Powder Electrodes Research Articles

Electrochemical Behavior of Li−CNT Composite Powder Electrodes for Stable Lithium Anodes

Li metal is considered a highly desirable anode material for next-generation high-energy-density rechargeable lithium batteries because of its extremely high specific capacity (3860 mAh g-1), large negative standard reduction potential, low mass density, and ability to enable battery chemistries with lithium free cathode materials. However, the practical application of Li metal anodes is still prohibited by its low Coulombic efficiency, uncontrolled dendritic growth, and poor solid electrolyte interphase (SEI) during the Li dissolution /deposition. Here, A new type of Li−CNT composite powder electrode (Li−CNT CE) was fabricated via mechanical blending of Li powders and CNT Ball produced by a spray dryer. The Li-CNT CE can suppress dendrite formation with its isolated Li powder and low current density caused by the large specific surface area of spherical Li powder. In our cycle life test of symmetric Li-CNT CE, void spaces between spherical Li powders and CNT Balls contributes to stable longer cycling properties, which works for more than 1000h, because it inhibits inevitable volume changes. Moreover, high electrical conductivity of CNT ball and lighter battery weight due to low mass density of CNT ball is sure of an advantage for the automotive battery. This work provides new insights into the development of Li powder and CNT Ball composite electrode for achieving dendrite-free, high CE and Low mass density Li-metal anodes in Li metal secondary battery (LMSB).

High-intensity magnetic separation for recovery of LiFePO4 and graphite from spent lithium-ion batteries

Numerous end-of-life LiFePO4 batteries will emerge soon due to their limited lifespan. High reagent cost and environmental pollution of hydrometallurgy are the main factors that prevent the economic recycling of spent LiFePO4. In this paper, an environment-friendly physical method, that is, high-intensity magnetic separation (HIMS), was introduced for the first time to demonstrate its feasibility in preconcentrating the LiFePO4 from spent LiFePO4 batteries. Numerical simulation combined with laboratory experiments of two typical HIMS separators, namely high gradient magnetic separator (HGMS) and induced roll magnetic separator (IRMS), were conducted. Simulation analysis indicated that the separation performance was related to the magnetic field strength. In the HGMS experiments using − 0.21 mm electrode powder (after grinding) as feed, the concentrate grade and recovery of LiFePO4 were 74.54% and 96.60%, respectively. By contrast, in the IRMS experiments using electrode pieces (after shredding) as feed, the concentrate grade and recovery of LiFePO4 cathode pieces were 93.30% and 98.69%, respectively. Surface morphological analysis of electrode powder implied that superfine LiFePO4 particles produced by grinding adhered to or were embedded in coarse graphite particles, which seriously deteriorated the separation performance. By contrast, electrode pieces were considerably larger size, and the generation of superfine LiFePO4 particles can thus be avoided.

Interfacial thermoelectric and mechanical properties of indigenously prepared Ni–Cr–Cu/Co4Sb12 skutterudite thermoelectric joints

Thermoelectric and mechanical properties of indigenously prepared Ni–Cr–Cu/Co4Sb12 skutterudite thermoelectric joints are reported. Co4Sb12 based skutterudite compounds are highly enticing mid-temperature thermoelectric materials for waste-heat harvesting. Ni–Cr–Cu electrode powder is prepared by ball milling, and a one-step sintering route is adopted to fabricate the Ni–Cr–Cu electrode/n-type Dy0.4Co3.2Ni0.8Sb12 thermoelectric joints. The processed Ni–Cr–Cu/skutterudite joint interface is continuous without having any crack and has low contact resistance (<12 μΩ cm2). The contact resistance at the interface of the joints decreases to 7 μΩ cm2 under thermal ageing at 823 K for 15 days in a vacuum. The mechanical properties of the joints are not degraded even after ageing at 823 K for 15 days. The theoretical lifetime of the skutterudite device using the Ni–Cr–Cu/Dy0.4Co3.2 Ni0.8Sb12 joints is calculated to be 11 years while maintaining the hot side temperature of the device at 773 K. Our results demonstrate that indigenously prepared Ni–Cr–Cu/Co4Sb12 thermoelectric joints can be effectively used for skutterudite module fabrication.

