Magnesium battery

A concentrated aluminum chloride (AlCl 3 )-diglyme (G2) electrolyte is used to prepare hard and corrosion-resistant aluminum (Al) electrodeposited films. The Al electrodeposits obtained from the electrolyte with an AlCl 3 /G2 molar ratio x = 0.4 showed a void-free microstructure composed of spherical particles, in stark contrast to flake-like morphologies with micro-voids for lower x. Neutral complexes rarely exist in the x = 0.4 electrolyte, resulting in a relatively high conductivity despite the high concentration and high viscosity. Nanoindentation measurements for the Al deposits with >99% purity revealed that the nanohardness was 2.86 GPa, three times higher than that for Al materials produced through electrodeposition from a well-known ionic liquid bath or through severe plastic deformation. Additionally, the void-free Al deposits had a <100> preferential crystal orientation, which accounted for better resistance to free corrosion and pitting corrosion. Discussions about the compact microstructure and <100> crystal orientation of deposits obtained only from the x = 0.4 concentrated electrolyte are also presented.

Reversible electrochemical magnesium plating/stripping processes are important for the development of high-energy-density Mg batteries based on Mg anodes. Ether glyme solutions such as monoglyme (G1), diglyme (G2), and triglyme (G3) with the MgTFSI2 salt are one of the conventional and commonly used electrolytes that can obtain the reversible behavior of Mg electrodes. However, the electrolyte cathodic efficiency is argued to be limited due to the enormous parasitic reductive decomposition and passivation, which is governed by impurities. In this work, a systematic identification of the impurities in these systems and their effect on the Mg deposition–dissolution processes is reported. The mitigation methods generally used for eliminating impurities are evaluated, and their beneficial effects on the improved reactivity are also discussed. By comparing the performances, we proposed a necessary conditioning protocol that can be easy to handle and much safer toward the practical applic...

Mg alloys have frequently been studied as anodes for Mg-ion batteries due to their high specific capacity and low electrochemical potential. In the present study, we investigated the interfacial stability of MgBi alloy anodes with solid-state electrolytes. The bubble-like solid electrolyte interface (SEI) was observed between the MgBi alloy anode and Mg(BH 4 ) 2 •1.9NH 3 solid-state electrolyte, leading to the unstable Mg stripping/plating on the MgBi alloy. Theoretical simulations suggest that the bubble-like SEI originates from the different Mg-ion dynamics on the eutectic region (e.g., Mg + Mg 3 Bi 2 phases) and the Mg matrix. The addition of MgBr 2 •2NH 3 nanoparticles in Mg(BH 4 ) 2 •1.9NH 3 suppresses the formation of a bubble-like SEI through the etching effect of Br -ions. Consequently, interfacial resistance is lowered and the interfacial stability is drastically enhanced, e.g., Mg stripping/plating for over 1,200 cycles at 0.1 mA cm -2 with a low overpotential around 0.05 V.

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Iron (Fe) metal batteries, such as Fe-ion batteries and all Fe flow batteries, are promising energy storage technologies for grid applications due to the extremely low cost of Fe and Fe salts. Nonetheless, the cycle life of Fe metal batteries is poor primarily due to the low Coulombic efficiency of the Fe deposition/stripping reaction. Current aqueous electrolytes based on Fe chloride or sulfate salts can only operate at a Coulombic efficiency of <91% under mild operation conditions (<5 mA/cm 2), largely due to undesired hydrogen evolution reaction (HER). This work reports a series of novel Fe electrolytes, Fe electrolytes reinforced with Mg ions (FERMI) and Ca ions (FERCI), which have remarkably better Coulombic efficiency, higher conductivity, and faster deposition/stripping kinetics. By the addition of 4.5 M MgCl 2 or CaCl 2 into the baseline FeCl 2 electrolyte, the Fe deposition/stripping efficiency can be significantly improved to 99.1%, which greatly boosts the cycling performance of Fe metal batteries in both half-cells and full-cells. Mechanistic studies reveal that the remarkably improved efficiency is due to a reduced amount of "dead Fe" as well as suppressed HER. By the combination of experiments and molecular dynamics and density functional theory computation, the electrolyte structure is revealed, and the mechanism for enhanced water reduction resistance is elucidated. These novel electrolytes not only enable a highly reversible Fe metal anode for low-cost energy storage technologies but also have the potential to address the HER side reaction problem in other electrochemical technologies based on aqueous electrolytes, such as CO 2 reduction, NH 3 synthesis, etc.

Atmospheric pressure plasma jets (APPJs) have more advantages regarding flexibility of operation than low pressure plasmas. Because the ions and/or electrons in the APPJ can be arbitrarily extracted to a gas-phase space by changing the DC bias voltage and efficiently deposited onto particle surfaces in an external electric field, this operating technique can be applied towards controlling particle charge. Several methods to control the particle charge using an APPJ system have already been reported. This article summarizes the specifications and operations of these systems, their mechanisms of charge transfer, and methods for particle charging, based on previously reported work. The methods are categorized into three groups, i.e., direct charging of particles, direct charging of a powder bed, and indirect charging of particles, and the corresponding experimental setups, procedures, results, and discussions are presented.

Atmospheric pressure plasma jets (APPJs) have more advantages regarding flexibility of operation than low pressure plasmas. Because the ions and/or electrons in the APPJ can be arbitrarily extracted to a gas-phase space by changing the DC bias voltage and efficiently deposited onto particle surfaces in an external electric field, this operating technique can be applied towards controlling particle charge. Several methods to control the particle charge using an APPJ system have already been reported. This article summarizes the specifications and operations of these systems, their mechanisms of charge transfer, and methods for particle charging, based on previously reported work. The methods are categorized into three groups, i.e., direct charging of particles, direct charging of a powder bed, and indirect charging of particles, and the corresponding experimental setups, procedures, results, and discussions are presented.

