Search

International audience; This work reports on the synthesis of hard carbon spheres (HCS) and the impact of the pyrolysis temperature (1500 to 1900 °C) on the properties of HC and its relationship with the electrochemical performance in potassium-ion batteries (KIBs). Comparison with commercial graphite performance is provided as well. Spherical morphology, disordered structure, and low surface area were obtained for the HCSs. Most properties (interlayer space, active surface area, and oxygen-based functional groups) were found to decrease with increasing pyrolysis temperature, except for the helium density and closed porosity, which increase. However, graphite presents a flake-like morphology with a larger particle size, a higher helium density, an ordered structure with a smaller interlayer distance, and no closed pores. Electrochemical tests in a half-cell vs K+/K showed that HCSs perform better than graphite with higher initial Coulombic efficiency (ICE) and better specific capacities. The HCSs pyrolyzed at 1500 and 1700 °C exhibit the best initial Coulombic efficiency, ICEs of 54 and 62%, and specific capacities of 254 and 247 mAh g–1 (C/20, 11.5 mA g–1), respectively. The ICE is affected by multiple surface and bulk parameters but also by electrolyte formulation (67% for 0.8 M KFSI vs 62% for 0.8 M KPF6). The capacity is governed by diffusive phenomena, and a larger interlayer graphitic spacing and defects favor a better insertion of K ions. Closed pores did not lead to an improvement in capacity. Furthermore, HCSs exhibit significantly better capacity retention (97%) than graphite (84%), especially when cycled at high current rates (up to 10C depotassiation rate).

To increase the energy density of lithium-ion batteries (LIBs), high-capacity anodes which alloy with Li ions at a low voltage against Li/Li+ have been actively pursued. So far, Si has been studied the most extensively because of its high specific capacity and cost efficiency; however, Ge is an interesting alternative. While the theoretical specific capacity of Ge (1600 mAh g-1) is only half that of Si, its density is more than twice as high (Ge, 5.3 g cm-3; Si, 2.33 g cm-3), and therefore the charge stored per volume is better than that of Si. In addition, Ge has a 400 times higher ionic diffusivity and 4 orders of magnitude higher electronic conductivity compared to Si. However, similarly to Si, Ge needs to be structured in order to manage stresses induced during lithiation and many reports have achieved sufficient areal loadings to be commercially viable. In this work, spinodal decomposition is used to make secondary particles of about 2 μm in diameter that consist of a mixture of ∼30 nm Ge nanoparticles embedded in a carbon matrix. The secondary structure of these germanium-carbon particles allows for specific capacities of over 1100 mAh g-1 and a capacity retention of 91.8% after 100 cycles. Finally, high packing densities of ∼1.67 g cm-3 are achieved in blended electrodes by creating a bimodal size distribution with natural graphite.

Metal–organic frameworks (MOFs) have found a potential application in various domains such as gas storage/separation, drug delivery, catalysis, etc. Recently, they have found considerable attention for energy storage applications such as Li- and Na-ion batteries. However, the development of MOFs is plagued by their limited energy density that arises from high molecular weight and low volumetric density. The choice of ligand plays a crucial role in determining the performance of the MOFs. Here, we report a nickel-based one-dimensional metal-organic framework, NiC4H2O4, built from bidentate fumarate ligands for anode application in Li-ion batteries. The material was obtained by a simple chimie douce precipitation method using nickel acetate and fumaric acid. Moreover, a composite material of the MOF with reduced graphene oxide (rGO) was prepared to enhance the lithium storage performance as the rGO can enhance the electronic conductivity. Electrochemical lithium storage in the framework and the effect of rGO on the performance have been investigated by cyclic voltammetry, galvanostatic charge–discharge measurements, and EIS studies. The pristine nickel formate encounters serious capacity fading while the rGO composite offers good cycling stability with high reversible capacities of over 800 mAh g−1.

Various high and medium entropy oxides with rock salt structures were prepared and studied as anodes for lithium batteries. All the systems had complex reaction mechanisms involving conversion reactions. Their capacity and reduction potential depend on the number of components and microstructure of the initial materials. However, the dependence is difficult to rationalize based on simple stability logic. This paper discusses the implication of our findings in the wider context of the science of high entropy materials.

Various applications of gallium telluride have been investigated, such as in optoelectronic devices, radiation detectors, solar cells, and semiconductors, owing to its unique electronic, mechanical, and structural properties. Among the various forms of gallium telluride (e.g., GaTe, Ga3Te4, Ga2Te3, and Ga2Te5), we propose a gallium (III) telluride (Ga2Te3)-based composite (Ga2Te3-TiO2-C) as a prospective anode for Li-ion batteries (LIBs). The lithiation/delithiation phase change mechanism of Ga2Te3 was examined. The existence of the TiO2-C hybrid buffering matrix improved the electrical conductivity as well as mechanical integrity of the composite anode for LIBs. Furthermore, the impact of the C concentration on the performance of Ga2Te3-TiO2-C was comprehensively studied through cyclic voltammetry, differential capacity analysis, and electrochemical impedance spectroscopy. The Ga2Te3-TiO2-C electrode showed high rate capability (capacity retention of 96% at 10 A g−1 relative to 0.1 A g−1) as well as high reversible specific capacity (769 mAh g−1 after 300 cycles at 100 mA g−1). The capacity of Ga2Te3-TiO2-C was enhanced by the synergistic interaction of TiO2 and amorphous C. It thereby outperformed the majority of the most recent Ga-based LIB electrodes. Thus, Ga2Te3-TiO2-C can be thought of as a prospective anode for LIBs in the future.

The hard carbon puzzle: Linking material properties and electrochemical reactivity of hard carbon anodes in lithium and sodium cells. Hard carbon (HC) is the negative electrode (anode) material of choice for sodium-ion batteries (SIBs). Despite its advantages in terms of cost and sustainability, a comprehensive understanding of its microstructure is not complete yet, thus hindering a rational design of high-performance HC electrodes. In this study, rather than investigating how the precursor and synthesis method influence on the electrochemical properties of HC anodes, we examine the microstructure and surface chemistry of three optimized HC anodes obtained from different precursors by using different synthesis routes. The main goal is to evaluate the influence of the final materials properties (in their optimized state) on the electrochemical reactivity in lithium and sodium cells after a comprehensive structural characterization performed by means of X-ray photoelectron spectroscopy (XPS), wide-angle X-ray scattering (WAXS), Raman spectroscopy, scanning electron microscopy (SEM), and gas sorption measurements. The different electrochemical performance observed in terms of cycling stability and rate capability, and the stability of the solid electrolyte interphase (SEI) formed on the various HCs have been comprehensively investigated. A correlation of the material properties with their electrochemical response upon sodium and lithium uptake and release is clarified. By comparing the Na- and Li-ion storage behavior, a structure-function relation is identified., publishedVersion