Influence of electrolyte and redox active electrode materials properties on working mechanism and performance of manganese oxide-based supercapacitors

In this work the pseudocapacitors based on graphite foil/manganese oxide powder electrodes, CelgardTM separator foil, and different water-based electrolytes were manufactured. Commercially available MnO2 (Sigma-Aldrich) with average grain size of 10 µm, milled – 0.1 µm, milled and reduced in 5vol.% of H2 in Ar atmosphere (10 h at 600 °C) were used for electrode formation. The influence of electrolytes on the performance of pseudocapacitors was tested using cyclic voltamperometry. The electrolytes were based on cations with different: valence (Na+, K+, Ca2+ and Al3+), activity (a), hydrated ion size (rh), specific ionic conductivity of electrolyte (λ), diffusion coefficient (D) and these parameters were correlated with determined capacitances. The highest capacitances were observed for K+-based electrolytes, which can be explained by the smallest rh and the highest D for this cation. Such direct explanation was not possible for other cations as the parameters describing the electrolyte properties are depends on each other and should be analyzed in conjunction. The observed correlations shows that the diffusion coefficient is the most valuable parameter for selection of the electrolyte for pseudocapacitor applications. The influence of electrode materials properties must be also taken into account, as the crystal structure, grain size, morphology or electrical properties influence the mechanism of charge accumulation of different ions, as it was simultaneously observed in this work.

Surface Modification towards Integral Bulk Catalysts of Transition Metal Borides for Hydrogen Evolution Reaction

Transition metal borides (TMBs) are promising catalysts for hydrogen evolution reaction (HER). While the commercially available TMBs indicate poor HER performance due to powder electrode and low activity sites density, optimizing commercial TMBs for better HER performance is urgent. To break through the challenge, a new strategy is proposed to compose integral bulk electrodes with needle surfaces in TMBs. The integral bulk electrodes in TiB2, ZrB2, and HfB2 are formed under high pressure and high temperature (HPHT), and the nanoneedle morphology is constructed by chemical etching. In the three materials, the smallest overpotential is 346 mV at 10 mA cm−2 in the HCl etched bulk TiB2 electrode, which is about 61.9% higher than commercial TiB2 powder. Better performance arises from better conductivity of the integral bulk electrode, and the nano morphology exposes the edge sides of the structure which have high activity site density. This work is significant for developing new kinds of bulk TMBs catalysts.

A Y-doped BaCo0.4Fe0.4Zn0.2O3-δ perovskite air electrode with enhanced CO2 tolerance and ORR activity for protonic ceramic electrochemical cells

Protonic ceramic electrochemical cells (PCECs) are ideally suited for efficient energy storage and conversion; however, two of the hinging factors to high performance are the insufficient electrocatalytic activity for oxygen reduction/evolution and the poor stability of the air electrode. Here we report our findings in improving the electrochemical performance and structural stability of a Y doped air electrode with a composition of BaCo0.4Fe0.4Zn0.1Y0.1O3-δ (BCFZY). When applied as the air electrode of a PCEC, high performance is demonstrated, achieving a polarization resistance of 0.04 Ω cm2 and a high peak power density of 870 mWcm−2 at 700 °C. In addition, the single-cell with BCFZY electrode displays a lower degradation rate of 4.2% per 100 h when operated at 0.5Acm−2 and 650 °C in fuel cell mode, much lower than that of 55% per 100 h for cells with BaCo0.4Fe0.4Zn0.2 (BCFZ) electrode under the same condition. The stable structure has been confirmed by the phase structure analyses of the electrode powder after a long-term heating treatment in air.

A multifunctional polyimide enabled high performance silicon composite anode materials for Li-Ion batteries

Herein, a conjugate carbonyl polyimide (MF-PI) and nano-silicon composite (MF-PI/Si) is designed and synthesized through a simple one-pot method to confront rapid capacity fading and complicated electrode material preparation in silicon-based electrodes for lithium ion battery. This composite can be directly used to prepare electrode without the need of further adding of binding materials. In this composite, MF-PI acts as binder for powder electrode, active reversible lithiation material, buffering media to alleviate volume change of silicon particles, and coating shell to avoid the direct contact between silicon particles and electrolyte. These functions from MF-PI collectively assigned the MF-PI/Si composite anode material a relative high specific capacity and excellent cycling stability. The electrode prepared by this as-synthesized MF-PI/Si shows preferable electrochemical interface and surface area, further enhancing the electrode kinetics and then electrochemical performance. The improved ionic and electronic conductivity compared to other binder materials also contributes the excellent performance.

