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Abstract: Li0.33MnO2 was prepared by solid-state reaction of CMD oxide and a lithium salt. The structure was studied by X-ray diffraction and Raman scattering during electrochemical discharging. The possibility of application as a positive electrode in rechargeable lithium batteries was investigated. The electrochemical properties of Li//Li0.33MnO2 cells were studied as a function of temperature in the range 25–55°C. The electrode material delivers an initial capacity of 194mAhg−1 and shows good reversibility at room temperature. Finally, the lithium insertion mechanism was examined by the determination of the ion kinetics. [Copyright &y& Elsevier]

Abstract: Raman scattering spectra have been investigated to evaluate the local structure of lithiated oxides used as electrode materials for lithium-ion batteries. We report the analysis of the vibrational spectra of ordered spinel phases including the partially delithiated λ-Li0.5Mn2O4 ( SG), the partial charge-ordered LiMn2O4 orthorhombic form (Fddd SG) and the LiNi0.5Mn1.5O4 substituted oxide (P4132 SG). Analysis of spectroscopic data is performed using the classical factor group theory and the vibration features are compared with those of the ordered lithium ferrite α-LiFe5O8 and the normal spinels LiMn2O4 and LiNi0.5Mn1.5O4 (Fd3m SG), and the inverse spinel LiNiVO4. [Copyright &y& Elsevier]

Abstract: This work presents the vibrational features of lithiated manganese oxides used as positive electrode materials in lithium-ion batteries. Vibrational spectroscopies (Raman and FTIR) yield reliable description of material lattice by probing the distortion of the basal MnO6 octahedra in these oxides. Lattice dynamics are studied using either a classical group theoretical analysis or a local environment model. The local arrangement in MnO2 structures is investigated including the lithiated Li0.33+x MnO2 (0≤ x ≤0.6) phase. The phase evolution as a function of the degree of lithium intercalation or deintercalation is reported and analyzed in a series of manganospinels Li1−x+y Mn2−y O4 with 0≤ x ≤1 and 0≤ y ≤0.33. A comparison with tetragonal Li2Mn2O4 and Li6.6Mn5O12 spinels shows the influence of the Jahn–Teller effect on the Raman features for this class of materials. A relationship between the cubic lattice parameter and the infrared mode frequency is also established. [Copyright &y& Elsevier]

Abstract: We report the structural and electrochemical characteristics of FePO4 dihydrate exhibiting a monoclinic structure (P21/n space group). We have applied Raman and FTIR spectroscopy to study the local structure. Vibrational features analyzed using the molecular group model show the strong inductive effect in the [FePO4] framework. The electrode FePO4·2H2O material inserts 0.7 Li ions per mole leading to coulombic efficiency of 74% for the first cycle and specific capacity of 106mAhg-1. Infrared spectrum of the lithiated product shows structural modifications due to the lithium insertion and the reduction of iron ions. [Copyright &y& Elsevier]

Abstract: We report the structural and electrochemical characteristics of Li4/3Me5/3O4 (Mepinel materials exhibiting nanostructured morphology. We have applied Raman and FTIR spectroscopy to study the local structure. Vibrational features are in good concordance with the factor group analysis (Oh 7 symmetry). The zero-strain insertion material Li4/3Ti5/3O4 delivers 150mAh/g while Li4/3Mn5/3O4 inserts 2.8 Li/mole of oxide leading to a specific capacity of 158mAh/g. [Copyright &y& Elsevier]

Raman scattering spectroscopy have been applied to the study of local structure of Li4/3Me5/3O4 (Me = Ti, Mn) spinel oxides used as electrode materials for rechargeable lithium batteries and hybrid supercapacitors. We report the analysis of their vibrational spectra using both the classical factor group analysis and a local environment model. Electrochemical performance was carried out using a lithium cell with solvent-free solid-polymer. Raman spectra of Li4/3+xMe5/3O4 spinels are compared and analyzed on the basis of structural modifications of their lattices upon lithium insertion. [Copyright &y& Elsevier]

Lithiated spinel manganese oxides with various amounts of lithium have been prepared through solid-state reaction and electrochemical intercalation and deintercalation. Local structure of the samples are studied using Raman scattering and Fourier transform infrared spectroscopy. We report vibrational spectra of lithiated manganese oxides LixMn2O4 as a function of lithium concentration in the range 0.1≤x≤2.0. Raman and Fourier transform infrared (FTIR) spectral results indicated multiple-phase reactions when the lithium content is modified in the spinel lattice. Lattice dynamics of lithiated spinel manganese oxides have been interpreted using either a classical factor-group analysis or a local environment model. The structural modifications have been studied on the basis of vibrations of LiO4 tetrahedral and MnO6 octahedral units when Li/Mn≤0.5, and LiO4, LiO6, and MnO6 structural units when Li/Mn>0.5. [Copyright &y& Elsevier]

