Lithium mobility in LiM2(PO4)3 compounds, with M= Ge, Ti, Sn, Zr and Hf, has been investigated by 7Li Nuclear Magnetic Resonance (NMR) spectroscopy in the temperature range 100-500 K. From the analysis of 7Li NMR quadrupole interactions (CQ and η parameters), Li sites occupancy and exchange processes between structural sites have been studied. Below 250K, Li ions are preferentially located at M1 sites in rhombohedral phases, but occupy M12 sites in triclinic ones. At increasing temperatures, Li mobility has been deduced from spin-spin () and spin-lattice relaxation () rates. In this analysis, the presence of two relaxation mechanisms in plots has been associated with departures of conductivity from the Arrhenius behavior. At high temperatures, residence times at M12−T11−T11−T1 and M12 sites become similar and conductivity significantly increase. This superionic state can be achieved by enlarged order-disorder transformations in rhombohedral phases, or by sharp first order transitions in triclinic ones. Results described in the LiTi2(PO4)3 sample have been compared with those obtained in rhombohedral Li1+xTi2-xAlx(PO4)3 and LiTi2-xZrx(PO4)3 series showing respectively higher and lower conductivities. In the case of Li1.2Ti1.8Al0.2(PO4)3, displaying the highest reported conductivity, NMR results are discussed in relation with those obtained by Neutron Diffraction (ND) and Impedance Spectroscopy (IS). Diffusion coefficients determined by NMR Pulse Field Gradient (PFG) technique are similar to those deduced from Impedance Spectroscopy and NMR relaxation data.

Lithium phosphorus oxynitride (Lipon) thin films have been deposited by a plasmaenhanced metalorganic chemical vapor deposition (PE-MOCVD) method using triethyl phosphate [(CH2CH3)3PO4] and lithium tert-butoxide [(LiOC(CH3)3] precursors. Growth rates were between 100 and 415 Å/min, and thicknesses ranged from 1 to 2.5 μm. X-ray powder diffraction showed that the films were amorphous, and X-ray photoelectron spectroscopy revealed approximately 6.9 at.% carbon in the films. The ionic conductivity of Lipon was measured using electrochemical impedance spectroscopy (EIS) and approximately 1.02 μS/cm was obtained, which is consistent with the ionic conductivity of Lipon deposited by radio frequency magnetron sputtering of Li3PO4 targets. An all-solid-state thin-film lithium microbattery such as Li/Lipon/LiCoO2/Au/substrate was successfully fabricated with Lipon deposited by PE-MOCVD. The battery has a capacity of ca. 22 μAh/cm2μm.

The intrinsic channel structure and low volume work makes olivines phosphates (LiMPO4) versatile for Li uptake and release. The understanding of Li cation diffusion/transport mechanisms inside olivines are crucial aspects, which we address using advanced molecular dynamics simulations. Activation energies calculated from DFT concluded 1D diffusion within channels as also indicated by neutron diffraction direct imaging techniques. On explicitly including temperature we find that - besides main conduction paths along the easy channels - distinct, less frequent but relevant diffusion paths exist. We point out that capacity and diffusion/conduction issues must be understood in a much more detail-rich framework, under realistic simulation conditions within finite temperature simulations. For evaluating electrical conductivity, we use advanced DFT methods to correctly capture the insulating states of the charged and discharged olivine materials. Based on the Kubo formalism, reliable conductivity/resistivity curves can be calculated for comparison with experiments and for anticipating properties.

The α-polymorph of Li3FeF6 has been prepared from aqueous-based solution by precipitation under different conditions to obtain small particles. Several alcohols have been used to vary the precipitation media. Among them 2-propanol has been found to provide particles of about 100 nm under controlled conditions of temperature and H2O: R-OH volume ratio. The average particle size of some of the as-prepared samples is smaller than that obtained for those samples obtained by precipitation in water. However, the expected enhancement of electrochemical performances does not occur for the as-prepared samples. Inserted amount of lithium into the cryolite structure of Li3FeF6 increases significantly only when composites of asprepared Li3FeF6 and carbon are milled mechanically. For example 12h milling is needed to reach 64 mAh/g (45% of theoretical capacity).

Density functional theory (DFT) calculations and classical molecular dynamics (MD) simulations have been performed to gain insight into the difference in cycling behaviors between the ethylene carbonate (EC)-based and the propylene carbonate (PC)-based electrolytes in lithium-ion battery cells. DFT calculations for the ternary graphite intercalation compounds (Li+(S)iCn: S=EC or PC), in which the solvated lithium ion Li+(S)i (i=1~3) was inserted into a graphite cell, suggested that Li+(EC)iCn was more stable than Li+(PC)iCn in general. Furthermore, Li+(PC)3Cn was found to be energetically unfavorable, while Li+(PC)2Cn was stable, relative to their corresponding Li+(PC)i in the bulk electrolyte. The calculations also revealed severe structural distortions of the PC molecule in Li+(PC)3Cn, suggesting a rapid kinetic effect on PC decomposition reactions, as compared to decompositions of EC. In addition, MD simulations were carried out to examine the solvation structures at a high salt concentration: 2.45 mo kg-1. The results showed that the solvation structure was significantly interrupted by the counter anions, having a smaller solvation number than that at a lower salt concentration (0.83 mol kg-1). We propose that at high salt concentrations, the lithium desolvation may be facilitated due to the increased contact ion pairs, so that a stable ternary GIC with less solvent molecules can be formed without the destruction of graphite particles, followed by solid-electrolyte-interface film formation reactions. The results from both DFT calculations and MD simulations are consistent with the recent experimental observations.

