Search

A hydrophobic CO 2 physisorbent Most materials for carbon dioxide (CO 2 ) capture of fossil fuel combustion, such as amines, rely on strong chemisorption interactions that are highly selective but can incur a large energy penalty to release CO 2 . Lin et al . show that a zinc-based metal organic framework material can physisorb CO 2 and incurs a lower regeneration penalty. Its binding site at the center of the pores precludes the formation of hydrogen-bonding networks between water molecules. This durable material can preferentially adsorb CO2 at 40% relative humidity and maintains its performance under flue gas conditions of 150°C. —PDS

We report on the synthesis of amphiphilic polymers with a composition shift of the hydrophobic block made by emulsion polymerization that is used as a water-based binder for LiFePO4 cathodes. The integrity of the electrode is sustained by using a unique chemical procedure for cross-linking the binder. This technique yields higher adhesion of the binder on aluminium collectors comparing with the state-of-the-art binders. Amphiphilic polymers are excellent for well-dispersed inorganic particles, and consequently demonstrate satisfactory electrochemical performances.

Concrete is the most widely used man-made material in the world. The production process of cement, a key component of concrete, contributes significantly to CO2 emissions. Every year, over 4 billion tonnes of cement are produced, releasing approximately 7%-8% of global CO2 emissions [1]. Cement flue gas, processes and raw materials, contain around 16% CO2 and 7-10% O2 and NOX /SOX (100-300 ppm), contingent on the fuel type. High amounts of NOX/SOX are a significant challenge for any carbon capture system. The presence of high O2 concentration in the emitted gas stream can chemically degrade typical amines via production of amides or other oxide derivatives. Therefore, it is crucial to conduct preliminary studies at a pilot scale using real cement flue gas conditions to develop a viable technology and accurate techno-economic analysis for large plants (1 million+ tonnes of captured CO2 per year). Svante (formerly Inventys) has a strong patent portfolio on Rapid Cycle Temperature Swing Adsorption (RC-TSA) processes using structured adsorbents, steam-assisted direct regeneration with fast kinetics (< 1.5 mins cycle time) as an alternative to traditional liquid amine technologies. This project utilized scaled up CALF-20 sorbent, one of the first Metal Organic Frameworks (MOFs) used in an industrial CO2 capture project. This MOF is robust with regards to steam, O2 and acidic contaminant gases (such a NOX/SOX) which make it an ideal candidate for the cement CO2 capture application. This article discusses efforts to scale up the CALF-20 MOF sorbent from lab scale to ton scale. A review of CALF-20 performance after 2300 hrs of VeloxoTherm™ capture process results on a boiler flue gas doped with CO2 and Air to simulate Cement kiln flue gas at 0.1 TPD capacity is presented. Also included are results from Phase 1 of the cement project related to NOX/SOX stability tests on CALF-20 sorbent.

Li metal batteries suffer from dendrite formation which causes short circuit of the battery. Therefore, it is important to understand the chemical composition and growth mechanism of dendrites that limit battery efficiency and cycle life. In this study, in situ scanning electron microscopy was employed to monitor the cycling behavior of all-solid Li metal batteries with LiFePO4 cathodes. Chemical analyses of the dendrites were conducted using a windowless energy dispersive spectroscopy detector, which showed that the dendrites are not metallic lithium as universally recognized. Our results revealed the carbide nature of the dendrites with a hollow morphology and hardness greater than that of pure lithium. These carbide-based dendrites were able to perforate through the polymer, which was confirmed by milling the polymer using focused ion beam. It was also shown that applying pressure on the battery can suppress growth of the dendrites.

Lithium titanium oxide (Li4Ti5O12)-based electrodes are very promising for long-life cycle batteries. However, the surface reactivity of Li4Ti5O12 in organic electrolytes leading to gas evolution is still a problem that may cause expansion of pouch cells. In this study, we report the use of Schiff base (1,8-diazabicyclo[5.4.0]undec-7-ene) as an additive that prevents gas evolution during cell aging by a new mechanism involving the solid electrolyte interface on the anode surface. The in situ ring opening polymerization of cyclic carbonates occurs during the first cycles to decrease gas evolution by 9.7 vol % without increasing the internal resistance of the battery.

