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Zinc-based batteries are gaining attention as a promising candidate for large-scale energy storage systems due to their safety, abundance of elemental zinc, low cost, and ease of handling in air. H...

Titanium alloys have good biocompatibility and good mechanical properties, making them particularly suitable for dental and orthopedic implants. Improving their osseointegration with human bones is one of the most essential tasks. This can be achieved by developing hydroxyapatite (HA) on the treating surface using the plasma electrolytic oxidation (PEO) method in molten salt. In this study, a coating of titanium oxide-containing HA nanoparticles was formed on Ti-6Al-7Nb alloy by PEO in molten salt. Then, samples were subjected to hydrothermal treatment (HTT) to form HA crystals sized 0.5 to 1 μm. The effect of the current and voltage frequency for the creation of the coating on the morphology, chemical, and phase composition was studied. The anti-corrosion properties of the samples were studied using the potentiodynamic polarization test (PPT) and electrochemical impedance spectroscopy (EIS). An assessment of the morphology of the sample formed at a frequency of 100 Hz shows that the structure of this coating has a uniform submicron porosity, and its surface shows high hydrophilicity and anti-corrosion properties (4.90 × 106 Ohm·cm2). In this work, for the first time, the process of formation of a bioactive coating consisting of titanium oxides and HA was studied by the PEO method in molten salts.

Aqueous Na-ion batteries are proposed as cheap, safe, environmentally friendly systems for large-scale energy storage owing to the high abundance of sodium in earth’s crust and the benign nature of...

One of the greatest challenges toward rechargeable magnesium batteries is the development of noncorrosive electrolyte solutions with high anodic stability that can support reversible Mg deposition/dissolution. In the last few years, magnesium electrolyte solutions based on Cl-free fluorinated alkoxyborates were investigated for Mg batteries due to their high anodic stability and ionic conductivity and the possibility of reversible deposition/dissolution in ethereal solvents. Here, the electrochemical performance of Mg[B(hexafluoroisopropanol)

Rechargeable metal–sulfur batteries (RMSBs) represent one of the most attractive electrochemical systems in terms of energy density and cost. In most of the proposed systems, the anode side is metallic and the cathode side is elemental sulfur impregnated in a porous matrix. Despite the relatively low voltage of these systems, they attract a lot of attention and are considered to be very promising as next-generation batteries for the following reasons: (1) utilization of active metal anodes enables a leap in specific energy due to the high capacity of metal anodes in comparison to intercalation compounds, (2) sulfur as a cathode exhibits high theoretical specific capacity (1675 mAh/g), and (3) system components make RMSBs low-cost, less toxic batteries. Nevertheless, the high reactivity of metallic anodes (e.g., Li, Na, Mg, and Al) and the solubility of sulfur species in the electrolyte render these batteries unstable and hinder their practical realization. In this Perspective, we focus on rechargeable sul...

One of the holy grails in research and development focused on rechargeable magnesium batteries is development of “conventional” electrolyte solutions that are compatible with both anode and cathode...

Recently, MgTFSI2/MgCl2 electrolyte solutions in dimethoxyethane (DME) have been shown to function as viable electrolyte solutions for secondary Mg batteries that can facilitate reversible magnesium deposition/dissolution. MgCl2 is a crucial component in these solutions. On its own, however, it is practically insoluble in DME. Therefore, the fact that it is readily dissolved in MgTFSI2/DME solution is remarkable. Addition of MgCl2 greatly improves the electrochemical performance of MgTFSI2/DME electrolyte solutions. Thus, identifying the species formed in MgTFSI2/MgCl2 solutions is intriguing. In this study, we implemented a wide variety of analytical tools, including single crystal X-ray diffraction, multinuclear NMR, and Raman spectroscopy, to elucidate the structure of these solutions. Various solution species were determined, and a suitable reaction scheme is suggested.

The selection of viable conventional magnesium salts in electrolyte solutions for Mg secondary batteries is very limited. Reversible magnesium deposition was demonstrated with only MgTFSI2, in ethereal solutions. A recent report has suggested that Mg can be reversibly deposited from a solution of Mg(PF6)2 in tetrahydrofuran and acetonitrile. In this paper, we dispute that claim and show that PF6– anions passivate Mg anodes and completely inhibit any Mg deposition/dissolution process. We show that addition of chlorides suppresses the passivation phenomena and allows reversible Mg deposition/dissolution processes to commence. The Mg deposits have been examined via elemental analysis, scanning electron microscopy, and X-ray diffraction measurements, depicting a highly oriented, preferential Mg growth. This study evaluates the feasibility of employing PF6-based electrolytes for Mg batteries and exemplifies the aptitude of chlorides for suppressing passivation phenomena.

X-ray photoelectron spectroscopy is one of the workhorses in today’s battery analysis and research. The potential of X-ray radiation damage and degradation during measurements with regularly used salts and organic compounds are often overlooked. In this study, we show that, under common analysis conditions, the exiting X-ray radiation (1468.6 eV) during the XPS analysis does have significant effect on some Mg and Li salts based on TFSI, FSI, and PF6 anions. In all cases, we show that the salts undergo significant photodegradation during the XPS measurements. With XPS, the photodegradation is detected as the solid degradation products remaining on the sample holder, and they are clearly identified by formation of new peaks at lower binding energies for the relevant elements. We were also able to show that in some cases, as expected, some gaseous byproducts evolve during the photodegradation process.