Raman scattering (RS) and Fourier transform–infrared (FT–IR) spectroscopy have been applied to the structural characterisation of manganese dioxides (MDOs). A variety of synthetic battery-grade MDOs are investigated for comparison to the natural phases. The RS and FT–IR spectra are analysed on the basis of the local environment in the MDO structures considering the vibrations of the MnO6 octahedral building the lattices. The vibrational modes of the MnO6 units expand over 400–650 cm−l with additional bands in the low-wavelength region. Structural trends are deduced from the comparison of the vibrational spectra of the MDO phases investigated: birnessite, bixbyite, coronadite, groutite, hausmannite, hollandite, manganosite, pyrolusite, ramsdellite, romanechite, spinel, and todorokite. [Copyright &y& Elsevier]

Raman scattering (RS) and Fourier transform infrared (FTIR) spectroscopy have been applied to the study of local structure of lithium manganese oxides. We report the analysis of the vibrational spectra of spinel LiMn2O4 structure using both the classical group factor analysis (Oh7) and a local environment model. The RS and FTIR spectra are analysed on the basis of LiO4 tetrahedra and MnO6 octahedra building the lattice. RS and FTIR line intensities and positions remained in good agreement with the Fd3m space group. Isotopic substitution of 6Li for 7Li leads the conclusion that the spectral features of the LiO4 remains in the 350–400 cm−l and the vibrational modes of the MnO6 expand over 450–650 cm−l. Vibrational spectra of the lithium-rich manganese oxide spinels are also presented for comparison with the λ-LiMn2O4 phase. [Copyright &y& Elsevier]

Numerous channel- or tunnel-structured compounds are interesting materials in which lithium intercalation occurs primarily without destruction of the host lattice assuming a complete charge transfer. In many cases, the rigid-band model (RBM) is a useful first approximation for describing the changes in electronic properties of the host material with intercalation. The applicability of the rigid-band model is taken as a test for the properties most desirable in a good intercalation material. This review paper presents experimental results, namely optical and electrical measurements, obtained on various intercalation materials such as dichalcogenides, trichalcogenides and oxides to probe the validity of the RBM. The impact of the lithium intercalation is discussed for various structural forms, from well-crystallised to amorphous compounds. We observed, nevertheless, that the rigid-band model is not applicable to all of the layered intercalation materials. This needs yet to be more extensively documented for their promising application as insertion electrode in rechargeable lithium batteries. Compounds such as TiS2, TaS2, MoS2, NiPS3, MoO3, V2O5, V6O13, LiCoO2, LiNiO2, LiMn2O4 and LiNiVO4 are tested in this work. Some guidelines are established for improving the performances of these materials in their most eminent applications. [Copyright &y& Elsevier]

Nanosized MnO 2 powders were grown using a green synthesis based on citrates via redox reaction between KMnO 4 and natural reducing agents, i.e. lemon juice and peel extracts, without generating hazardous waste. X-ray diffraction (XRD) and Raman studies show that the samples grow as cryptomelane polymorph, α-MnO 2 , crystallized with the tetragonal cryptomelane structure. Both J-MnO 2 prepared from lemon juice and P-MnO 2 prepared from citrus peel consist of nanosized particles as observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Thermogravimetric analysis (TGA) confirms the typical thermal decomposition of MnO 2 at temperatures of up to 500 °C. Improved electrochemical properties are obtained and discussed for P-MnO 2 , with a reversible capacity that reaches 160 mAh g −1 (initial capacity of 212 mAh g −1 ) at a current density of 10 mA g −1 and a good rate capability. [ABSTRACT FROM AUTHOR]