A technique to characterize the native passivation layer (NPL) on pure lithium metal foils in a scanning electron microscope (SEM) is described in this paper. Lithium is a very reactive metal, and consequently, observing and quantifying its properties in a SEM is often compromised by rapid oxidation. In this work, a pure lithium energy-dispersive x-ray spectrum is obtained for the first time in a high vacuum SEM using a cold stage/cold trap with liquid nitrogen reservoir outside the SEM chamber. A nanomanipulator (OmniProbe 400) inside the microscope combined with x-ray microanalysis and windowless energy dispersive spectrometer is used to fully characterize the NPL of lithium metal and some of its alloys by a mechanical removal procedure. The results show that the native films of pure lithium and its alloys are composed of a thin (25 nm) outer layer that is carbon-rich and an inner layer containing a significant amount of oxygen. Differences in thickness between laminated and extruded samples are observed and vary depending on the alloy composition.

We report a new sol-gel approach of synthesis of LiFePO 4 (LFP) thin film and its application as cathode materials for transparent Li-ion battery in half-cell configuration. LFP thin films were obtained from an alcoholic colloidal suspension of iron acetylacetonate (Fe(AcAc) 3 ) and aqueous lithium dihydrogen phosphate (LiH 2 PO 4 ) deposited on fluorine tin oxide (FTO) glass substrate, followed by heating at 450 °C under nitrogen gas for 1 h. X-ray diffraction (XRD) confirmed that the LFP films have an orthorhombic crystal system with space group Pnma (62). Scanning electron microscopy (SEM) shows spherical LFP nanoparticles aggregates homogenously deposited all over the surface of FTO substrate containing 3-D open pores. The electrochemical behaviors of thin film vs Li/Li + cell were investigated by cyclic voltammetry and galvanostatic charge-discharge measurements. The cycle life was evaluated by running 1000 cycles of charge-discharge at a current density of 20 μA/cm 2 . The transmission spectra reveal 85–90% of transparency versus FTO as reference, which makes it a potential candidate as a complementary electrode in electrochromic devices (ECDs).

Lithium titanates were synthesized from solid reagents injected into a radiofrequency inductive thermal plasma in a continuous tubular reactor. Various types of nanomorphologies were synthetized, including nanoparticles, nanowires and nanoplatelets. Their formation mechanism was investigated by varying the reagents chemical ratio, the nature of the plasma gases and the inclusion of an autocatalytic effect induced by solid seed materials. Scanning Electron Microscopy (SEM), electrical conductivity measurements, nitrogen surface absorption (BET) and X-ray diffraction (XRD) combined with a Rietveld refinement were used to quantify the phase composition and to characterize the materials. The yield in nanowires and nanoplatelets was observed to be qualitatively increased by a reducing plasma sheath gas composition containing hydrogen. Moreover, reducing plasma conditions correlated with drastically faster treatment to achieve improved electrical conductivity. It was also shown that the addition of solid nanosized seed material in the reagents significantly improved the yield of the desired phase following what is expected to be an incomplete atomization of its molecular bonds. Thermodynamic calculations are presented to support the reaction conditions and mechanisms observed.

In this paper, we report the synthesis of cross-linked copolymers of glycidyl methacrylate (GMA) and poly (ethylene glycol) methyl methacrylate (PEGMA) for use as solid polymer electrolytes (SPE). The cross-linking is performed with volatile ethylene diamine, thus preventing the accumulation of undesirable precursors in the final membrane. The structure of the cross-linked polymer electrolyte was investigated by 13C solid NMR and its physical properties were examined by DSC, TGA and stress-strain tests. The ionic conductivities were determined by AC Impedance, which showed that the SPEs have good conductivities (10−5 Scm−1) at 80 °C. The highest capacity measured with these polymers was 151 mAh g−1 at C/6 and 80 °C for a LFP/SPE/Lithium battery. The retention capacity is high, at 97% after 80 cycles at different rates of cycling. The Young's modulus of the membranes is as high as 1 GPa. The SEM images showed no evidence of lithium dendrites and no degradation after cycling. Therefore, the polymer is a good candidate for battery operation over a long time. Especially important is the ability of this polymer to prevent growth of dendrites on the Li-metal electrode.

This work focuses on the stability of hybrid electrochromic displays that use only one electrochromic film, an industrial solid polymer electrolyte and a metallic counter electrode. The lifetime of these devices exceeds 200,000 cycles in tests with three different voltage ranges. Traces of metal deposits were found during cycling, which indicates that the metallic counter electrode combines the functions of current collector and counter electrode.