Colloidal Cu2O nanocrystal layers on Au substrates are studied as photocathodes in the context of solar electrochemical water-splitting applications. The photoelectrochemical response of the nanocrystal layers in aqueous solutions under simulated solar light conditions depends strongly on the interfacial chemistry and its impact on the transport of the charge carriers across the Au/nanocrystals/liquid interfaces. The Cu2O nanocrystals are originally stabilized with octadecylamine ligands. While octadecylamine is an efficient capping ligand for the colloidal synthesis of highly uniform nanocrystals, its low conductivity impedes the charge transport across the Au/nanocrystals/liquid interfaces. The photoresponse of the nanocrystals can be enhanced by the replacement of the octadecylamine ligands with more conductive and hydrophilic molecules, such as 1,2-ethanedithiol and benzene-1,4-dithiol. The conductivity and hydrophilicity of the ligands were investigated and found to be important for the photo-induced charge separation and transport across the Au/nanocrystals/liquid interfaces and transfer to the liquid. Furthermore, the interfacial energetics of the Au/nanocrystals/liquid junction and the resulting photoresponse of the Cu2O nanocrystal photocathode can be optimized by rational design of the exchanging ligands with desired functionalities and dipoles at the specific interfaces. A comparison of the photoresponse of Cu2O nanocrystal layers to that of electrodeposited Cu2O layers shows that the former is, yet, lower, due to the apparent low conductivity of the ligands. However, the nanocrystal organic ligands impart high hydrophobicity, which prevents the contact of the aqueous solution with the nanocrystals and improves their stability against photocorrosion and reduction to Cu0, as confirmed by X-ray diffraction measurements.

The specific capacity of activated carbon electrodes for supercapacitors may be enhanced with additional faradaic redox reactions by grafting of electroactive aromatic molecules with heteroatoms that act as redox centers. Such enrichment was demonstrated recently with anthraquinone and catechol using diazonium chemistry. Here, trihydroxybenzene, which has obvious advantages, was successfully grafted, yielding a mass enrichment of 25%. Electrochemical characterization in acidic aqueous solution after in situ methoxy deprotection demonstrated an initial specific capacity of 65 mAh g−1, which faded only slightly to 55 mAh g−1 after about 2000 cycles and remained stable for over 4500 cycles.

Mg(N(SO2CF3)2)2 (MgTFSI2) solutions with dimethoxyethane (DME) exhibit a peculiar behavior. Over a certain range of salt content, they form two immiscible phases of specific electrolyte concentrations. This behavior is unique, as both immiscible phases comprise the same constituents. Thus, this miscibility gap constitutes an exceptionally intriguing and interesting case for the study of such phenomena. We studied these systems from solutions structure perspective. The study included a wide variety of analytical tools including single-crystal X-ray diffraction, multinuclei NMR, and Raman spectroscopy coupled with density functional theory calculations. We rigorously determined the structure of the MgTFSI2/DME solutions and developed a plausible theory to explain the two-phase formation phenomenon. We also determined the exchange energy of the “caging” DME molecules solvating the central magnesium ion. Additionally, by measuring the ions’ diffusion coefficients, we suggest that the caged Mg2+ and TFSI– move...

Rechargeable magnesium batteries (RMBs) have attracted a lot of attention in recent decades due to the theoretical properties of these systems in terms of energy density, safety, and price. Nevertheless, to date, fully rechargeable magnesium battery prototypes with sufficient longevity and reversibility were realized only with low voltage and low capacity intercalation cathode materials based on Cheverel phases. The community is therefore actively looking for high-capacity cathodes that can work with metallic magnesium anodes in viable RMB systems. One of the most promising cathode materials, in terms of very high theoretical specific capacity, is, naturally, sulfur. A number of recent works studied the electrochemical performances of rechargeable sulfur cathodes in RMB, with success to some extent on the cathode side. Nevertheless, as known from the lithium-sulfur rechargeable battery systems, the formation of soluble polysulfides during discharge affects strongly the behavior of the anode side. In this article and the work it describes, we focus on soluble polysulfides impact on Mg-S electrochemichal systems. We carefully designed herein conditions that mimic the Mg-S battery prototypes containing balanced Mg and elemental sulfur electrodes. Under these conditions, we extensively studied the Mg anode behavior. The study shows that when elemental sulfur cathodes are discharged in the Mg-S cells containing electrolyte solutions in which Mg anodes behave reversibly, the polysulfide species thus formed migrate to the anode and eventually fully passivate it by the formation of very stable surface layers. The work involved electrochemical, spectroscopic, and microscopic studies. The present study clearly shows that to realize practical rechargeable Mg-S batteries, the transport of any sulfide moieties from the sulfur cathode to the magnesium anode has to be completely avoided. Such a condition is mandatory for the operation of secondary Mg-S batteries.

MgTFSI2 is the only ether-soluble "simple" magnesium salt. The poor electrochemical performance of Mg electrodes in its solutions hinders its practicality as a viable electrolyte for Mg batteries. MgTFSI2/DME solutions were demonstrated to dissolve large quantities of MgCl2 and produce electrolyte solutions with superior performance, though the electrochemical performance, mainly in terms of reversibility, of MgTFSI2/MgCl2 (DME) solutions cannot yet compete with that of organometallic based electrolyte solutions. We believe that the solutions' purity level governs the overall electrochemical performance, especially in solutions where a strong reductant (i.e Grignard reagent) is not present to act as an impurity scavenger. In this work, we alter the performance of the MgTFSI2/MgCl2 (DME) solutions through chemical and electrochemical conditioning and demonstrate the effect on the solutions' electrochemical characteristics. We demonstrate relatively high reversible behavior of Mg deposition/dissolution with crystalline uniformity of the Mg deposits, complemented by a fully reversible intercalation/de-intercalation process of Mg ions into Mo6S8 cathodes. We also investigated LiTFSI/MgCl2 solutions which exhibited even higher reversibility than MgTFSI2/MgCl2 (DME) solutions, which we attribute to the higher purity level available for the LiTFSI salt.