Layered Li(Co 0.5 Ni 0.5 ) 1−y Fe y O 2 (0.0 ≤ y ≤ 0.25) oxides were prepared by citric-acid assisted sol–gel method. Elemental and structural properties were investigated by energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman scattering (RS) and Mössbauer spectroscopy, and magnetometry. EDX images show a homogeneous distribution of Fe ions. XRD and RS spectroscopy reveal that the materials crystallize as a LiNiO 2 LiCoO 2 LiFeO 2 solid solution with the typical rhombohedral α-NaFeO 2 structure ( R 3 ¯ m S.G.) up to y = 0.2 at which composition a secondary phase was observed. For y > 0.2 the XRD results show the appearance of the α-LiFeO 2 phase with the cubic structure ( Fm 3 m S.G.). The degree of cation mixing investigated by XRD analysis and magnetic measurements is z < 0.04, for y < 0.2. Electrochemical tests of Li(Co 0.5 Ni 0.5 ) 1−y Fe y O 2 (0.0 ≤ y ≤ 0.1) oxides in lithium cells show the influence of iron substitution. The best results have been obtained for the composition y(Fe) = 0.05, where the electrical conductivity is maximum. A specific capacity 32 mAh g −1 is maintained at 8C rate. [ABSTRACT FROM AUTHOR]

In an attempt to enhance the microstructural and electrochemical properties, LiCoO 2 thin films were doped with titanium or zirconium. RF magnetron sputtering technique has been employed for the deposition of films on Au/Ti/SiO 2 /Si substrates from lithium-rich LiCoO 2 target with mosaic configuration. The as-deposited and Ti- and Zr-doped LiCoO 2 thin films at lower doping concentration exhibited the α-NaFeO 2 structure with R 3 ¯ m symmetry as confirmed from X-ray diffraction and Raman studies. The cyclic voltammogram of micro-electrodes in aqueous electrolyte exhibited perfect redox peaks with good reversibility. The chronopotentiometry studies revealed that the discharge capacity of pure LiCoO 2 was 64 μAh cm −2 μm −1 , while 2% Ti- and Zr-doped films showed enhanced capacities 69 and 68 μAh cm −2 μm −1 (248 mC cm −2 μm −1 , 245 mC cm −2 μm −1 ) respectively. The Zr-doped films exhibited good structural stability even after 25 cycles with the capacity retention of 95%. [ABSTRACT FROM AUTHOR]

In-situ Raman spectroscopy is employed to investigate the valence state variations of nickel and manganese, as well as the local structure change of LiMn 1.45 Ni 0.45 M 0.1 O 4 ( M = Cr, Co) cathodes (LMN) during galvanostatic charge–discharge. Raman spectra are collected between 3.5 and 4.9 V in the wave number range of 100–800 cm −1 . The Raman observations showed that the pristine cathodes of Cr- and Co-doped LMN have essentially the same spectra, and they also have similar evolution patterns during cycling showing their reversible behaviour in the de-lithiation and lithiation processes. The Raman spectra of the pristine cathodes have eleven bands, located at 162, 220, 378, 408, 486, 498, 528, 593, 613, 639 and 672 cm −1 . The bands with wave number <300 cm −1 are attributed to the translation mode of molecular vibration; the 486, 593 and 639 cm −1 bands are assigned to the stretching mode of Mn–O bond; and the vibration modes at 408, 498, 528 and 613 cm −1 originated from the Ni–O bond; The band at 672 cm −1 is attributed to A 1g mode of Cr 3+ –O/Co 3+ –O. During cycling, several new bands are detected near the end of charge, among which the T 2g ( T ) band at 170 cm −1 is attributed to the translation mode of lattice vibration in which the lithium concentration is low, and the T 2g band at 538 cm −1 is due to the presence of Ni 4+ –O bond in the crystal structure. The T 2g ( T ) and T 2g (Ni 4+ –O) bands are clearly evident at V ≥ 4.78 ( x ∼ 0.32) and V ≥ 4.82 ( x ∼ 0.28) for Cr- and Co-doped LMN, respectively. [ABSTRACT FROM AUTHOR]

Abstract: MoO3 nanofibers have been synthesized by hydrothermal reaction from acidified ammonium heptamolybdate tetrahydrate precursor. Characterization included X-ray diffraction (XRD), scanning electron microscopy (SEM), SQUID magnetometry and Raman scattering (RS) spectroscopy. Structural analysis shows that MoO3 nanofibers 50–80 nm in diameter and a several micrometers in length are grown in the orthorhombic system (Pbnm S.G.). The composition MoO2.9975 was determined by Rietveld refinement and magnetic susceptibility measurements. The electrochemical performance of Li//MoO3 cells with nanofibers deliver a better discharge capacity after 40 cycles than MoO3 bulk. Raman spectroscopy studies revealed the structural modulation upon Li intercalation in MoO3 nanofibers. The possible mechanism of intercalation is discussed. [Copyright &y& Elsevier]