The potential safety hazards and limited lithium resources of lithium‐ion batteries (LIBs) have restricted their practical application. Potassium‐ion batteries (KIBs) are a novel energy storage technology with great cost advantages and are a promising alternative to LIBs. However, because of the large ionic radius of K+, the common anode materials used in LIBs exhibit a large volumetric expansion and structural collapse in the process of charging and discharging in a KIB. In this work, the prepared nitrogen‐doped porous carbon fibers (P‐CFs) from bombyx mori silk cocoons via a simple KCl activation and high‐temperature carbonization method. The P‐CFs possess a large specific surface area and one‐dimensional porous structure, offering facile storage and fast transport channels for K+ ions. When used as an anode for KIBs, the P‐CFs exhibit a high reversible specific capacity of 275 mAh·g−1 at a current density of 0.1 A·g−1 after 500 cycles and even retain a capacity of 100 mAh·g−1 after 5000 cycles at 2 A·g−1. This study demonstrates a simple strategy for the low‐cost synthesis of nitrogen‐doped porous carbon fibers from an environmental friendly biomaterial, with excellent electrochemical performance as an anode for KIBs.

High-entropy oxides based on transition metals, such as Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O (TM-HEO), have recently drawn special attention as potential anodes in lithium-ion batteries due to high specific capacity and cycling reversibility. However, the lithiation/delithiation mechanism of such systems is still controversial and not clearly addressed. Here, we report on an operando XAS investigation into TM-HEO-based anodes for lithium-ion cells during the first lithiation/delithiation cycle. This material showed a high specific capacity exceeding 600 mAh g-1 at 0.1 C and Coulombic efficiency very close to unity. The combination of functional and advanced spectroscopic studies revealed complex charging mechanisms, developing through the reduction of transition-metal (TM) cations, which triggers the conversion reaction below 1.0 V. The conversion is irreversible and incomplete, leading to the final collapse of the HEO rock-salt structure. Other redox processes are therefore discussed and called to account for the observed cycling behavior of the TM-HEO-based anode. Despite the irreversible phenomena, the HEO cubic structure remains intact for ∼60% of lithiation capacity, so proving the beneficial role of the configuration entropy in enhancing the stability of the HEO rock-salt structure during the redox phenomena.

A saturable reactor is one of the important components of converter valves in high-voltage direct current transmission systems. With the ever-increasing capacities of converter valves, the heat losses generated by saturable reactors are also increasing. Thus, a thermal–fluid mechanics coupled heat dissipation model for saturable reactors is proposed. In order to study the factors affecting the thermal dissipation in the saturable reactor, the epoxy resin insulating layers with different thermal conductivity were considered in this work. The simulation results showed that the hot spots in the saturable reactor are on the iron core and close to the pipe inlet that most of the generated heat can be extracted by a cooling pipe and that the effect of heat dissipation can be improved by raising the thermal conductivity of the epoxy resin. The thermal conductivities of the epoxy resin used in the two reactors were 0.8 and 1.2 W/mK, respectively. The time dependence of the iron core temperature was in accordance with the simulation results and the maximum temperatures of the saturable reactor were also consistent with the simulation results. By increasing the thermal conductivity of the epoxy insulation layer, the temperature of the iron core could be significantly reduced.

The authors aimed to impart hydroxyapatite formation ability to ultra-high molecular weight polyethylene (UHMWPE) by deposition of apatite nuclei (ApN) by the following two methods. The first method was electrophoretic deposition (EPD). A porous UHMWPE was placed between electrodes in the ApN-dispersed ethanol and constant voltage was applied. By this treatment, the ApN were migrated from anode-side surface to the cathode one through the pores by an electric field in the pores of the UHMWPE and deposited inside the pores. The second method was direct precipitation (DP) of the ApN. A porous UHMWPE was soaked in a simulated body fluid (1.0SBF) with higher pH than the physiological one and subsequently, its temperature was raised. By this treatment, the ApN were precipitated in the pores of the UHMWPE directly in the reaction solution. For both methods, the ApN-deposited UHMWPE showed HAp formation ability not only on the top surface but also inside the pores near the surface of the porous UHMWPE in 1.0SBF although the adhesion strength of thus-formed HAp layer was higher in the case of the EPD in comparison with the DP, oxygen plasma treatment before the DP enabled to achieve a similar level of the HAp layer adhesion to the EPD., Special Section: Selected Extended Papers from the International Conference of the 19th Asian BioCeramic Symposium

Graphene-based negative electrodes in lithium-ion batteries have recently been the focus of interest. In this study, sulfur (S)–doped graphene powders in different functionality have been prepared in one step by using Yucel’s method for the first time in the literature and they have been used as anode materials of Li-ion batteries. By changing the scanned potential during the preparation of S-doped graphene powders, the graphenic surface is covalently doped by –C-S-C- and –C-SOx-C- (x:2, 3) groups at different amount. When the potential has been scanned in wider potential range (- 1.0 and 2.5 V), 48 sp2-hybridized carbon rings have been determined on the powders by using Raman analysis. It is the lowest as 16 for graphenic powder prepared at narrower potential range (1.5 and 2.5 V) and chronoamperometric method. S-doped graphene powders have been investigated by microscopic methods. Electrochemical properties of the prepared S-doped graphene powders and their potential use in Li-ion batteries have been assessed. At a 50-mA/g current density, the 915-mAh/g specific capacity has been determined as the highest discharge capacity in the powder which was prepared by the chronoamperometric method. Specific capacities of 710 mAh/g, 594 mAh/g, and 642 mAh/g have been observed in the powders prepared between - 1.0–(+ 2.5 V), 0.6–(+ 2.5 V), and 1.5–(+ 2.5 V) samples, respectively. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

Series arcing faults have been recognised as a hazardous phenomenon in the power system of more electric aircraft (MEA), especially with the increasing voltage level and power supply. Instead of the electrical method, the optical method can be used as an approach to detect arc fault with the advantages of fast response and immunity to electromagnetic interference. It is the basis of optical arc detection to determine the distribution spectrum range of direct current (DC) arc fault. Aiming at series arc optical detection in the MEA DC system, a DC series arc test platform was established to measure the series arc spectrum. The spectrum was disassembled though empirical mode decomposition to extract characteristic wavelengths of arc light and de-noised by means of wavelet decomposition and reconstruction (wavelet transformation) to reduce equipment noise. To resolve the baseline drift, the baseline of the arc spectrum measured was calculated and corrected based on Savitzky−Golay. The experimental results indicate that there are several series arc characteristic spectra of the MEA DC system, including 309.3 and 324.5 nm in the ultraviolet range. Moreover, the arc spectrum with different metals, copper and aluminium, were contrasted, indicating the arc spectral behaviour is related to the melting/boiling point and chemical properties of the anode material. The measurement of the series arc spectrum makes it more effective to apply optical detection in the MEA discharging faults diagnosis.