In this chapter, selected and the most important aspects of the electrochemistry of organoaluminum compounds are described. It is focused on two main implementations: electrochemical aluminum plating and rechargeable Mg batteries. Electrochemical aspects of organoaluminum-based electroplating baths are discussed in detail and the effects of the solutions formulation on the electrochemical properties are explained. The role of organoaluminum compounds, acting as Lewis acids, in the formulation of the electrolyte solutions for rechargeable Mg batteries, and their effect on the performance of electrolyte solutions is described. Keywords: aluminum; organoaluminum compounds; electrodeposition; ionic liquids; magnesium batteries; non-aqueous electrochemistry

Prototype cells of hybrid capacitor were developed, comprising activated carbon (AC) cloth and magnesium (Mg) foil as the positive and negative electrodes, respectively. The electrolyte solution included ether solvent (TBF) and a magnesium organo-halo-aluminate complex 0.25 M Mg2Cl3+-Ph2AlCl2-. In this solution Mg can be deposited/dissolved reversibly for thousands of cycles with high reversibility (100% cycling efficiency). The main barrier for integrating porous AC electrodes with this electrolyte solution was the saturation of the pores with the large ions in the AC prior to reaching the potential limit. This is due to the existence of bulky Mg and Al based ionic complexes consisting Cl, alkyl or aryl (R), and THF ligands. This problem was resolved by adding 0.5 M of lithium chloride (LiCl), thus introducing smaller ionic species to the solution. This Mg hybrid capacitor system demonstrated a stable cycle performance for many thousands of cycles with a specific capacitance of 90 Fg(-1) for the AC positive electrodes along a potential range of 2.4 V. (C) 2014 The Electrochemical Society. All rights reserved.

Rechargeable magnesium batteries (RMBs) have attracted a lot of attention in recent decades due to the theoretical properties of these systems in terms of energy density, safety, and price. Nevertheless, to date, fully rechargeable magnesium battery prototypes with sufficient longevity and reversibility were realized only with low voltage and low capacity intercalation cathodes. The community is therefore actively looking for high-capacity cathodes that can work with metallic magnesium anodes in viable RMB systems. One of the most promising cathode materials, in terms of very high theoretical specific capacity is sulfur. A number of recent works studied the electrochemical performances of rechargeable sulfur cathodes in RMB, with success to some extent on the cathode side. Nevertheless, the formation of soluble polysulfide’s during discharge affects strongly the behavior of the anode side. we are focusing on soluble polysulfide impact on Mg–S electrochemical systems. We carefully designed herein conditions that mimic the Mg–S battery prototypes containing balanced Mg and elemental sulfur electrodes. Under these conditions, we extensively studied the Mg anode behavior. The study shows that when elemental sulfur cathodes are discharged in the Mg–S cells containing electrolyte solutions in which Mg anodes behave reversibly, the polysulfide species thus formed migrate to the anode and eventually fully passivate it by the formation of very stable surface layers.

Electrochemical, surface, and structural studies related to rechargeable Mg batteries were carried out with monolithic thin-film cathodes comprising layered V2O5 and MoO3. The reversible intercalation reactions of these electrodes with Mg ion in nonaqueous Mg salt solutions were explored using a variety of analytical tools. These included slow-scan rate cyclic voltammetry (SSCV), chrono-potentiometry (galvanostatic cycling), Raman and photoelectron spectroscopies, high-resolution microscopy, and XRD. The V2O5 electrodes exhibited reversible Mg-ion intercalation at capacities around 150-180 mAh g(-1) with 100% efficiency. A capacity of 220 mAh g(-1) at >95% efficiency was obtained with MoO3 electrodes. By applying the electrochemical driving force sufficiently slowly it was possible to measure the electrodes at equilibrium conditions and verify by spectroscopy, microscopy, and diffractometry that these electrodes undergo fully reversible structural changes upon Mg-ion insertion/deinsertion cycling.

