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One-step ball-milling method is proposed to synthesize Ni-Ti-Si composites as anode materials for Li-ion batteries. From this approach it is possible to obtain the ternary compound Ni4Ti4Si7, which is poorly crystallized and does not show significant electrochemical activity. More interesting performances have been obtained for the Si-rich composite with the chemical composition Ni0.12Ti0.12Si0.76. The specific capacity is of about 700 mAh g−1 with a coulombic efficiency of 99.8% at the 50th cycle. This composite is formed by small Si particles embedded in a matrix mainly composed of the binary phases of the Ni-Ti-Si system and Ni4Ti4Si7. The analysis of the reaction mechanism by differential capacity and in situ X-ray diffraction (XRD) indicates that Si particles react with Li to form LixSi amorphous phases while most of the intermetallic phases are electrochemically inactive. A particular attention has been devoted to the evaluation of the integral intensity of some XRD structures to determine the main trends in the formation of species during the first discharge-charge cycle. The results confirm the electrochemical inactivity of the matrix that maintains the dispersion of the Si particles and buffers the volume variations.

In this article, a novel anode material with high electrochemical performance, made of elements abundant on the Earth, is reported for use in lithium ion batteries. A chemically synthesised material (SiO2/ZrO2) containing Si-O-Zr bonds, exhibits as much as 2.1 times better electrochemical performance at the 10th cycle than a physically mixed material (SiO2 + ZrO2) of the same elements. When compared to synthesized SiO2 or conventional graphite-based electrodes, the SiO2/ZrO2 anode shows superior capability and cycling performance. This superior performance is ascribed to the effect of ternary compounds, which contributes not only to increasing the packing density, but also to creating the Si-O-Zr bond that makes additional reactions between SiO2/ZrO2 and lithium ions possible. The Si-O-Zr bond also contributes to improved conductivity for SSZ and provides facile paths for charge transfer at the electrode/electrolyte interface. Therefore, the overall internal resistance in a battery would be decreased and better performance could thus be obtained, with this type of anode. In every result, the positive influence of the Si-O-Zr bonds in the anode of a lithium ion battery was confirmed.

Nanostructured NiCo 2 O 4 spinel was fabricated with a facile, low-cost coprecipitation process. The ethylene glycol was applied to serve as a stabilizer to govern over the nucleation, growth, and agglomeration processes. The influence of the calcination time was also studied on the coprecipitation reaction. Both the reaction conditions have statistically significant effects on the size distribution, crystallinity, electronic conductivity and the electrochemical performances of the products. The optimized, 5–10 nm NiCo 2 O 4 spinel, calcinated at 375 °C for 8 h, had excellent crystallinity and electric conductivity. It showed a superior-specific capacitance of 671 F g −1 at a current density of 1 A g −1 . The delay in the specific capacitance was insignificant, after a 7000-cycle test, revealing the high stability of the product. The simplicity and practicability of the modified coprecipitation process may facilitate the successful commercial applications in electrochemical capacitors for nanostructured NiCo 2 O 4 spinel.

Energy storage devices that can perform both high power and high energy operations are greatly needed for hybrid and plug-in hybrid electric vehicles and for systems by which the power generation is distributed. Here we show an easily prepared electrode material for lithium ion batteries which demonstrates high energy density, outstanding rate capabilities and long cycle life, comparable to those of supercapacitors. At a rate equivalent to a 6-minute total charge/discharge, the as-prepared metatitanic acid exhibits a life of over 7000 charge/discharge cycles while still retaining up to 87.5% of its original capacity. Furthermore, the electrode using this material can be fully charged in one minute while still maintaining a high energy density.

Highly uniform lithium vanadium oxide nanoribbons were successfully prepared in large quantities using a facile hydrothermal approach without employing any surfactants or templates. The as-prepared products were up to hundreds of micrometers in length, about 200 nm in width, and 20 nm in thickness. These nanoribbons and nafion composite were employed to modify glassy carbon electrode, which displayed excellent electrochemical sensitivity and rapid response in detecting dopamine in phosphate buffer solution. Lithium ions can greatly increase the electron transfer between the electrode and biological materials, and significantly increase the reversibility of electrochemical process. A linear relationship between the concentrations of dopamine and its oxidation peak currents was obtained. The linear range for the detection of dopamine was 2.0 × 10 −6 to 1.0 × 10 −4 M with a detection limit of 1.0 × 10 −7 M. In addition, the good reproducibility and long-term stability of the sensor make it valuable for further application.

This paper investigates one step electrodeposition of copper indium gallium metallic precursor layers for preparing CuIn1−xGaxSe2 (CIGS) absorber layers in thin film solar cells (0 ≤ x ≤ 1). Electrodeposition was carried out in acidic aqueous solutions at about pH 2. At first partial single or binary electrodeposition systems Cu, In, Ga, Cu–Ga, Cu–In were investigated by cyclic voltammetry. Then ternary Cu–In–Ga electrodeposition system was studied. The nature of the supporting electrolyte (sodium sulfate vs. sodium chloride) and the influence of sodium citrate were more specifically investigated. The applied potential, the pH and the nature of the electrolyte were optimized to obtain x values around 0.3 needed for high efficiency devices. Depositions were carried out under potentiostatic conditions in a paddle cell configuration. The electrodeposited Cu–In–Ga alloys were annealed under Se atmosphere at temperatures between 400 and 600 °C to produce CIGS absorbers. Films were characterized by XRF, SEM and XRD analysis. Device efficiencies up to 9.3% are achieved for optimal gallium content.