Polymer-derived-ceramics (PDCs) and PDC-based fibers are being studied as potential high capacity electrode materials for electrochemical energy storage applications. Among these, silicon oxycarbide (SiOC) has shown most promise, especially as electrodes in lithium ion batteries (LIB). The study of PDCs for supercapacitor electrodes is, however, very limited. This work investigates the fabrication of SiOC-based PDC fiber mats via electrospinning and pyrolysis of three commercial pre-ceramic silicone resins (MK, H44, RSN) of varying composition, and their use as supercapacitor and LIB electrodes. Electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy was performed to study the effect of precursor chemical composition, pyrolysis time and temperature on the morphology, polymer to ceramic transformation and free carbon content. As supercapacitor electrodes, the H44 (a methyl-siloxane) derived SiOC showed the best performance with maximum specific capacitance of 50 F g-1 with capacity retention of ~100% after 2000 cycles. Similarly, as LIB electrodes, H44 derived SiOC fiber mat showed highest reversible capacity of 578 mAh g-1 at a current density of 50 mA g-1.

Nickel sulfide has been widely studied as an anode material for lithium-ion batteries due to its environmental friendliness, low cost, high conductivity, and high theoretical capacity. A simple hydrothermal method was used to prepare NiS nanospheres materials with the size in the range of 100–500 nm. The NiS nanospheres electrodes exhibited a high reversible capacity of 1402.3 mAh g−1 at 200 mA g−1 after 280 cycles and a strong rate capability of 814.8 mAh g−1 at 0.8 A g−1 and 1130.5 mAh g−1 when back to 0.1 A g−1. Excellent electrochemical properties and the simple preparation method of the NiS nanospheres make it possible to prepare NiS on a large scale as the anode of lithium-ion batteries.

Lepidocrocite-type titanates that reversibly intercalate sodium ions at low potentials (∼0.6 V vs Na/Na+) are promising anode candidates for sodium-ion batteries. However, large amounts of carbon additives are often used to improve their electrical conductivity and overcome poor cycling performance in the electrode composites. To ameliorate electronic transport issues of lepidocrocite titanate (K0.8Ti1.73Li0.27O4, KTL) in sodium-ion batteries, we have designed and synthesized heterostructures of exfoliated lepidocrocite-type titanium oxide (LTO) nanosheets with alternating carbon layers via a solution-based self-assembly approach. Positively charged dopamine (Dopa) was used as the carbon precursor and intercalated between negatively charged exfoliated titania nanosheets through electrostatic interaction. Dopa-intercalated LTO was then annealed under argon to form conductive carbon layers between titania sheets. The carbon content in the heterostructures was controlled by modifying the self-assembly conditions (i.e., pH, stirring duration, and Dopa-to-LTO ratio). Electrodes were prepared using carbonized heterostructures (LTO-C) without adding more carbon to the composites and tested in sodium half-cell configurations. Higher capacities and improved capacity retention over 250 cycles and lower impedance were observed, as the carbon content of LTO-C heterostructures was increased from 0% (LTO nanosheets) to 30%. These results indicate that the self-assembly approach for 2D heterostructured electrode materials is a promising strategy to overcome electronic transport limitations of layered transition-metal oxides and improve their electrochemical performance for next-generation energy storage applications.

Pre lithiation via electrolysis, herein defined as electrolytic pre lithiation, using cost efficient electrolytes based on lithium chloride LiCl , is successfully demonstrated as a proof of concept for enabling lithium ion battery full cells with high silicon content negative electrodes. An electrolyte for pre lithiation based on amp; 947; butyrolactone and LiCl is optimized using boron containing additives lithium bis oxalato borate, lithium difluoro oxalate borate and CO2 with respect to the formation of a protective solid electrolyte interphase SEI on silicon thin films as model electrodes. Reversible lithiation in Si Li metal cells is demonstrated with Coulombic efficiencies CEff of 95 96 for optimized electrolytes comparable to 1 m LiPF6 EC EMC 3 7. Formation of an effective SEI is shown by cyclic voltammetry and X ray photoelectron spectroscopy XPS . electrolytic pre lithiation experiments show that notable amounts of the gaseous product Cl2 dissolve in the electrolyte leading to a self discharge Cl2 Cl amp; 8722; shuttle mechanism between the electrodes lowering pre lithiation efficiency and causing current collector corrosion. However, no significant degradation of the Si active material and the SEI due to contact with elemental chlorine is found by SEM, impedance, and XPS. In NCM111 Si full cells, the capacity retention in the 100th cycle can be significantly increased from 54 to 78 by electrolytic pre lithiation, compared to reference cells without pre lithiation of Si

Graphite is the material most used as an electrode in commercial lithium-ion batteries. On the other hand, it is a material with low energy capacity, and it is considered a raw critical material given its large volume of use. In the current energy context, we must promote the search for alternative materials based on elements that are abundant, sustainable and that have better performance for energy storage. We propose thin materials based on silicon, which has a storage capacity eleven times higher than graphite. Nevertheless, due to the high-volume expansion during lithiation, it tends to crack, limiting the life of the batteries. To solve this problem, hydrogenated amorphous silicon has been researched, in the form of thin film and nanostructures, since, due to its amorphous structure, porosity and high specific surface, it could better absorb changes in volume. These thin films were grown by plasma-enhanced chemical vapor deposition, and then the nanowires were obtained by chemical etching. The compositional variations of films deposited at different temperatures and the incorporation of dopants markedly influence the stability and longevity of batteries. With these optimized electrodes, we achieved batteries with an initial capacity of 3800 mAhg−1 and 82% capacity retention after 50 cycles, This research has been funded by the Spanish of Ministry of Economy and Competitiveness under projects SCALED (PID2019-109215RB-C42/ https://scaled-project.com/, accessed on June 2020), NanoCat-Com (PID2021-124667OB-I00, accessed on September 2022) and by the European Project STORIES (LC-GD-9-1-2020-European Research Infrastructures capacities and services to address European Green Deal challenges /https://www.eera-energystorage.eu/stories.html, accessed on November 2021

Due to the high theoretical capability, copper-based oxides were widely investigated. A facile water bath method was used to synthesis CuO nanowires and CuO/Cu2O/Cu nanocomposites. Owing to the synergetic effect, the CuO/Cu2O/Cu nanocomposites exhibit superior electrochemical performance compared to the CuO nanowires. The initial discharge and charge capacities are 2,660.4 mAh/g and 2,107.8 mAh/g, and the reversible capacity is 1,265.7 mAh/g after 200 cycles at 200 mA/g. Moreover, the reversible capacity is 1,180 mAh/g at 800 mA/g and 1,750 mAh/g when back to 100 mA/g, indicating the excellent rate capability. The CuO/Cu2O/Cu nanocomposites also exhibit relatively high electric conductivity and lithium-ion diffusion coefficient, especially after cycling. For the energy storage mechanism, the capacitive controlled mechanism is predominance at the high scan rates, which is consistent with the excellent rate capability. The outstanding electrochemical performance of the CuO/Cu2O/Cu nanocomposites indicates the potential application of copper-based oxides nanomaterials in future lithium-ion batteries.