Recently, MgTFSI2/MgCl2 electrolyte solutions in dimethoxyethane (DME) have been shown to function as viable electrolyte solutions for secondary Mg batteries that can facilitate reversible magnesium deposition/dissolution1. MgCl2 is a crucial component in these solutions. On its own, however, it is practically insoluble in DME. Therefore, the fact that it is readily dissolved in MgTFSI2/DME solution is remarkable. Addition of MgCl2 greatly improves the electrochemical performance of MgTFSI2/DME electrolyte solutions. MgTFSI2 /DME electrolyte show large overpotential for deposition (-0.6 V vs Mg) and dissolution (1.5V vs Mg). Furthermore this electrolyte exhibit poor magnesium deposition reversibility. Adding MgCl2 to this electrolyte reduces the overpotentials for both deposition and dissolution and showed 98% columbic efficiency. Thus, identifying the species formed in MgTFSI2/MgCl2 solutions are very intriguing. In this study, we identified numerus solution species that some of them were not previously identified. We believe that the newly discovered MgxCly complexes play a crucial rule in the improved electrochemical performance of the MgTFSI2 /DME electrolyte solutions. The complexes that were identified were Mg3Cl4 2+ (figure 1)2, Mg2Cl2 2+.Furthermore we showed that the hexacoordinated nature of magnesium effectively dictate the solution structure. We showed that in THF based electrolyte Mg2Cl3 + is the dominant solution specie and we didn’t see any evidence for its existence in DME based electrolytes(. We implemented a wide variety of analytical tools, including single crystal X-ray diffraction, multinuclear NMR, and Raman spectroscopy, to elucidate the structure of these solutions. Various solution species were determined, and a suitable reaction scheme is suggested(figure 1). We believe that this type of fundamental study is essential for designing new and improved electrolyte solutions for secondary magnesium batteries. Shterenberg, I.; Salama, M.; Yoo, H. D.; Gofer, Y.; Park, J.-B.; Sun, Y.-K.; Aurbach, D. Evaluation of (CF3SO2) 2N−(TFSI) based electrolyte solutions for Mg batteries. J. Electrochem. Soc. 2015, 162, A7118-A7128. Salama, M.; Shterenberg, I.; JW Shimon, L.; Keinan-Adamsky, K.; Afri, M.; Gofer, Y.; Aurbach, D. Structural Analysis of Magnesium-Chloride Complexes in Dimethoxyethane Solutions in the Context of Mg Batteries Research. The Journal of Physical Chemistry C 2017. Figure 1

About 20–40 mol% Ni/ZrO2 catalysts doped with Ce and Sm were synthesized by an ultrasound-assisted method and characterized by a number of physico-chemical methods (XRD, HR TEM, BET, XPS). It was demonstrated that the synthesized catalysts had a mesoporous structure, where ca. 10 nm size Ni nanoparticles were incorporated into the rare earth metal modified tetragonal zirconium oxide. The Ni particles formed during the reduction treatment could support the porous structure in the supports, and thus the porous properties of the catalysts were related to the Ni-loading. The maximum porous volume and size were obtained for the catalyst with a 30 mol% Ni loading, which coincidentally exhibited the highest catalytic activity for the methanation of CO2. After an oxidation–reduction pretreatment, the catalytic activity could be further improved. The increase in the catalytic activity was attributed to the formation of additional active centers on the catalysts’ surface.

In this paper we compare the behavior of LiNi 0.5 Mn 0.5 O 2 , LiNi 0.33 Mn 0.33 Co 0.33 O 2 (NMC) and LiNi 0.4 Mn 0.4 Co 0.2 O 2 as cathode materials for advanced rechargeable Li-ion batteries. These materials were prepared by a self-combustion reaction (SCR) from the metal nitrates and sucrose, followed by calcination at elevated temperatures. The temperature and duration of calcination enabled the adjustment of the average particle size and size distribution. It was established that the annealing temperature (700–900 °C) of the as-prepared oxides influences strongly the crystallite and particle size, the morphology of the material, and the electrochemical performance of electrodes in Li-cells. Capacities up to 190, 180 and 170 mAh g −1 could be obtained with Li[NiMn]O 2 , LiNi 0.4 Mn 0.4 Co 0.2 O 2 and LiNi 0.33 Mn 0.33 Co 0.33 O 2 , respectively. In terms of rate capability, the order of these electrodes is NMC 0.4 Mn 0.4 Co 0.2 O 2 ≪ Li[NiMn]O 2 . Many hundreds of cycles at full DOD could be obtained with Li[NiMn]O 2 and NMC electrodes in Li-cells, at room temperature. All of these materials develop a unique surface chemistry that leads to their passivation and stabilization in standard electrolyte solutions (alkyl carbonates/LiPF 6 ). The surface chemistry was studied by FTIR, XPS and Raman spectroscopy and is discussed herein.

In this study, we examined the electrochemical behavior of titanium and Ti4+ compounds in THF solutions. Tetra butyl ammonium chloride (TBACl) was used as supporting electrolyte in order to increase the ionic conductivity of the solutions. Electrodeposition of pure titanium could not be obtained. A variety of analytical techniques have been used in conjunction with electrochemical methods in order to analyze the reduction process of Ti4+. These included Raman and UV–vis spectroscopy, ICP and CHNS elemental analyses. Ti4+ is being reduced to Ti3+ in TiCl4/THF/TBACl solutions. In addition we show that metallic titanium can be electrochemically dissolved from an organo-metallic electrolyte solution comprising EtAlCl2 and LiCl in THF. The product is Ti4+. While LiCl is insoluble in THF it reacts with EtAlCl2 to form ionic species. Hence, these solutions possessed reasonable ionic conductivity. We could not obtain electroactive Ti4+ with TiBr4 or TiI4 as starting materials, in similar solutions.

Received 5 July 2006; accepted 30 October 2006DOI 10.1002/app.25813Published online in Wiley InterScience (www.interscience.wiley.com).ABSTRACT: Silver nanoparticles were deposited on thesurface of natural wool with the aid of powered ultra-sound. The average particle size was 5–10 nm, but largeraggregates of 50–100 nm were also observed. The sono-chemical irradiation of a slurry containing wool fibers, sil-ver nitrate, and ammonia in an aqueous medium for 120 minunder an argon atmosphere yielded a silver–wool nano-composite. By varying the gas and reaction conditions, wecould achieve control over the deposition of the metallicsilver particles on the surface of the wool fibers. Theresulting silver-deposited wool samples were characterizedwith X-ray diffraction, transmission electron microscopy,high-resolution transmission electron microscopy, high-re-solution scanning electron microscopy, electron-dispersiveX-ray analysis, Brunauer, Emmett, and Teller physicaladsorption method, X-ray photoelectron spectroscopy,and Raman and diffused reflection optical spectroscopy.The results showed that the strong adhesion of the sil-ver to the wool was a result of the adsorption and interac-tion of silver with sulfur moieties related to the cysteinegroup.