The lithium titanate Li2Ti6O13 has been prepared from Na2Ti6O13 by Li ion exchange in molten LiNO3 at 325ºC. Chemical analysis and powder X-ray diffraction study of the reaction product, respectively, indicate that total Na/Li exchange takes place and the Ti-O framework of the Na2Ti6O13 parent structure is kept under those experimental conditions. The electrochemical characterization shows that Li2Ti6O13 is able to insert ca. 5 Li per formula unit under equilibrium conditions in the voltage range 1.5-1.0 V vs. Li+/Li. This corresponds to a specific discharge capacity of 250 mAh g-1. Lithium insertion occurs at an average equilibrium voltage of 1.5 V which is typical for oxides and titanates where Ti(IV)/Ti(III) is the active redox couple. After the first redox cycle a high reversible capacity is obtained (ca. 160 mAh g-1 at C/12, with a 70% capacity retention related to a phase transformation upon cycling). On the basis of these results, we are proposing Li2Ti6O13 as new lithium battery anode material to be further investigated.

Rechargeable batteries are in high demand for future hybrid vehicles and electronic devices markets. Among various kinds of rechargeable batteries, Li-ion batteries are most popular for their obvious advantages of high energy and power density, ability to offer higher operating voltage, absence of memory effect, operation over a wider temperature range and showing a low self-discharge rate. Researchers have shown great deal of interest in developing new, improved electrode materials for Li-ion batteries leading to higher specific capacity, longer cycle life and extra safety. In the present study, we have shown that an anode prepared from interface-controlled multiwall carbon nanotubes (MWCNT), directly grown on copper current collectors, may be the best suitable anode for a Li-ion battery. The newly developed anode structure has shown very high specific capacity (almost 2.5 times as that of graphite), excellent rate capability, nil capacity degradation in long-cycle operation and introduced a higher level of safety by avoiding organic binders. Enhanced properties of the anode were well supported by the structural characterization and can be related to very high Li-ion intercalation on the walls of CNTs, as observed in HRTEM. This newly developed CNT-based anode structure is expected to offer appreciable advancement in performance of future Li-ion batteries.

In this work novel approaches to fabricate silicon-based electrodes are shown. Starting from silicon nano-particles it is possible to create nano-structured porous thin films. Both the synthesis of the Si nano-particles and the electrode assembly are performed via aerosol routes. This guarantees a very good control on the particle size and the particle size distribution, on the purity of the product and on the morphology and texture of the deposited layers. Particles are produced via Laser assisted Chemical Vapor Pyrolysis whereas electrode thin layers are deposited via Electro Spray method. The range of particle sizes can be tailored according to the selected application. Here, particles of a mean size of about 10 nm have been synthesized. Since Si is well known to forms highly lithiated intermetallic compounds [1], it is regarded as one of the most promising material for energy storage [2], especially looking at high energy density applications, such as hybrid/electric vehicle traction. In this work its promising performance are presented. The role of the additives in the composite formulation is also taken into account for a more clear understanding of the capacity fading mechanism of such electrodes.

We present combined modeling and simulation studies of Li insertion in amorphous SiCO ceramics. Atomistic models of amorphous SiCO with and without so-called “free” carbon have been crafted using a network modeling approach and subsequently relaxed and optimized within density functional theory.

In a first series, Li atoms are randomly inserted to test for sites with high binding energy. We find that Li prefers always bonding to O. The enthalpy of insertion, however, depends strongly on electronic states available in the SiCO host matrix. While Li inserted into insulating SiO2 is an energetically unfavorable process, the enthalpy of insertion in SiCO glass is decreased. Some glassy SiCO models exhibit favorable sites for Li insertion, which share a common motif in their local atomic environment. The presence of “free” carbon in SiCO then promotes Li insertion, because carbon-related structural imperfections give rise for low-lying unfilled electronic states. Consequently, strong and irreversible bonding of Li into SiCO is provided, if bonding of Li-cations in Li-O bonds outweighs the promotion energy for the electron to occupy unfilled electronic states.

The dependence of Li mobility on structure and composition of quenched Li0.5-xNax La0.5TiO3 (0 ≤ x < 0.5) and slowly cooled Li0.2-xNaxLa0.6TiO3 (0 ≤ x < 0.2) perovskite series, has been investigated by means of Neutron Diffraction (ND), Nuclear Magnetic Resonance (NMR) and Impedance Spectroscopy (IS). The first series displays rhombohedral (√2ap, √2ap, 2√3ap; S.G. R-3c) symmetry and vacancies are randomly distributed on A-sites (disordered phases), while Li0.2-xNaxLa0.6TiO3 series, presents orthorhombic unit cells (2ap, 2ap, 2ap; S.G. Cmmm) and the vacancies are preferentially located in alternating layers along the c-axis (ordered phases). In both cases, Li ions are shifted from A sites to a fourfold coordination at unit cell faces of the single cubic perovskite and octahedral are tilted along the rombohedral axis in Li-rich and along b-axis in Li- poor series. By heating the elimination of the octahedral tilting takes place changing the symmetry from rhombohedral to cubic in Li-rich samples, and from orthorhombic to tetragonal in Li-poor samples; however no changes were detected in La-vacancy distributions. For a particular value of sodium content (x=0.3 for Li0.5-xNaxLa0.5TiO3 and x=0.17 for Li0.2-xNaxLa0.6TiO3), the conductivity drops several orders of magnitude indicating that the amount of vacancies approaches the percolation threshold. In the temperature range 77-500 K, conductivity of Na-doped samples displays departures from the Arrhenius behavior, decreasing activation energy from 0.37 to 0.25 eV in disordered samples and from 0.37 to 0.12 eV in ordered ones. The structural sites occupancy has been investigated by ND, while Li mobility was evaluated through NMR and Impedance spectroscopy. The temperature dependence of thermal BLi factors has been related to the increment of conductivity that precede structural transformations, suggesting that Li motion trigger detected transitions in both series.