Sonochemical Synthesis of Pt Ion Substituted TiO2 (Ti0.9Pt0.1O2): A High Capacity Anode Material for Lithium Battery

Doping of TiO2 with a suitable metal ion where dopant redox potential couples with that of titanium (Ti4+) and act as catalyst for additional reduction of Ti4+ to Ti2+ (Ti4+ -> Ti3+ -> Ti2+) is envisaged here to enhance lithium storage even higher than one Li/TiO2. Accordingly, 10 atom% Pt ion substituted TiO2, Ti0.9Pt0.1O2 nanocrystallites was synthesized by sonochemical method using diethylenetriamine (DETA) as complexing agent. Powder X-ray diffraction pattern (XRD), Rietveld refinement and TEM study reveals that Ti0.9Pt0.1O2 nanocrystallites of similar to 4 nm size crystallize in anatase structure. X-ray photo-electron spectroscopy (XPS) study confirms that and both Ti and Pt are in 4+ oxidation state. Due to Pt4+ ion substitution in TiO2, reducibility of TiO2 was enhanced and Ti4+ was reduced up to Ti2+ state via coupling of Pt states (Pt4+/Pt2+/Pt-0) with Ti states (Ti4+/Ti3+/Ti2+). Galvanostatic cycling of Ti0.9Pt0.1O2 against lithium showed very high capacity of 430 mAhg(-1) or exchange of similar to 1.5Li/Ti0.9Pt0.1O2. (C) 2012 The Electrochemical Society. DOI: 10.1149/2.029208jes] All rights reserved.

Study of Ion Transport in Lithium Perchlorate-Succinonitrile Plastic Crystalline Electrolyte via Ionic Conductivity and in Situ Cryo-Crystallography

Ion transport mechanism in lithium perchlorate (LiClO4)-succinonitrile (SN), a prototype of plastic crystalline soft matter electrolyte is discussed in the context of solvent configurational isomerism and ion solvation. Contributions of both solvent configurational isomerism and ion solvation are reflected in the activation energy for ion conduction in 0-1 M LiClO4-SN samples. Activation energy due to solvent configurational changes, that is, trans-gauche isomerism is observed to be a function of salt content and decreases in presence of salt (except at high salt concentrations, e.g. 1 M LiClO4-SN). The remnant contribution to activation energy is attributed to ion-association. The X-ray diffraction of single crystals obtained using in situ cryo-crystallography confirms directly the observations of the ionic conductivity measurements. Fourier transform infrared spectroscopy and NMR line width measurements provide additional support to our proposition of ion transport in the prototype plastic crystalline electrolyte.

Resistivity Maxima in Lithium Fast-Ion Conductors at High Pressure

The resistivity of two types of lithium fast-ion conductors, Li16-2xZnx(GeO4)4 (x=1,2) and Li3+xGexV1-xO4 (x=0.25,0.6,0.72), showed pronounced maxima as a function of pressure. For the first type, ln(ρ / ρ0) peaked at values of 0.12 (x=1) and 0.35 (x=2) near 20 kbar and decreased thereafter up to 80 kbar. Thermal activation energies and prefactors also showed corresponding maxima. For the second type, ln(ρ / ρ0) increased to 3-4 between 20 and 32 kbar. Near 80 kbar, ρ decreased (for x=0.25) by a factor of 250. The results are interpreted in terms of negative activation volumes.

Oxidative extraction and ion-exchange of lithium in Li2MoO3: synthesis of Li2âxMoO3 and H2MoO3

It is shown that lithium can be oxidatively extracted from Li2MoO3 at room temperature using Br2 in CHCl3. The delithiated oxides, Li2â��xMoO3 (0 < x â�¤ 1.5) retain the parent ordered rocksalt structure. Complete removal of lithium from Li2MoO3 using Br2 in CH3CN results in a poorly crystalline MoO3 that transforms to the stable structure at 280�°C. Li2MoO3 undergoes topotactic ion-exchange in aqueous H2SO4 to yield a new protonated oxide, H2MoO3.

Soft matter lithium salt electrolytes: ion conduction and application to rechargeable batteries

Soft matter provides diverse opportunities for the development of electrolytes for all solid state lithium batteries. Here we review soft matter solid electrolytes for lithium batteriesthat are primarily obtained starting from liquid electrolytic systems. This concept of solid electrolyte synthesis from liquid is significantly different from prevalent approaches. The novelty of our approach is discussed in the light of various fundamental issues and in relation to its application to rechargeable lithium batteries.