The two technical limitations of iron-air batteries are: (1) Hydrogen evolution reaction (HER) and (2) Passivation. While HER account for low charging efficiency while passivation in Fe-air batteries account for its inability to fully discharge at a high rate due to the formation of iron hydroxide. As a result of this, many studies have has been dedicated to inhibiting inhibit these problems. Just like in recent literatures, the enhancement of Fe-air anode for commercialization is not trivial. With high purity carbonyl Fe-MoS 2 composites electrode and the influence of 2 mM Na 2 S additives in 6M KOH electrolyte solution and 1.88 wt. % polyacrylic acid as the gelling agent, during cycling process, we have demonstrated a high performance carbonyl Fe anodes comprising of with 3 wt. % MoS 2 (F3M), 5 wt. % MoS 2 (F5M), and 10 wt. % MoS 2 (F10M) as additive additives to in Fe anodes. In conjunction with the unique structure and synergistic effect that characterizes two excellent anode materials, F3M shows excellent performance, low side effects (corrosion and passivation), superior capacity retention and efficiency during cycling compare to F5M and F10M. The result of the various electrodes characterized via field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) reveals that the additives produce a distinct surface morphology and crystallographic patterns that correspond to fundamental crystallographic growth patterns. Additionally, Energy dispersive spectroscopy (EDS) and SEM mapping affirms that both the Fe and additive (weight (Wt. %) and atomic percent (At. %)) were well dispersed in the electrode. According to Tafel test, Tafel test shows that F3M, F5M, and F10M exhibits corrosion inhibition efficiency of 51.2 %, 21.1 % and 5.6 % respectively. Thus, the corrosion rate decreased in the order of bare Fe > F10M > F5M > F3M. While drastic capacity retention drops occur in the bare Fe electrode around 300 th cycle, we were able to regenerate the battery back to full capacity via our choice of additives (F3M). During regeneration at 800 th cycles, the capacity retention of F3M, F5M and F10M electrodes were was 97%, 93%, and 76% respectively. F3M, F5M and F10M electrodes. Therefore, in conjunction with the unique structure and synergistic effect that characterizes two excellent anode materials, F3M is best choice for a highperformance Fe-air battery due to its excellent performance, low side effects (corrosion and passivation), low float current, superior capacity retention and efficiency during cycling compare to F5M and F10M.

The two technical limitations of iron-air batteries are: (1) Hydrogen evolution reaction (HER) and (2) Passivation. While HER account for low charging efficiency while passivation in Fe-air batteries account for its inability to fully discharge at a high rate due to the formation of iron hydroxide. As a result of this, many studies have has been dedicated to inhibiting inhibit these problems. Just like in recent literatures, the enhancement of Fe-air anode for commercialization is not trivial. With high purity carbonyl Fe-MoS 2 composites electrode and the influence of 2 mM Na 2 S additives in 6M KOH electrolyte solution and 1.88 wt. % polyacrylic acid as the gelling agent, during cycling process, we have demonstrated a high performance carbonyl Fe anodes comprising of with 3 wt. % MoS 2 (F3M), 5 wt. % MoS 2 (F5M), and 10 wt. % MoS 2 (F10M) as additive additives to in Fe anodes. In conjunction with the unique structure and synergistic effect that characterizes two excellent anode materials, F3M shows excellent performance, low side effects (corrosion and passivation), superior capacity retention and efficiency during cycling compare to F5M and F10M. The result of the various electrodes characterized via field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) reveals that the additives produce a distinct surface morphology and crystallographic patterns that correspond to fundamental crystallographic growth patterns. Additionally, Energy dispersive spectroscopy (EDS) and SEM mapping affirms that both the Fe and additive (weight (Wt. %) and atomic percent (At. %)) were well dispersed in the electrode. According to Tafel test, Tafel test shows that F3M, F5M, and F10M exhibits corrosion inhibition efficiency of 51.2 %, 21.1 % and 5.6 % respectively. Thus, the corrosion rate decreased in the order of bare Fe > F10M > F5M > F3M. While drastic capacity retention drops occur in the bare Fe electrode around 300 th cycle, we were able to regenerate the battery back to full capacity via our choice of additives (F3M). During regeneration at 800 th cycles, the capacity retention of F3M, F5M and F10M electrodes were was 97%, 93%, and 76% respectively. F3M, F5M and F10M electrodes. Therefore, in conjunction with the unique structure and synergistic effect that characterizes two excellent anode materials, F3M is best choice for a highperformance Fe-air battery due to its excellent performance, low side effects (corrosion and passivation), low float current, superior capacity retention and efficiency during cycling compare to F5M and F10M.

Many studies recognize that membrane lithium air batteries (LABs) are preferable to non-membrane lithium air batteries for future applications as an energy source. An intensive collection of work was published several years ago regarding air cathodes, lithium metal anodes, and electrolytes, among others. Typically, the membrane is sandwiched between an air cathode and a lithium metal anode and protects the anode from any impurities such as oxygen and water that diffuse from cathode to anode in LABs. Membranes have been used as electrolytes and separators and have been used at the outer side of the cathode and the inner side of the cathode and anode in LABs. Therefore, there is an urgent need to discuss the potential advantages of different membranes to understand the possible mitigations of challenges related to LABs. This review examines the effectiveness of various membranes in the primary components of LABs, including air cathodes, lithium metal anodes, electrolytes and electrodes. Several membranes were effective in limiting the gas permeation and water permeability in LABs. The prospects of these membranes in LABs are determined by their efficacy in overcoming the related problems that work against the energy storage in LABs for future studies. Li+ +½ O 2 +e − ↔½ Li 2 O 2 (reaction at cathode) (4)

An attempt has been made to synthesize chloride free Magnesium salt. Magnesium Diethylphosphate (Mg(DEP)) by adopting a novel and economically viable chemical route. The salt is dissolved in N,N-Dimethylformamide (DMF) and used as electrolyte for rechargeable magnesium battery (RMB). Reversible magnesium dissolution and deposition was examined in Mg-half cell and full cell at varying potential windows. The reversible Mg intercalation and de-intercalation at graphite cathode was analyzed by cyclic voltammetry, galvanostatic charge-discharge and impedance analysis. Mg-Graphite full cell has shown a discharge capacity of 70 mAh/g for 180 cycles. The cycled electrode's SEM, XRD, XPS analysis conclude the plausible Mg-ions intercalation into the graphite. The studies could help in the development of chloride free Mg salts with potential application to serve as electrolyte for RMBs.

Hydrogen atoms, THF of crystallization, and second component of disorder are omitted for clarity. Reprinted with permission from ref 52. Copyright 2011 Nature Publishing Group. (b) ORTEP plot (25% thermal probability ellipsoids) of (Mg 2 (μ-Cl) 3 •6THF)(Ph 2 AlCl 2) (APC); 50% thermal probability ellipsoids; hydrogen atoms omitted for clarity. Reprinted with permission from ref 9.

