aluminum ion 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...

Insertion mechanisms of multivalent ions in transition metal oxide cathodes are poorly understood and subject to controversy and debate, especially when performed in aqueous electrolytes. To address this issue, we have here investigated the reversible reduction of nanostructured amorphous TiO 2 electrodes by spectroelectrochemistry in mild aqueous electrolytes containing either a multivalent metal salt as AlCl 3 or a weak organic acid as acetic acid. Our results show that the reversible charge storage in TiO 2 is thermodynamically and kinetically indistinguishable when carried out in either an Al 3+ -or acetic acidbased electrolyte, both leading under similar conditions of pH and concentrations to an almost identical maximal charge storage of $115 mA h g À1 . These observations are in agreement with a mechanism where the inserting/deinserting cation is the proton and not the multivalent metal cation. Analysis of the data also demonstrates that the proton source is the Brønsted weak acid present in the aqueous electrolyte, i.e. either the acetic acid or the aquo metal ion complex generated from solvation of Al 3+ (i.e. [Al(H 2 O) 6 ] 3+ ). Such a proton-coupled charge storage mechanism is also found to occur with other multivalent metal ions such as Zn 2+ and Mn 2+ , albeit with a lower efficiency than Al 3+ , an effect we have attributed to the lower acidity of [Zn(H 2 O) 6 ] 2+ and [Mn(H 2 O) 6 ] 2+ . These findings are of fundamental importance because they shed new light on previous studies assuming reversible Al 3+ -insertion into metal oxides, and, more generally, they highlight the unsuspected proton donor role played by multivalent metal cations commonly involved in rechargeable aqueous batteries.

Insertion mechanisms of multivalent ions in transition metal oxide cathodes are poorly understood and subject to controversy and debate, especially when performed in aqueous electrolytes. To address this issue, we have here investigated the reversible reduction of nanostructured amorphous TiO 2 electrodes by spectroelectrochemistry in mild aqueous electrolytes containing either a multivalent metal salt as AlCl 3 or a weak organic acid as acetic acid. Our results show that the reversible charge storage in TiO 2 is thermodynamically and kinetically indistinguishable when carried out in either an Al 3+-or acetic acidbased electrolyte, both leading under similar conditions of pH and concentrations to an almost identical maximal charge storage of $115 mA h g À1. These observations are in agreement with a mechanism where the inserting/deinserting cation is the proton and not the multivalent metal cation. Analysis of the data also demonstrates that the proton source is the Brønsted weak acid present in the aqueous electrolyte, i.e. either the acetic acid or the aquo metal ion complex generated from solvation of Al 3+ (i.e. [Al(H 2 O) 6 ] 3+). Such a proton-coupled charge storage mechanism is also found to occur with other multivalent metal ions such as Zn 2+ and Mn 2+ , albeit with a lower efficiency than Al 3+ , an effect we have attributed to the lower acidity of [Zn(H 2 O) 6 ] 2+ and [Mn(H 2 O) 6 ] 2+. These findings are of fundamental importance because they shed new light on previous studies assuming reversible Al 3+-insertion into metal oxides, and, more generally, they highlight the unsuspected proton donor role played by multivalent metal cations commonly involved in rechargeable aqueous batteries.

Li-ion battery is currently considered to be the most proven technology for energy storage systems when it comes to the overall combination of energy, power, cyclability and cost. However, there are continuous expectations for cost reduction in large-scale applications, especially in electric vehicles and grids, alongside growing concerns over safety, availability of natural resources for lithium, and environmental remediation. Therefore, industry and academia have consequently shifted their focus towards ‘beyond Li-ion technologies’. In this respect, other non-Li-based alkali-ion/polyvalent-ion batteries, non-Li-based all solid-state batteries, fluoride-ion/ammonium-ion batteries, redox-flow batteries, sand batteries and hydrogen fuel cells etc. are becoming potential cost effective alternatives. While there has been notable swift advancement across various materials, chemistries, architectures, and applications in this field, a comprehensive overview encompassing high-energy ‘beyond Li-ion’ technologies, along with considerations of commercial viability, is currently lacking. Therefore, in this review article, a rationalized approach is adopted to identify notable ‘post-Li’ candidates. Their pros and cons are comprehensively presented by discussing the fundamental principles in terms of material characteristics, relevant chemistries, and architectural developments that make a good high-energy ‘beyond Li’ storage system. Furthermore, a concise summary outlining the primary challenges of each system is provided, alongside the potential strategies being implemented to mitigate these issues. Additionally, the extent to which these strategies have positively influenced the performance of these ‘post-Li’ technologies is discussed.