a b s t r a c t The crystal structure and proton conductivity of cerium pyrophosphate are investigated to explore its potential electrolyte applications for intermediate temperature fuel cell. Among the CeP2O7 thin plates, which are sintered at 300-900 ◦ C, the 450 ◦ C CeP2O7 sample exhibits superior proton conduc- tivity under humidified conditions. Its conductivity, measured with impedance spectroscopy, is higher than 10 −2 S cm −1 in the intermediate temperature range, with a maximum value 3.0 × 10 −2 S cm −1 at 180 ◦C. When 10 mol% Mg is doped on the Ce site of CeP2O7, the maximum conductivity is raised to 4.0 × 10 −2 S cm −1 at 200 ◦ C. The Mg doping not only raises the conductivity, but also shifts and widens its temperature window for electrolyte applications. Ce0.9Mg0.1P2O7 is considered a more appropriate composition, with conductivity >10 −2 S cm −1 between 160 and 280 ◦ C. Accordingly, a hydrogen-air cell is built with the Ce0.9Mg0.1P2O7 electrolyte and its performance is measured. The fuel cell generates electricity up to 122 mA cm−2 at 0.33 V using 50% H2 at 240 ◦C.

The amorphous hydrated precursor of Li1.2V3O8 was synthesized by soft chemistry method, and then heat-treated in air at several temperatures within the range 200-400 degrees C. The heat-treatment changed its morphological, structural and charging/discharging performance. The product obtained upon the treatment at 300 degrees C. consisting of uniform, rod-shaped particles, 100-150 nm in diameter and 300-800 nm in length, displayed the best electrochemical performance in aqueous LiNO3 solution. Its initial discharge capacity amounted to 136.8 mAh g(-1) at a rate of C/5, which upon 50 charging/discharging cycles decreased for only 12%. (C) 2011 Elsevier Ltd. All rights reserved.

Lithium ion dynamics in Li4+xTi5O12 spinel are investigated from first principles calculations. The diffusion pathways are optimized and the energy barriers of lithium migration under four types of dilute defect extremes: Li4+δTi5O12, Li4−δTi5O12, Li7+δTi5O12 and Li7−δTi5O12 (δ ≪ 1) are calculated with the nudged elastic band method. Results show that lithium diffusion in the charged state (energy barriers are 1.0 and 0.7 eV for interstitial Li and Li vacancy diffusion, respectively) is much slower than in the discharged state (energy barriers are 0.13 and 0.35 eV for interstitial Li and Li vacancy diffusion, respectively). The diffusion coefficients are evaluated based on lattice gas model and hopping mechanism. The obtained results are compared with available experimental data within a two-phase co-existence framework.

LaBO 3 (B = Ni, Co, Fe and Mn) were prepared by microwave-assisted citrate method. The electrocatalytic activity toward hydrogen evolution reaction (HER) was investigated. XRD characterization showed that pure perovskite crystals were indeed formed. SEM images showed that changing the type of the B-site metal ion affected the morphology of the prepared perovskites. The influence of the type of B-cation on the catalytic activity toward hydrogen evolution was studied and the order of the electrocatalytic activity was LaFeO 3 > LaCoO 3 > LaNiO 3 > LaMnO 3 , that was related to the calculated values of the activation energy 51.61, 45.37, 41.15 and 55.05 kJ mol −1 for LaBO 3 (B = Ni, Co, Fe and Mn), respectively. The reaction order and the reaction mechanism for all the prepared perovskites were identified. In addition, the effect of the partial substitution at the B-site in LaNi 1 − x Co x O 3 was also studied. It was found that among ternary perovskites, the catalytic activity of LaNiO 3 decreased by increasing the fraction of doped-Co.

Electrochemical behaviors of 2.5 V Li[Li 1/3 Ti 5/3 ]O 4 (LTO)/Li[Li 0.1 Al 0.1 Mn 1.8 ]O 4 (LAMO) cells for the first-generation 12 V lead-free battery were examined at −10, 25, and 55 °C. The LTO/LAMO cells showed the same rechargeable capacity in temperature ranging from −10 to 55 °C when the cells were examined at 0.5 mA cm −2 in cell potential ranging from 0 to 3.0 V. Capacity fading after 250 cycles was negligibly small at −10 °C. Rechargeable capacities, however, faded 5% at 25 °C and 15% at 55 °C after 250 cycles. In the discharged LTO/LAMO cell after 250 cycles at 55 °C, the state of charge (SOC) of the positive electrode was 16% while SOC of the negative electrode was 0%, indicated that the capacity fading was due to an imbalance in SOC between the positive and negative electrodes. To understand the progress of an imbalance in SOC, the LTO/LAMO cell with a lithium auxiliary electrode was fabricated and examined at 55 °C for 400 cycles, and the possible origin of capacity fading was discussed.

The Li–V–O composite (nLi:nV = 1:3.5) was synthesized by a hydrothermal method and post-treated at 300 °C. XRD analysis confirms that the composite is a binary LiV3O8–V2O5 composite system with the formula of 0.8LiV3O8·0.2V2O5. The composite consists of small laminar nanocrystallites with numerous cavities between the stacked laminar nanocrystallites, which can provide good channels for Li+ transfer during charge–discharge cycling. The initial discharge capacities of LiV3O8 and 0.8LiV3O8·0.2V2O5 samples were 276 and 365 mAh/g after 20 cycles, the discharge capacities of the two samples were 197.6 and 304 mAh/g, respectively. Smaller capacity loss indicates that the capacity retention of the composite is superior to that of bare LiV3O8 cathode.