Crystalline lithium disulfide (Li2S2) is identified, for the first time, as a transient species in the lithium-sulfur cell, by using an operando X-ray diffraction (XRD) technique. The observed XRD pattern precisely matches with the predicted pattern based on the density function theory. The formation of Li2S2 crystals is repetitively found in the highly concentrated (7 M Li+) electrolyte at high voltage region (>2 V) near the end of the first charge cycle and before the end of the second discharge cycle. These conditions indicate that crystalline Li2S2 exists in the non-equilibrium regime. The formation of crystalline Li2S2 under only the specified conditions suggests that it is not formed as an intermediate discharge product, contrary to what is generally believed, but as a transient species by the disproportionation reaction from higher order polysulfides which is facilitated by the “solvent-in-salt” conditions.

Lithium/solid polymer electrolyte (SPE)/sulfur cells were studied in operando by two techniques: Scanning Electron Microscope (SEM) and ultraviolet–visible absorption spectroscopy (UV–vis). During the operation of the cell, extensive polysulfide dissolution in the solid polymer electrolyte (cross-linked polyethylene oxide) leads to the formation of a catholyte. A clear micrograph of the thick passivation layer on the sulfur-rich anode and the decreased SPE thickness by cycling confirmed the failure mechanism; the capacity decays by reducing the amount of active material, and by contributing to a charge inhibiting mechanism called polysulfide shuttle. The formation of elemental sulfur is clearly visible in real time during the charge process beyond 2.3 V. The non-destructive in operando UV–vis study also shows the presence of characteristic absorption peaks evolving with cycling, demonstrating the accumulation of various polysulfide species, and the predominant formation of S42− and of S62− during discharge and charge, respectively. This finding implies that the charge and discharge reactions are not completely reversible and proceed along different pathways.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) using a focused ion-beam scanning electron microscope (FIB-SEM) is a promising and economical technique for lithium detection and quantification in battery materials because it overcomes the limitations with detecting low Li content by energy dispersive spectroscopy (EDS). In this work, an experimental calibration curve was produced, which to our best knowledge allowed for the first time, the quantification of lithium in standard nickel manganese cobalt oxide (NMC-532) cathodes using 20 nm resolution. The technique overcomes matrix effects and edges effects that makes quantification complex. This work shows the high potential of TOF-SIMS tool for analytical characterization of battery materials, and demonstrates its tremendous capabilities towards identification of various chemical or electrochemical phenomena in the cathodes via high-resolution ion distributions. Various phenomena in the ion distributions are also assessed, such as edge effects or measurement artifacts from real signal variations.

In this work, we demonstrate that a new mechanical attrition process can be used to prepare nanosilicon powder from metallurgical grade silicon lumps. Composite Li-ion anode made from this nanometer-size powder was found to have a high reversible capacity of 2400 mAh g −1 and an improved cycling stability compared to micrometer-sized powder. It is proposed that improved battery cycling performance is ascribed to the nanoscale silicon particles which supresses the volume expansion owing to its superplasticity.

We report results obtained with lithium 4,5-dicyano-2-(trifluoromethyl) imidazolide (LiTDI), which we believe is a promising lithium salt for electrolytes in lithium-ion batteries. This “Huckel”- type salt has high charge delocalizations which contribute to good lithium-ion dissociation. In addition, it has high thermal stability and safer degradation products compared to LiPF 6 , which were identified by TGA-MS. It also does not corrode but passivate the aluminum current collector. Cyclic voltammetry measurements showed a stability up to 4.5 V, which is sufficient for use with standard cathode materials. The power capability of half cells containing LiTDI in EC/DEC was evaluated with standard cathodes used in lithium-ion batteries: LFP, NMC, LCO and LMO. Two LiTDI concentrations were investigated: 1 M and 0.6 M and compared with a reference electrolyte: 1 M LiPF 6 . In spite of a slightly lower conductivity than the LiPF 6 , LiTDI (1 M and 0.6 M) shows similar power capability up to 2C with LFP (84% of specific capacity recovered), 10C with NMC (61% of specific capacity recovered), and up to 20C for LMO (88% of specific capacity recovered). Furthermore, better power capability was obtained with 0.6 M LiTDI with LCO, which yielded 82% of specific capacity recovered at 1C (67% for 1 M LiTDI and 1 M LiPF 6 ).