Immense progress is required in the field of energy conversion and storage to achieve cost-effective high-performance batteries which could meet future energy demands. It also becomes mandatory to utilize the abundant materials from the earth’s crust, along with safe conversion and storage of electrochemical reactions. In this perspective, aluminium ion batteries (AIBs) could be a viable alternative for the conventional lithium-ion batteries (LIBs). In this mini-review, we focus on the challenges and the latest growth related to the cathode active materials (metal oxides, metal sulfides and other hybrid systems) in AIBs. The development of highly efficient, low cost and safe energy storage systems based on aluminium ion batteries is much explored. Still, commercialization remains a theoretical one, hence this review highlights the significance of the developed materials and their shortcomings that need to be addressed for the commercialization of aluminium ion batteries in the future.

Immense progress is required in the field of energy conversion and storage to achieve cost-effective high-performance batteries which could meet future energy demands. It also becomes mandatory to utilize the abundant materials from the earth’s crust, along with safe conversion and storage of electrochemical reactions. In this perspective, aluminium ion batteries (AIBs) could be a viable alternative for the conventional lithium-ion batteries (LIBs). In this mini-review, we focus on the challenges and the latest growth related to the cathode active materials (metal oxides, metal sulfides and other hybrid systems) in AIBs. The development of highly efficient, low cost and safe energy storage systems based on aluminium ion batteries is much explored. Still, commercialization remains a theoretical one, hence this review highlights the significance of the developed materials and their shortcomings that need to be addressed for the commercialization of aluminium ion batteries in the future.

To meet future energy demands, currently, dominant lithium‐ion batteries (LIBs) must be supported by abundant and cost‐effective alternative battery materials. Potassium‐ion batteries (KIBs) are promising alternatives to LIBs because KIB materials are abundant and because KIBs exhibit intercalation chemistry like LIBs and comparable energy densities. In pursuit of superior batteries, designing and developing highly efficient electrode materials are indispensable for meeting the requirements of large‐scale energy storage applications. Despite using graphite anodes in KIBs instead of in sodium‐ion batteries (NIBs), developing suitable KIB cathodes is extremely challenging and has attracted considerable research attention. Among the various cathode materials, layered metal oxides have attracted considerable interest owing to their tunable stoichiometry, high specific capacity, and structural stability. Therefore, the recent progress in layered metal‐oxide cathodes is comprehensively re...

Batteries using a water-based electrolyte have the potential to be safer, more durable, less prone to thermal runaways, and less costly than current lithium batteries using an organic solvent. Among the possible aqueous battery options, ammonium-ion batteries (AIBs) are very appealing because the base materials are light, safe, inexpensive, and widely available. This review gives a concise and useful survey of recent progress on emerging AIBs, starting with a brief overview of AIBs, followed by cathode materials, anode materials, electrolytes, and various devices based on ammonium-ion storage. Aside from summarizing the most updated electrodes/ electrolytes in AIBs, this review highlights fundamental mechanistic studies in AIBs and state-of-the art applications of ammonium-ion storage. The present work reviews various theoretical efforts and the spectrum studies that have been used to explore ionic transport kinetics, electrolyte structure, solvation behavior of ammonium ions, and the intercalation mechanism in the host structure. Furthermore, diverse applications of ammonium-ion storage apart from aqueous AIBs are discussed, including flexible AIBs, AIBs that can operate across a wide temperature range, ammonium-ion supercapacitors, and battery−supercapacitor hybrid devices. Finally, the review is concluded with perspectives of AIBs, challenges remaining in the field, and possible research directions to address these challenges to boost the performance of AIBs for real-world practical applications.