Pristine Ni 0.5 TiOPO 4 was prepared via a traditional solid-state reaction, and then Ni 0.5 TiOPO 4 /C composites with core–shell nanostructures were synthesized by hydrothermally treating Ni 0.5 TiOPO 4 in glucose solution. X-ray diffraction patterns indicate that Ni 0.5 TiOPO 4 /C crystallizes in monoclinic P 2 1 / c space group. Scanning electron microscopy and transmission electron microscopy show that the small particles with different sizes are coated with uniform carbon film of ∼3 nm in thickness. Raman spectroscopy also confirms the presence of carbon in the composites. Ni 0.5 TiOPO 4 /C composites presented a capacity of 276 mAh g −1 after 30 cycles at the current density of 42.7 mA g −1 , much higher than that of pristine Ni 0.5 TiOPO 4 (155 mAh g −1 ). The improved electrochemical performances can be attributed to the existence of carbon shell.

Sm x Sr 1 − x CoO 3 − δ (SSCx) materials are promising cathodes for IT-SOFCs. The influence of Sm content in SSCx (0.2 ≤ x ≤ 0.8) oxides on their oxygen nonstoichiometry, oxygen desorption, thermal expansion behavior, electrical conductivity and electrochemical activity for oxygen reduction is systematically studied by iodometric titration, oxygen-temperature programmed desorption (O 2 -TPD), dilatometer, four-probe DC conductivity, electrochemical impedance spectroscopy (EIS) and three-electrode polarization test, respectively. Iodometric titration experiments demonstrate that the electrical charge neutrality compensation in SSCx proceeds preferably through the oxidation of cobalt ion for high Sm 3+ contents ( x ≥ 0.6). However, it proceeds mainly through the creation of oxygen vacancies at x ≤ 0.5. O 2 -TPD shows SSC5 possesses the highest oxygen desorption ability among the range of SSCx materials tested. The thermal expansion coefficients (TECs) are high between the transition temperature and 900 °C, showing values typically larger than 20 × 10 −6 K −1 . All dense materials show high electrical conductivity with a maximum value of ∼1885 S cm −1 for SSC6 in air, while SSC5 has the highest electrical conductivity in nitrogen. EIS analysis of porous electrodes demonstrates that SSC5 has the lowest area specific resistance (ASR) value (0.42 Ω cm 2 ) at 600 °C. Cathodic overpotential testing demonstrates that SSC5 also has the largest exchange current density of 60 mA cm −2 at 600 °C in air.

In this work, bare and Ta-substituted Nb 2 O 5 nanofibers are prepared by electrospinning followed by sintering at temperatures in the 800–1100 °C range for 1 h in air. Obtained bare and Ta-substituted Nb 2 O 5 polymorphs are characterized by X-ray diffraction, scanning electron microscopy, density measurement, and Brunauer, Emmett and Teller surface area. Electrochemical properties are evaluated by cyclic voltammetry and galvanostatic techniques. Cycling performance of Nb 2 O 5 structures prepared at temperature 800 °C, 900 °C, and 1100 °C shows following discharge capacity at the end of 10th cycle: 123, 140, and 164 (±3) mAh g −1 , respectively, in the voltage range 1.2–3.0 V and at current rate of 150 mA g −1 (1.5 C rate). Heat treated composite electrode based on M-Nb 2 O 5 (1100 °C) in argon atmosphere at 220 °C, shows an improved discharge capacity of 192 (±3) mAh g −1 at the end of 10th cycle. The discharge capacity of Ta-substituted Nb 2 O 5 prepared at 900 °C and 1100 °C showed a reversible capacity of 150, 202 (±3) mAh g −1 , respectively, in the voltage range 1.2–3.0 V and at current rate of 150 mA g −1 . Anodic electrochemical properties of M-Nb 2 O 5 deliver a reversible capacity of 382 (±5) mAh g −1 at the end of 25th cycle and Ta-substituted Nb 2 O 5 prepared at 900 °C, 1000 °C and 1100 °C shows a reversible capacity of 205, 130 and 200 (±3) mAh g −1 (at 25th cycle) in the range, 0.005–2.6 V, at current rate of 100 mA g −1 .

To clarify the electrochemical properties of Al-doped CaZrO 3 , the electrical conductivity of the poly-crystalline specimen was measured by employing the two-terminal AC method. By examining the H/D isotope effect of the electrical conductivity, it was found that protons are the dominant charge carrier at temperatures from 873 to 1373 K, both in hydrogen-rich and oxygen-rich atmospheres. At higher temperatures of 1373–1673 K, the atmospheric dependence of the electrical conductivity shows that the dominant charge carrier is the positive hole in oxygen-rich atmospheres, whereas it is the oxide ion vacancy in hydrogen-rich atmospheres.

To improve the stability of potassium ferrate(VI) (K 2 FeO 4 ) cathode and its properties of charge transfer in alkaline battery system, K 2 FeO 4 cathodes are coated by yttria (Y 2 O 3 ) doped zirconia (ZrO 2 ) composites, denoted as Y 2 O 3 –ZrO 2 composite coatings. These composite coatings are derived from the conversion of yttrium nitrate (Y(NO 3 ) 3 ·6H 2 O) and Zirconium oxychloride (ZrOCl 2 ·6H 2 O) in ether medium. Examinations by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR) show that K 2 FeO 4 cathodes are coated by Y 2 O 3 –ZrO 2 overlayer. Alternatively, results of discharge properties and electrochemical impedance spectroscopes (EIS) indicate that when the molar ratio between Y 2 O 3 and ZrO 2 is 0.09, denoted as Y 2 O 3 (9 mol%)–ZrO 2 , the stability and charge transfer of Y 2 O 3 (9 mol%)–ZrO 2 coated K 2 FeO 4 cathodes are improved greatly compared to that of uncoated or ZrO 2 coated K 2 FeO 4 cathodes. Therefore, Y 2 O 3 –ZrO 2 composite coatings are a potential choice to improve the stability and charge transfer of K 2 FeO 4 cathodes in alkaline electrolyte.