Elastic properties of fast ion conducting lithium based borate glasses

Elastic properties of Li2O-PbO-B2O3 glasses have been investigated using sound velocity measurements at 10 MHz. Four series of glasses have been investigated with different concentrations of Li2O, PbO and B2O3. The variations of molar volume have been examined for the influences of Li2O and PbO. The elastic moduli reveal trends in their compositional dependence. The bulk and shear modulus increases monotonically with increase in the concentration of tetrahedral boron which increases network dimensionality. The variation of bulk moduli has also been correlated to the variation in energy densities. The Poisson's ratio found to be insensitive to the concentration of tetrahedral boron in the structure. The experimental Debye temperatures are in good agreement with the expected theoretical values. Experimental observations have been examined in view, the presence of borate network and the possibility of non-negligible participation of lead in network formation. (c) 2005 Elsevier B.V. All rights reserved.

Ab initio molecular orbital calculations on ion-molecule and ion pair-molecule complexes of the water-lithium cyanide system

Ab initio molecular orbital (MO) calculations with the 3-21G and 6-31G basis sets were performed on a series of ion-molecule and ion pair-molecule complexes for the H2O + LiCN system. Stabilisation energies (with counter-poise corrections), geometrical parameters, internal force constants and harmonic vibrational frequencies were evaluated for 16 structures of interest. Although the interaction energies are smaller, the geometries and relative stabilities of the monohydrated contact ion pair are reminiscent of those computed for the complexes of the individual ions. Thus, interaction of the oxygen lone pair with lithium leads to a highly stabilised C2v structure, while the coordination of water to the cyanide ion involves a slightly non-linear hydrogen bond. Symmetrical bifurcated structures are computed to be saddle points on the potential energy surface, and to have an imaginary frequency for the rocking mode of the water molecule. On optimisation the geometries of the solvent shared ion pair structures (e.g. Li+cdots, three dots, centered OH2cdots, three dots, centered CN−) revealed a proton transfer from the water molecule leading to hydrogen bonded forms such as Li-O-Hcdots, three dots, centered HCN. The variation in the force constants and harmonic frequencies in the various structures considered are discussed in terms of ion-molecular and ion pair-molecule interactions.

Influence of water and thermal history on ion transport in lithium salt-succinonitrile plastic crystalline electrolytes

Important issues of water and thermal history affecting ion transport in a representative plastic crystalline lithium salt electrolyte: succinonitrile (SN)-lithium perchlorate (LiClO4) are discussed here. Ionic conductivity of electrolytes with high lithium salt amounts (similar to 1 M) in SN at a particular temperature is known to be influenced both by the trans-gauche isomerism and ion association (solvation), the two most important intrinsic parameters of the plastic solvent. In the present study both water and thermal history influence SN and result in enhancement of ionic conductivity of 1 M LiClO4-SN electrolyte. Systematic observations reveal that the presence of water in varying amounts promote ion-pair dissociation in the electrolyte. While trace amounts (approximate to 1-15 ppm) do not affect the trans-gauche isomerism of SN, the presence of water in large amounts (approximate to 5500 ppm) submerges the plasticity of SN. Subjugating the electrolyte to different thermal protocol resulted in enhancement of trans concentration only. This is an interesting observation as it demonstrates a simple and effective procedure involving utilization of an optimized set of external parameters to decouple solvation from trans-gauche isomerism. Observations from the ionic conductivity of various samples were accounted by changes in signature isomer and ion-association bands in the mid-IR regime and also from plastic to normal crystal transition temperature peak obtained from thermal studies. (C) 2010 Elsevier B.V. All rights reserved.

High-pressure studies on lithium fast-ion conductors

The variation of resistivity of the lithium fast-ion conductor Li3+y Ge1−yO4 (y = 0.25, 0.6, 0.72) has been studied with hydrostatic pressure up to 70 kbar and compared with that of Li16−2x Znx (GeO4)4(x = 1, 2). Both types showed pronounced resistivity maxima between 20–30 kbar and marked decrease thereafter. Measurements as a function of temperature between 120–300 K permitted the determination of activation energies and prefactors that also showed corresponding maxima. The activation volumes (ΔV) of the first type of compound varied between 4.34 to −4.90 cm3/mol at 300 K and decreased monotonically with increasing temperature. For the second type ΔV was much smaller, varied with pressure between 0.58 and −0.24 cm3/mol, and went through a maximum with increasing temperature. High-pressure studies were also conducted on aged samples, and the results are discussed in conjunction with results of impedance measurements and nuclear magnetic resonance (NMR) studies. The principal effect of pressure appears to be variations of the sum of interatomic potentials and hence barrier height, which also causes significant changes in entropy.

Ion transport studies in lithium phospho-molybdate glasses containing Cl- ion

Ion conducting glasses in xLiCl-20Li(2)O-(80-x) 0.80P(2)O(5)-0.20MoO(3)] glass system have been prepared over a wide range of composition (X = 5, 10, 15, 20 and 25 mol%). The electrical conductivity and dielectric relaxation of these glasses were analyzed using impedance spectroscopy in the frequency range of 10 Hz-10 MHz and in the temperature range of 313-353 K. D.c. activation energies extracted from Arrhenius plots using regression analysis, decreases with increasing LiCl mol%. A.c. conductivity data has been fitted to both single and double power law equation with both fixed and variable parameters. The increased conductivity in the present glass system has been correlated with the volume increasing effect and the coordination changes that occur due to structural modification resulting in the creation of non-bridging oxygens (NBO's) of the type O-Mo-O- bonds in the glass network. Dielectric relaxation mechanism in these glasses is analyzed using Kohlrausch-Williams-Watts (KWW) stretched exponential function and stretched exponent (beta) is found to be insensitive to temperature.