Since the discovery of batteries in the 1800s, their fascinating physical and chemical pro­perties have led to much research on their synthesis and manufacturing. Though lithium-ion batteries have been crucial for civilization, they can still not meet all the growing demands for energy storage because of the geographical distribution of lithium resources and the intrinsic limitations in the cell energy density, performance, and reliability issues. As a result, non-Li-ion batteries are becoming increasingly popular alternatives. Designing novel materials with desired properties is crucial for a quicker transition to the green energy ecosystem. Na, K, Mg, Zn, Al ion, etc. batteries are considered the most alluring and promising. This article covers all these Li, non-Li, and metal-air cell chemistries. Recently, com­putational screening has proven to be an effective tool to accelerate the discovery of active materials for all these cell types. First-principles methods such as density f...

Aqueous rechargeable zinc-ion batteries (ARZIBs) have drawn enormous attention because of their lowcost and eco-friendly cell components. However, designing high-performance cathode materials towards practical application of ARZIBs remains a major challenge. Therefore, in this contribution, a comprehensive study on K + intercalated V 2 O 5 (KVO) nanorods with exposed facets as a highperformance cathode for ARZIBs is presented. The KVO cathode exhibits remarkable discharge capacities of 439 and 286 mAh g À1 at current densities of 50 and 3000 mA g À1 , respectively. Furthermore, it recovers 96% of the capacity after 1500 cycles at 8000 mA g À1. Impressively, the Zn/KVO battery offers a specific energy of 121 W h kg À1 at high specific power of 6480 W kg À1. The storage mechanism of the KVO cathode in an ARZIB is systematically elucidated using in operando synchrotron X-ray diffraction, ex situ synchrotron X-ray absorption spectroscopy, ex situ TEM analyses and firstprinciples calculations. The superior performance of the cathode is attributed to its unique exposed layer structure with high surface energy, high conductivity and low migration barrier for Zn 2+ migration. This study provides insight into designing high-performance cathode materials for ARZIBs and other electrochemical systems.

Recently, aluminum ion batteries (AIBs) have attracted great attention across the globe by virtue of its massive gravimetric and volumetric capacities in addition to its high abundance. Though carbon derivatives are excellent cathodes for AIBs, there is much room for further development. In this study, flexuous graphite (FG) was synthesized by a simple thermal shock treatment and, for the first time, an Al/FG battery was applied as a cathode for AIBs to reveal the real-time intercalation of AlCl 4into FG with high flexibility using in situ scanning electron microscope (SEM) measurements exclusively. Similarly, in situ X-ray diffraction (XRD) and in situ Raman techniques have been used to understand the anomalous electrochemical behavior of FG. It was found that FG adopts a unique integrated intercalation-adsorption mechanism where it follows an intercalation mechanism potential above 1.5 V and an adsorption mechanism potential below 1.5 V. This unique integrated intercalation-adsorption mechanism allows FG to exhibit superior properties, like high capacity (≥140 mAh/g), remarkable long-term stability (over 8000 cycles), excellent rate retention (93 mAh/g at 7.5 A/g) and extremely rapid charging and slow discharging.

A new type of battery known as metal-ion batteries promises better performance than existing batteries. In terms of energy storage, they could prove useful and eliminate some of the problems existing batteries face. This review aims to help academics and industry work together better. It will propose ways to measure the performance of metal-ion batteries using important factors such as capacity, convertibility, Coulombic efficiency, and electrolyte consumption. With the development of technology, a series of metal ion-based batteries are expected to hit the market. This review presents the latest innovative research findings on the fabrication of metal-ion batteries with new techniques.

Rational architecture design of the artificial protective layer on the zinc (Zn) anode surface is a promising strategy to achieve uniform Zn deposition and inhibit the uncontrolled growth of Zn dendrites. Herein, a red phosphorous-derived artificial protective layer combined with a conductive N-doped carbon framework is designed to achieve dendrite-free Zn deposition. The Zn-phosphorus (ZnP) solid solution alloy artificial protective layer is formed during Zn plating. Meanwhile, the dynamic evolution mechanism of the ZnP on the Zn anode is successfully revealed. The concentration gradient of the electrolyte on the electrode surface can be redistributed by this protective layer, thereby achieving a uniform Zn-ion flux. The fabricated Zn symmetrical battery delivers a dendrite-free plating/stripping for 1100 h at the current density of 2.0 mA cm-2. Furthermore, aqueous Zn//MnO 2 full cell exhibits a reversible capacity of 200 mAh g-1 after 350 cycles at 1.0 A g-1. This study suggests an effective solution for the suppression of Zn dendrites in Zn metal batteries, which is expected to provide a deep insight into the design of high-performance rechargeable aqueous Zn-ion batteries.