The thermal behavior of three cathode materials for the lithium/sulfur (Li/S) cell, namely – sulfur, sulfur-LiFePO 4 (S-LFP) composite and sulfur-LiV 3 O 8 (S-LVO) composite was studied using Isothermal Micro-Calorimetry (IMC) at various discharge rates. A continuum model was used to calculate the reversible entropic heat and irreversible resistive heat generated over the discharge process and the model data was compared to the experimental data to elucidate contributions of reversible and irreversible heats to the overall heat generated during discharge. The reaction enthalpy (ΔH Rx ) was measured using IMC for each elementary reaction step and in combination with the calculated reversible entropic heat and irreversible resistive heat was fitted against the experimental total heat measurement. The model showed an excellent fit against the experimental data. Further, Accelerating Rate Calorimetry (ARC) was used to study the thermal safety of these three cells. The cell with the S-LVO composite cathode was found to have the highest onset temperature for thermal runaway and also the lowest maximum self-heat rate. Results of this study suggest that S-LVO composite is a promising electrode for Li/S cells.

In this paper we report on the synthesis of comb-like copolymers as solid polymer electrolytes (SPE). The synthesis involved anionic polymerization of styrene (St) and 4-vinylanisole (VA) as the followed by grafting of poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) by Atom Transfer Radical Polymerization (ATRP). The comb-like copolymer's structure was analyzed by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The membranes were made by solvent casting and the morphologies were analyzed by atomic forces microscopy (AFM) and scanning electron microscopy (SEM). We observed that a nano and micro phase separation occurs which improves ionic conductivity. The ionic conductivities were determined by AC Impedance, which showed that the SPEs have good conductivities (10−5 Scm−1) at room temperature owing to the negligible values (

Lithium titanium oxide (Li

One of the main challenges in improving fast charging lithium-ion batteries is the development of suitable active materials for cathodes and anodes. Many materials suffer from unacceptable structural changes under high currents and/or low intrinsic conductivities. Experimental measurements are required to optimize these properties, but few techniques are able to spatially resolve ionic transport properties at small length scales. Here we demonstrate an atomic force microscope (AFM)-based technique to measure local ionic transport on LiFePO4 to correlate with the structural and compositional analysis of the same region. By comparing the measured values with density functional theory (DFT) calculations, we demonstrate that Coulomb interactions between ions give rise to a collective activation energy for ionic transport that is dominated by large phase boundary hopping barriers. We successfully measure both the collective activation energy and the smaller single-ion bulk hopping barrier and obtain excellent ...

The effects of moisture contamination in the Li-O2 battery system were investigated by comparing the electrochemical performance and post-mortem analysis of batteries prepared under different atmospheres: sealed container in an ambient atmosphere vs. sealed container in a dry-room or in a glove-box. The performance of the cells strongly depended on the atmosphere; furthermore it was found that the performance degradation of the Li metal anode comes from moisture contamination from the feed lines. In an ambient atmosphere, the cells showed higher 1st discharge capacity, higher impedance and significant increase of the cell weight owing to contamination of the oxygen by moisture. Post-mortem analysis revealed that the deterioration of lithium metal anode leads to the cell failure mechanism, and this comes from the moisture contamination. It was found that the performance of Li-O2 batteries is very sensitive to even traces of moisture contamination and every single part of the cell design including the choice of fitting parts and water permeability of the fitting material should be verified in order to obtain credible and reproducible results. This finding supports the idea that protection of the lithium metal electrode is indispensable to realize the practical application of Li-O2 or Li-air batteries.

C-LiFePO 4 positive electrode materials were prepared by hydrothermal synthesis in which the solution was stirred with a rotation frequency varying from 50 to 1150 revolutions per minute (rpm), before carbon coating. The different synthesized cathode materials are discussed and compared in terms of structural, surface-morphological and electrochemical properties. The best C-LiFePO 4 electrodes have been obtained using rotation frequencies in the range 280–360 rpm, in which case the capacity retention reaches ∼137 mAh g −1 at coulombic efficiency >99% at C/12, against 106 mAh g −1 in the absence of agitation. Better cycling stability at high current rates (1C) were also obtained. The improved performance of the C-LiFePO 4 material obtained by controlled rotating agitation-hydrothermal solution synthesis is attributed to the production of less aggregated particles with high surface area and smaller concentrations of impurities. The controlled rotating agitation of the solution during the synthesis provides a scalable and eco-friendly way of producing better performing electrode particles for use in Li-ion batteries.

