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Surface of $$\hbox {TiO}_{2}$$ is known to chemically bind the polysulfides in Li–S cell. In the present study, the effect of surface defects or oxygen vacancies in $$\hbox {TiO}_{2}$$ present as a composite with sulfur cathode on the performance of Li–S cell was investigated by using $$\hbox {NaBH}_{4}$$ reduced (black colour) $$\hbox {TiO}_{2}$$ and pristine (white) $$\hbox {TiO}_{2}$$ in cathode. Results show that former is superior in performance.

Achieving high energy density has been the focus of research in rechargeable batteries. Lithiumsulfur system is attractive due to its high theoretical energy density (2500 Wh kg-1). The major problem in Li-S system is associated with the dissolution of lithium polysulfides formed at the cathode during discharge. Shuttling of polysulfides between the cathode and anode during cycling reduces the efficiency of cycling. In the present study, TiO2 nanotubes are prepared from nanoparticles by hydrothermal route. Titania-sulfur composite has been prepared by infiltrating sulfur solution into the TiO2 nanotubes and studied as a cathode material in a non-aqueous electrolyte. Cycling behavior of Li-S cells fabricated using pristine sulfur and TiO2 nanoparticle-sulfur composite is also studied for comparison. Cells with TiO2 nanotubes exhibit better discharge capacity and coulombic efficiency than the cells with TiO2 nanoparticles and pristine sulfur.

In the present work, Li2-x MnO3-y (LMO) thin films have been deposited by radio frequency (RF) reactive magnetron sputtering using acid-treated Li2MnO3 powder target. Systematic investigations have been carried out to study the effect of RF power on the physicochemical properties of LMO thin films deposited on platinized silicon substrates. X-ray diffraction, electron microscopy, surface chemical analysis and electrochemical studies were carried out for the LMO films after post deposition annealing treatment at 500 A degrees C for 1 h in air ambience. Galvanostatic charge discharge studies carried out using the LMO thin film electrodes, delivered a highest discharge capacity of 139 mu Ah mu m(-1) cm(-2) in the potential window 2.0-3.5 V vs. Li/Li+ at 100 W RF power and lowest discharge capacity of 80 mu Ah mu m(-1) cm(-2) at 75 W RF power. Thereafter, the physicochemical properties of LMO films deposited using optimized RF power 100 W on stainless steel substrates has been studied in the thickness range of 70 to 300 nm as a case study. From the galvanostatic charge discharge experiments, a stable discharge capacity of 68 mu Ah mu m(-1) cm(-2) was achieved in the potential window 2.0-4.2 V vs. Li/Li+ tested up to 30 cycles. As the thickness increased, the specific discharge capacity started reducing with higher magnitude of capacity fading.

In the preset study dye-sensitized solar cells (DSSC) have been fabricated on a flexible titanium metal foil substrate with mesoporous anatase Titania microsphers (TMS) as the electron transport layer for photo anode. These microspheres perform dual function of light scattering and efficient dye absorption. A light to electricity conversion efficiency of 2.93% is achieved with illumination through the counter electrode. Additionally electrochemical impedance spectroscopy (EIS) is used to analyze the electron transport processes occurring at the various interfaces. Copyright © 2013 VBRI press.

LiCoO2 thin films used as cathode layers in thin-film solid-state batteries have been deposited from LiCoO2 powder target using radio frequency (rf) magnetron sputtering in a cost effective approach in terms of material consumption and processing time. Xray diffraction (XRD) studies of the films after post deposition annealing treatment revealed (104) orientation, which is the characteristic of rf sputtered LiCoO2 films. Raman spectroscopy was used to identify the different modes of vibration of atoms in the film. The surface morphology and cross-section of the samples were characterized using field emission scanning electron microscopy (SEM). The chemical analysis of LiCoO2 thin films was examined by X-ray photoelectron spectroscopy (XPS) showed atomic ratio of Li/Co as 0.9 which is close to the ideal value 1. Electrochemical characterization such as charge – discharge and cyclic voltammetry were conducted for LiCoO2 films deposited on platinized silicon substrates in the potential range 3.0 to 4.2 V vs Li/Li + . The maximum discharge capacity of 64 µAh.µm -1 . cm -2 and 52 µAh. µm -1 .cm -2 were achieved when discharged at a current of 5 µA and 50 µA for the first discharge cycle respectively. Moreover the electrochemical investigations of LiCoO2 thin films on flexible copper substrates also investigated and achieved an initial discharge capacity of 83 mAh/g. The possible reasons for degradation in the electrochemical properties have been discussed. The present work indicates suitability of sputtering from powder targets for thin film battery fabrication. Copyright © 2013 VBRI press.

The effects of physical aging on the conductivity of a PEO:LiClO4 (8:1)–Al2O3 (20 wt.%, 24 nm) composite electrolyte were investigated and analyzed. The rate of physical aging was temperature dependent and peaked at 50 °C. Aging causes the structure to densify, leading to a reduction in the size of the coordinating sphere around lithium. The conductivity of the electrolyte also exhibited a memory effect, i.e., at a given temperature the conductivity depended not only upon the temperature but also on prior thermal history. The solvent-less electrolyte displays high conductivity with low temperature coefficient in the 20–100 °C range.

A composite solid polymer electrolyte (CSPE) consisting of polyethyleneoxide (PEO), LiClO4 and Al2O3 of particle size 24 nm was prepared by a melt-cast method. The differential scanning calorimetry (DSC) data suggested that the CSPE is in an amorphous state due to the presence of nanophase alumina. The specific conductivity versus temperature follows Vogel–Tamman–Fulscher (VTF) behavior and the activation energy has been calculated. By analogy with the Marcus theory of solvent reorganization during electron-transfer reactions, the reorganization energy of the polymer chain has been calculated from the energy of activation of ionic conduction. The ac impedance data was analyzed using a non-linear least square (NLLS) fitting program, and the resistance of the passivating film on Li and the charge-transfer resistance of the Li reaction have been evaluated. The charge-transfer resistance has been shown to follow Arrhenius behavior through the standard rate constant for the reaction. Cyclic voltammograms provided evidence of electrochemical activity at the Li/CSPE interface near ambient temperature.

Several solid electrolytes derived from poly(ethylene oxide) doped with lithium tetrafluoroborate and a high conductivity lithium borosulfate glass were formulated and investigated for their electrochemical performance. The electrochemical characterization included a.c. impedance measurements, the temperature dependence of conductivity, scanning electron microscopy (SEM), cyclic voltammetry (CV), and the charge/discharge cycling of symmetric cells. the ionic conductivities of these electrolytes at ambient temperature were around 10 −7 S cm −1 . Although no significant improvement in conductivity was observed, the cyclic voltammetry, impedance spectroscopy, and cycling data on Li/polymer/Li and Li/polymer/ Ni cells reveal that the electrode reactions are facilitated by the glass incorporation.

Studies were undertaken to examine the effect of substrate materials on impedance behaviour of lithium dipthalocyanine (Li2Pc). Several symmetrical cells were assembled using stainless steel (SS), gold foil, gold sputtered SS, copper, nickel and lithium electrodes. It was found that the Nyquist impedance spectrum obtained with SS electrodes consisted of two semicircles with total resistance of 1700 kOhm. But the cell with gold electrodes produced a single semicircle with resistance of 450 kOhm. Similarly, different values of impedance were obtained by varying the substrate materials. It was concluded that Li2Pc exhibits chemical reactivity with metallic substrates used in the study.