Abstract: C-LiFePO4 nanoparticles were used as surface coating for the LiMn1.5Ni0.5O4 spinel. However, it is impossible to prepare LiFePO4-coated LiMn1.5Ni0.5O4 by traditional sol–gel methods in Ar. Therefore, we used a new mechano-fusion dry process that provides a simple way to obtain surface coating for battery materials. Surface elemental analyses indicate that LiFePO4 nanoparticles were not simply mixed with the LiMn1.5Ni0.5O4, but successfully coated on its surface. This new composite was tested as a cathode for Li-ion batteries. LiMn1.5Ni0.5O4 showed better capacity retention after LiFePO4 coating, especially at high rate (>10C). After 100 cycles at 1C, the capacity declined from 105 to 65mAhg−1 for the bare LiMn1.5Ni0.5O4. In contrast, 82mAhg−1 of capacity was still obtained for the LiFePO4-coated LiMn1.5Ni0.5O4 with 75% of capacity retention after 140 cycles under 1C. The results suggest that the improved performance is due to the improvement of the surface conductivity due to the carbon coated LiFePO4 covering, end the protection against reactions of LiMn1.5Ni0.5O4 with the electrolyte. [Copyright &y& Elsevier]

Abstract: Nanosized cryptomelane manganese dioxide (MDO) and its SnO2-coated product were prepared through a redox reaction between KMnO4 and Mn(II) acetate. XRD analysis showed the cryptomelane-type structure for both materials. Chemical analysis detected the presence of K in parent and K and Sn in coated oxide. The coating was evidenced by TEM images, which display a thin layer of SnO2 at the surface of nanosized MnO2 particles. Vibrational spectroscopic measurements confirmed the integrity of the MnO2 lattice. The net effect of the SnO2 coating results in better electrochemical performance of the Li//MnO2 cells. [Copyright &y& Elsevier]

Abstract: Nanosized pure, Ag-coated and doped manganese dioxides (MDO) were prepared through a redox reaction between KMnO4 and fumaric acid. XRD analysis showed cryptomelane crystal structure for pure, coated and doped α-phases. Chemical analysis detected the presence of silver in doped and coated MDO. Scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS) analyses confirmed the presence of silver in doped and coated oxides. Transmission electron microscope (TEM) images confirmed the nanosized particles of the prepared oxides. Magnetic measurements showed reduction in Mn3+ ions in the crystal structure after coating and doping with silver. The electrochemical performance showed that Ag-coated and doped MnO2 samples have better initial capacities than pristine MnO2. Ag-coated MnO2 material showed the best capacity retention upon cycling among all prepared MnO2 oxides, i.e. 140mAh/g after the 40th cycle at C/5 rate in the potential window 1.5–4.0V vs. Li/Li+. [Copyright &y& Elsevier]

Abstract: A novel lithium iron phosphate has been synthesized by a solution route at moderate temperature. The structure was determined from powder by XRD, HRTEM and SAED experiments. LiFe2P3O10 tripolyphosphate crystallizes in the monoclinic system, space group P21 /m, with lattice constants a =4.597(7)Å, b =8.566(4)Å, c =9.051(4)Å, β =97.47° and Z =2. Internal and external vibrational modes (Raman and FTIR) show that the dominant spectral features come from the (P3O10)5− oxo-anions displaying internal and external modes along with the P–O–P bridging modes. Magnetic measurements are consistent with the high-spin configuration of Fe2+ cation with an effective magnetic moment 5.51μB. A weak antiferromagnetic ordering is observed below the Néel temperature at T N =19K. Electron paramagnetic resonance spectroscopy confirms this electronic configuration and provides evidence of the presence of a carbonaceous layer onto the particle surface. Electrochemical measurements were carried out in lithium cells with LiPF6–EC–DEC electrolyte at 25°C. The material delivered a capacity 70mAh/g in the voltage range 2.7–3.9V, close to the theoretical value (72mAh/g). The resulting cyclic voltammogram indicates a stable structure with a good reversibility with the redox peaks at 3.26 and 3.13V vs. Li0/Li+. [Copyright &y& Elsevier]