Nanosheet-Assembled MnO2-Integrated Electrode Based on the Low-Temperature and Green Chemical Route

The development of superior electrochemical energy-storage devices designed through a facile, cost-efficient, and green synthesis technique is the key to addressing the intermittent nature of renewable energy sources such as solar and wind energy. In our present work, we design a simple, surfactant-free, and low-temperature chemical strategy to prepare novel integrated, MnO2 composite electrodes with two-dimensional (2D) nanosheet film directly supported on three-dimensional (3D) conductive nickel foam. Benefiting from the specific 2D nanosheet architecture to provide a large interfacial contact area and highly conductive metal scaffolds to facilitate fast electron transfer, the novel nanosheet-assembled MnO2-integrated electrodes exhibit higher specific capacitance of 446 F g−1 at the current density of 1 A g−1 compared with nanostructured MnO2 and commercial MnO2 powder electrodes. More importantly, the as-synthesized devices are able to achieve an outstanding cycling performance of 95% retention after 3000 cycles. The present work, which is based on the low-temperature chemical route to deposit active materials on the conductive substrate, provides new insights into designing a binder-free supercapacitor system to improve the specific capacitance, cycling, and rate performance as next-generation, energy-storage devices.

Researching of the structure and properties of FCAW hardfacing based on Fe-Ti-Mo-B-C welded under low current

The aim of this work was to obtain a wear-resistant coating by surfacing with powder electrodes of the multi-component system Fe-Ti-Mo-B-C using surfacing currents that are lower than standard values. The theoretical calculation of the thermal cycle during the surfacing process was performed to determine the impact on the working surface outside the melting zone. An experimental determination of the temperature effect was performed for comparison with the calculated one. Structure of the harfacing coating were investigated by method of scanning electron microscopy (SEM), phase composition investigated by X-ray diffraction analysis (XRD). It was investigated that hardfacing with proposed electrodes under the low current provides high hardness and wear resistance of the coating in the first deposited layer. Testing of the hardfacings deposited in one and three layers showed a slight difference in the hardness and wear resistance of the layers. Investigation of the fusion zone shown that hardfacing with proposed electrodes provides fusion zone with an absents of defects. It was established that proposed experimental electrodes could be used for increasing the durability of the equipment parts, where overheat of the base material is undesirable.

Strengthening and reconstructionof drilling core pipe for engineeringand geological exploration

Currently, there is a tendency to increase the depth of gaseous and liquid fossils extraction. Therefore, prospecting and developing new deposits is promising. There is also a need to create new freshwater sources and implement relevant geological work based on this need. It is essential to have information about the characteristics of the explored slabs and the geology of the fields in general. Implementation of engineering and geological core drilling exploration is the most acceptable and provides the necessary data. Here, the peculiarities of the technological schemes of the process implementation make it possible to obtain separate sections of structures at a depth of the drilling equipment. It is essential to use traditional equipment, recommended for decades and provides the necessary results [1–3]. In the drilling process, you can achieve different diameters and depths of wells execution, obtain fossil samples etc. Engineering and geological exploration drilling is now taking on increased use in various industries [3]. Therefore, the problem of providing high- quality drilling tools, the stability of their operating characteristics, and the possibility of usage in different conditions is an urgent need today. Modern drilling problems determine the usage of components of the core set with the appropriate physical and mechanical characteristics. Especially it relates to elements close to the drilling tool and the place of fossil; destruction – drill pipe. It is installed immediately after the crown core drill and receives almost the same loads and effects during working [1–3]. Conditions for the implementation of the process of core drilling are characterized primarily by the effect on the elements of the significant axial and twisted core set forces. There is the influence of the corrosive and active environment of the fossil in the washing and lubricating liquids well, etc. High temperatures are also observed at the drilling sites [3], which negatively affect the working tool and speed up its operation. As a result, there is an intensive shock, and abrasive core pipe wear and operation indicators change their constructive size. As a result, it is necessary to replace the operated drill string periodically. Considering modern technical and economic factors, it may be decided to repair a pipe to its original size in many cases. There are tasks for providing the appropriate characteristics of the core pipe surface. It is possible to model such properties of the new surface that functionally the best meet the conditions of the drilling process of a given geological formation. The peculiarities of applying the therapeutic layer on the surface of the core pipe are investigated in work. The experience shows that using electric arc surfacing under the flux layer is expedient. This provides the necessary adhesion of the applied layer and promotes obtaining resistance to the operation surface of the core pipe. At the same time, there is high-quality protection and the possibility of additional alloying through the flux-slaggy welding bath. Using electrode powder type wires creates conditions for flexibility to achieve the established characteristics of functional layers [4–6]. The filling flux, located in the cross-section of the electrode wire, can be easily changed by chemical composition. At the same time, it is possible to make relatively small parties of a wire with the set characteristics. The technological scheme justification about the core pipe surfacing is performed. It provides the previous displacement of the electrode butt size from the zenith of the core pipe to prevent the welding bath from spreading. The structural pipe size , the requirements for residual deformations, and the conditions of shapping the welded layer show the practicality of welding on a helix.