Silica fume, which is a by-product of metallurgical-grade silicon production, is a low cost material with high SiO2 concentration and small particle size (

MnO2 nanowires were used to synthesize the spinel-type LiMn1.45Ni0.45Cr0.1O4 (Cr–LMN) materials by solid-state impregnation. Structural analyses revealed that the final product consisted of sub-micrometric Cr–LMN particles of octahedral shape well-crystallized in the cation-disordered phase. This powder delivered a specific capacity ~127 mAh g−1 up to 2C rate. At 5C rate, the capacity was still 115 mAh g−1 without significant capacity loss in 25 cycles. The remarkable improvement in electrochemical properties with respect to prior works suggests that the sub-micrometric Cr–LMN prepared by this synthesis process is a promising cathode material for high power and long-cycle lithium-ion batteries. Keywords: Li-ion batteries, 5-V electrode material, Impregnation method, Nanowires

In addition of the poor intrinsic conductivity of LiFePO4 particle, surface effects become increasingly important, and can eventually dominate the physical and the chemical properties when the size decreases below 100 nm. Carbon coating appeared to overcome the drawback of highly resistive LiFePO4 powders and to cure the disordered surface layer that reduces the electrochemical performance of non-coated sample. Here, we analyze the effect of the carbon coating on the LiFePO4 particles that meets a worldwide success as a positive electrode for commercial Li-ion batteries.

In situ and ex situ scanning electron microscopy of nano Si and SiO anode particles was carried out during the first cycles, and at various stages of charge. The particle size effects were explored in the range 0.1-20 μm, providing a new insight into the micro-structural evolution of the particles as a function of their size, and into the 'mechanical' resistance upon important volume change upon phase transformation of these anodes. For small particles, the failure of the battery comes from an electrochemical sintering that compacts the whole electrode, which results in its cracking. The particles keep their integrity when the discharge is stopped at a voltage 0.1V, which corresponds to the chemical composition Li12Si7, while the particles are known to crack at deeper discharge up to Li22Si5. Replacing the Si particles by SiO particles in an attempt to avoid these structural effects did not help, because of the different chemical reactions during cycling, with the loss of oxygen. Upon deeper discharge, the particles of size d

The robustness of conductive networks and the accessibility of electrolyte into the network are important factors in designing the cathode electrode for lithium/sulfur (Li/S) batteries containing liquid electrolytes that involve liquid phase electrochemical reactions. We show that the performance of Li/S cells can be significantly improved by simply optimizing the electrode processing conditions to have open pore structures and mechanical integrity of the electrode architecture. It is demonstrated that the capacity of 1000 mAh g −1 at 0.1 C and the stable capacity retention of >700 mAh g −1 after 200 cycles at 0.5 C can be achieved with relatively high sulfur content of 68%. 417 Wh kg −1 in specific energy and 623 Wh l −1 in energy density are achievable with this new technology.

LiFePO4(LFP)-coated sulfur (S-LFP) particles were synthesized using a dry mechano-fusion method and electrochemically tested in a liquid electrolyte. This synthesis process (encapsulation) is completed in a few minutes without a solvent drying step, thus it is easily scalable for volume production. The S-LFP cathode showed an initial capacity of 1200 mAh/g at 0.1 C, and 80% capacity retention after 90 cycles at 0.5 C. 417 Wh/kg in specific energy and 623 Wh/l in energy density are achievable with this new technology. The results suggest that the LFP layer enhances the utilization of active sulfur and lowers the polarization for oxidation of Li2S2/Li2S. Keywords: Lithium/sulfur battery, Core–shell composite, LiFePO4, Mechano-fusion, Encapsulation

We report the structure and morphology of the solid-solution series LiMnyFe1EyPO4 isomorphous with olivine synthesized by the hydrothermal route. Experimental studies include combined characterizations such as XRD, FTIR, SEM and HRTEM. Carbon-coated nanoparticles were prepared by the lactose route, which quality was investigated by Raman spectroscopy.

A new post-annealing treatment at ca. 600 °C was used to modify the oxygen deficiency during the synthesis of the spinel LiMn1.45Cr0.1Ni0.45O4 cathode for Li-ion batteries. It is an effective way to eliminate the impurity phase without changing the crystal chemistry. Small amount of substituting Cr leads to better rate performance and cyclability at room temperature, compared to commercial LiMn1.5Ni0.5O4. LiMn1.45Cr0.1Ni0.45O4 delivered a reversible capacity of 104 mAh g-1 at 1C rate. After 125 cycles, about 99% of reversible capacity was retained for the LiMn1.45Cr0.1Ni0.45O4 in contrast with 6% capacity loss for the commercial LiMn1.5Ni0.5O4. Electrochemical impedance spectroscopy measurements revealed that the LiMn1.45Cr0.1Ni0.45O4 had a smaller surface resistance, which may be due to the segregation of Ni from the surface to the bulk.

