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The Li(NiCoMn)O (LNCMO) cathode material is prepared by poly(vinyl pyrrolidone) (PVP)-assisted sol-gel/hydrothermal and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly (ethylene glycol) (Pluronic-P123)-assisted hydrothermal methods. The compound prepared by PVP-assisted hydrothermal method shows a comparatively higher electrical conductivity of ~2 × 10 S cm and exhibits a discharge capacity of 152 mAh g in the voltage range of 2.5 to 4.4 V, for a C-rate of 0.2 C, whereas the compounds prepared by P123-assisted hydrothermal method and PVP-assisted sol-gel method show a total electrical conductivity in the order of 10 S cm and result in poor electrochemical performance. The structural and electrical properties of LNCMO (active material) and its electrochemical performance are correlated. The difference in percentage of ionic and electronic conductivity contribution to the total electrical conductivity is compared by transference number studies. The cation disorder is found to be the limiting factor for the lithium ion diffusion as determined from ionic conductivity values. [ABSTRACT FROM AUTHOR]

LiMn2O4 compound are synthesized by polymer precursor method using polyvinyl pyrrolidone (PVP) at temperatures (T), 650, 750 and 850°C which was coated by a thin La0.61Li0.17TiO3 (LLT). The structure and the morphology of the compounds are studied by the Rietveld refined X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques, respectively. To investigate the effect of LLT coating galvanostatic charge-discharge cycling (60 mA g-1) studies are made in the voltage range of 3.5-4.3 V vs. Li at elevated temperature (55 deg. C). The high-temperature electrochemical performance of the LiMn2O4 was significantly improved by the LLT coating. [ABSTRACT FROM AUTHOR]

Abstract: (Li, Al)-co-doped manganese oxide spinel compounds, Li(Li0.1Al0.1Mn1.8)O4 are prepared at temperatures (T), 600, 650 and 750°C by polymer precursor method using polyvinyl pyrrolidone (PVP). The structure and morphology of the porous and sub-micron size particles of the compounds are characterized by the Rietveld refined X-ray diffraction (XRD), infrared and Raman spectroscopy, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM) and Brunauer, Emmett and Teller (BET) surface area techniques. Galvanostatic charge–discharge cycling in the voltage range of 3.5–4.3V vs. Li at various current (C) rates, 0.5–3C at 24°C up to 60 cycles and at 0.5C and at 55°C up to 50 cycles is carried out. The influence of the Li-excess, the type of Al3+ dopant cation and the amount of fuel (polyvinyl pyrrolidone) used in the synthesis on the electrochemical behavior of the spinel in a Li-cell at room (24°C) and at elevated temperature (55°C) has been studied. Results show that at 24°C and at 0.5C, the phases prepared at 600°C (I) and 650°C (II) showed reversible capacities of 79 and 105mAhg−1 and retained 99 (±1)% of the capacity after 50 cycles. At 1C, 2C and 3C rates, II showed stable capacities of 97, 83 and 57mAhg−1, respectively. At 55°C and at 0.5C, II showed a reversible capacity of 114mAhg−1 and retains 92% of it at the end of 50 cycles, signifying the best cathodic performance for a doped-LiMn2O4. Complementary cyclic voltammetry, impedance spectra and ex situ XRD data are described and discussed. [Copyright &y& Elsevier]

Abstract: Tavorite-structured LiFePO4F is synthesized by solid-state reaction and characterized by Rietveld refined X-ray diffraction, scanning electron microscopy, BET surface area, IR and Raman spectroscopy techniques. The ionic conductivity (σ ionic) of LiFePO4F estimated using impedance analysis at 27°C and at 50°C are 0.6(±0.1)×10−7 and 5.4(±0.1)×10−7 Scm−1, respectively, with an energy of activation (E a)=0.75eV. Its electrochemical behavior were examined by galvanostatic charge–discharge cycling up to 100 cycles, cyclic voltammetry (CV) and electrochemical impedance spectroscopy using Li-metal as the counter and reference electrode, at 0.1C rate in the voltage range, 1.5–4V. LiFePO4F delivers an initial discharge capacity of 115(±3)mAhg−1 which increases to 119(±3)mAhg−1 at the 20th cycle. The capacity degrades slowly thereafter over 100 cycles, with a capacity loss of 19%. CV data show a clear indication of the Fe3+/2+ redox couple at 3.3–2.6V that involves a two-phase reaction. Electrochemical impedance spectra measured at various voltages at selected cycles were fitted to an equivalent circuit and the variation of impedance parameters interpreted. [Copyright &y& Elsevier]

Abstract: LiCoPO4 has been prepared by the Pechini-type polymerizable precursor method. The formation of the compound is confirmed by XRD analysis. Ion transport mechanism has been analyzed using the AC impedance technique. The conductivity parameters such as ion hopping frequency (ω p) and the charge carrier concentration term (K) have been calculated using Almond and West formalisms. The conductivity relaxation time (τ c) is calculated from the peak frequency of the modulus spectra. [Copyright &y& Elsevier]

Lithium samarium oxide has been prepared by solid-state reaction method and characterized by X-ray diffraction (XRD) and impedance spectroscopy. XRD pattern of the sample reveals the formation of the sample. The conductivity studies, dielectric studies, and modulus analysis of the samples have been carried out for different temperatures. The bulk conductivity of the sample has been found to be 1.21 × 10−5 Scm−1 at 420 °C. The temperature variation of the direct current conductivity obeys the Arrhenius relation. The modulus analysis of the sample indicates the non-Debye nature of the sample which corresponds to long-time slow polarization and relaxation of hopping charges. [ABSTRACT FROM AUTHOR]