Artificial neural network based modeling to predict micro-hardness during EDM of cryo-treated titanium alloys

In the present paper, an attempt have been made to predict the surface micro-hardness of cryogenically treated titanium alloys using powder mixed electric discharge machining (PMEDM) process with artificial neural network (ANN) approach and Taguchi methodology through transfer of various elements on machined components. The investigated control parameters were pulse off-time, peak current, pulse-on time, manganese/tungsten powder suspended dielectric fluid, electrode material, workpiece material and cryogenic-treatment (shallow and deep) of both electrode and workpiece. A special orthogonal array having a mixture of two and three levels (L18 Orthogonal Array) of Taguchi methodology was used to assign the parameters and conduct the experiments accordingly. Micro-hardness and surface properties were highly influenced by changing the value of peak current. More hardness of specimens was observed at higher current than low value. The presence of different elements of electrode material and powder mixed dielectric was noticed on the machined surface resulted in alter the surface properties. The ANN predicted values of micro-hardness and actual experimental values of micro-hardness were observed within the limit of the agreeable error.

Efficient symmetrical electrodes based on LaCrO3 via microstructural engineering

Novel nanostructured electrodes, La0.98Cr0.75B0.25O3δ (B = Mn, Fe, Ti and Cu), are prepared by a single spray-pyrolysis deposition method directly on the electrolyte and a porous Ce0.9Gd0.1O1.95 (CGO) scaffold. These perovskite-type electrodes without alkaline-earth metals exhibit low ionic/electronic conductivity; however, the polarization resistance is greatly enhanced by microstructural design. The best results are obtained for La0.98Cr0.75Mn0.25O3-δ deposited into a porous CGO-scaffold due to the synergetic effect of CGO, with high ionic conductivity, and doped-LaCrO3 with a predominantly electronic conductivity. The materials are investigated as both air and fuel electrodes for solid oxide fuel cells (SOFCs) by different structural, microstructural and electrochemical techniques. Low values of polarization resistance are achieved for nanostructured La0.98Cr0.75Mn0.25O3-δ-CGO electrodes, i.e. 0.057 Ω cm2 in air at 800 °C, compared to 0.96 Ω cm2 for the same powder electrode obtained by screen-printing deposition. An electrolyte-supported symmetrical cell generates a stable maximum power output of 475 mW cm−2 at 800 °C.

Investigation an assisting electrode powder mixed electrical discharge machining of nonconductive ceramic

This research is aimed to describe a new approach for machining zirconia ceramics. The purpose is to develop an electrical discharge machining with assisting electrode and dielectric mixed with graphite powder to enable processing of nonconductive material and improve machining performance. Methodology that used in this paper is Box-Behnken design. Three controllable parameters were selected, namely discharge current, pulse duration, and graphite powder concentration. The material removal rate, surface roughness, and relative tool wear were chosen as machining performances. The proposed approach uses the concept of response surface methodology to develop mathematical models. Although the discharge current and pulse duration proved to be the most influential input parameters, the finding that resulted in this research is the positive effect of graphite powder on machining performance. The proposed approach provides a very beneficial option of EDM input parameters to achieve the performance improvement: increase in material removal rate, reduction in surface roughness and relative tool wear.

Upcycling Real Waste Mixed Lithium-Ion Batteries by Simultaneous Production of rGO and Lithium-Manganese-Rich Cathode Material.