We report electrochemical quartz crystal microbalance (EQCM) results for electrodeposition of titanocene derivatized polypyrrole p(Tc3Py) films and redox transformation of polypyrrole matrix and titanocene centers immobilized in the film. Films of p(Tc3Py), Tc3Py = Tc(CH 2 ) 3 NC 4 H 4 (Tc = Cl 2 TiCpCp′, Cp = C 5 H 5 , Cp′ = C 5 H 4 ) were obtained from acetonitrile solutions of monomer on a Pt disc or thin Au layer evaporated on 10 MHz quartz crystals. Polymerization efficiency, derived from the slope of the change of resonant frequency as a function of the deposition charge ranged from 54% to 75%. A gradual loss of redox activity of Tc centers during consecutive redox cycles of p(Tc3Py) film in TBAFP 6 /THF solutions is discussed in terms of elimination of Cl − ions from the Tc complex and accommodation of solvent molecule. The EQCM data are supported by XPS results. The preliminary studies performed in TEACl in AN solution have shown that the presence of Cl − ions in the solution markedly inhibits the loss of redox activity of Tc centers immobilized in the polymer matrix.

This paper reports a study of the neutralization of Li–SOCl2 batteries. Immersion of these batteries in acidic seawater solutions leads to their complete discharge by short circuit, followed by corrosion of the positive pin (made of an Fe/Ni alloy). This corrosion process is desirable because it allows penetration of water into the battery, and hence, neutralization of the active mass of the batteries through their reaction with water. The most efficient corrosion of Fe/Ni electrodes is obtained in seawater containing both HCl and H2SO4 in a situation of no separation between the electrode compartments, due to the reaction of the H2 liberated at the cathode with the surface films on the anode (Fe/Ni pin electrodes). This reaction prevents passivation of the positive pin. Indeed, used Li–SOCl2 batteries whose insulating covers were removed, corroded much quicker than regular batteries because of the impact of H2 evolved at the case (the negative pole of the battery) on the dissolution of the positive pin.

The electrochemical properties of clean and oxygen-contaminated polycrystalline Ag surfaces have been examined in LiClO{sub 4}/polyethylene oxide solutions in ultrahigh vacuum (UHV) environments at temperatures in the range 323--333 K. Unlike the behavior observed for Au and Ni under the same experimental conditions, no clearly defined voltammetric peaks were found during the first and subsequent cycles in the range 2.20-0.25 V vs. Li/Li{sup +} initiated at the open-circuit potential, 1.75 V vs. Li/Li{sup +}. Instead, the scans in the negative direction were characterized by two adjoining regions in which the current increased linearly with potential, albeit at different rates, and the subsequent scans in the positive direction yielded comparatively much smaller currents largely independent of the applied potential. Integration of the voltammetric curves over the potential range 0.25 < E < 2.20 V vs. Li/Li{sup +} revealed a pronounced imbalance between the charges obtained in the scans in the negative (Q{sub {minus}}) and positive (Q{sub +}) directions. This phenomenon was attributed, by and large, to the high rates of Li dissolution into Ag at these temperatures, consistent with the presence of a low-temperature eutectic in the Li-Ag phase diagram. Additional support for this view was obtained from UHV nonelectrochemical measurementsmore » involving vapor-deposited Li onto Ag, for which the amount of Li on the surface, as monitored by Auger electron spectroscopy, decreased markedly upon increasing the temperature from ca. 300 to 350 K. The voltammetry of oxygen-contaminated Ag surfaces was characterized by a well-defined peak in the scan in the positive direction centered at ca. 1.3 V, which persisted upon continuous cycling. Although the process responsible for this feature has not yet been identified, it provides a marker for detecting oxygen impurities on Ag in this electrolyte.« less

The underpotential deposition (UPD) of lithium on polycrystalline Ni and Ni(111) from LiClO 4 /poly(ethylene))-oxide (PEO) and LiI/PEO electrolytes was examined by cyclic voltammetry in ultrahigh vacuum (UHV) at temperatures, T, in the range 330-340 K. At least two well-defined UPD peaks (A and B), and their corresponding stripping counterparts (A' and B'), were identified in the region 0.25-2.0 V vs. Li[C/R]. Their combined charge, Q A - B (or Q A +B ), estimated from the smoother Ni(111) specimen, was about 40 μC/cm 2 , i.e. equivalent to a Li coverage (θ Li ) of ca. 0.15, assuming Li + undergoes full discharge. The presence of more than a single Li UPD voltammetric feature is consistent with low energy electron diffraction (LEED) studies of K, Cs and Li adsorbed on Ni(111), which revealed different surface superstructures as a function of the alkali metal coverage (θ alk ) for 300 < T < 350 K. Furthermore, the small values of θ Li found just prior to bulk Li electrodeposition, are in harmony with (i) additional LEED information, which indicates that a second alkali metal layer begins to form for θ alk ≤0.5 and (it) the rapid decrease in the work function of Ni. O Ni (and other high work function metals) as a function of θ alk to values lower than O alk for θ alk < 0.3. Electrodeposition of bulk Li on Ni displayed a nucleation growth loop and a sharp stripping peak with no evidence for alloy formation. Marked changes in the voltammetric features could be observed after dosing polycrystalline Ni surfaces with carbon, and especially oxygen, supporting the view that peaks A and B (and A' and B') can indeed be ascribed to Li UPD (and stripping) and not to effects associated with superficial impurities.