Cone beam computed tomography (CBCT) is now widely used in dentistry and growing areas of medical imaging. The presence of strong metal artifacts is however a major concern of using CBCT especially in dentistry due to the presence of highly attenuating dental restorations, fixed appliances, and implants. Virtual monoenergetic images (VMIs) synthesized from dual energy CT (DECT) datasets are known to reduce metal artifacts. Although several techniques exist for DECT imaging, they in general come with significantly increased equipment cost and not available in dental clinics. The objectives of this study were to investigate the feasibility of developing a low-cost dual energy CBCT (DE-CBCT) by retrofitting a regular CBCT scanner with a carbon nanotube (CNT) x-ray source with dual focal spots and corresponding low-energy (LE) and high-energy (HE) spectral filters. A testbed with a CNT field emission x-ray source (NuRay Technology, Chang Zhou, China), a flat panel detector (Teledyne, Waterloo, Canada), and a rotating object stage was used for this feasibility study. Two distinct polychromatic x-ray spectra with the mean photon energies of 66.7keV and 86.3keV were produced at a fixed 120kVp x-ray tube voltage by using Al+Au and Al+Sn foils as the respective LE and HE filters attached to the exist window of the x-ray source. The HE filter attenuated the x-ray photons more than the LE filter. The calculated post-object air kerma rate of the HE beam was 31.7% of the LE beam. An anthropomorphic head phantom (RANDO, Nuclear Associates, Hicksville, NY) with metal beads was imaged using the testbed and the images were reconstructed using an iterative volumetric CT reconstruction algorithm. The VMIs were synthesized using an image-domain basis materials decomposition method with energy ranging from 30 to 150keV. The results were compared to the reconstructed images from a single energy clinical dental CBCT scanner (CS9300, Carestream Dental, Atlanta, GA). A significant reduction of the metal artifacts was observed in the VMI images synthesized at high energies compared to those from the same object imaged by the clinical dental CBCT scanner. The ability of the CNT x-ray source to generate the output needed to compensate the reduction of photon flux due to attenuation from the spectral filters and to maintain the CT imaging time was evaluated. The results demonstrated the feasibility of DE-CBCT imaging using the proposed approach. Metal artifact reduction was achieved in VMIs synthesized. The x-ray output needed for the proposed DE-CBCT can be generated by a fixed-anode CNT x-ray source.

We thank the EPSRC (EP/K025112/1) and the Leverhulme Trust (RPG-2016-323) for funding and Diamond Light Source for rapid access to synchrotron radiation facilities. The conjugated dicarboxylate, sodium naphthalene-2,6-dicarboxylate (Na2NDC), has been prepared by a low energy consumption reflux method and its performance as a negative electrode for sodium-ion batteries evaluated in electrochemical cells. The structure of Na2NDC was solved for the first time (monoclinic P21/c) from powder X-ray diffraction data and consists of π-stacked naphthalene units separated by sodium-oxygen layers. Through an appropriate choice of binder and conducting carbon additive Na2NDC exhibits a reversible two electron sodium insertion at around 0.4 V vs. Na+/Na with remarkably stable capacities of ca. 200 mA h g-1 at a rate of C/2 and good rate capability (~133 mA h g-1 at 5C). In parallel the high thermal stability of the material is demonstrated by HT-X-ray diffraction, the framework remaining intact to above 500 °C. Postprint

Lower-quality petroleum coke with higher levels of sulfur and metal impurities will have to be used for the manufacturing of anodes for aluminum production in the future. The sulfur and metallic impurities affect the anode properties in the aluminum production process, but the chemical identity of the metal species in the coke is not known. In this study, industrial petroleum cokes with high sulfur levels were analyzed by X-ray absorption near edge structure (XANES) and Extended X-ray absorption fine structure (EXAFS) in order to determine the identity of the V, Ni, and Fe impurities. The XANES spectra were compared with pure-phase standards. EXAFS was used to compare the impurity metal structures with known crystal structures. It was found that V is present mainly as hexagonal V3S4. Ni is present mainly as hexagonal NiS, and Fe is present as hexagonal FeS. This knowledge of the chemical states of the metal elements in coke, which are known to affect anode performance, is the first step in understanding the mechanism of the action of these elements on anode reactivity. This is a post-peer-review, pre-copyedit version of an article. Locked until 4.09.2020 due to copyright restrictions. The final authenticated version is available online at: 10.1007/s11663-019-01676-z

In this work, hematite microdisks (500 nm to 1 μm in diameter, ∼200 nm in thickness) have been synthesized by a facile hydrothermal method which exhibited good cycling stability at a current density of 200 mA g−1 and 1000 mA g−1, and excellent rate performance at various current densities ranging from 100 mA g−1 to 4000 mA g−1.

International audience; During the operation of Solid Oxide Cell (SOC) fuel electrodes, the mobility of nickel can lead to significant changes in electrode morphology, with accompanying degradation in electrochemical performance. In this work, the dewetting of nickel films supported on yttria-stabilized zirconia (YSZ), hereafter called 2D cells, is studied by coupling in-situ environmental scanning electron microscopy (E-SEM), image analysis, cellular automata simulation and electrochemical impedance spectroscopy (EIS). Analysis of experimental E-SEM images shows that Ni dewetting causes an increase in active triple phase boundary (aTPB) length up to a maximum, after which a sharp decrease in aTPB occurs due to Ni de-percolation. This microstructural evolution is consistent with the EIS response, which shows a minimum in polarization resistance followed by a rapid electrochemical degradation. These results reveal that neither evaporation-condensation nor surface diffusion of Ni are the main mechanisms of dewetting at 560–800 °C. Rather, the energy barrier for pore nucleation within the dense Ni film appears to be the most important factor. This sheds light on the relevant mechanisms and interfaces that must be controlled to reduce the electrochemical degradation of SOC electrodes induced by Ni dewetting.

In this work, we introduce Ni nanopyramid arrays (NPAs) supported amorphous Ge anode architecture and demonstrate its effective improvement in sodium storage properties. The Ni−Ge NPAs are prepared by facile electrodeposition and sputtering method, which eliminates the need for any binder or conductive additive when used as a Na‐ion battery anode. The electrodes display stable cycling performance and enhanced rate capabilities in contrast with planar Ge electrodes, which can be owing to the rational design of the architectured electrodes and firm bonding between current collector and active material (i. e. Ni and Ge, respectively). To validate improvement of nanostructures on electrochemical performance, sodium insertion behavior of crystalline Ge derived from Mg2Ge precursor has been investigated, in which limited but effective enhancement of sodium storage properties are realized by introducing porous nanostructure in crystalline Ge. These results show that elaborately designed configuration of Ge electrodes may be a promising anode for Na‐ion battery applications.