Recently, intensive efforts are dedicated to convert and store the solar energy in a single device. Herein, dye-synthesized solar cell technology is combined with lithium-ion materials to investigate light-assisted battery charging. In particular we report the direct photo-oxidation of lithium iron phosphate nanocrystals in the presence of a dye as a hybrid photo-cathode in a two-electrode system, with lithium metal as anode and lithium hexafluorophosphate in carbonate-based electrolyte; a configuration corresponding to lithium ion battery charging. Dye-sensitization generates electron–hole pairs with the holes aiding the delithiation of lithium iron phosphate at the cathode and electrons utilized in the formation of a solid electrolyte interface at the anode via oxygen reduction. Lithium iron phosphate acts effectively as a reversible redox agent for the regeneration of the dye. Our findings provide possibilities in advancing the design principles for photo-rechargeable lithium ion batteries., Photo-rechargable energy storage cells can provide plug-free power for various applications. Here the authors integrate a photo-absorbing dye complex with LiFePO4 nanocrystals as a lithium-ion battery cathode in a two-electrode system demonstrating its photo-charging and galvanostatic discharging.

The cyclability of Li ion transfer in Li-ion rechargeable batteries depends mainly on the dimensional stability of the host material during insertion and deinsertion of Li+. Recently, it was found that redox reactions of non stoichiometric or doped LiMyMn2−yO4 (M=Li, Co, Cr, Ni, Al, etc.) spinels are much better than that of the pure LiMn2O4 ceramics, which exhibit a slight capacity fading. These materials have been investigated to improve the cycling performance of LiMn2O4, showing a tetragonal distortion induced by the excess of Mn Jahn–Teller ions in deeply discharged electrode. However, all the reported doping methods have led to a decreased specific charge compared to the undoped LiMn2O4 materials so far. The search of high-voltage material electrodes has been focused on two categories: the inverse spinels, e.g., LiMVO4, and the normal spinels, LiMyMn2−yO4. Recent investigations have shown that, among the Ni-substituted LiMn2O4 spinels, the composition LiNi0.5Mn1.5O4 possesses specific electrochemical characteristics such as a high capacity of 130–140 mAh/g associated with a highvoltage plateau in the 5-V range Gao et al. [1] investigated the origin of the voltage profile for LiNiyMn2−yO4. For the same system, Zhong et al. [2] showed the effects of the synthesis route (sol-gel vs. solid state) on some structural and electrochemical properties. The almost flat voltage profile was confirmed by Ohzuku et al. [3]. All these works only reported on structural and electrochemical information, Also the cycle life was find very poor due the instability of the electrolyte at high voltage (5V). The olivine coated spinel (5V) was not reported before. The stability of the electrolyte is one the most important key for cycling the cell at high voltage. The aim of this communication is the growth and characterization of the LMN : LiNi0.5Mn1.5O4 (spinel) materials prepared by different techniques. Because the standard electrolyte is very stable in contact with olivine, we applied the olivine coated spinel 5 V system for high energy lithium batteries. Figure 1 shows the voltage profile of LiFePO4 (LFP) coated LMN, the LFP show a voltage activity at 3.5 V and the spinel material at 4. 7 V. The capacity with non coated is 103 mAh/g , the first coulombic efficiency (1 CE) is 67 %, for the LFP coated LMN, the capacity is 120 mAh/g and the 1 CE is 76 %. The olivine coating increases the reversible capacity and also the 1 CE %. Figure 2 shows the comparison of the rate performances of uncoated and LFP coated spinel. The LFP coated spinel increases the capacity at high rate. The high power performance was improved with LFP-coated LMN. For the safety of point of view, the DSC peaks (not shown) is shifted to high temperature side by olivine coating spinel. LFP coating has more shifted than LiMnPO4, LiNiPO4, or LiCoPO4. Thermal stability is improved by LFP coating LMN.

International audience; We report the electrochemical properties of submicron-sized particles of NaFePO4. Two materials have been studied and characterized by XRD, SEM, EDX, EIS and Raman experiments: the maricite phase synthesized by hydrothermal method and the olivine phase obtained from delithiation of LiFePO4. NaFePO4 materials have an electrochemical activity in Na cell using NaPF6-EC-DEC electrolyte, but only in the heterosite phase, and the capacity is reduced already in the second cycle. The two-phase system at intermediate compositions has also been analyzed

Sodium insertion is investigated in sub-micron particles of FePO4 prepared in the olivine structure by chemical delithiation of synthetic LiFePO4 by the bromide route. The electrochemical activity in Na cell is investigated using NaPF6-EC-DEC electrolyte. The structure and composition of the electrode is analyzed as function of the cell potential by means of XRD, SEM and EDX experiments.