The electrochemical insertion of lithium into the basal plane of highly ordered pyrolytic graphite (HOPG-(bp)) from a LiClO{sub 4}/PEO solid polymer electrolyte has been examined in ultrahigh vacuum (UHV) using a carefully designed electrochemical cell. On the basis of a comparison of the data obtained with those recorded for the same interfacial system in an inert gas at atmospheric pressure, it has been concluded that the electrochemical behavior observed in UHV is indeed characteristic of the Li/LiClO{sub 4}(PEO)/(HOPG)(bp) system and therefore not affected in any discernible way by the ultralow pressures. Coulometric analysis of cyclic voltammetry experiments showed that the charge associated with lithium intercalation is larger than that observed during subsequent deintercalation, particularly during the first few intercalation-deintercalation cycles. However, the total amount of impurities observed in Auger electron spectra of emersed HOPG(bp) surfaces following lithium intercalation was very low. This last finding is inconsistent with the presence of a film of any significant thickness on the surface, suggesting that the charge imbalance for this interface is due to kinetic hindrances during lithium deintercalation. 10 refs., 3 figs.

Rechargeable Mg batteries are the focus of extensive work, throughout the world1-3. The high abundance of magnesium in the earth's crust and the chance to gain high volumetric energy density and prolonged cycle-life with non-aqueous rechargeable Mg batteries, make them very attractive. Over the years, we see an interesting and impressive evolution of the electrolyte solutions in which Mg anodes are reversible and their electrochemical windows exceed 3V. In this presentation we focus on the challenge of electrolyte solutions for rechargeable Mg batteries. In general, such solutions should be based on ether solvents. Highly interesting are poly-ethers, which are not volatile and may be easily purified. The first generations of electrolyte solutions for rechargeable Mg batteries were complexes which included electrolyte moieties with organo-metallic bonds (with elements such as aluminum or boron). Such complex electrolyte solutions cannot be compatible with high capacity/high voltage cathode materials based on transition metal oxides. In turn, conventional electrolyte solutions comprising Mg salts, in which transition metal oxides may intercalate reversibly with Mg ions, are irrelevant for reversible Mg anodes due to complicated passivation phenomena. Electrolyte solutions based on “simple” salts are assumed to be the most practical candidates for rechargeable Mg battery systems if Mg anodes can behave reversibly in them. By simple we mean Mg salts, with non-organometallic components, similar to the ones regularly used in lithium ion battery systems with anions such as TFSI-, ClO4 -, PF6 - etc. Due to reactivity issues, only ethers are considered as viable solvents for secondary Mg-metal based batteries, as they were shown to be inert with Mg metal and do not form passivation layers. Until now, Mg(N(SO2CF3)2)2 (denoted as MgTFSI2) is the only ethers-soluble “simple” salt reported that forms ethereal solutions which allow reversible behavior of Mg anodes4 , 5. MgTFSI2 is an attractive salt for Mg batteries electrolyte solutions, endowed with a high thermal and oxidation stability .It also forms highly ionic conductive solutions with ether solvents. Magnesium can be reversibly deposited, to some extent, from MgTFSI2/glyme solutions, indicating that the MgTFSI2 salt is stable with Mg metal anodes. Although its long-term electrochemical cycling performance is rather poor, it can be significantly enhanced with addition of chlorides and through conditioning process5. A highly interesting ether solvent for Mg batteries is dimethoxyethane - DME. We encounter very interesting phenomenon with DME based solutions. At certain salt concentrations MgTFSI2/DME mixtures may form two immiscible solution phases with DME. This phenomenon is extremely unique and, as far as we know, had not been investigated deeply. This phenomenon resembles miscibility-gap to a great extent. We studied this phenomenon using a wide variety of analytical tools, such as SCXRD SSNMR, and Raman coupled with DFT calculations. In this study we were able to determine the solutions structures of the different MgTFSI2/DME phases and theorize a plausible explanation for the two-phase phenomenon. Knowing the arrangement of the solvent/anion/cation in the solution matrix can help explains the properties of these electrolyte solutions and produces a viable model for their electrochemical behavior. We believe that our study can help to improve the relevance of MgTFSI2/poly-ether solutions for practical rechargeable Mg batteries. References 1 Liao, C. et al. The unexpected discovery of the Mg(HMDS)2/MgCl2 complex as a magnesium electrolyte for rechargeable magnesium batteries. Journal of Materials Chemistry A 3, 6082-6087(2015). 2 Tutusaus, O. et al. An Efficient Halogen-Free Electrolyte for Use in Rechargeable Magnesium Batteries. Angewandte Chemie International Edition 54, 7900-7904(2015). 3 Pour, N., Gofer, Y., Major, D. T. & Aurbach, D. Structural Analysis of Electrolyte Solutions for Rechargeable Mg Batteries by Stereoscopic Means and DFT Calculations. Journal of the American Chemical Society 133,6270-6278(2011). 4 Ha, S.-Y. et al. Magnesium(II) Bis(trifluoromethane sulfonyl) Imide-Based Electrolytes with Wide Electrochemical Windows for Rechargeable Magnesium Batteries. ACS applied materials & interfaces 6, 4063-4073(2014). 5 Shterenberg, I. et al. Evaluation of (CF3SO2)2N− (TFSI) Based Electrolyte Solutions for Mg Batteries. Journal of the Electrochemical Society 162, A7118-A7128(2015).