Pyrite-type FeS2 is regarded as a promising anode material for sodium ion batteries. The synthesis of FeS2 in large quantities accompanied by an improved cycling stability, as well as retaining high theoretical capacity, is highly desirable for its commercialization. Herein, we present a scalable and simple strategy to prepare a foam-like FeS2 (F-FeS2) nanostructure by combining solution combustion synthesis and solid-state sulfurization. The obtained F-FeS2 product is highly uniform and built from interconnected FeS2 nanoparticles (∼50 nm). The interconnected feature, small particle sizes and porous structure endow the product with high electrical conductivity, good ion diffusion kinetics, and high inhibition capacity of volume expansion. As a result, high capacity (823 mA h g−1 at 0.1 A g−1, very close to the theoretical capacity of FeS2, 894 mA h g−1), good rate capability (581 mA h g−1 at 5.0 A g−1) and cyclability (754 mA h g−1 at 0.2 A g−1 with 97% retention after 80 cycles) can be achieved. The sodium storage mechanism has been proved to be a combination of intercalation and conversion reactions based on in situ XRD. Furthermore, high pseudocapacitive contribution (i.e. ∼87.5% at 5.0 mV s−1) accounts for the outstanding electrochemical performance of F-FeS2 at high rates.

Structural and microstructural investigations of Pd-doped lanthanum strontium ferrite with stoichiometry La0.6Sr0.4Fe0.95Pd0.05O3-? (LSFPd) were carried out under oxidizing and reducing conditions using XRD, Rietveld refinement, XPS, SEM, and TEM analyses. LSFPd exhibited a smart behaviour with a reversible redox structural transformation occurring upon switching from air to hydrogen and then back to air. Exsolution of nanometric metal particles was observed after reduction, and reincorporation of metal cations onto the perovskite structure was confirmed after reoxidation. The electrochemical performances were evaluated on electrolyte supported cells using LSFPd as symmetric electrodes. The self-regenerating redox process largely improved the anodic performance of LSFPd-based SOFCs because it mitigates the coarsening of metallic electrocatalysts at high temperature promoting a redox stable behaviour. Fuel cell tests revealed promising performance in terms of maximum power output and redox stability.

Building a lithium-ion cell with a third reference electrode which is stable and does not disturb the cell characteristics promises deep insights into the cell performance and aging behavior. In this study, a lithium titanium oxide coated aluminum mesh is introduced into lab size 28 mAh pouch cells, which allows the cells to be braced as usual. The influence of inserting the coated mesh together with an additional separator is analyzed using electrochemical impedance spectroscopy and cyclic aging tests. Cells with this reference electrode show small deviations in the Nyquist plot and an increased capacity fade compared to the standard cells. Nonetheless, these 3-electrode cells already allowed C-rate performance tests in a fresh and aged cell state. According to this, the charge current profiles for fresh and aged cells are optimized as step wise protocols to improve the utilization of the anode overpotential reserve while avoiding lithium plating. In order to realize this, the aged cells require a 60% slower protocol. This work shows that the overpotentials on the anode side increase during aging, which makes the cells more susceptible to lithium plating. However, compared to a constant current charge, a reduction in charging time of 30% is possible. © 2019 The Electrochemical Society.

Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries as green energy storage devices because of their similar working principles and the abundance of low-cost sodium resources. Nanostructured carbon materials are attracting great interest as high-performance anodes for SIBs. Herein, a simple and fast technique to prepare carbon nanofibers (CNFs) is presented, and the effects of carbonization conditions on the morphology and electrochemical properties of CNF anodes in Li- and Na-ion batteries are investigated. Porous CNFs containing graphene were fabricated via centrifugal spinning, and MoS2 were decorated on graphene-included porous CNFs via hydrothermal synthesis. The effect of MoS2 on the morphology and the electrode performance was examined in detail. The results showed that the combination of centrifugal spinning, hydrothermal synthesis, and heat treatment is an efficient way to fabricate high-performance electrodes for rechargeable batteries. Furthermore, CNFs fabricated at a carbonization temperature of 800 °C delivered the highest capacity, and the addition of MoS2 improved the reversible capacity up to 860 mAh/g and 455 mAh/g for Li- and Na-ion batteries, respectively. A specific capacity of over 380 mAh/g was observed even at a high current density of 1 A/g. Centrifugal spinning and hydrothermal synthesis allowed for the fabrication of high-performance electrodes for sodium ion batteries.

ispartof: ADVANCED SUSTAINABLE SYSTEMS vol:6 issue:8 status: published

Despite the high potential impact of aqueous battery systems, fundamental characteristics such as cost, safety, and stability make them less feasible for large-scale energy storage systems. One of the main barriers encountered in the commercialization of aqueous batteries is the development of large-scale electrodes with high reversibility, high rate capability, and extended cycle stability at low operational and maintenance costs. To overcome some of these issues, the current research work is focused on a new class of material based on phenethylammonium bismuth iodide on fluorine doped SnO2-precoated glass substrate via aerosol-assisted chemical vapor deposition, a technology that is industrially competitive. The anode materials were electrochemically investigated in Zn2+ aqueous electrolytes as a proof of concept, which presented a specific capacity of 220 mAh g−1 at 0.4 A g−1 with excellent stability after 50 scans and capacity retention of almost 100%.

Máster en Ingeniería Química

Zero-excess Li metal batteries (ZELMB), in which the Li-metal anode is plated in situ on the anode current collector during initial charging, have received considerable attention in recent years. Such batteries hold enormous potential for increasing energy density and simplifying battery production, thus reducing costs, material, and energy requirements. However, transfer into application has so far been limited by challenges related to the non-uniform deposition behavior of lithium, which leads to inadequate performance and safety concerns. To meet these challenges, the electrochemical deposition behavior of lithium must be very well understood to derive and evaluate knowledge-based optimization approaches. For this purpose, advanced characterization methods are urgently needed. Herein the use of operando electrochemical dilatometry (OED) to study Li deposition and dissolution in ZELMB is demonstrated. We show how OED not only provides information on thickness changes during Li deposition and stripping, but also allows insights regarding morphology evolution and quantification of dead Li. The present work is intended to serve as an example to demonstrate the valuable insights that can be gained with OED and to encourage the scientific community to use it to support the development of advanced Li-, Na-, or K-metal batteries.