An alluaudite Na-2+Fe-2x(2-x)(SO4)(3)(x=0.2) derivative phase as insertion host for lithium battery

A new desodiated derivative compound, Na0.89Fe1.8(SO4)(3), was prepared by the chemical oxidation of alluaudite Na2.4Fe1.8(SO4)(3) Phase using NOBF4 as oxidant. The structure and valency of Fe were characterized by X-ray diffraction (XRD) and Fe-57 Mossbauer spectroscopy. Intercalation behavior of lithium ions in the structure of Na0.89Fe1.8(SO4)(3) was gauged by electrochemical analyses and ex-situ X-ray diffraction. A high capacity of 110 mAh g(-1) at 0.1 C was obtained with a good rate kinetics within a range of 0.1-10 C(1 C = 118 mAh g-1) involving a high Fe3+/Fe2+ redox potential of 3.75 V (vs. Li/Li+). These results confirmed that the Na2.4-delta Fe1.8(SO4)(3) framework was stable even after oxidation and forms a new competitive cathode for the reversible intercalation of lithium ions. (C) 2014 Elsevier B.V. All rights reserved.

Energy-savvy solid-state and sonochemical synthesis of lithium sodium titanate as an anode active material for Li-ion batteries

Lithium sodium titanate insertion-type anode has been synthesized by classical solid-state (dry) and an alternate solution-assisted (wet) sonochemical synthesis routes. Successful synthesis of the target compound has been realized using simple Na- and Li-hydroxide salts along with titania. In contrast to the previous reports, these energy-savvy synthesis routes can yield the final product by calcination at 650 -750 degrees C for limited duration of 1-10 h. Owing to the restricted calcination duration (dry route for 1-2 h and wet route for 1-5 h), they yield homogeneous nanoscale lithium sodium titanate particles. Sono-chemical synthesis reduces the lithium sodium titanate particle size down to 80-100 nm vis-a-vis solid-state method delivering larger (200-500 nm) particles. Independent of the synthetic methods, the end products deliver reversible electrochemical performance with reversible capacity exceeding 80 mAh.g(-1) acting as a 1.3 V anode for Li-ion batteries. (C) 2015 Elsevier B.V. All rights reserved.

Binder free three-dimensional sulphur/few-layer graphene foam cathode with enhanced high-rate capability for rechargeable lithium sulphur batteries.

A novel ultra-lightweight three-dimensional (3-D) cathode system for lithium sulphur (Li-S) batteries has been synthesised by loading sulphur on to an interconnected 3-D network of few-layered graphene (FLG) via a sulphur solution infiltration method. A free-standing FLG monolithic network foam was formed as a negative of a Ni metallic foam template by CVD followed by etching away of Ni. The FLG foam offers excellent electrical conductivity, an appropriate hierarchical pore structure for containing the electro-active sulphur and facilitates rapid electron/ion transport. This cathode system does not require any additional binding agents, conductive additives or a separate metallic current collector thus decreasing the weight of the cathode by typically ∼20-30 wt%. A Li-S battery with the sulphur-FLG foam cathode shows good electrochemical stability and high rate discharge capacity retention for up to 400 discharge/charge cycles at a high current density of 3200 mA g(-1). Even after 400 cycles the capacity decay is only ∼0.064% per cycle relative to the early (e.g. the 5th cycle) discharge capacity, while yielding an average columbic efficiency of ∼96.2%. Our results indicate the potential suitability of graphene foam for efficient, ultra-light and high-performance batteries.

STUDIES OF SPINEL LICRXMN2-XO4 FOR SECONDARY LITHIUM BATTERY

X-ray and electrochemical studies of spinel-related manganese chromium oxides, LiCrxMn2-xO4 (0 less-than-or-equal-to x less-than-or-equal-to 1) were carried out in a lithium nonaqueous cell. X-ray diffraction spectra indicated that the substitution of manganese in LiMn2O4 by trivalent transition metals (Cr3+) cause the linear decrease of lattice parameter with the x in the LiCrMn2-xO4. Some discharge-capacity loss was obtained due to the lattice contraction of LiCrMn2-xO4, but it has a better rechargeability than LiMn2O4. Cyclic voltammetry and electrochemical impedance experiments have shown that the excellent rechargeability of LiCrxMn2-xO4 may be attributed to the good reversibility of the change in its crystal structure for the insertion and extraction of lithium ions.