A cathode material, LiV 3 O 8 , for rechargeable lithium-based batteries has been prepared via a combined freeze-drying method and appropriately post-treated in argon atmosphere. It was found that the sample post-treated at 300 °C in Ar has the optimal performance. Electrochemical tests performed on this material demonstrated its very high insertion capacity of 347 mAh g −1 (3.7 Li + per LiV 3 O 8 ) at a current density of 50 mA g −1 (C/6). Most important is that it displayed an excellent cycling stability and after 60 cycles, a discharge capacity with 351 mAh g −1 was obtained. It was proposed that a short-range crystallographic order had a stronger influence on the electrochemical performance of an electrode material in this work, instead of the surface area, particle size and crystalline degree, etc.

In this work, we report a basic study on the mechanism of lithium ion de-insertion/insertion process from/into LiMn2O4 cathode material in aqueous Li2SO4 solution using electrochemical impedance spectroscopy (EIS). An equivalent circuit distinguishing the kinetic parameters of lithium ion de-insertion/insertion is used to simulate the experimental impedance data. The fitting results are in good agreement with the experimental results and the parameters of the kinetic process of Li+ de-insertion and insertion in LiMn2O4 at different potentials during charge and discharge are obtained using the same circuit. The results indicate that the de-insertion/insertion behavior of lithium ions at LiMn2O4 cathode in Li2SO4 aqueous solution is similar to that reported in the organic electrolytes. The charge transfer resistance (Rct), warburg resistance, double layer capacitance and chemical diffusion coefficient ( D L i + ) vary with potentials during de-insertion/insertion processes. Rct is lowest at the CV peak potentials and the important kinetic parameter, D L i + exhibits two distinct minima at potentials corresponding to CV peaks during de-insertion–insertion and it was found to be between 10−8 and 10−10 cm2 s−1during lithium de-insertion/insertion processes.

In this work a gas diffusion layer (GDL) prepared with metallic ceramics TIC for a unitized regenerative fuel cell (URFC) was first investigated By the measurements of morphological characteristic electrical conductivity absolute through-plane permeability and electrochemical stability the characteristics of the novel GDLs and the conventional one were compared A high corrosion-resistive and low-cost GDL with 80 wt % TiC and 20 wt % IrTiO(x) was expected to enhance the cycle performance of URFC And the total loading of Ir in the novel URFC was only 1 3 mg cm(-2) The URFC with the novel GDL exhibited the similar initial performance under both fuel cell and electrolysis modes as that using the conventional GDL. However the life cycle testing over 60 h showed that the URFC with the novel GDL was more stable than the URFC with the traditional GDL indicating that the GDL with TiC and IrTiO(x) was beneficial to improve the cycle life of the URFC (C) 2010 Elsevier Ltd All rights reserved

Hierarchical layered hydrous lithium titanate and Li4Ti5O12 microspheres assembled by nanosheets have been successfully synthesized via a hydrothermal process and subsequent thermal treatment. The electrochemical properties of the two samples have been investigated by galvanostatic methods. The former, with the obvious layered structure and a large surface area, delivers a reversible capacity of 180 mA h g−1 after 200 cycles at 200 mA g−1. As for Li4Ti5O12, with the intriguing and unique sawtooth-like morphology, it presents exceptional high rate performance and excellent cycling stability. Up to 132 mA h g−1 is obtained after 200 cycles at 10,000 mA g−1 (57 C), proving itself promising for high-rate applications.

An original carbothermal synthesis of ramsdellites phases under specific atmosphere (Ar, Ar/H 2 , N 2 , N 2 /H 2 ) allowed creating in situ composites which showed good electrochemical properties as negative active materials of Li-ion batteries. The combination of chemical, XRD and electrochemical analyses enabled to identify the as-formed composite electrodes. It consists in ramsdellite/spinel for the synthesis under Ar/H 2 , TiO 2 ramsdellite/Li 2 TiO 3 for the synthesis under N 2 /H 2 , and Li 2± x Ti 3 O 7 /Li 2± x ′ Ti 3 O 7 for the samples prepared under both N 2 and Ar. Carbon is partially inserted inside channels of titanate structure for the sample obtained under Ar/H 2 . For the first time, one of these composites allowed reaching a specific capacity close to the theoretical value of 198 mAh g −1 .

The kinetic behaviors of Li-ion insertion/extraction in LiV 3 O 8 thin film have been investigated using cyclic voltammetry (CV), potentiostatic intermittent titration (PITT) and electrochemical impedance spectroscopy (EIS) method. This LiV 3 O 8 thin film with a mixed amorphous-nanocrystalline microstructure was fabricated by RF sputtering. For the first time, the intrinsic kinetics of LiV 3 O 8 thin film electrode is obtained. The D L i + value is about 10 −13 cm 2 /s in mixed amorphous-nanocrystalline microstructure LiV 3 O 8 thin film. Different to crystalline LiV 3 O 8 thin film, the D L i + values do not change a lot with the increase of cell potential which is due to the absence of structural phase transition behavior in mixed microstructure LiV 3 O 8 thin film during Li + insertion/extraction process. This is also the reason for excellent capacity retention performance of LiV 3 O 8 film with a mixed microstructure.

Nanotubes were coated on the surface of active LiCoO 2 particles using electrostatic heterocoagulation to enhance the electrochemical properties of a Li-ion battery. Only 0.5 wt% of multiwalled carbon nanotubes (MWCNTs) was added as a conducting agent into the LiCoO 2 cathode, which had a density of 4.0 g cm −3 . We found that our electrode that was prepared using heterocoagulation with 0.5 wt% of thin MWCNTs maintained a volumetric capacitance of 403 mAh cm −1 after 40 cycles from the initial 624 mAh cm −1 , compared with previous result of 310 mAh cm −1 obtained from simple mixing with 3 wt% MWCNTs. The high volumetric capacity with smaller swelling using less amount of MWCNTs was attributed to the self-assembled nanotube network formed between active particles during coagulation, which was maintained with volume expansion during cycle testing.