The direct synthesis of high-value products from end-of-life Li-ion batteries (LIBs), avoiding the complex and costly separation of the different elements, can be reached through a competitive recycling strategy. Here, we propose the simultaneous synthesis of reduced graphene oxide (rGO) and lithium-manganese-rich (Li1.2Mn0.55Ni0.15Co0.1O2 - LMR) cathode material from end-of-life LIBs. The electrode powder recovered after LIBs mechanical pretreatment was directly subjected to the Hummers’ method. This way, quantitative extraction of the target metals (Co, Ni, Mn) and oxidation of graphite to graphene oxide (GO) were simultaneously achieved, and a Mn-rich metal solution resulted after GO filtration, owing to the use of KMnO4 as an oxidizing agent. This solution, which would routinely constitute a heavy-metal liquid waste, was directly employed for the synthesis of Li1.2Mn0.55Ni0.15Co0.1O2 cathode material. XPS measurements demonstrate the presence in the synthesized LMR of Cu2+, SO42–, and SiO44– impurities, which were previously proposed as effective doping species and can thus explain the improved electrochemical performance of recovered LMR. The GO recovered by filtration was reduced to rGO by using ascorbic acid. To evaluate the role of graphite lithiation/delithiation during battery cycling on rGO production, the implemented synthesis procedure was replicated starting from commercial graphite and from the graphite recovered by a consolidated acidic–reductive leaching procedure for metals extraction. Raman and XPS analysis disclosed that cyclic lithiation/delithiation of graphite during battery life cycle facilitates the graphite exfoliation and thus significantly increases conversion to rGO.

Beyond Thin Films: Clarifying the Impact of c-Li15Si4 Formation in Thin Film, Nanoparticle, and Porous Si Electrodes

The formation of the c-Li15Si4 phase has well-established detrimental effects on the capacity retention of thin film silicon electrodes. However, the role of this crystalline phase with respect to the loss of capacity is somewhat ambiguous in nanoscale morphologies. In this work, three silicon-based morphologies are examined, including planar films, porous planar films, and silicon nanoparticle composite powder electrodes. The cycling conditions are used as the lever to induce, or not induce, the formation of c-Li15Si4 through application of constant-current (CC) or constant-current constant-voltage (CCCV) steps. In this manner, the role of this phase on capacity retention and Coulombic efficiency can be determined with few other convoluting factors such as alteration of the composition or morphology of the silicon electrodes themselves. The results here confirm that the c-Li15Si4 phase increases the rate of capacity decay in planar films but has no major effect on capacity retention in half-cells based on porous silicon films or silicon nanoparticle composite powder electrodes, although this conclusion is nuanced. Besides using a constant-voltage step, formation of the c-Li15Si4 phase is influenced by the dimensions of the Si material and the lithiation cutoff voltage. Porous Si films, which, in this work, comprise primary Si particle sizes that are smaller than those in the preformed Si nanoparticle slurries, do not undergo the formation of c-Li15Si4 at 50 mV, whereas Si nanoparticle slurries are accompanied by the formation of c-Li15Si4 up to 80 mV. The solid-electrolyte interphase (SEI) formed from reaction of the c-Li15Si4 with the carbonate-based electrolyte causes polarization in both nanoparticle and porous film silicon electrodes and lowers the average Coulombic efficiency. A comparison of the cumulative irreversibilities due to SEI formation between different lithiation cutoff voltages in silicon nanoparticle slurry electrodes confirmed the connection between higher SEI buildup and formation of the c-Li15Si4 phase. This work indicates that concerns about the c-Li15Si4 phase in silicon nanoparticles and porous silicon electrodes should mainly focus on the stability of the SEI and a reduction of irreversible electrolyte reactions.

Influence of the Ti Content on the Electrochemical Performance and Surface Properties of (La0.6Sr0.4)0.99Co1− xTixO3− δ Oxygen Electrode