The battery market is undergoing quick expansion owing to the urgent demand for mobile devices, electric vehicles and energy storage systems, convoying the current energy transition. Beyond Li-ion batteries are of high importance to follow these multiple-speed changes and adapt to the specificity of each application. This review-study will address some of the relevant post-Li ion issues and battery technologies, including Na-ion batteries, Mg batteries, Ca-ion batteries, Zn-ion batteries, Al-ion batteries and anionic (F-and Cl-) shuttle batteries. MH-based batteries are also presented with emphasize on NiMH batteries, and novel MHaccommodated Li-ion batteries. Finally, to facilitate further research and development some future research trends and directions are discussed based on comparison of the different battery systems with respect to Li-ion battery assumptions. Remarkably, aqueous systems are most likely to be given reconsideration for intensive, cost-effective and safer production of batteries; for instance to be utilized in (quasi)-stationary energy storage applications.

Organic carbonyl molecules have recently been investigated as redox-active electrode materials in rechargeable organic batteries (ROBs), and although redox-active polymers offer high specific energy density and tunable redox potential windows, their undesirable dissolution into aprotic electrolytes during charge/discharge cycling and their poor electronic conductivity compromised their utilization in ROBs. To overcome these challenges, we synthesized, for the first time, two 3,4:9,10-perylenetetracarboxylic dianhydride (PTCDA)-based polyimides, namely, perylenediimide-benzidine (PDI-Bz) and perylenediimide-urea (PDI-Ur), and utilized them as organic cathode materials for lithium-ion batteries and sodium-ion batteries. These cathode materials are synthesized through imidization of a non-bay-substituted PTCDA unit by using bifunctional amine compounds (i.e., benzidine and carbonyl diamine (urea)) via a simple one-step reaction. Our organic metal-ion batteries employing PDI-Bz demonstrate a high discharge capacity of 120 mAh/g (with a reversible capacity of ∼54 mAh/g) vs Li + /Li and the second discharge capacity of 111 mAh/g (∼74 mAh/g) vs Na + /Na with two discharge voltage plateaus in the range of 1.9−2.4 V. The cells retained a capacity retention of 46% vs Li + /Li and 55.2% vs Na + /Na over 50 cycles. PDI-Ur exhibits higher lithiation capacity of ∼119 mAh/g at the 14th cycling (increased discharge capacity of ∼118 mAh/g at the 25th cycling). In SIBs, PDI-Ur shows an initial discharge capacity of ∼119 mAh/g with a single discharge voltage plateau around 1.9 V vs Na + /Na and the capacity retention of ∼78.7% (∼93 mAh/g) over 50 cycles, both of which are suggesting a potential feasibility of these PTCDA-based polyimides as promising organic cathode materials for high-capacity metal-ions batteries.

Ag/C, Mn3O4/C and AgMnO2/C electrocatalysts were selected for nanocatalyst structure and electrochemical activity characterisation by transmission electron microscopy (TEM), X-ray spectroscopy (EDX), cyclic voltammetry (CV), X-ray diffraction (XRD) and oxygen reduction reaction (ORR). The nanocatalysts displayed ethanol-tolerance for ORR in KOH solution electrolyte at different temperatures. All electrocatalysts prevented oxidation from ethanol crossover through the membrane from the anode to cathode compartments in alkaline direct ethanol fuel cells (ADEFCs). ORR results confirmed that AgMnO2/C significantly improved the current activity.

Mg-air batteries, with their intrinsic advantages such as high theoretical volumetric energy density, low cost, and environmental friendliness, have attracted tremendous attention for electrical energy storage systems. However, they are still in an early stage of development and suffer from large voltage polarization and poor cycling performance. At present, Mg-air batteries with high rechargeability remain difficult to achieve, mainly because the discharge products [Mg(OH)2, MgO and MgO2] are thermodynamically and kinetically difficult to decompose at moderate voltage ranges. Therefore, it is crucial to optimize the reaction paths and kinetics from the electrodes to the batteries via the combination of materials design and first-principles calculations. In this review, remarkable progress is highlighted regarding the currently used materials for Mg-air batteries, including anodes, electrolytes, and cathodes. In addition, the corresponding reaction mechanisms are comprehensively sur...

Nanotechnology is a field of research with objects up to 100 nm in size. Nanomaterials belong to a wide area in the field of material engineering. These include nanolayers, nanoslabs, nanopores, nanotubes, nanofibers, nanoparticles and quantum dots. Nanostructures are characterized by special properties due to their nanometric dimensions. The natural properties of nanostructures allow their wide application in various industries. The paper presents an overview of the application and significance of nanostructures in fuel cell technology, with particular emphasis on nanocatalysts. The article includes the classification of nanomaterials, new hybrid nanostructures, types of surface modification, division by area of application, with particular emphasis on nanomaterials in the advanced energy system. The design and operation of fuel cells and the role of nanoparticles have been described taking into account existing solutions to reduce generator costs. The high price of low temperature fuel cells depends on the number of nanoparticles used. The article describes the risk associated with using products at the nano scale. Higher concentrations of these extremely active materials can be dangerous and can cause ecological problems and harm natural ecosystems.

The paper discusses development under an ESA TRP activity (Contract No. 4000109879/13/NL/LvH) with a target of high specific energy Lithium-ion cells, capable of operating under low temperature conditions, i.e.-40 o C. Such cells may be encountered in future exploration missions, which do not consider the use of Radioisotope Heater Units. During the activity, ≥1 Ah silicon-based high energy density prototype cells, following components characterization and optimization, were designed, developed, manufactured and tested under room and subzero temperature conditions down to-40 o C. The developed and tested prototype cells exhibited energy density of around 208 Wh/Kg at room temperature under C/10 charge-discharge rate within voltage range of 2.8 V and 4.1 V. Moreover, the prototype cells could retain and deliver more than 75% of their capacity at room temperature upon cycling at-40 o C, demonstrating an energy density of 140 Wh/kg.

� Nonstoichiometric SmMn 2 O 5-δ with tunable oxygen deficiency are successfully prepared. � ORR activity in NaCl exhibits a volcanoshaped correlation with oxygen deficiency. � SMO 4.86 shows greatly improved ORR activity and stability in pH-neutral electrolyte. � DFT calculations show that oxygen vacancies lead to easier electron transfer. � Liquid/solid Mg-air batteries assembled with SMO 4.86 show outstanding performance.

Recently, many works have demonstrated that tuning the A-site deficient and excessive stoichiometry can yield the positive effects on the catalytic activity of the ABO 3 perovskite toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Whereas, the universality of the deficient or excessive effects and their resulting improving mechanisms on ABO 3 perovskite are still ambiguous and need to be clarified. In this work, the simplest Mn-based perovskite (LaMnO 3) is selected to elucidate the deficient/excessive effects and improving mechanisms on both ORR and OER. We find that A-site deficient stoichiometry is favor to the catalytic activity and stability of LaMnO 3 toward both ORR and OER, whereas A-site excessive stoichiometry is deleterious to the oxygen catalytic activity and stability of LaMnO 3. The high oxygen catalytic activity of La 0$9 MnO 3 (La90) with A-site deficiency toward ORR and OER can be related to its proper Mn cation valence, large amount of oxygen vacancies, upper shift of dband center and strong adsorption capacity to oxygenated species. The results of this work highlight the A-site deficient Mn-based perovskite as the high efficient and commercially viable bifunctional catalyst for aqueous and solid-state flexible zinc-air battery (ZAB) applications.