Embedding silicon nanoparticles in an intermetallic matrix is a promising strategy to produce remarkable bulk anode materials for lithium-ion (Li-ion) batteries with low potential, high electrochemical capacity and good cycling stability. These composite materials can be synthetized at a large scale using mechanical milling. However, for Si-Ni3Sn4 composites, milling also induces a chemical reaction between the two components leading to the formation of free Sn and NiSi2, which is detrimental to the performance of the electrode. To prevent this reaction, a modification of the surface chemistry of the silicon has been undertaken. Si nanoparticles coated with a surface layer of either carbon or oxide were used instead of pure silicon. The influence of the coating on the composition, (micro)structure and electrochemical properties of Si-Ni3Sn4 composites is studied and compared with that of pure Si. Si coating strongly reduces the reaction between Si and Ni3Sn4 during milling. Moreover, contrary to pure silicon, Si-coated composites have a plate-like morphology in which the surface-modified silicon particles are surrounded by a nanostructured, Ni3Sn4-based matrix leading to smooth potential profiles during electrochemical cycling. The chemical homogeneity of the matrix is more uniform for carbon-coated than for oxygen-coated silicon. As a consequence, different electrochemical behaviors are obtained depending on the surface chemistry, with better lithiation properties for the carbon-covered silicon able to deliver over 500 mAh/g for at least 400 cycles.

Highlights One-dimensional elongated TiS2-modified and S-doped TiO2/C nanofibers electrode was synthesized through electrospinning, which exhibited a high specific capacity, excellent cyclic stability, and rate capability in sodium-ion battery.An enhanced pseudo-capacitive capacity because of S doping and TiS2 decoration contributes to noticeable sodium storage performance. High capacity of 161 mAh g−1 (at 3000 mA g−1) after 1500 cycles and 58 mAh g−1 (at 10,000 mA g−1) after 10,000 cycles is delivered outstandingly. Electronic supplementary material The online version of this article (10.1007/s40820-020-00506-1) contains supplementary material, which is available to authorized users., Pseudo-capacitive mechanisms can provide higher energy densities than electrical double-layer capacitors while being faster than bulk storage mechanisms. Usually, they suffer from low intrinsic electronic and ion conductivities of the active materials. Here, taking advantage of the combination of TiS2 decoration, sulfur doping, and a nanometer-sized structure, as-spun TiO2/C nanofiber composites are developed that enable rapid transport of sodium ions and electrons, and exhibit enhanced pseudo-capacitively dominated capacities. At a scan rate of 0.5 mV s−1, a high pseudo-capacitive contribution (76% of the total storage) is obtained for the S-doped TiS2/TiO2/C electrode (termed as TiS2/S-TiO2/C). Such enhanced pseudo-capacitive activity allows rapid chemical kinetics and significantly improves the high-rate sodium storage performance of TiO2. The TiS2/S-TiO2/C composite electrode delivers a high capacity of 114 mAh g−1 at a current density of 5000 mA g−1. The capacity maintains at high level (161 mAh g−1) even after 1500 cycles and is still characterized by 58 mAh g−1 at the extreme condition of 10,000 mA g−1 after 10,000 cycles. Electronic supplementary material The online version of this article (10.1007/s40820-020-00506-1) contains supplementary material, which is available to authorized users.

echargeable metal–sulfur batteries show great promise for energy storage applications because of their potentially high energy and low cost. The multivalent-metal based electrochemical system exhibits the particular advantage of the feasibility of dendrite-free metal anode. Calcium (Ca) represents a promising anode material owing to the low reductive potential, high capacity, and abundant natural resources. However, calcium–sulfur (Ca–S) battery technology is in an early R&D stage, facing the fundamental challenge to develop a suitable electrolyte enabling reversible electrochemical Ca deposition, and at the same time, sulfur redox reactions in the system. Herein, a study of a room-temperature Ca–S battery by employing a stable and efficient calcium tetrakis(hexafluoroisopropyloxy) borate Ca[B(hfip)4]2 electrolyte is presented. The Ca–S batteries exhibit a cell voltage of ≈2.1 V (close to its thermodynamic value) and good reversibility. The mechanistic studies hint at a redox chemistry of sulfur with polysulfide/sulfide species involved in the Ca-based system., publishedVersion

An innovative strategy enabled by spansules is rationally designed for the lithium metal anode to realize an ultralong cycle life., The lithium metal anode (LMA) is considered as a promising star for next-generation high-energy density batteries but is still hampered by the severe growth of uncontrollable lithium dendrites. Here, we design “spansules” made of NaMg(Mn)F3@C core@shell microstructures as the matrix for the LMA, which can offer a long-lasting release of functional ions into the electrolyte. By the assistance of cryogenic transmission electron microscopy, we reveal that an in situ–formed metal layer and a unique LiF-involved bilayer structure on the Li/electrolyte interface would be beneficial for effectively suppressing the growth of lithium dendrites. As a result, the spansule-modified anode affords a high Coulombic efficiency of 98% for over 1000 cycles at a current density of 2 mA cm−2, which is the most stable LMA reported so far. When coupling this anode with the Li[Ni0.8Co0.1Mn0.1]O2 cathode, the practical full cell further exhibits highly improved capacity retention after 500 cycles.

Geobacter spp. enrichment biofilms were cultivated in batch using one-chamber and two-chamber bioelectrochemical reactors. Time-resolved substrate quantification was performed to derive physiological parameters as well as incremental coulombic efficiency (i.e., coulombic efficiency during one batch cycle, here every 6h) during early stage biofilm development. The results of one-chamber reactors revealed an intermediate acetate increase putatively due to the presence of acetogens. Total coulombic efficiencies of two-chamber reactors were considerable lower (19.6±8.3% and 49.3±13.2% for 1st and 2nd batch cycle, respectively) compared to usually reported values of mature Geobacter spp. enrichment biofilms presumably reflecting energetic requirements for biomass production (i.e., cells and extracellular polymeric substances) during early stages of biofilm development. The incremental coulombic efficiency exhibits considerable changes during batch cycles indicating shifts between phases of maximizing metabolic rates and maximizing biomass yield. Analysis based on Michaelis-Menten kinetics yielded maximum substrate uptake rates (vmax,Ac, vmax,I) and half-saturation concentration coefficients (KM,Ac,KM,I) based on acetate uptake or current production, respectively. The latter is usually reported in literature but neglects energy demands for biofilm growth and maintenance as well as acetate and electron storage. From 1st to 2nd batch cycle, vmax,Ac and KM,Ac, decreased from 0.0042-0.0051 mmol Ac- h-1 cm-2 to 0.0031-0.0037 mmol Ac- h-1 cm-2 and 1.02-2.61 mM Ac- to 0.28-0.42 mM Ac-, respectively. Furthermore, differences between KM,Ac/KM,I and vmax,Ac/vmax,I were observed providing insights into the physiology of Geobacter spp. enrichment biofilms. Notably, KM,I considerably scattered while vmax,Ac/vmax,I and KM,Ac remained rather stable indicating that acetate transport within biofilm only marginally affects reaction rates. The observed data variation mandates the requirement of a more detailed analysis with an improved experimental system, e.g., using flow conditions and a comparison with Geobacter spp. pure cultures.