Energy-storage systems are considered as a key technology for energy and mobility transition. Because traditional batteries have many drawbacks, there are tremendous efforts to develop so-called postlithium systems. The magnesium-sulfur (MgS) battery emerges as one alternative. Previous studies of Mg-S batteries have addressed the environmental footprint of its production. However, the potential impacts of the use-phase are not considered yet, due to its premature stage of development. Herein, a first prospective look at the potential environmental performance of a theoretical Mg-S battery for different use-phase applications is given to fill this gap. By means of the life cycle assessment (LCA) methodology, an analysis of different scenarios and a comparison with other well-established technologies are conducted. The results suggest that the environmental footprint of the Mg-S is comparable with that of the commercially available counterparts and potentially outperforms them in several impact categories. However, this can only be achieved if a series of technical challenges are first overcome.

Nanoscale ZnO, directly grown on current collector through ALD, shows high electrochemical performance as a binder-free cathode for rechargeable Al-ion batteries (AIBs). Al coin cell fabricated using binder-free ALD grown ZnO cathode (ZnO-ALD-E) manifests an initial discharge capacity of 2563 mAh g-1 , and remains at 245 mAh g-1 at a current rate of 400 mA g-1 after 50 cycles with almost 95% Coulombic efficiency. Distinct and consistent plateaus in discharge/charge curves reveal the Alion insertion/extraction process and electrochemical stability of the battery. The delivered discharge capacity of the battery with ZnO-ALD-E cathode is significantly higher (1000%) than that of batteries fabricated using a conventional ZnO cathode composed of ZnO powder (nanoparticles or bulk) and binder with conductive carbon. Ex-situ XRD and Photoluminescence spectroscopy in different discharge/charge states of Al/ZnO-ALD-E battery reveal the structural information of ZnO-ALD-E, upon Al-ion intercalation/deintercalation. Such remarkable electrochemical performance is attributed to the binder-free, well-defined textured nanostructures of ALD grown ZnO cathode with c-axis orientation along the surface normal, facilitating good electrical contact and enhanced pathways for electron/ion transfer/transport kinetics. First principle based DFT calculations explain the Al-ion intercalation phenomena in the framework of c-axis oriented ZnO. The proposed concept provides a strategy for transitioning to next-generation AIBs with a binder-free cathode.

Energy-storage systems are considered as a key technology for energy and mobility transition. Because traditional batteries have many drawbacks, there are tremendous efforts to develop so-called postlithium systems. The magnesium-sulfur (MgS) battery emerges as one alternative. Previous studies of Mg-S batteries have addressed the environmental footprint of its production. However, the potential impacts of the use-phase are not considered yet, due to its premature stage of development. Herein, a first prospective look at the potential environmental performance of a theoretical Mg-S battery for different use-phase applications is given to fill this gap. By means of the life cycle assessment (LCA) methodology, an analysis of different scenarios and a comparison with other well-established technologies are conducted. The results suggest that the environmental footprint of the Mg-S is comparable with that of the commercially available counterparts and potentially outperforms them in several impact categories. However, this can only be achieved if a series of technical challenges are first overcome.

The demand for large scale, sustainable, eco-friendly and safe energy storage systems are ever increasing. Currently, lithium-ion battery (LIB) is being used in large scale for various applications due to its unique features. However, its feasibility and viability as a long-term solution is under question due to the dearth and uneven geographical distribution of the lithium resources. It is in this context that alternative energy storage systems become significant. Potassium-ion battery (KIB) is one of the latest entrants into this arena. Researchers have demonstrated that this technology has potential to become a competing technology to the LIBs and sodium ion batteries (NIB). This review summarizes the research progress achieved in this technology including electrode materials, electrolyte, binders etc. along with a brief discussion about the future prospects and opportunities.