Understanding CO electro-oxidation is crucial towards designing catalysts for electrochemically oxidizing complex organic molecules. Earth-abundant Copper (Cu) has recently been demonstrated to exhibit high alkaline CO electro-oxidation activity, rivaling the previously acclaimed Gold (Au). Herein, we combine single crystal rotating 1

Thermally treated caffeine doped active carbon (Caffeine-Norit) is studied as a catalyst for the oxygen reduction reaction (ORR) with application in metal-air systems and neutral aqueous electrolytes. Catalytic activity is characterized by polarization curves and Tafel plots and the results are compared with 5% Platinum (5% Pt-Norit) and 4% Silver (4% Ag-Norit) catalysts. The Tafel slopes of all three catalysts are the same, the activity of Ag-Norit being somewhat smaller then both Caffeine-Norit and Pt-Norit. The polarization curves are also comparable, especially in the low current density region. The increase of overpotential for the Caffeine-Norit at current density higher than 50 mA cm-2 is due to accumulation of H2O2 in the catalyst layer. This was demonstrated by using a simple method for detection of peroxides in neutral electrolytes based on indigo carmine indicator.

The Mg battery electrolyte complex [Mg2Cl3]+ [AlPh4]− is prepared in high yield with 100% atom economy via a AlCl3/MgPh2 ligand exchange reaction. Spectroscopic studies suggest a simpler solution ionic composition than seen previously whilst maintaining high electrochemical performance.

Using density functional calculations, we examine insertion/extraction of Mg ions in Mg 3 Bi 2 , an interesting Mg-ion battery anode. We found that a (110) facet is the most stable termination. Vacating a Mg 2+ ion from the octahedral site is more favourable for both surface and bulk regions of the material. However, the diffusion barriers among the tetrahedral sites are ~ 3 times smaller than those among octahedral sites. Consequently, during the magnesiation/demagnesiation process, Mg ions first vacate the octahedral sites and then diffuse through the tetrahedral sites. The spin-orbit interaction lowers Mg's vacancy formation energy but has a minor effect on diffusion barriers.

Childhood, student, or adolescent, middle-aged, etc. are the short and long journeys of each person's life. In the early stages, people have changed the most, both physically and mentally. In the next stages, the change occurs more slowly but contributes to deepening our sense of life. And, PhDs: the tortuous passage that I have been in for three years. Three-unforgettable-year help a person become more individual, confidant, and especially more human. And I have to sincerely thank some people for what they brought me: First of all, I want to thank my supervisors: Prof. Jean-Claude Lepretre and Dr. Fannie Alloin. Most likely, I'm not their easiest case they've supervised to explain things more complicated than they are, particularly regarding my habit. I am nevertheless pleased with their input and assistance in clarifying my thoughts and words whenever appropriate. During my first year at LEPMI in particular, their inspiring words were extremely helpful when times were tough. Fannie has always been there, she's paid a lot of attention to my job every time and during these three years she's taken the right choice every time. To be more accurate, I have learned a considerable amount of skills in all the fields: how to address a new subject, the working technique, the analysis of data not limited to the outcome that can be obtained at first glance, the ability to carry on having the most from the job. And there may be more to the chart. Thank you above everything, and all the work you poured into my study, with all its facets. I would like to express my deepest appreciation to the Jury that accepted to examine and referee for my thesis. Thank you for all the interesting questions and fruitful comments on this work. I'd also like to extend my gratitude to my erstwhile supervisor: Prof. Le Ngoc Thach and Ass. Prof. Le My Loan Phung that have been belonged to me and gave me helpful and sincere advice since I was a student up to now. I am also grateful to all MIEL team even if they did not directly supervise my thesis from Dr.

Understanding CO electro-oxidation is crucial towards designing catalysts for electrochemically oxidizing complex organic molecules. Earth-abundant Copper (Cu) has recently been demonstrated to exhibit high alkaline CO electro-oxidation activity, rivaling the previously acclaimed Gold (Au). Herein, we combine single crystal rotating 1 ar X iv :2 10 9. 15 26 9v 2 [ ph ys ic s. ch em -p h] 1 8 O ct 2 02 1 disc electrode (RDE) experiments and ab initio microkinetic modeling to understand the underlying reaction mechanisms on Cu and Au surfaces. Cu exhibits a facetdependent activity with Cu(111) having a 0.27 V lower overpotential than Au(111) and a comparable CO oxidation current density. Using Koutecky-Levich analysis and DFT based microkinetic modeling, we identify the rate-limiting pathway to be LangmuirHinshelwood on Cu whereas Eley-Rideal on Au. We additionally present strikingly variant RDE responses on four Cu facets (111, 100, 110 and 211) and long-term stability analysis on Cu...

Potential oscillation was observed during the template-free galvanostatic deposition in the 58/42 mol% AlCl 3 /trimethylamine hydrochloride ionic liquid, and resulted in the formation of unique periodic (accordion-like) aluminum wires with variable periodicity and diameter controlled by the deposition current density. Factors leading to this phenomenon are postulated.

Two room temperature ionic liquids based on the bis ((trifluoromethyl)sulfonyl)-imide anion (TFSI anion), the tributylmethylammonium-TFSI (Bu3MeN-TFSI) and the butylmethylpyrrolidinium-TFSI (BuMePy-TFSI), have been prepared for the electrochemical study of Li+/Li redox couple, the electrodeposition of Mn, Zn-Mn alloys and Cu-Mn alloys, and the extraction of Cu(II) ions from aqueous solutions, respectively. The best coulombic efficiency of Li+/Li couple is 97%. Mn(II), Zn(II) and Cu(I) species were introduced into the Bu3MeN-TFSI or BuMePy-TFSI by the anodic dissolution of the respective metallic electrodes. Coatings containing Mn, Zn, Cu, Zn-Mn or Cu-Mn can be obtained by controlled-potential electrolysis. The current efficiencies of Mn electrodeposition in either ionic liquid approach 100%. The Zn-Mn and Cu-Mn alloy deposits obtained in this study were compact and adherent. The surface morphology of these deposits depended on the Mn/Zn and Mn/Cu ratio, respectively. The BuMePy-TFSI...