Gd 2 (Zr 1− x Nb x ) 2 O 7+ x (0 ≤ x ≤ 0.2) ceramics are prepared via the solid state reaction process at 1973 K for 10 h in air. Gd 2 (Zr 1− x Nb x ) 2 O 7+ x ( x = 0.1, 0.2) ceramics exhibit an ordered pyrochlore-type structure, whereas Gd 2 Zr 2 O 7 has a defective fluorite-type structure. The electrical property of Gd 2 (Zr 1− x Nb x ) 2 O 7+ x ceramics is investigated by electrochemical impedance spectroscopy over a frequency range of 10 Hz to 8 MHz from 623 to 923 K. The electrical conductivity obeys the Arrhenius equation. The grain conductivity of Gd 2 (Zr 1− x Nb x ) 2 O 7+ x ceramics varies with doping different Nb contents, and exhibits a maximum at the Nb content of x = 0.1 in the temperature range of 623–923 K. The conductivity in hydrogen atmosphere is a little bit higher than in air in the temperature range of 723–923 K, which indicates that the doping of Zr 4+ by Nb 5+ can increase the proton-type conduction and reduce the oxide-ionic conduction. The conduction of Gd 2 (Zr 1− x Nb x ) 2 O 7+ x is not a pure oxide-ionic conductor.

The compounds, Li(MMn11/6)O4 (M = Mn1/6, Co1/6, (Co1/12Cr1/12), (Co1/12Al1/12), (Cr1/12Al1/12)) are synthesised by the polymer precursor method. 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. Density and the Brunauer, Emmet and Teller surface area (BET) of the compounds are also studied. The cobalt doped compound, Li(Co1/6Mn11/6)O4 is found to be nanosized particles in the range of 60–100 nm, when compared to the other compounds in our present study. The oxidation state and the local structure of the compounds are analysed by the X-ray absorption spectroscopy (XAS) technique. Cyclic voltammetry (CV) and the galvanostatic charge–discharge cycling (30 mA g−1) studies are made in the voltage range of 3.5–4.3 V at room temperature for all the compounds under study. The bare and (Co1/6), and (Co1/12Cr1/12) substituted spinels are cycled at high current rates of 1, 2 and 5C (assuming 1C∼120 mA g−1). Cycling results of Co-substituted spinels show better and long-term capacity retention at all the current rates. At the end of the second cycle, Li(Co1/6Mn11/6)O4 compound delivers a discharge capacity value of 100 (±3) and 87 (±3) mAh g−1 for the current rate of 2 and 5C, respectively. An excellent capacity retention value of 94% is observed at the end of the 1000 cycles for both 2 and 5C rates.

Nanosized CaSnO3 is synthesized by a hydrothermal process and characterized by X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). The SEM observation shows the sample has a porous flowerlike morphology. The electrochemical results exhibit that the stable and reversible capacity of 547 mAh g−1 is obtained after 50 cycles at 60 mA g−1 (0.1 C) and the corresponding charge capacity is determined to be 316 mAh g−1 at the current density of 2.5 C. Cyclic voltammetry and electrochemical impedance spectroscopy data are analyzed to complement the galvanostatic results. The observed excellent performance is attributed to the porous structure and large surface area of flowerlike CaSnO3.

Perovskite-type LaCrO3 used as negative electrode for Ni/MH batteries was prepared by Pechini method and characterized by XRD and SEM. The electrochemical properties under various temperatures and electrolyte concentrations were investigated. The results showed that the discharge capacity of LaCrO3 electrodes increased with the increase of temperature and electrolyte concentration. Meanwhile, the electrochemical properties of LaCrO3 electrodes were found to be greatly influenced by the dimension of Ni powders, which served as catalyst in electrodes. EIS was employed to study the phenomena above.

This work presents a method of enhancing the kinetics of the interfacial reaction using 1,3,5-trifluorobenzene (TFB) which is used as an electron acceptor due to its locally biased polarity and as a source of rearranging the layer of the electrolyte around LiCoO 2 electrode, not a SEI layer source. The full cells with TFB show a decrease in irreversible capacity loss during the first charge-to-discharge process, regardless of the SEI layer formation, and also show better discharge properties even at high rate conditions. The charge transfer resistance ( R ct ) of the LiCoO 2 half cell with TFB shows the smaller resistance than that of the TFB free half cell, and the activation energy calculated from the R ct was 24.7 kJ/mol for the TFB free half cell and 19.3 kJ/mol for the half cell with TFB. In addition, the film resistance of the half cell with TFB shows higher value when the temperature is below 283 K. Since R ct is related to the transfer resistance of the solvated Li + ions on the surface of the LiCoO 2 electrode, it will help design the electrolyte to improve the transfer velocity of Li + ions around the cathode electrode for high power Li ion battery.

Micrometer-scale pristine and phosphate-doped spinel LiMn 2 O 4 materials with homogeneous size distribution were synthesized by a one-step hydrothermal method. The composition, structure and morphology of the as-prepared samples were characterized using inductively coupled plasma atomic emission spectroscopy (ICP-AES), chemical analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of phosphate doping on the structural and electrochemical properties of spinel LiMn 2 O 4 was investigated by Fourier transform infrared (FT-IR) spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The phosphate-doped LiMn 2 O 4 cathode (with a molar ratio of PO 4 3− :LiMn 2 O 4 = 1.5%) exhibits good high-rate discharge capability with 94 mAh/g at a current density of 2960 mA/g. The analyses demonstrate that compared with the pristine LiMn 2 O 4 sample, the phosphate-doped samples have a relatively large Li-ion diffusion coefficient and smaller charge-transfer resistance due to the increase of the unit cell volume of spinel LiMn 2 O 4 caused by the doping of phosphate.