The correlation between Li cycling efficiency, Li morphology, Li surface chemistry, and the properties of the Li-solution inter-phase was investigated in the THF, 2Me-THF, 2Me-Furan (MF), LiAsF{sub 6} electrolyte system. Surface sensitive FTIR, EDAX-X-ray microanalysis, SEM, and impedance spectroscopy were used in conjunction with standard electrochemical techniques. Using THF as a cosolvent to 2Me-THF decreases the detrimental impact of contaminants such as water as it is more reactive toward lithium than 2Me-THF. The presence of MF (a few percent) influences the Li surface chemistry since its reduction to surface compounds with alloy groups suppresses solvent and salt reduction. However, its effect on Li morphology and cycling efficiency is marginal. It is concluded that the main positive impact of this additive reported in the literature is due to the stabilizing effect of the ethers by its possible reaction with trace Lewis acid contaminants in the solutions. The superiority of LiAsF{sub 6} as an electrolyte for these solutions is attributed to the precipitation of elementary arsenic and arsenic compounds (e.g., Li{sub 3}As, Li{sub x}AsF{sub y}) on lithium, which modifies Li deposition to become uniform and smooth.

Our recent studies on the correlation between Li-cycling efficiency, morphology, interfacial properties and surface chemistry in a variety of Li battery electrolyte solutions are reviewed. The solvent systems include alkyl carbonate mixtures, ether and ether alkyl carbonate mixtures, and methyl formate solutions. The techniques include surface sensitive Fourier-transform infrared spectroscopy and standard electrochemical techniques. The principal points are: (i) the surface chemistry of Li is determined by a delicate balance between reduction processes of the solvents, salts and common contaminants; (ii) the surface films initially formed are subjected to ageing processes which gradually change their structure and properties; (iii) the heterogeneous chemical structure of the Li electrode's surface films induces non-uniform Li deposition; (iv) the cycling efficiency is high in systems where Li deposition is smooth and/or the Li deposited is efficiently passivated by the surface species instantaneously formed on it, and (v) it is evident that less hygroscopic surface species passivate the active metal in solution (e.g., Li2CO3, LiF) more effectively.

The Li cycling efficiency surface chemistry and Li morphology in ethylene carbonate (EC) and propylene carbonate (PC) based electrolyte solutions were investigated and correlated. Surface sensitive ex situ FTIR spectroscopy, X-ray microanalysis and scanning electron microscopy were used in conjunction with standard electrochemical techniques. EC is more reactive than PC in electroreduction processes and is reduced on noble metals to ethylene dicarbonate. The difference in reactivity between the two solvents is discussed, based on MO ab initio calculations of their radical anions (and Li+ stabilized radical anions). In spite of the high reactivity of these systems to lithium, the Li cycling efficiency is strongly dependent on the presence of additives and contaminants at the ppm level that modify the Li surface chemistry in solutions. The two alkyl carbonate solvents decompose when stored over activated Al2O3 and CO2 is formed. The presence of CO2 in solutions increases the Li cycling efficiency considerably due to the formation of Li2CO3 on the Li surfaces.

The electrochemical behavior of contaminated 1,3-dioxolane (DN)—LiClO4 solutions with lithium and noble metals (e.g gold, platinum) electrodes was investigated using surface sensitive FT-ir, scanning electron microscopy, (SEM), X-ray microanalysis, linear sweep voltammetry and other electrochemical techniques. The contaminants included products of polymerization of DN, water and oxygen. It was found that the above contaminants considerably influence surface chemistry of lithium or noble metal electrodes in DN solution. The presence of polymeric species (resulting from solvent reactions) in solutions increases the solubility of solvent, water or oxygen reduction products and therefore reduces the “natural” passivation of lithium or noble metals at low potentials in solutions. Consequently, water or solvent reduction at low potentials is more feasible compared to other polar aprotic systems. Thus, the voltammetric behavior of contaminated DN solutions is quite different compared to other ethereal solutions. The presence of the above contaminants in DN solutions is detrimental to the performance of Li electrodes. This is in contrast to several polar aprotic systems where the presence of O2 or even H2O increases Li cycling efficiency.

A revolution in modern electronics has led to the miniaturization and evolution of many portable devices, such as cellular telephones and laptop computers, since the 1980s. This has led to an increasing demand for new and compatible energy storage technologies. Furthermore, a growing awareness of pollution issues has provided a strong impetus for the science and technology community to develop alternatives with ever-higher energy densities, with the ultimate goal of being able to propel electric vehicles. Magnesium's thermodynamic properties make this metal a natural candidate for utilization as an anode in high-energy-density, rechargeable battery systems. We report herein on the results of extensive studies on magnesium anodes and magnesium insertion electrodes in nonaqueous electrolyte solutions. Novel, rechargeable nonaqueous magnesium battery systems were developed based on the research. This work had two major challenges: one was to develop electrolyte solutions with especially high anodic stability in which magnesium anodes can function at a high level of cycling efficiency; the other was to develop a cathode that can reversibly intercalate Mg ions in these electrolyte systems. The new magnesium batteries consist of Mg metal anodes, an electrolyte with a general structure of Mg(AlX(3-n)R(n)R')(2) (R',R = alkyl groups, X = halide) in ethereal solutions (e.g., tetrahydrofuran, polyethers of the "glyme" family), and Chevrel phases of MgMo(3)S(4) stoichiometry as highly reversible cathodes. With their practical energy density expected to be >60 Wh/Kg, the battery systems can be cycled thousands of times with almost no capacity fading. The batteries are an environmentally friendly alternative to lead-acid and nickel-cadmium batteries and are composed of abundant, inexpensive, and nonpoisonous materials. The batteries are expected to provide superior results in large devices that require high-energy density, high cycle life, a high degree of safety, and low-cost components. Further developments in this field are in active progress.