Abstract: We present the magnetic properties of LiNi0.5Mn1.5O4 spinels prepared by the sol–gel and pyrolysis techniques. Structural properties show that the material synthesized by pyrolysis method exhibit an ordered spinel structure. Characterization methods include SQUID magnetometry and ESR spectroscopy. Magnetic measurements have evidenced the ferromagnetic ordering below in LiNi0.5Mn1.5O4. Results show that actually no impurity phase is detected in LiNi0.5Mn1.5O4, thus the ferrimagnetic behavior is attributed to an intrinsic property of this material. The magnetic order in this case is trivially a collinear ferrimagnetic ordering in which both the Ni sublattice and the Mn sublattice are ferromagnetic. ESR measurements show a two-component signal with a complex shape. The dominant band is assigned to Mn4+ ions that are the only paramagnetic entities in this compound. [Copyright &y& Elsevier]

Abstract: The essential structural features of lithium-metal phosphates (LMP) have been studied using FTIR spectroscopy which is a sensitive tool to probe the local environment in the solid materials. Various LMP materials where M is iron have been investigated including phospho-olivine LiFePO4, diphosphate LiFeP2O7, Nasicon-type phosphate Li3Fe2(PO4)3 and dihydrate FePO4·2H2O. Vitreous and amorphous materials are also considered. Analysis of internal and external modes of vibration allows to distinguish between the different phases and the type of cationic environment in the framework. Results corroborate the contribution of the main factors which are responsible for the complexity of the spectra, i.e. departure from ideal symmetry, interactions between polyhedra, bridging atoms and lattice distortion. [Copyright &y& Elsevier]

Abstract: We report the structural and electronic characterization of Li2FeSiO4 synthesized by solid-state reaction. X-ray diffraction, Raman scattering, Fourier transform infrared (FTIR) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy and magnetization measurements are analyzed. Magnetic susceptibility experiments give evidence that Li2FeSiO4 powders possess an antiferromagnetic ordering below T N =25K due to long range Fe–O–Li–O–Fe interactions. Analysis of the paramagnetic region giving the Curie–Weiss parameters θ p =−93.5K and C p =4.13emuKmol−1 shows the divalent state of Fe cations. Electron paramagnetic resonance experiments confirm this electronic configuration. Electrochemical measurements were carried out in lithium cells with LiTFSI in a poly(ethylene oxide) (PEO) polymer electrolyte at 80°C. The resulting cyclic voltammogram indicates a stable structure for the first cycle with redox peaks at 2.80 and 2.74V versus Li0/Li+. [Copyright &y& Elsevier]

Abstract: We present the synthesis, characterization and electrode behaviour of LiMn2−y Co y O4 (0≤ y ≤1) spinel oxides prepared by the wet-chemical route assisted by carboxylic acid. The phase evolution was studied as a function of the cobalt substitution and the modification on the intercalation and deintercalation of Li ions. Characterization methods include TG-DTA, XRD, SEM, Raman, FTIR, and SQUID. LiMn2−y Co y O4 samples crystallize with the cubic spinel-like structure (Fd3m S.G.). Raman scattering and FT-infrared spectroscopy indicate that the vibrational mode frequencies and relative intensities of the bands are sensitive to the covalency of the (Co, Mn)–O bonds. MEB micrographs show that the particle dimension of the LiMn2−y Co y O4 powders ranges in the sub-micron-sized domain with a narrow grain-size distribution. The overall electrochemical capacity of LiMn2−y Co y O4 oxides have been reduced due to the 3d6 metal substitution. However, a more stable charge–discharge cycling performances has been observed when the electrodes are charged up to 4.3V as compared to the performance of the native oxide. For such a cut-off voltage, the charge capacity of the Li//LiMn1.8Co0.2O4 cell is ca. 101mAh/g. Differences and similarities between LiMn2O4 and Co-substituted oxides are discussed there from. [Copyright &y& Elsevier]

We report the structural properties of Li0.3MnO2 positive electrode materials for secondary lithium batteries. The crystal structure examined by X-ray diffraction corresponds to a new MnO2 with an ordered alternation of (1×2) and (1×1) channels of the γ-MnO2 phase. The vibrational properties studied by Raman scattering (RS) and Fourier transform infrared (FTIR) spectroscopy as local probes show that lithium ions are located in octahedral sites in the (1×2) channels. Significant changes are seen in the MnO6 octahedral arrangement from sample to sample by examining the spectra in high-frequency region compared with their parents that are pyrolusite and ramsdellite manganese dioxides. The cycling behavior of the Li0.3MnO2 electrode exhibits a practical material utilization capacity of 155 mA h g−1 over 60 cycles. [Copyright &y& Elsevier]