Micro-spherical particle of MnCO 3 has been successfully synthesized in CTAB–C 8 H 18 –C 4 H 9 OH–H 2 O micro-emulsion system. Mn 2 O 3 decomposed from the MnCO 3 is mixed with Li 2 CO 3 and sintered at 800 °C for 12 h, and the pure spinel LiMn 2 O 4 in sub-micrometer size is obtained. The LiMn 2 O 4 has initial discharge specific capacity of 124 mAh g −1 at discharge current of 120 mA g −1 between 3 and 4.2 V, and retains 118 mAh g −1 after 110 cycles. High-rate capability test shows that even at a current density of 16 C, capacity about 103 mAh g −1 is delivered, whose power is 57 times of that at 0.2 C. The capacity loss rate at 55 °C is 0.27% per cycle.

Present paper describes electrochemical performance of the all solid-state lithium polymer battery (LBP) using spinel-type Li 4/3 Ti 5/3 O 4 which has been known as the potential candidate of anode materials. The assembled LPB with Li|solid polymer electrolyte(SPE)|Li 4/3 Ti 5/3 O 4 construction showed stable charge–discharge cycles more than 300 times at 1 C condition. On the other hand, strong charge–discharge rate dependence for the specific capacity and initial capacity loss was indicated. Such a poor rate performance stemmed from low diffusivity of Li + ion in the by-products produced by the decomposition of SPE components at the SPE|Li 4/3 Ti 5/3 O 4 interface.

In order to overcome severe capacity fading of LiMn 2 O 4 /graphite Li-ion cells at high temperature at 60 °C, fluoroethylene carbonate (FEC) was newly evaluated as an electrolyte additive. With 2 wt.% FEC addition into the electrolyte (EC/DEC/PC with 1 M LiPF 6 ), the capacity retention at 60 °C after 130 cycles was significantly improved by about 20%. To understand the underlying principle on the capacity retention enhancement, the electrochemical properties of the cells including cell performance, impedance behavior as well as the characteristics of the interfacial properties were examined. Based on these results, it is suggested that the improved capacity retention of LiMn 2 O 4 /graphite Li-ion cells with addition of FEC especially at high temperature is mainly originated from the thin and stable SEI layer formed on the graphite anode surface.

International audience; A device based on an electrochemical transfer junction (constituted by MxMo6S8 or MxMo6Se8) placed between two tanks allows the transfer of cations by application of current density controlled between electrodes placed in tanks. The transfer protocol was tested on different mixed electrolytes containing cations directly engaged in the batteries industry (M2+ = Co2+, Ni2+, Cd2+, Zn2+, Mn2+, Cu2+). Good performances of the process are provided until 1.6 mA cm−2. The electrolysis through an electrochemical transfer junction made of Chevrel phases represents a suitable method for the selective extraction of cations with appreciable selectivity rates with an appropriate choice of the host lattice (sulfide or selenide). Remarkable separations between Co/Ni, Zn/Mn with Mo6S8 and Cd/Zn, Cd/Ni, Cd/Co and Zn/Ni, with Mo6Se8 were observed.

We report the preparation of Li 0.33 MnO 2 nanorods from γ-MnO 2 nanorods reacted with LiNO 3 by a low temperature solid-state reaction method. The Li 0.33 MnO 2 nanorods tend to be oriented along the b -axis, and show an improved rate capability and cycling performance as positive electrode for lithium battery. It delivers a discharge capacity of 199 and 129 mAh/g at the current rate of 0.1 C (20 mA/g) and 2 C, respectively, and keeps 92% of initial capacity over 100 cycles. Li 0.33 MnO 2 nanorods reduce both the electrode bulk resistance and charge-transfer resistance for lithium-ion intercalation. The advantage of nanorods results from good electrical conduction, appropriate length of nanorod and small volume expansion from appropriate orientations of tunnels structure.

In this paper, Li4Ti5O12 (LTO) hollow microspheres with the shell consisting of nanosheets have been synthesized via a hydrothermal route and following calcination. Because of the favorable transport properties of this hollow structure, it is the rate performance at high current densities which is exceptional. When the LTO hollow microspheres were used as the anode material in lithium ion battery, they exhibited superior rate performance and high capacity even at a very high rate (131 mAh g−1 at 50 C).

National Natural Science Foundation of China [29925310, 20473068, 20433060]; National Basic Research Program of China [2007CB209702]

The Li 1+ x V 3 O 8 material was successfully synthesized at 450 °C in short sintering duration by microwave sol–gel route. X-ray diffraction suggests oxygen defects in the lattice. Based on Randles–Sevcik formula, cyclic voltammograms measurements were conducted to measure Li + ion diffusion coefficient. The material exhibits high discharge capacity of 250 mA g −1 at 0.2 mA/cm 2 after 30 cycles in the range of 2.0–4.0 V. Alternating current impedance tests show that the growth of the charge transfer resistance at 0.4 mA/cm 2 is more rapid than that of at 0.2 mA/cm 2 as the galvanostatical charge–discharge continues.