Rechargeable metal-air batteries are considered a promising energy storage solution owing to their high theoretical energy density. The major obstacles to realising this technology include the slow kinetics of oxygen reduction and evolution on the cathode (air electrode) upon battery discharging and charging, respectively. Here, we report non-precious metal oxide catalysts based on spinel-type manganese-cobalt oxide nanofibres fabricated by an electrospinning technique. The spinel oxide nanofibres exhibit high catalytic activity towards both oxygen reduction and evolution in an alkaline electrolyte. When incorporated as cathode catalysts in Zn-air batteries, the fibrous spinel oxides considerably reduce the discharge-charge voltage gaps (improve the round-trip efficiency) in comparison to the catalyst-free cathode. Moreover, the nanofibre catalysts remain stable over the course of repeated discharge-charge cycling; however, carbon corrosion in the catalyst/carbon composite cathode d...

Aluminium-air battery is a type of battery that offers high energy density (up to 8.1 kWh/kg) with a theoretical voltage of 2.71 V. Because of the high energy density and versatility, the battery attracts many users. Similar to other batteries, it consists of electrodes and electrolytes. The study aims to investigate the voltage generated by the battery when different electrolytes are employed. Since different electrolytes discharge different amounts of electron charge, the voltage will also differ from one to another. It also holds true when different pH of electrolyte is used. Using NaCl with a pH of 7, NaOH a with pH of 11 and KOH with a pH of 14, the investigation shows that increasing the level of pH results in a higher generated voltage but has the side effect of making Al more easily dissolved into the electrolyte. For the electrolyte which is considered neutral, i.e. NaCL, the lifetime of the battery was the longest as shown by the stability of the generated voltage compared to the other two electrolytes. NaOH and KOH which are categorized as strong bases showed a considerable decrease in generated voltage during the investigation.

The electrodeposition of Mg metal from an ionic liquid-glyme mixture was investigated at room temperature. The mixture contains a glyme, a simple amide salt Mg(Tf 2 N) 2 (Tf = SO 2 CF 3), and a quaternary-ammonium Tf 2 N ionic liquid. Using the mixture bath, substantial cathodic electrodeposition of Mg at a large current density (∼10 mA cm −2) was observed, suggesting a change in coordination geometry around Mg 2+ cation together with improved conductivity. By mixing diglyme, the conductivity increased by an order of magnitude (2.5-2.6 mS cm −1) compared to the glyme-free ionic liquid (0.35 mS cm −1) and the viscosity became as low as that of pure glyme. Additionally, potentiostatic electrolysis resulted in a non-dendritic thin film of elemental Mg with metallic luster.

Rechargeable magnesium batteries are poised to be viable candidates for large-scale energy storage devices in smart grid communities and electric vehicles. However, the energy density of previously proposed rechargeable magnesium batteries is low, limited mainly by the cathode materials. Here, we present new design approaches for the cathode in order to realize a high-energy-density rechargeable magnesium battery system. Ion-exchanged MgFeSiO 4 demonstrates a high reversible capacity exceeding 300 mAh?g 21 at a voltage of approximately 2.4 V vs. Mg. Further, the electronic and crystal structure of ion-exchanged MgFeSiO 4 changes during the charging and discharging processes, which demonstrates the (de)insertion of magnesium in the host structure. The combination of ion-exchanged MgFeSiO 4 with a magnesium bis(trifluoromethylsulfonyl)imide-triglyme electrolyte system proposed in this work provides a low-cost and practical rechargeable magnesium battery with high energy density, free from corrosion and safety problems.

Thermally treated caffeine doped active carbon (Caffeine-Norit) is studied as a catalyst for the oxygen reduction reaction (ORR) with application in metal-air systems and neutral aqueous electrolytes. Catalytic activity is characterized by polarization curves and Tafel plots and the results are compared with 5% Platinum (5% Pt-Norit) and 4% Silver (4% Ag-Norit) catalysts. The Tafel slopes of all three catalysts are the same, the activity of Ag-Norit being somewhat smaller then both Caffeine-Norit and Pt-Norit. The polarization curves are also comparable, especially in the low current density region. The increase of overpotential for the Caffeine-Norit at current density higher than 50 mA cm-2 is due to accumulation of H2O2 in the catalyst layer. This was demonstrated by using a simple method for detection of peroxides in neutral electrolytes based on indigo carmine indicator.

Rechargeable magnesium batteries are poised to be viable candidates for large-scale energy storage devices in smart grid communities and electric vehicles. However, the energy density of previously proposed rechargeable magnesium batteries is low, limited mainly by the cathode materials. Here, we present new design approaches for the cathode in order to realize a high-energy-density rechargeable magnesium battery system. Ion-exchanged MgFeSiO 4 demonstrates a high reversible capacity exceeding 300 mAh?g 21 at a voltage of approximately 2.4 V vs. Mg. Further, the electronic and crystal structure of ion-exchanged MgFeSiO 4 changes during the charging and discharging processes, which demonstrates the (de)insertion of magnesium in the host structure. The combination of ion-exchanged MgFeSiO 4 with a magnesium bis(trifluoromethylsulfonyl)imide-triglyme electrolyte system proposed in this work provides a low-cost and practical rechargeable magnesium battery with high energy density, free from corrosion and safety problems.

Tetramethylguanidine (TMG) is an organic superbase which has recently found use as a primary functional group in alkaline anion exchange membranes (AAEM). In this study we demonstrate the potential of aqueous TMG alkaline electrolyte as a substitute for NaOH (aq) /KOH (aq) with greater chemical similarity to AAEM functional groups. The water redox activities of Pt and Pd electrodes in 0.1 M TMG and 0.1 M KOH are compared, while hydrogen evolution/oxidation reactions (HER/HOR) and the oxygen reduction reaction (ORR) are studied in depth. Aqueous TMG supports comparable redox activity to KOH of equal concentration, but modifies surface processes through potentialdependent adsorptive behaviors. Rotating electrode, capacitance, and slow polarization measurements suggest that TMG and its decomposition species delay and participate in HER. HOR on Pt resembles that of a perfectly flat (111) surface in KOH, while hydrogen absorption on Pd is significantly hindered. ORR activity is dependent upon overpotential on both electrodes. But unlike most acid and alkaline electrolytes, TMG appears to alter the reaction pathway on Pt toward a 1.5e − route. We propose that native or modified analogues of TMG might be optimized for compatibility with various catalysts so as to be utilized in alkaline electrochemical devices in place of NaOH and KOH.

