaxation curves. An NMR study has shown that Li+ ions are not mobile in LiW3O9F and have a high mobility in intercalated materials at RT.

Lithium intercalation in the van der Waals gap of InSe occurs with a very weak electronic charge transfer. Indeed, though strongly intercalated, absorption and luminescence spectra of the two excitons bound to the direct transitions between the two uppermost valence bands and the conduction band are not modified much: we observe no metal-insulator transition. On the other hand, no new phonon modes are seen in the Raman spectrum of the intercalated sample. Only strong intensity fluctuations of the peaks have been recorded. The last effect is due to the shift of the Raman resonance on the second exciton energy of the Li-intercalated InSe.

Synthesis of monoclinic Na 0.33 V 2 O 5 bronze by sol-gel processes and its electrochemical behaviour have been investigated. The four well defined processes evidenced in the potential window 3.5–2 V versus Li/Li + are discussed in terms of crystallographic data. The high reversibility of Li + ion insertion (≈70% of the initial faradaic yield after the 80th cycle) makes this compound a promising cathodic material for secondary lithium cells.

In 2 Se 3 exists in several polymorphic modifications with complex defect structure. We report optical and transport measurements for quenched and annealed samples of layered α-In 2 Se 3 , the phase stable below 200° C. Measurements are also reported for lithium intercalation. Chemical diffusivities of order 5 × 10 −10 cm 2 /sec have been obtained for single crystal annealed α-In 2 Se 3 samples.

Intercalation process kinetics have been studied theoretically for the case of potential sweep voltammetry. The influence of the thickness (or the particle radius) of the “host” material and the potential sweep rate has been determined between the limits of thin film diffusion and semi-infinite diffusion for a reversible process. Experimental data have been obtained with the cell: RuO2/LiClO4-PEO/Li. The theoretical results have been used to calculate the diffusion coefficient of lithium in the “host” structure RuO2 at 80°C, giving an approximate value of 1.6 × 10−11 cm2 s−1

Infrared spectra (700-30 cm-1) of several lithium intercalates (chemically prepared) LixMPS3, with M=Fe, Ni and 0