Br-doped Li4Ti5O12 in the form of Li4Ti5O12−xBrx (0 ≤ x ≤ 0.3) compounds were successfully synthesized via solid state reaction. The structure and electrochemical properties of the spinel Li4Ti5O12−xBrx (0 ≤ x ≤ 0.3) materials were investigated. The Li4Ti5O12−xBrx (x = 0.2) presents the best discharge capacity among all the samples, and shows better reversibility and higher cyclic stability compared with pristine Li4Ti5O12, especially at high current rates. When the discharge rate was 0.5 C, the Li4Ti5O12−xBrx (x = 0.2) sample presented the excellent discharge capacity of 172 mAh g−1, which was very close to its theoretical capacity (175 mAh g−1), while that of the pristine Li4Ti5O12 was 123.2 mAh g−1 only.

To improve the coulombic efficiency of GeO2 electrode, a Cu-containing ternary metal oxide (CuGeO3) was prepared and the electrochemical behavior of Cu component was studied. The GeO2 electrode shows a low coulombic efficiency in the first cycle (43%), which is mainly caused by a poor Ge oxidation kinetics (Ge + 2Li2O → GeO2 + 2Li+ + 2e−). The X-ray absorption spectroscopy (XAS) data illustrate that the Cu component in CuGeO3 is converted to nano-sized metallic Cu in the earlier stage of lithiation but idles thereafter. In contrast, the Ge component in CuGeO3 behaves like the GeO2 electrode. It is converted to nano-sized Ge by a conversion reaction and further lithiated by alloying reaction. The de-lithiation proceeds in the reverse order. The CuGeO3 electrode shows a much improved coulombic efficiency (74%) in the first cycle, which is indebted to a facilitated Ge oxidation with a much reduced electrode polarization. This feature has been explained by the favorable roles provided by the in situ generated nano-sized metallic Cu particles that make such an intimate contact with the nano-sized Ge and Li2O that they can catalyze Li2O decomposition and provide an electronic conductive network for Ge oxidation. A similar favorable effect was observed with the other ternary oxides (FeGeO3 and CoGeO3), wherein the formation of nano-sized metallic Fe and Co can be assumed.

Ferrate is considered to be a potential cathode material for high-energy batteries, due to its high capacity based on three-electron transfer in electrochemical reactions. In this work, high-purity potassium ferrate (K2FeO4) was synthesized by a direct hypochlorite oxidation method. X-ray diffraction (XRD) and a charge-coupled device (CCD) were used to characterize the structure of the K2FeO4 as well as the channels for intercalation–deintercalation of Li ions. The one-dimension channel was observed in the direction of the a and b axes in the unit cell, with a radius 0.93 A, which is beneficial for Li ion (radius = 0.76 A) intercalation and deintercalation in K2FeO4. The experimental super-iron Li ion battery was assembled with 1 M LiPF6 organic electrolyte (PC:EC:DMC = 1:3:6, v/v), a K2FeO4 cathode, and a metal lithium anode. The electrochemical performance of the K2FeO4 cathode was evaluated by a galvanostatic method and cyclic voltammetry (CV) in the potential range of 4.3–0.5 V at room temperature. It was demonstrated that one Li ion intercalates into the lattice of the K2FeO4 cathode along the channels of the a and b axes of the K2FeO4 unit cell, followed by a two-Li ion intercalation of isotropy in the initial discharge process. Amorphization of the K2FeO4 cathode is the main cause of its electrochemical performance decay.

The electrochemical reduction process of Bi 3+ , HTeO 2 + , Sb III and their mixtures in nitric acid medium was investigated by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The reduction products electrodeposited at various potentials were examined using X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The results show that cathodic process in the nitric acid solution containing Bi 3+ , HTeO 2 + and Sb III involves the following reduction reactions in different polarizing potential ranges: In low polarizing potential ranges, Te 0 is formed firstly on the electrode surface through the electrochemical reduction of HTeO 2 + ; with the negative shift of the cathodic polarizing potential, the reduction reaction of Bi 3+ with Te 0 to form Bi 2 Te 3 takes place; when the cathodic polarizing potential is negative enough, Bi 3+ and Sb III react with Te 0 to form Bi 0.5 Sb 1.5 Te 3 . The results indicate that Bi 0.5 Sb 1.5 Te 3 films can be fabricated by controlling the electrodepositing potential in a proper high potential ranges.

This study investigated the effect of a specific adsorption ion, copper (II) ion, on the kinetics of the charge transfer reaction at a LiMn 2 O 4 thin film electrode/aqueous solution (1 mol dm −3 LiNO 3 ) interface. The zeta potential of LiMn 2 O 4 particles showed a negative value in 1 × 10 −2 mol dm −3 LiNO 3 aqueous solution, while it was measured as positive in the presence of 1 × 10 −2 mol dm −3 Cu(NO 3 ) 2 in the solution. The presence of copper (II) ions in the solution increased the charge transfer resistance, and CV measurement revealed that the lithium insertion/extraction reaction was retarded by the presence of small amount of copper (II) ions. The activation energy for the charge transfer reaction in the solution with Cu(NO 3 ) 2 was estimated to be 35 kJ mol −1 , which was ca. 10 kJ mol −1 larger than that observed in the solution without Cu(NO 3 ) 2 . These results suggest that the interaction between the lithium ion and electrode surface is a factor in the kinetics of charge transfer reaction.