Developing an organo-metallic free electrolytic solution is crucial step towards a practical magnesium battery system. Implementing Grignard reagents in a commercial battery would pose a great impediment owing to the material’s high cost, its hazardous nature, and high susceptibility towards oxidation. The Magnesium Aluminum Chloro Complex (MACC) solutions, developed at the Bar Ilan University in conjunction with its allies at Pellion, Cambridge, MA, consist of solely inorganic salts; MACC is the reaction products of the acid base reaction between MgCl2 and AlCl3 in the right proportion in THF. MACC solutions are endowed with high Mg deposition/stripping cycling efficiency, upwards of 99%, low over-potential for magnesium deposition and a wide electrochemical window of 3.1V. Reversible intercalation/de-intercalation of Mg ions into Chevrel-phase Mo6S8, from a MACC solution has also been demonstrated. Normally, freshly synthesized MACC solution exhibits very poor magnesium deposition/dissolution reversibility. However, it was discovered serendipitously that by an electrochemical process, coined “conditioning”, it is possible to significantly enhance the electrochemical characteristics of such electrolyte solutions. The electrochemical “conditioning” consist of slowly electrochemically cycling the solutions in a sealed cell, using Pt as WE and Mg foil as CE in the potential range of -1.2V and 2.8V. This study is an important step forward, eliminating the need for Grignard/organo-metallic based electrolytes with their intrinsic disadvantages, and towards a more “simple salt” based system.

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The first working Mg rechargeable battery prototypes were ready for presentation about 13 years ago after two breakthroughs. The first was the development of non-Grignard Mg complex electrolyte solutions with reasonably wide electrochemical windows in which Mg electrodes are fully reversible. The second breakthrough was attained by demonstrating high-rate Mg cathodes based on Chevrel phases. These prototypes could compete with lead–acid or Ni–Cd batteries in terms of energy density, very low self-discharge, a wide temperature range of operation, and an impressive prolonged cycle life. However, the energy density and rate capability of these Mg battery prototypes were not attractive enough to commercialize them. Since then we have seen gradual progress in the development of better electrolyte solutions, as well as suggestions of new cathodes. In this article we review the recent accumulated experience, understandings, new strategies and materials, in the continuous R&D process of non-aqueous Mg batteries. This paper provides a road-map of this field during the last decade.

LiMnPO4 nanoparticles synthesized by the polyol method were examined as a cathode material for advanced Li-ion batteries. The structure, surface morphology, and performance were characterized by X-ray diffraction, high resolution scanning electron microscopy, high resolution transmission electron microscopy, Raman, Fourier transform IR, and photoelectron spectroscopies, and standard electrochemical techniques. A stable reversible capacity up to 145 mAh g(-1) could be measured at discharge potentials > 4 V vs Li/Li+, with a reasonable capacity retention during prolonged charge/discharge cycling. The rate capability of the LiMnPO4 electrodes studied herein was higher than that of LiNi0.5Mn0.5O2 and LiNi0.8Co0.15Al0.05O2 (NCA) in similar experiments and measurements. The active mass studied herein seems to be the least surface reactive in alkyl carbonate/LiPF6 solutions. We attribute the low surface activity of this material, compared to the lithiated transition-metal oxides that are examined and used as cathode materials for Li-ion batteries, to the relatively low basicity and nucleophilicity of the oxygen atoms in the olivine compounds. The thermal stability of the LiMnPO4 material in solutions (measured by differential scanning calorimetry) is much higher compared to that of transition-metal oxide cathodes. This is demonstrated herein by a comparison with NCA electrodes. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3125765] All rights reserved.

Lithium electrodes in a few selected polar aprotic electrolyte systems were investigated using electrochemical techniques in conjunction with surface‐sensitive Fourier transform infrared spectroscopy and scanning electron microscopy. The solvents used were γ‐butyrolactone (BL), propylene carbonate (PC), and tetrahydrofuran (THF), and the salts included and . Cycling efficiency of lithium electrodes was correlated to their surface chemistry and morphology in the various solvent systems. The effects of both water and oxygen contamination were rigorously studied. It was found that the presence of oxygen in solutions considerably increased the cycling efficiency of the lithium electrode. This effect correlates well with the influence of the presence of oxygen on the surface morphology of lithium electrodes in solutions. The presence of water increases cycling efficiency of Li electrodes in PC, and decreases cycling efficiency of Li electrodes in ethers. These results are discussed in light of the surface chemistry of lithium electrodes in the various solvent systems.

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Electrolyte solutions of magnesium organo-halo-aluminates in ethers are suitable for rechargeable magnesium batteries as they enable highly reversible electrodeposition for magnesium while they possess a wide electrochemical window (>2.2 V). Adding LiCI or tetrabutylammonium chloride to these solutions considerably improves their ionic conductivity, the kinetics of the Mg deposition-dissolution processes, and the intercalation behavior of Mg x MO 6 S 8 Chevrel cathodes. The dissolution of both salts in the electrolytic solutions involves acid-base reactions with complex species. Multinuclei nuclear magnetic resonance and Raman spectroscopy were used in conjunction with electrochemical techniques to study these systems. The nature of these reactions, their products, and the way they influence the various properties of these solutions, are discussed herein.