Metal–air batteries have been designed and developed as an essential source of electric power to propel automobiles, make electronic equipment functional, and use them as the source of power in remote areas and space. High energy and power density, lightweight, easy recharge capabilities, and low cost are essential features of these
batteries. Magnesium air batteries, both primary and rechargeable, show great promise. In this study, we will concentrate on the fundamentals of Mg–air cell electrode reaction kinetics. Anode materials made of magnesium as well as magnesium alloys, air cathode design and
composition, and promising electrolytes for magnesium–air batteries have all been examined. A brief note on the possible and proposed improvements in design and functionality is also incorporated. This article may serve as the primary and premier document in the critical research area of Mg-air battery systems .

The formation and the morphological change of surface film on a Au͑111͒ electrode in propylene carbonate solution containing 0.1 M LiClO 4 in the potential region between 0.8 and 2.5 V (Li/Li ϩ) were studied by in situ scanning tunneling microscopy. The surface film was observed on a gold electrode at potentials more negative than 1.5 V ͑Li/Li ϩ), and many nuclei appeared on the flat terrace of the electrode at potentials more negative than 0.9 V, where underpotential deposition of lithium on gold was started. Many holes on the surface film were observed after the dissolution of lithium and were thought to be formed as a result of breakdown of the film in nanometer order. The deposition and dissolution of the submonolayer lithium affected the surface morphology in nanometer order.

We address sustainable energy issues via scrutinizing magnesium-air reserve batteries. Such energy storage systems can hold their energy indefinitely, releasing it on demand, in emergency situations. Main advantage of water-activated batteries is that their electrolyte is supplied by the environment, where they get deployed, hence, only light weight electrodes and battery frames should be transported, rather than the significantly heavier aqueous electrolyte. Recent literature in the field is reviewed. One merit of this account is that recently, battery storage has become an effective way to increase share of renewables in photovoltaic energy systems utilized in farming. While the specific energy of reserve batteries can be determined unequivocally, their energy density calculation needs a clear definition of the considered battery volume. Therefore, this paper proposes a new modality of evaluating specific energy and energy density of seawater-activated metal-air reserve batteries ...

A concentrated aluminum chloride (AlCl 3)−diglyme (G2) electrolyte is used to prepare hard and corrosion-resistant aluminum (Al) electrodeposited films. The Al electrodeposits obtained from the electrolyte with an AlCl 3 /G2 molar ratio x = 0.4 showed a void-free microstructure composed of spherical particles, in stark contrast to flake-like morphologies with micro-voids for lower x. Neutral complexes rarely exist in the x = 0.4 electrolyte, resulting in a relatively high conductivity despite the high concentration and high viscosity. Nanoindentation measurements for the Al deposits with >99% purity revealed that the nanohardness was 2.86 GPa, three times higher than that for Al materials produced through electrodeposition from a well-known ionic liquid bath or through severe plastic deformation. Additionally, the void-free Al deposits had a <100> preferential crystal orientation, which accounted for better resistance to free corrosion and pitting corrosion. Discussions about the compact microstructure and <100> crystal orientation of deposits obtained only from the x = 0.4 concentrated electrolyte are also presented.

A concentrated aluminum chloride (AlCl 3)−diglyme (G2) electrolyte is used to prepare hard and corrosion-resistant aluminum (Al) electrodeposited films. The Al electrodeposits obtained from the electrolyte with an AlCl 3 /G2 molar ratio x = 0.4 showed a void-free microstructure composed of spherical particles, in stark contrast to flake-like morphologies with micro-voids for lower x. Neutral complexes rarely exist in the x = 0.4 electrolyte, resulting in a relatively high conductivity despite the high concentration and high viscosity. Nanoindentation measurements for the Al deposits with >99% purity revealed that the nanohardness was 2.86 GPa, three times higher than that for Al materials produced through electrodeposition from a well-known ionic liquid bath or through severe plastic deformation. Additionally, the void-free Al deposits had a <100> preferential crystal orientation, which accounted for better resistance to free corrosion and pitting corrosion. Discussions about the compact microstructure and <100> crystal orientation of deposits obtained only from the x = 0.4 concentrated electrolyte are also presented.

In the present work, we tried to obtain flat and smooth silver-grayish aluminum (Al) deposits as is common with plated metal layers. Combination of bath conditions (preliminary electrolysis and additives) and electroplating conditions (pulse waveforms) gave Al layer with several appearances. While a rectangular pulse waveform gave flake-like Al grains, a triangular one gave spherical ones, resulting in flat and smooth Al layer with silver-grayish appearance.

A new kind of ionic liquid (IL) with strong Brønsted acidity, i.e., a hydronium (H 3 O +) solvate ionic liquid, is reported. The IL can be described as [H 3 O + · 18C6]Tf 2 N, where water exists as the H 3 O + ion solvated by 18-crown-6-ether (18C6), of which the counter anion is bis(trifluoromethylsulfonyl)amide (Tf 2 N-; Tf = CF 3 SO 2). The hydrophobic Tf 2 N-anion makes [H 3 O + · 18C6]Tf 2 N stable in air. The Hammett acidity function (H 0 = −4.4) of molten [H 3 O + · 18C6]Tf 2 N, evaluated using the indicator method, is a new record for ILs and indicates strong aciditiy. The findings regarding this proton-condensed solvate IL are of fundamental interest, and will help in the design of media for new acid-base reactions.