Pseudo-capacitive mechanisms can provide higher energy densities than electrical double-layer capacitors while being faster than bulk storage mechanisms. Usually, they suffer from low intrinsic electronic and ion conductivities of the active materials. Here, taking advantage of the combination of TiS2 decoration, sulfur doping, and a nanometer-sized structure, as-spun TiO2/C nanofiber composites are developed that enable rapid transport of sodium ions and electrons, and exhibit enhanced pseudo-capacitively dominated capacities. At a scan rate of 0.5 mV s−1, a high pseudo-capacitive contribution (76% of the total storage) is obtained for the S-doped TiS2/TiO2/C electrode (termed as TiS2/S-TiO2/C). Such enhanced pseudo-capacitive activity allows rapid chemical kinetics and significantly improves the high-rate sodium storage performance of TiO2. The TiS2/S-TiO2/C composite electrode delivers a high capacity of 114 mAh g−1 at a current density of 5000 mA g−1. The capacity maintains at high level (161 mAh g−1) even after 1500 cycles and is still characterized by 58 mAh g−1 at the extreme condition of 10,000 mA g−1 after 10,000 cycles. Highlights: 1 One-dimensional elongated TiS2-modified and S-doped TiO2/C nanofibers electrode was synthesized through electrospinning, which exhibited a high specific capacity, excellent cyclic stability, and rate capability in sodium-ion battery.2 An enhanced pseudo-capacitive capacity because of S doping and TiS2 decoration contributes to noticeable sodium storage performance. High capacity of 161 mAh g−1 (at 3000 mA g−1) after 1500 cycles and 58 mAh g−1 (at 10,000 mA g−1) after 10,000 cycles is delivered outstandingly.

Carbon xerogels (CXs) with the same chemical composition and BET surface area but different pore sizes (10–200 nm), which had been easily produced in large amounts via a cost-effective microwave-based process, are investigated as anodes for sodium-ion batteries (SIBs). The role of textural properties of CXs in the process of sodium ions storage was evaluated. The most suitable anode for SIBs was CX-100 with a pore size of 100 nm, the largest micropore volume and the lowest external surface area (Sext), which gives an idea of the most accessible surface of the material, along with relatively high open porosity. Larger pore sizes facilitate electrolyte penetration, thus improving Na+ ions diffusion inside the electrode, while microporosity is crucial in increasing electrode capacity since Na+ ions storage on CXs is mainly due to absorption on the surface and in structural defects (i.e., microporosity). Moreover, lowering Sext leads to a decrease in the Na+ ions used in the formation of the SEI layer and irreversibly absorbed during initial cycles, therefore improving electrode performance. In summary, an optimal combination of textural properties, including pore structure and Sext, should be considered in order to effectively design CXs for SIBs., Financial support from the Spanish Ministry of Science, Innovation and Universities (Project RTI2018-094286-A-100) and Asturias Regional Government (GRUPIN 2018, Ref. IDI/2018/000234) is gratefully acknowledged. I. Cameán is grateful for funding from the Fundación General CSIC (Programa ComFuturo, II Edition).

The performance of anodes of lithium-ion batteries relies largely on the architecture and composition of the hybrid active materials. We present a two-step, seed-free, solution-based method for the direct growth of hierarchical charantia-like TiO2/Fe2O3 core/shell nanotube arrays on carbon cloth substrates. An ultrahigh loading of the nanomaterial on carbon fibers was achieved with this method without the use of a binder. This three-dimensional porous hollow architecture and its direct contact with the CC current collector ensure an efficient electronic pathway. The hollow TiO2 framework effectively protects the hierarchical charantia-like TiO2/Fe2O3 hollow core/shell arrays from collapsing because of its negligible volume change during cycling. Meanwhile, the self-assembled α-Fe2O3 hollow nanospheres guarantee a large capacity and contact area with the electrolyte. This flexible anode with a 3D porous charantia-like hollow architecture exhibits high cycle performance, reversible capacity, and rate capability. These nanotube arrays maintain a high reversible capacity of 875 mAh g−1 after 200 cycles at a current density of 200 mA g−1. This simple, cost-effective, and scalable electrode fabrication strategy can be implemented in the fabrication of high-performance wearable energy storage devices.

Hybrid nanotubes of cation disordered rock salt structured Li2FeTiO4 nanoparticles embedded in porous CNTs were developed. Such unique hybrids with continuous 3D electron transportation paths and isolated small particles have been shown to be an ideal architecture that brought out enhanced electrochemical performances. Meanwhile, they exhibited improved extrinsic capacitive characteristics. In addition, we demonstrate a successful example to use cathode active material as anode for lithium-ion batteries (LIBs). More importantly, our hybrids had much superior electrochemical performances than most of the reported Li4Ti5O12-based nanocomposites. Therefore, it is concluded that Li2FeTiO4 can be a prospective anode material for LIBs.

The effect of chromium(VI) on the kinetics of disproportionation of hypochlorous acid and hypochlorite was established in the solution for the electrolytic production of chlorate. The hexavalent chromium species Cr2O7 2-, HCrO4 - and CrO4 2- present in the solution catalyze the disproportionation reaction. In both the absence and presence of chromium(VI), disproportionation is a third-order reaction with respect to HClO and ClO-P, and a first-order reaction with respect to the hexavalent chromium species. In the presence of chromium(VI) ions, four parallel reactions probably take place in the solution i.e. uncatalyzed disproportionation and three parallel reactions catalyzed by Cr2O7 2-, HCrO4 - and CrO4 2-ions. Most likely, the hexavalent chromium species do not change the sequence of elementary reactions in the disproportionation mechanism but only speed up the rate-determining step through interaction with its reactants. In the chlorate production process, as chromium(VI) concentration increases, the optimum pH which ensures the maximum rate of disproportionation is shifted to an acid environment. This is due to an increase in the concentration of the catalytically most active species HCrO4 - with increasing acidity of the solution. A mathematical model of the kinetics of the chromium(VI)-catalyzed disproportionation of hypochlorite and hypochlorous acid into chlorate was set up. Good agreement was obtained between theoretical and experimental data. © 2018 The Electrochemical Society. This is the peer-reviewed version of the paper: Spasojević, M., Marković, D., Trišović, T., Spasojević, M., 2018. Mathematical model of the catalytic effect of chromium(VI) on hypochlorite disproportionation in chlorate electrolysis. Journal of the Electrochemical Society 165, E8–E19. [https://doi.org/10.1149/2.0291802jes]

Unique Fe3O4/polyaniline (PANI) composite with yolk-shell micro/nanostructure (FPys) has been successfully synthesized by a facile silica-assisted in-situ polymerization and subsequent etching strategy. The structural and compositional studies of the FPys composites are performed by employing X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The yolk-shell morphology of the products is confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. When evaluated as anode material for lithium-ion batteries, the as-prepared FPys electrodes deliver superior capacity, better cycling stability and rate capability than those of bare Fe3O4 micro/nanospheres and Fe3O4/PANI core-shell (FPcs) electrodes. Moreover, FPys also exhibits excellent electromagnetic wave absorption performance when comparing to the synthesized Fe3O4-based electromagnetic wave absorbers, in which strong reflection loss and extensive response bandwidth can be achieved simultaneously. The excellent bifunctional properties of FPys material are associated with the specially designed hierarchical micro/nanostructures. The current strategy that application directed structural design can be applied to the synthesis of other multifunctional materials.