In the as-quenched state, 13%Cr–4%Ni martensitic stainless steels are essentially 100% martensitic. However, a certain amount of austenite is formed during the tempering of this alloy. This reformed austenite is thermally stable at room temperature but can transform to martensite under stress. This transformation is known to happen during impact testing but it has never been established if it occurs during fatigue crack propagation. This study presents the results of X-ray diffraction measurements of reformed austenite before and after crack growth testing. It has been found that reformed austenite does transform to martensite at the crack tip and that this transformation occurs even at a low stress intensity factor. Low-cycle fatigue tests were conducted to verify austenite transformation under cyclic straining. It was found that reformed austenite transforms only partially during the first strain reversal but that essentially all austenite has disappeared after 100 cycles. The relation between austenite transformation under low-cycle fatigue and its transformation during crack growth is also discussed.

Zr–2.5Nb pressure tubes used in CANDU (CANada Deuterium Uranium) reactors have a very complex microstructure, with two major crystallographic phases, α and β. These phases include a fair amount of deformation from the extrusion process and the cold working (∼25%) performed at the end of the manufacturing process. This microstructure (texture, grain aspect ratio, etc.) changes along the tube’s length and differs from tube to tube. In order to better understand the deformation mechanisms, these microstructural differences must be statistically characterized. Scanning electron microscopy combined with direct image analysis or with electron backscattered diffraction (EBSD) are good techniques for carrying out such a measurement. However it is not possible, using specimen preparation methods specific for each of these techniques, to reveal all of the grain and phase boundaries. We have thus developed post-treatment algorithms to be able to partially analyze the revealed Zr–2.5Nb microstructure. The first algorithm was used for image analysis treatments of micrographs taken at 5 kV on the radial–tangential plane of etched samples using a reactive ion etch (RIE, CF4 + O2). The second was developed for EBSD grain mapping and can be used to characterize α-Zr grain shape and orientation. The two techniques are complementary: EBSD gives information about the micro-texture and the relationship between the microstructure and micro-texture while image analyses of SEM micrographs reveal the direction and distribution of the α-Zr lamellae more easily and over a greater sample area than EBSD. However, the SEM micrographs that were used did not reveal any grain boundary (only phase boundary). An analysis of EBSD grain maps reveals that the average α-Zr grain size, mainly in the elongated direction (tangential), is smaller than what is normally obtained from an image analysis of SEM micrographs. The grain size distribution of type I α-Zr grains (deformed original (prior) α-Zr) and type II (stress-induced β-Zr → α-Zr phase transformation) is also shown to be different for sizes greater than 0.4 μm2.

Pressure tubes holding the uranium rods of a CANDU (CANada Deuterium Uranium) reactor show deformation with time in service. At a certain point, this deformation becomes too severe and the tubes must be decommissioned. This reduces the reactor’s energy output. It has been observed that the microstructure of the pressure tubes is indicative of creep behavior. This paper presents the image analysis procedure used to characterize the level of anisotropy and the α-phase dimension of the Zr-2.5Nb alloy used in pressure tubes. The techniques used to evaluate experimental error and to correct for sampling bias are also explained.

Based on neutron powder diffraction (NPD) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), we show that calcium ions help eliminate the Fe-antisite defects by controlling the nucleation and evolution of the LiFePO4 particles during their hydrothermal synthesis. This Ca-regulated formation of LiFePO4 particles has an overwhelming impact on the removal of their iron antisite defects during the subsequent carbon-coating step since (i) almost all the Fe-antisite defects aggregate at the surface of the LiFePO4 crystal when the crystals are small enough and (ii) the concomitant increase of the surface area, which further exposes the Fe-antisite defects. Our results not only justify a low-cost, efficient and reliable hydrothermal synthesis method for LiFePO4 but also provide a promising alternative viewpoint on the mechanism controlling the nanosizing of LiFePO4, which leads to improved electrochemical performances. © 2016 American Chemical Society.