We prepared less volatile and halide-free electrolytes for room temperature non-dendritic magnesium (Mg) electrodeposition by mixing a Mg 2+-amide-containing ionic liquid (IL) with equimolar glyme (Mg 2+ +IL : glyme = 1:1). Raman spectroscopy suggested that in the equimolar mixture most glyme molecules are coordinated to Mg 2+ cations and/or IL cations, which is also supported by a single crystal X-ray diffraction study. The glyme-coordinated IL electrolytes showed sizable redox currents (order of mA cm-2), while aging deterioration of electrochemical properties was observed for the triglyme mixture due to partial bath decomposition. The tetraglyme-coordinated IL electrolyte enabled flat electrodeposition of Mg with a metallic luster and showed with very high anodic stability (ca. +4 V vs. Mg) because of decrease in uncoordinated glymes, which can be used for high-voltage Mg ion batteries. In the last few decades elemental magnesium (Mg) has come to be viewed as one of the most interesting negative electrode materials for post lithium ion secondary batteries because of its high-theoretical capacity (3839 mAh cm-3), low electrode potential (-2.356 V vs. SHE), and natural abundance. The well-known electrolytes for elec-trodepositing Mg metal at room temperature are Grignard electrolytes comprised of an ether solvent tetrahydrofuran (THF) and alkylmagne-sium halides RMgX (R = alkyl or aryl groups; X = Cl, Br). Addition of AlCl 3 makes more electroactive species of organo-halo-aluminates, giving larger current density and/or higher anodic stability. 1-10 However , the highly volatile THF and the highly moisture sensitive RMgX and AlCl 3 are difficult to use practically. Safer alternatives to both solvents and solutes for Mg-ion battery electrolytes are still being sought. Several groups have reported deposition of elemental Mg without using THF or RMgX. Ionic liquids (ILs) are one of the least volatile solvents and efforts have been made to electrodeposit Mg from ILs. For example, Mg redox behavior has been observed in an IL solution of Mg(ClO 4) 2 or MgCl 2 , although their current densities were significantly lower than those for RMgX-dissolved ILs. 11 Some organic solvents that enable redox of Mg are less volatile than THF; these include 2-methyl-tetrahydrofuran, 12 and ethyleneglycol dimethylethers (glymes), 13-15 where Mg halides and hydrides were dissolved. Notably , glymes have boiling points above 150 • C and are relatively safe at room temperature. However, in halide or hydride solutions hazardous halogen gas or hydrogen gas may evolve through anodic oxidation. From this viewpoint amide electrolytes are quite desirable as they hardly yield dissociated halogen ions. Glyme solutions of magnesium amides such as bis[(trifluoromethyl)sulfonyl] amide Mg(Tf 2 N) 2 , where Tf denotes (trifluoromethyl)sulfonyl or CF 3 SO 2 , have recently been reported to show successful electrodeposition of Mg metal. 16-19 We have also reported an amide-containing glyme-IL solution with which room temperature electrodeposition of Mg metal was successfully demonstrated. In these Mg 2+-amide-containing glyme solutions, however, sizable amounts of free glyme molecules exists, as in IL-free glyme electrolytes, and thus all the reported electrolytes are either volatile and/or have limited anodic stability to some extent. If free glymes were absent or decreased in an Mg 2+-containing electrolyte like in glyme-lithium salt equimolar complexes, 20 it would be a relatively safe electrolyte with lower vapor pressure and higher oxidative stability compared to the reported glyme-rich Mg amide * Electrochemical Society Active Member. z E-mail: murase.kuniaki.2n@kyoto-u.ac.jp solutions. Furthermore, we speculate that glymes can coordinate the ammonium cations of ILs since macrocyclic polyethers and open-chain polyethers can coordinate alkylammonium cations through hydrogen bonding, 21 and in fact no phase separation occurred in our previous study. 16 Therefore, it is of special interest to investigate glyme-based electrolytes where all glymes coordinate to any cations such as metal cations and/or ammnonium cations of ILs. Notably, the reversible deposition/dissolution cycle of Mg was reported using Mg 2+-amide-containing ILs without glymes; 22-25 this was found to be highly suspicious in subsequent studies. 8,11,16,26-28 In this paper, we studied the room temperature electrochem-istry of metallic Mg using relatively safe electrolytes consisting of a Mg(Tf 2 N) 2 and IL/glyme mixture. Addition of equimolar glyme to Mg 2+-containing ILs gave high stabilities toward oxidation of glymes, all of which seems to be coordinated to Mg 2+ or IL cations. Aging variation of electrochemical behaviors were observed, although the bulk properties of electrolytes were similar. Raman spectroscopy measurements suggested that the first coordination environment in solutions is comprised by oxygen atoms of glyme and of Tf 2 N-. Furthermore, galvanostatic electrolysis gave a thin and adherent film of elemental Mg with a metallic luster. Experimental Reagents.-All reagents were used as received. Battery-grade Mg(Tf 2 N) 2 was purchased from Kishida Kagaku. An ionic liquid PP13-Tf 2 N (N-methyl-N-propylpiperidinium bis[(trifluoromethyl) sulfonyl]amide) was purchased from Kanto Chemical. Electrochemistry-grade diethylene glycol dimethyl ether (diglyme; G2) was also received from Kanto Chemical. Ethylmagnesium bromide (EtMgBr) in THF (Kanto Chemical, 0.95 mol dm-3) was used for electrolyte of the reference electrode (described later). Tri-ethyleneglycol dimethyl ether (triglyme; G3) and tetraethyleneglycol dimethyl ether (tetraglyme; G4) were obtained from Tokyo Chemical Industry. Bath preparation.-First, we made 0.5 mol dm-3 Mg(Tf 2 N) 2 / PP13-Tf 2 N (molar ratio 1 : 7) by mixing at 80 • C overnight under an inert atmosphere in a glove box. Then we mixed the IL solution with each glyme (Mg(Tf 2 N) 2 : PP13-Tf 2 N : glyme = 1:7:8 by mole) with glass-coated stirrers for 30 min in a glove box to make 0.324 or 0.298 or 0.272 mol dm-3 Mg(Tf 2 N) 2 in IL/G2 or IL/G3 or IL/G4 solution. The water content of each bath was less than 50ppm, determined by Karl Fischer titration.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.54.110.71 Downloaded on 2015-06-04 to IP