The demand for large scale, sustainable, eco-friendly and safe energy storage systems are ever increasing. Currently, lithium-ion battery (LIB) is being used in large scale for various applications due to its unique features. However, its feasibility and viability as a long-term solution is under question due to the dearth and uneven geographical distribution of the lithium resources. It is in this context that alternative energy storage systems become significant. Potassium-ion battery (KIB) is one of the latest entrants into this arena. Researchers have demonstrated that this technology has potential to become a competing technology to the LIBs and sodium ion batteries (NIB). This review summarizes the research progress achieved in this technology including electrode materials, electrolyte, binders etc. along with a brief discussion about the future prospects and opportunities.

Herein, recent advancements in battery materials’ research post-Li-ion era, from both the perspective of experimental investigations and theoretical analysis, are focused on. A plethora of materials family, which has been proven to be impactful for Al-, K-, and Zn-ion batteries, leverages the advanced synthesis and characterization along with the first-principles electronic structure calculations. However, the adequate amalgamation between experimental findings and theoretical study of materials’
properties needs to be well addressed. This paves the way to the present article, where the recent progress in Al, K, and Zn battery materials, with a common string of connections between experiment and theory, is critically reviewed. The advanced characteristics relevant to Al-, Zn-, and K-ion battery technology, along with theoretical tools like molecular dynamics simulation, transition pathway, and voltage profiles, are discussed. It also sheds light on the treatment of solid-liquid interfaces and how one can achieve an optimum electrochemical performance for the next-generation battery advancement. An extensive status quo of the Al-, Zn-, and
K-ion battery research would certainly be instrumental for the energy storage community, where one can perceive broader viewpoints in battery technology from fundamental understanding.

Nanoscale ZnO, directly grown on current collector through ALD, shows high electrochemical performance as a binder-free cathode for rechargeable Al-ion batteries (AIBs). Al coin cell fabricated using binder-free ALD grown ZnO cathode (ZnO-ALD-E) manifests an initial discharge capacity of 2563 mAh g-1 , and remains at 245 mAh g-1 at a current rate of 400 mA g-1 after 50 cycles with almost 95% Coulombic efficiency. Distinct and consistent plateaus in discharge/charge curves reveal the Alion insertion/extraction process and electrochemical stability of the battery. The delivered discharge capacity of the battery with ZnO-ALD-E cathode is significantly higher (1000%) than that of batteries fabricated using a conventional ZnO cathode composed of ZnO powder (nanoparticles or bulk) and binder with conductive carbon. Ex-situ XRD and Photoluminescence spectroscopy in different discharge/charge states of Al/ZnO-ALD-E battery reveal the structural information of ZnO-ALD-E, upon Al-ion intercalation/deintercalation. Such remarkable electrochemical performance is attributed to the binder-free, well-defined textured nanostructures of ALD grown ZnO cathode with c-axis orientation along the surface normal, facilitating good electrical contact and enhanced pathways for electron/ion transfer/transport kinetics. First principle based DFT calculations explain the Al-ion intercalation phenomena in the framework of c-axis oriented ZnO. The proposed concept provides a strategy for transitioning to next-generation AIBs with a binder-free cathode.

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.

Electrochemically active species in aluminum (Al) electrodeposition baths using AlCl 3 and less volatile solvents i.e. glymes were investigated. Raman spectroscopy revealed that all the glyme baths contained AlCl 4 À anions and Al-Cl-glyme cations as ionic species. Room temperature conductivities were as high as the order of 10 À3 S cm À1 for the diglyme (G2), triglyme (G3) and tetraglyme (G4) baths, whereas that for the butyl diglyme (butylG2) bath was only 10 À4 S cm À1 due to a lower concentration of ionic species. Surprisingly, electrochemical measurements showed that, among the glyme baths, only the G2 bath enabled electrodeposition of Al. Consequently, despite the similar structures of Al-Cl-glyme complex cations, only the G2 complex cations are electrochemically active. This suggests that the desolvation of glymes from Al-Cl-glyme cations and their subsequent reduction is exceptionally easy for the G2 complexes. ã

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