Mixed ionic and electronic conducting (MIEC) oxides are being used as solid oxide fuel cell (SOFC) electrode materials [1, 2]. La1− xSrxCoO3− δ (LSC) oxygen electrode has perovskite-type (ABO3) structure. The properties of these materials are determined by chemical composition, crystallographic structure and oxidation state of B-site elements. These electrode materials have good catalytic activity towards oxygen reduction reaction and oxide ion oxidation, but they have limited durability if carbon dioxide or humidity are presented in the electrode gas compartment. It is important to increase the long-term durability of these electrode materials at natural gas conditions, i.e. in gas from the external environment with micro-concentrations of impurities like water and carbon dioxide [3, 4, 5].The SOFC oxygen electrode powders with different stoichiometry ((La0.6Sr0.4)0.99Co1− xTixO3− δ , x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) were prepared by using the thermal combustion method [6]. X-ray diffraction (XRD) analysis was used to characterize the crystallographic structure of the synthesized powders. Symmetrical cells for Electrochemical Impedance Spectroscopy (EIS), Focused Ion Beam Time of Flight Secondary Ions Mass Spectrometry (FIB-TOF-SIMS) and X-Ray Photoelectron Spectroscopy (XPS) were made using synthesized powders. Prepared symmetrical cells were characterized at different temperatures, potentials, gas compositions i.e. conditions.Systematic impedance analysis showed that materials with bigger cation (Ti4+), doped into the LSC B-site, increase the material long-term stability against impurities like carbon dioxide and water. As a result of the work, the optimal amount of dopant (Ti4+) was found, which increased the stability of the material in the environment with impurities.[1] C. Singhal, K. Kendall (Eds.), High-Temperature Solid Oxide Fuel Cells: Fundamentals, Design and Applications, Elsevier, Oxford, (2003).[2] Weber, E. Ivers-Tiffée, J. Power Sources 127, 273 (2004).[3] Kivi, J. Aruväli, K. Kiresimäe, A. Heinsaar, G. Nurk, E. Lust, J. Electrochemical Society, 160, F1022 (2013).[4] Kivi, J. Aruväli, K. Kirsimäe, P. Möller, A. Heinsaar, G. Nurk, E. Lust, J. Solid State Electrochem, 21, 361 (2017).[5] P. Jiang, Int J. Hydrogen Energy, 44, 7448 (2019).[6] P. Bansal, Z. Zhong, J. Power Sources, 158, 148 (2006).

Influence of Sr2+ Concentration and A-Site Deficiency on Surface Stability of (La1 - ySry)xCr0.5Mn0.45 Ni0.05O3 -δ

(La1– xSrx)yCr0.5Mn0.45Ni0.05O3– δ (LSCMN) is a perovskite (ABO3) type mixed ionic-electronic conductive (MIEC) oxide and has been proposed as an electrode material for high temperature fuel cell [1]. The material is catalytically active for oxidation of hydrogen and hydrocarbons [2]. A significant amount of attention has been paid to clarify the dependence between crystallographic and electrical properties of LSCM-based materials [1, 3]. Some papers also deal with stability issues if the material is used as an anode in a solid oxide fuel cell [3, 4]. So far, there is a lack of information about the dependence between A-site stoichiometry and stability of chemical composition- and electrochemical performance of LSCMN surface.In this work, La/Sr ratio and deficiency of A-site, i.e. A-site stoichiometry of (La1– xSrx)yCr0.5Mn0.45 Ni0.05O3–δ were varied and chemical composition of LSCMN surface and electrochemical performance was monitored. The electrochemical measurements of symmetric cells (100 h tests) show that small stochiometric changes in A-site significantly influence the activity and initial degradation rate of the electrode. The chemical and structural changes of the material surface (segregation of some LSCMN components onto the surface and decomposition of perovskite phase) have a key role in the electrochemical performance of the electrode [3].The electrode materials were analysed using XRD, TOF SIMS and electrochemical methods. XRD results for studied electrode powders showed significant dependence on the lattice parameters on the A-site composition. Materials were treated in two different gas environments – in synthetic air and in H2 environment, both at 1123 K for one hundred hours. TOF SIMS analysis demonstrated the dependence of the surface stoichiometry on the A-site stoichiometry of bulk electrode as well as on gas environment during heat treatment. The results from impedance spectroscopy (measured at temperatures from 973 to 1123 K in H2 environment, at OCV) demonstrate a significant influence of the A-site deficiency and La/Sr ratio on the series- and polarization resistance of the electrode. The electrochemical activity and surface compositions were correlated and reasons of relative stoichiometric changes of the surface compared with bulk were discussed. Yue and J.T.S. Irvine, Solid State Ionics, 225, 131 (2012).Bidrawn, G. Kim, G. Corre, J.T.S. Irvine, J.M. Vohs, R.J. Gorte, Electrochem. Solid-State Lett. 11, B167 (2008).Korjus, J. Aruväli, P. Paiste, K.Kooser, S. Granroth, H. Mändar, M. Kodu, R. Härmas, M. Maide, M. Ainsar, E. Lust, G. Nurk, Fuel Cell, 20, 6, 741 (2020).C. Lu, J. H. Zhu, Solid State Ionics, 178, 1467 (2007).