The molybdenum cluster compounds, LiYMo3O8 and Mn2Mo3O8 are prepared by the carbothermal reduction method and characterized by various techniques. The FT-IR at ambient temperature (RT), and Raman spectra at various temperatures (78–450 K) are reported for the first time and results are interpreted. Magnetic studies on Mn2Mo3O8 in the temperature range, 10–350 K confirm that it is ferrimagnetic, with TC = 39 K. Magnetic hysteresis and magnetization data at various fields and temperatures are presented. The Li-cyclability is investigated by galvanostatic cycling in the voltage range, 0.005–3.0 V vs. Li at 30 mA/g (0.08 C). LiYMo3O8 shows a total first-discharge capacity of 305 ±5 mAh/g whereas the first-charge capacity is only 180 mAh/g at RT. However, both values increased systematically with an increase in the cycle number and yielded a reversible capacity of 385 ±5 mAh/g at the end of 120th cycle. At 50 °C, the reversible capacity is 418 ±5 mAh/g at the 60th cycle. The coulombic efficiency ranges from 94% to 98%. The Li-cyclability behavior of Mn2Mo3O8 is entirely different from that of LiYMo3O8. The total first-discharge and charge capacities are 710 ± 5 and 565 ±5 mAh/g, but drastic capacity-fading occurs during cycling. The reversible capacity at the end of 50th cycle is only 205 ±5 mAh/g. Plausible reaction mechanisms are proposed and discussed based on the galavanostatic cycling, cyclic voltammetry, ex situ XRD, ex situ TEM and impedance spectral data.

The electrodeposition of Cu(In,Ga)Se 2 has been investigated by cyclic voltammetry (CV) in a DMF-aqueous solution that contained citrate as a complexing agent. The effects of the citrate ion on the reduction potentials of Cu 2+ , In 3+ , Ga 3+ and H 2 SeO 3 were examined for a unitary system. Furthermore, a cyclic voltammetry study was performed in a ternary Cu–In–Se system, a quaternary Cu–In–Ga–Se system, and binary Cu–Se, In–Se and Ga–Se systems. The insertion of In and Ga into the solid phase may proceed by an underpotential deposition mechanism, which involves two different routes: In 3+ and Ga 3+ reduction by a surface-induced effect from Cu 3 Se 2 and/or reaction with H 2 Se.

Uniform crystalline MgSn(OH) 6 nanocubes were synthesized by a hydrothermal method. The influences of reaction conditions were investigated and the results showed that the solvent constituents significantly affected the shape and size of MgSn(OH) 6 ·SnO 2 /Mg 2 SnO 4 has been obtained by thermal treatment at 850 °C for 8 h under a nitrogen atmosphere using MgSn(OH) 6 as the precursor. The electrochemical tests of SnO 2 /Mg 2 SnO 4 revealed that SnO 2 /Mg 2 SnO 4 has a higher capacity and better cyclability compared to pure SnO 2 or Mg 2 SnO 4 . The electrochemical performance of SnO 2 /Mg 2 SnO 4 was sensitive to the size of the nanoparticles. The lithium-driven structural and morphological changes of the electrode after cycling were also studied by the ex-situ XRD pattern and TEM tests. This work indicates that SnO 2 /Mg 2 SnO 4 is a promising anode material candidate for application in Li-ion batteries.

Bi2Te3-7Sey thin films were grown on Au(1 1 1) substrates using an electrochemical co-deposition method at 25 degrees C. The appropriate co-deposition potentials based on the underpotential deposition (upd) potentials of Bi, Te and Se have been determined by the cyclic voltammetric studies. The films were grown from an electrolyte of 2.5 mM Bi(NO3)(3), 2 mM TeO2, and 0.3 mM SeO2 in 0.1 M HNO3 at a potential of -0.02 V vs. Ag/AgCl (3 M NaCl). X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) were employed to characterize the thin films. XRD and EDS results revealed that the films are single phase with approximate composition of Bi2Te2.7Se0.3. SEM studies showed that the films are homogeneous and have micronsized granular crystallites. (C) 2008 Elsevier Ltd. All rights reserved.

Lanthanum-doped LiCoO2 composite cathode materials, containing 0.1–10 mol% of La were synthesized by citric acid aided combustion technique. Thermal analyses showed that the sharp decomposition reaction for pristine LiCoO2 became sluggish upon addition of lanthanum. X-ray diffraction analyses of the composites revealed existence of minute quantities of lanthanum-rich perovskite phases—rhombohedral LaCoO3 ( R 3 ¯ ) and tetragonal La2Li0.5Co0.5O4 (14/mmm), along with rhombohedral LiCoO2 ( R 3 ¯ m ) . Electron microscopy showed a distinct grain growth with increasing La content. An increase of about two orders of magnitude in the electrical conductivity (1.09 × 10−3 S cm−1) was observed for 1.0 mol% La-doped LiCoO2. An excellent cycling performance with capacity retention by a factor of ∼10 in comparison to the pristine LiCoO2 was observed for the composite cathode containing 5.0 mol% La, when 2032 type coin cells were cycled at 5C rate. This has been ascribed to the structural stability induced by La doping and presence of the ion-conducting phase La2Li0.5Co0.5O4 which acts as a solid electrolyte for Li+ ions. A negligible growth of impedance upon repeated cycling has been observed. Cyclic voltammetry showed a remarkable improvement in reversibility and stability of the La-doped electrodes. These composite cathodes might be very useful for high rate power applications.

The changes of Li + /vacancy arrangement in Li 2+ x Ti 3 O 7 with a ramsdellite-type structure upon topo-electrochemical Li + insertion were investigated by the entropy measurement of reaction combined with the Monte Carlo simulation. The experimental entropy measurement was conducted by potentiometric and calorimetrical methods. The obtained experimental data were in good accordance with simulated results. The results indicated that the ordered Li + /vacancy arrangement appeared at the compositions of x ∼ 0.45 and ∼1.20, where the observed entropy of reaction humped. The ordering of Li/vacancy were also indicated at the composition x ∼ 0.24 and 1.16 in Li 2+ x Ti 3 O 7 by the Monte Carlo simulation which considers the most stable Li/vacancy arrangement in terms of Coulombic interaction. This substantial agreement between electrochemical behaviors and computational results confirmed that the formation of superstructure arising from Li/vacancy arrangement during the electrochemical reaction deeply related to the atomic level Coulombic interactions.