Lithium is the key element for the development of battery and new technology and the development of an analytical technique to spatially and quantitatively resolve this element is of key importance. Detection of Li K in pure metallic lithium is now possible in the Scanning Electron Microscope (SEM) with newly designed Energy Dispersive Spectroscopy (EDS). However, this work is clearly showing, for the first time using EDS, the detection of Li K in several binary lithium compounds (LiH, Li

The properties of lithium titanates anodes in Li-ion batteries are highly dependent on their secondary constituents. While their main phase is usually constituted of Li4Ti5O12, significant quantity of lithium titanates compounds of various stoichiometry are often present, due to either the processing, usage or aging of the material. These may go underreported, as many of these spectrums overlap or display low signal in X-ray diffraction (XRD). Samples of nanosized lithium titanates synthetized by inductive plasma were characterized by XRD and scanning electron microscopy (SEM), as they provide a regular yet typical crystallite size and shape including multiple phases. A Rietveld refinement was developed to extract the composition of these samples. Mass balance through further annealing and differential scanning calorimetry (DSC) enthalpy measurements from phase transformations were also used as identification and validation techniques.

Nanostructured lithium metal orthosilicate materials hold a lot of promise as next generation cathodes but their full potential realization is hampered by complex crystal and electrochemical behavior. In this work Li2FeSiO4 crystals are synthesized using organic-assisted precipitation method. By varying the annealing temperature different structures are obtained, namely the monoclinic phase at 400°C, the orthorhombic phase at 900°C and a mixed phase at 700°C. The three Li2FeSiO4 crystal phases exhibit totally different charge/discharge profiles upon delithiation/lithiation. Thus the 400°C monoclinic nanocrystals exhibit initially one Li extraction via typical solid solution reaction, while the 900°C orthorhombic crystals are characterized by unacceptably high cell polarization. In the meantime the mixed phase Li2FeSiO4 crystals reveal a mixed cycling profile. We have found that the monoclinic nanocrystals undergo phase transition to orthorhombic structure resulting in significant progressive deterioration of the material's Li storage capability. By contrast, we discovered when the monoclinic nanocrystals are cycled initially at higher rate (C/20) and subsequently subjected to low rate (C/50) cycling the material's intercalation performance is stabilized. The discovered rate-dependent electrochemically-induced phase transition and stabilization of lithium metal silicate structure provides a novel and potentially rewarding avenue towards the development of high capacity Li-ion cathodes.

Quantitative x-ray analysis of spherical inclusions embedded in a matrix is not possible using the classical ZAF and ϕ(ρ)Z methods based on specimens of homogeneous composition. Gauvin et al. (1992) have demonstrated that Monte Carlo simulations can be used to perform quantitative analysis of spherical inclusions of homogeneous composition. In this paper, this method is extended to obtain an analytical expression to perform such quantification. Also, Monte Carlo simulations are used to simulate x-ray and electron backscattering images of spherical inclusions in order to improve our understanding of contrast mechanism.

The performance of the energy dispersive spectrometer (EDS) detectors has to be established in its original state and monitored periodically to ensure the stability and long-term performance of the system. Because EDS detectors are cooled by liquid nitrogen and because the environment is not an ultra-high vacuum, ice and contaminants will buld up in front of the detector crystal, decreasing the detection efficiency at low energy. Few performance tests are suitable for the specifics problems found at low energy. The proposed test is based on a new procedure for the modelling of the decrease of detection efficiency (DODE) with time (Hovington et al. 1993). It was found that the deposition rate of both ice and carbon increased significantly when porous uncoated samples were observed. Significant difference between spectra acquired immediately after different conditioning was also found. The proposed procedure can be used to determine the optimum time before a conditioning cycle, to detect an abnormal accumulation of contaminant both in front of the detector and at the sample surface, and to diagnose a broken window and a malfunction in the conditioning apparatus.

This paper is a guide to the ANSI standard C code of CASINO program which is a single scattering Monte CArlo SImulation of electroN trajectory in sOlid specially designed for low-beam interaction in a bulk and thin foil. CASINO can be used either on a DOS-based PC or on a UNIX-based workstation. This program uses tabulated Mott elastic cross sections and experimentally determined stopping powers. Function pointers are used for the most essential routine so that different physical models can easily be implemented. CASINO can be used to generate all of the recorded signals (x-rays, secondary, and backscattered) in a scanning electron microscope either as a point analysis, as a linescan, or as an image format, for all the accelerated voltages (0.1–30 kV). As an example of application, it was found that a 20 nm Guinier-Preston Mg2Si in a light aluminum matrix can, theoretically, be imaged with a microchannel backscattered detector at 5 keV with a beam spot size of 5 nm.