The electrodeposition of Mg metal from an ionic liquid-glyme mixture was investigated at room temperature. The mixture contains a glyme, a simple amide salt Mg(Tf 2 N) 2 (Tf = SO 2 CF 3), and a quaternary-ammonium Tf 2 N ionic liquid. Using the mixture bath, substantial cathodic electrodeposition of Mg at a large current density (∼10 mA cm −2) was observed, suggesting a change in coordination geometry around Mg 2+ cation together with improved conductivity. By mixing diglyme, the conductivity increased by an order of magnitude (2.5-2.6 mS cm −1) compared to the glyme-free ionic liquid (0.35 mS cm −1) and the viscosity became as low as that of pure glyme. Additionally, potentiostatic electrolysis resulted in a non-dendritic thin film of elemental Mg with metallic luster. Elemental magnesium (Mg) is anticipated as a negative electrode material for post lithium-ion secondary batteries because of its high-theoretical capacity (3839 mAh cm −3), high negative electrode potential (-2.356 V vs. SHE) and natural abundance. Because aqueous electrolytes are not available for electrodeposition of Mg, as is also the case for Li, the electrochemistry of magnesium has been studied in aprotic organic solvents since the early 1900's. 1-6 As Mg ion batteries attract increasing interest, electrodeposition of Mg has been investigated over the last thirty years by several groups, using mainly electrolytes consisting of an ether solvent tetrahydrofuran (THF) and alkylmagnesium halides RMgX (R = alkyl, aryl groups; X = Cl, Br), and some reports indicate that addition of AlCl 3 to form an organo-halo-aluminate is effective in Mg deposition and/or dissolution. 7-16 However, THF is so volatile and alkylmagnesium halides react so vigorously with water that they cannot be used practically. Thus, both the solvents and solutes for Mg deposition baths should be altered in interests of safety. Since ionic liquids (ILs) have attractive characteristics such as lower volatility, incombustibility, high ion conductivity, and electro-chemical stability, several studies on the redox behaviors of metallic Mg using IL have been conducted. Some studies recommend decreasing the volatility and increasing conductivity by mixing ILs with THF solutions of RMgX, where reversible Mg deposition/dissolution at room temperature is reported. 17 Cheek et al. demonstrated the reversible process of Mg deposition/dissolution in THF-free IL solutions of RMgX at 150 • C. 18 Alternative solvents include glymes because they have boiling points and flash points above 100 • C and relatively low volatilities. Aurbach et al. showed the Mg deposition/dissolution cycle with high coulomb efficiency in the tetraglyme-Grignard mixture. 15 Nevertheless, these mixtures still remain dangerous for commercial use since they contain RMgX. Deposition of elemental Mg without THF and/or RMgX has been reported. 18-24 Cheek et al. showed Mg deposition redox behavior at room temperature in an IL dissolving Mg(ClO 4) 2 or MgCl 2 , although their reduction currents were significantly lower than that in RMgX-containing ILs. 18 Abe et al. demonstrated the reversible deposi-tion/dissolution cycle of Mg with high coulombic efficiency in 2Me-THF where MgBr 2 dissolved. 19 In addition, they also showed that some kinds of glyme solution, where MgCl 2 and AlCl 3 were dissolved, gave reversible deposition/dissolution behavior at room temperature. 20 Nevertheless, the abovementioned Mg salts contain halide anions, which can form halogen gas through anodic oxidization. 18 Because halogen gases carry a high environmental burden, non-halide an-ion electrolytes such as Mg(Tf 2 N) 2 are favorable. Although NuLi * Electrochemical Society Active Member. z E-mail: murase.kuniaki.2n@kyoto-u.ac.jp et al. reported the reversible deposition/dissolution cycle of Mg in Mg(Tf 2 N) 2-containing ILs, 21-24 subsequent studies by other groups have not reproduced their results, 14,18,25 indicating that their results of reversible deposition/dissolution are highly questionable. In this paper, we studied the electrodeposition of Mg metal at room temperature from relatively safe electrolytes consisting of IL/diglyme mixture (1 : 4 by volume) dissolving a simple amide salt Mg(Tf 2 N) 2. Addition of an ionic liquid as supporting electrolyte resulted in increased conductivity by an order of magnitude (2.5-2.6 mS cm −1) compared to the IL-free diglyme solution (0.50 mS cm −1). Although certain flammability and volatility still exist in the glyme solution with an IL additive, this plating bath enabled the deposition of a thin and adherent film of elemental Mg with a metallic luster on Cu substrate. Experimental Preparation of the baths.-Trimethyl-n-hexylammonium bis[(trifluoromethyl)sulfonyl]amide (TMHA-Tf 2 N) was synthesized from TMHABr and LiTf 2 N via metathesis as reported previously. 26 N-methyl-N-propylpiperidinium bis[(trifluoromethyl)sulfonyl]amide (PP13-Tf 2 N) and battery-grade diethyleneglycol dimethylether i.e. diglyme (G2) were purchased from Kanto Chemical. Battery-grade Mg(Tf 2 N) 2 was purchased from Kishida Kagaku. First, we made 0.5 mol dm −3 Mg(Tf 2 N) 2 /TMHA-Tf 2 N and 0.5 mol dm −3 Mg(Tf 2 N) 2 /PP13-Tf 2 N (molar ratio 1 : 7) by mixing under an inert atmosphere in a glove box, and then we mixed these IL solutions with diglyme (1 : 4 by volume or 1 : 56 by mole) in the glove box to make 0.1 mol dm −3 Mg 2+-containing IL/G2 solutions. Conductivity and viscosity measurements.-The water content of each solution was about 200-400 ppm, determined by Karl Fischer titration. Conductivity measurements were performed at 25 • C using Radiometer Analytical CDM230. Kinematic viscosity measurements were conducted using SEKONIC VM-10A and VM-1 G calibrated using a standard solution (NIPPON GREASE Co., Ltd.). The densities of 0.5 mol dm −3 Mg 2+-containing ILs were calculated to be 1.41 g cm −3 for TMHA-Tf 2 N and 1.46 g cm −3 for PP13-Tf 2 N using the measured value of weight and volume, while those of G2-mixed solutions were assumed to be 1.03-1.04 g cm −3 for 0.1 mol dm −3 Mg(Tf 2 N) in IL/G2 and 1.01 g cm −3 for 0.125 mol dm −3 Mg(Tf 2 N) in G2 using the reported density of pure G2 (0.937 g cm −3). Electrochemical measurements and characterization of deposits.-Within an hour after bath preparation, electrochemical measurements were conducted in the glove box with a potentiostat/galvanostat (BAS, ALS ELECTROCHEMICAL ANALYZER 660C) at 30 • C. Cyclic voltammetry (CV) was performed without stirring in an electrode cell ecsdl.org/site/terms_use address. Redistribution subject to ECS license or copyright; see 130.54.130.246 Downloaded on 2014-01-21 to IP

Magnesium-air battery is a promising energy storage device because of its high theoretical voltage, high specific energy, low cost, and greater safety. Due to the passivation of Mg surface with Mg(OH) 2 in alkaline electrolyte (pH 411) prevents further reaction of the anode, Mg-air battery typically works in pH-neutral aqueous electrolyte. However, developing electrocatalysts for pH-neutral oxygen reduction with high activity at low cost remains a significant challenge. Here, we report a mixed-phase mullite (SmMn 2 O 5) electrocatalyst as an efficient substitute for Pt/C in pH-neutral oxygen reduction reaction (ORR). The mixed-phase mullite exhibits similar catalytic activity but superior stability to Pt/C in 1 M NaCl solutions. Density functional theory simulations reveal that the catalytic activity is correlated to the strength of p-d hybridization between octahedral Mn and lattice O in the mullite structure, which results in a moderate bond strength between adsorbed O atoms and square-pyramidal Mn dimer sites. The presence of CeO 2 phase also facilitates the adsorption and diffusion of oxygen atoms on mullite surface. Finally, the feasibility of utilizing mixed-phase mullite catalyst is demonstrated by fabricating Mg-air batteries to power a red light-emitting diode. Published by Elsevier Ltd.