Influence of Sr2+ Concentration and A-Site Deficiency on Surface Stability of (La1 - ySry)xCr0.5Mn0.45 Ni0.05O3 -δ

(La1–ySry)xCr0.5Mn0.45Ni0.05O3–δ (LSCMN) is a perovskite (ABO3) type mixed ionic-electronic conductive (MIEC) oxide and has been proposed as an electrode material for high temperature fuel cell. The material is catalytically active for oxidation of hydrogen and hydrocarbons. A significant amount of attention has been paid to stability issues if the material is used as an anode in a solid oxide fuel cell. So far, there is a lack of information about the dependence between A-site stoichiometry and stability performance of LSCMN surface. The La/Sr ratio and deficiency of A-site, i.e. A-site stoichiometry of (La1–ySry)xCr0.5Mn0.45Ni0.05O3–δ were varied and chemical composition of LSCMN surface and lattice parameters was studied. The chemical and structural changes of the material surface (segregation of some LSCMN components onto the surface and decomposition of perovskite phase) have a key role in the electrochemical performance and initial degradation rate of the electrode. XRD results for studied electrode powders showed significant dependence of the lattice parameters on the A-site composition. Materials were treated in synthetic air and in H2 environment. TOF SIMS analysis demonstrated the dependence of the surface stoichiometry on the A-site composition of bulk electrode as well as on the different gas environments after heat treatment. To improve the durability of the solid oxide cell fuel electrodes, it is inevitable to understand the degradation mechanisms during the cell operation and during cell fabrication.

Chemical heterogeneities in tungsten containing TiAl alloys processed by powder metallurgy

During the last decade, it has been shown that the W-containing IRIS-TiAl alloy displays promising properties for structural applications at high temperatures. The manufacturing process of this alloy is divided into three successive steps: electrode production, powder atomisation and spark plasma sintering (SPS) densification. However, an IRIS alloy densified by using pre-alloyed powders atomized by EIGA process (Electrode Induction melting Gas Atomisation) has recently been found to exhibit chemical heterogeneities. The aim of the present work is to look for the origin of such heterogeneities all along this manufacturing process. The microstructures and the chemical compositions of the material obtained after these different steps are thus investigated at intermediate and local scales by using various experimental tools. A particular attention is paid to the distribution of tungsten atoms in correlation to the constituent phases. Effects of these heterogeneities on mechanical properties are measured by performing tensile tests at room and high temperatures. It will be demonstrated that these heterogeneities are issued from tungsten segregation occurring during the first stage of the initial solidification of the electrode, thus prior to atomisation.

Resynthesis of NMC111 Cathodic Material from Real Waste Lithium Ion Batteries

In this work, the role of the experimental conditions during the synthesis of LiNi1/3Mn1/3Co1/3O2 cathodic material (NMC) precursor was evaluated. Precursor synthesis was carried out starting from the electrodic powder obtained from the mechanical treatment of spent lithium ion batteries. Metals were extracted by acid-reducing leaching of the electrodic powder with an extraction yield higher than 90%. Cobalt was the most concentrated metals followed by manganese and nickel. Iron, copper and aluminium, coming from battery cases and current collectors, were present as impurities in the leachate. Selective precipitation of the impurities was performed prior to precipitate the mixed hydroxide. Ni1/3Mn1/3Co1/3(OH)2 precipitations were carried out using two concentrations of NH4OH and under nitrogen or air atmosphere. The effect of these parameters was evaluated on the NMCs structure by XRD analysis and on the electrochemical performance by the galvanostatic cycling of the NMCs when assembled in half lithium cells. XRD analysis of the NMCs have showed the obtainment of the typical layered structure of LiNi1/3Mn1/3Co1/3O2 for any synthesized NMC and no other phases related to single oxides were found. The evaluation of the electrochemical performance has showed a significant role of the precipitation atmosphere and an improvement of the specific capacity was attained using the lowest concentration of NH4OH. Remarkably, specific capacity values of recovered NMCs were comparable to NMCs synthesized under the same experimental conditions but using synthetic reagents.