The existing electrode materials for lithium‐ion batteries (LIBs) generally suffer from poor rate capability at low temperatures, severely limiting their applications in winter and cold climate area. Here, partially reduced TiNb24O62 (PR‐TNO) are reported that demonstrates excellent electrochemical performance in a broad temperature range, notably at low temperatures. Its crystal structure is similar to that of Ti2Nb10O29 upon partial reduction in H2. The titanium and niobium ions in PR‐TNO enable multielectron transfer, safe operation, and high Coulombic efficiencies. Benefiting from the increased electronic conductivity of the partially reduced phase and its robust crystal structure with a large interlayer spacing, PR‐TNO shows fast electron and Li+ transport, small volume change associated with Li+ storage, and notable capacitive behavior, resulting in good electrochemical performance even at very low temperatures. At −20 °C, a large reversible capacity of 313 mAh g−1 is obtained at 0.1C, reaching 83.3% of that at 25 °C. At 5C, high rate capability (58.3% of that at 0.5C) is achieved, only slightly lower than that at 25 °C (60.7%). Furthermore, PR‐TNO demonstrates excellent cyclic stability with 99.2% of the initial capacity after 1680 cycles, confirming its excellent suitability for low‐temperature LIBs.

The authors acknowledge financial support from Science and Engineering Research Board (SERB), India (File No. EMR/2017/ 002107). S.B., A.G., and J.D.H. acknowledge Science Foundation Ireland (Grant No. 14/IA/2513). Divya Srivastava would like to acknowledge CSC—the Finnish IT Center for Science for computational resources. Germanium (Ge) plays a crucial role in setting up important functionalities for silicon-compatible photonics. Diamond cubic germanium is an extensively studied semiconductor, although its other exotic forms, like BC8, ST8, ST12 phases, may possess distinct electronic properties. We have fabricated stable ST12-Ge nanowires via a self-seeded bottom-up three phase growth in a confined supercritical toluene environment. Here, we report on the direct evidence of the presence of the ST12 phase by a combination of Raman spectroscopy and first-principles calculations using density functional theory (DFT). It is important to remark that the DFT calculation predicts all the Raman active optical phonon modes of the P 4321 structure, and it is in very good agreement with the experimental results. The phonon dynamics as a function of temperature is investigated through Raman measurements at temperatures varying from 80 to 300 K. First-order temperature coefficients for all the observed Raman modes are estimated from the linear temperature dependence of the phonon shifts. A complete set of isobaric Grüneisen parameters is reported for all Raman modes of ST12-Ge nanowire, and the values are lower compared to the same for Si, dc-Ge bulk, and Ge nanowire. These results have important implications for understanding thermal properties of ST12-Ge nanowire.

Sodium-ion batteries (SIBs) have been increasingly studied due to sodium (Na) being an inexpensive ionic resource (Na) and their battery chemistry being similar to that of current lithium-ion batteries (LIBs). However, SIBs have faced substantial challenges in developing high-performance anode materials that can reversibly store Na+ in the host structure. To address these challenges, molybdenum sulfide (MoS2)-based active materials have been considered as promising anodes, owing to the two-dimensional layered structure of MoS2 for stably (de)inserting Na+. Nevertheless, intrinsic issues of MoS2—such as low electronic conductivity and the loss of active S elements after a conversion reaction—have limited the viability of MoS2 in practical SIBs. Here, we report MoS2 embedded in carbon nanofibers encapsulated with a reduced graphene oxide (MoS2@CNFs@rGO) composite for SIB anodes. The MoS2@CNFs@rGO delivered a high capacity of 345.8 mAh g−1 at a current density of 100 mA g−1 for 90 cycles. The CNFs and rGO were synergistically taken into account for providing rapid pathways for electrons and preventing the dissolution of S sources during repetitive conversion reactions. This work offers a new point of view to realize MoS2-based anode materials in practical SIBs.

Increasing the durability of trimming dies used to clean anodes is a very important goal in order to reduce the costs involved in obtaining aluminum. The research focused both on choosing an optimal material for the execution of trimming dies and on the application of technologies for plating active areas and, at the same time, on optimizing the geometric shape of the active area of the trimming die. In order to choose an optimal material from which to make the trimming dies, it was taken into account that they are usually made of X210Cr12 steel. In the stage of choosing an optimal material for the execution of the trimming dies, five steels were taken into account, namely: K105, K107, K110, K360, and K460. Analyses of the metallographic structure of the passage area were performed between the metal deposited by welding and the base material, demonstrating the fact that hot welding plating allows obtaining a more homogeneous metallographic structure compared to cold welding plating. The choice of new material was not a solution to increase the durability of the trimming die. Change in the trimming die geometry determined a reduction in deformations of about 13.8 times and of the equivalent stresses of about 7 times compared to those obtained in the case of the old trimming die. In addition, the durability of the trimming die with the new construction shape increases approximately three times compared to the trimming die with the old geometric shape. This demonstrates that the solution to increasing the durability of the trimming die is to adopt an optimal geometry of the active part at the expense of choosing an optimal material.

This paper presents a detailed study of catalyst deactivation as a result of simultaneous sulfur poisoning and coke deposition during biogas dry reforming. Experiments are performed at 700 and 800 degrees C with 5 and 10 ppm of H2S in model biogas with CH4/CO2 = 1.5 and 2.0. To assess the relative effect of chemisorbed sulfur in deactivating the supported Ni catalyst as compared to that of coke deposition, the experiments are performed with and without H2S in the feed. The catalyst deactivation is found to be faster in the presence of H2S. The deactivation due to sulfur chemisorption is not reversible at 700 degrees C, while at 800 degrees C the catalytic activity of Ni starts to recover on removing H2S from the feed stream. The results show that the exit CO mole fraction goes up for the sulfur poisoned catalyst which suggests that the reverse water gas shift and coke gasification reactions are not suppressed to the same degree as the reforming reaction. The fresh and the spent catalysts are characterized using XRD, BET, EDS, and TEM. The characterization of the spent catalyst shows that dry reforming of model biogas, with and without the presence of H2S, leads to the formation of multiwalled carbon nanotubes for the chosen operating conditions.