Electrochemical Metal Deposition Research Articles

Deposition and Stripping Behavior of Lithium Metal in Electrochemical System: Continuum Mechanics Study

Metallic lithium (Li) is a promising anode candidate for high-energy-density rechargeable batteries because of its low redox potential and high theoretical capacity. However, its practical application is not imminent because of issues related to the dendritic growth of Li metal with repeated battery operation, which presents a serious safety concern. Herein, various aspects of the electrochemical deposition and stripping of Li metal are investigated with consideration of the reaction rate/current density, electrode morphology, and solid electrolyte interphase (SEI) layer properties to understand the conditions inducing abnormal Li growth. It is demonstrated that the irregular (i.e., filamentary or dendritic) growth of Li metal mostly originates from local perturbation of the surface current density, which stems from surface irregularities arising from the morphology, defective nature of the SEI, and relative asymmetry in the deposition/stripping rates. Importantly, we find that the use of a stripping rate of Li metal that is slower than the deposition rate seriously aggravates the formation of disconnected Li debris from the irregularly grown Li metal. This finding challenges the conventional belief that high-rate stripping/plating of Li in an electrochemical cell generally results in more rapid cell failure because of the faster growth of Li metal dendrites. Figure 1

Electrodeposition of indium from the ionic liquid trihexyl(tetradecyl)phosphonium chloride.

The electrochemical behavior of indium in the ionic liquid trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101) was studied. Cyphos IL 101 first had to be purified, as the impurities present in commercial Cyphos IL 101 interfered with the electrochemical measurements. Electrochemical deposition of indium metal from this electrolyte occurs without hydrogen evolution, increasing the cathodic current efficiency compared to deposition from water and avoiding porosity within the deposited metal. Indium(iii) is the most stable oxidation state in the ionic liquid. This ion is reduced in two steps, first from indium(iii) to indium(i) and subsequently to indium(0). The high thermal stability of Cyphos IL 101 allowed the electrodeposition of indium at 120 °C and 180 °C. At 180 °C indium was deposited as liquid indium which allows for the easy separation of the indium and the possibility to design a continuous electrowinning process. On molybdenum, indium deposits as liquid droplets even below the melting point of indium. This was explained by the combination of melting point depression and undercooling. The possibility to separate indium from iron and zinc by electrodeposition was tested. It is possible to separate indium from zinc by electrodeposition, but iron deposits together with indium.

Deposition and Stripping Behavior of Lithium Metal in Electrochemical System: Continuum Mechanics Study

Metallic lithium (Li) is a promising anode candidate for high-energy-density rechargeable batteries because of its low redox potential and high theoretical capacity. However, its practical application is not imminent because of issues related to the dendritic growth of Li metal with repeated battery operation, which presents a serious safety concern. Herein, various aspects of the electrochemical deposition and stripping of Li metal are investigated with consideration of the reaction rate/current density, electrode morphology, and solid electrolyte interphase (SEI) layer properties to understand the conditions inducing abnormal Li growth. It is demonstrated that the irregular (i.e., filamentary or dendritic) growth of Li metal mostly originates from local perturbation of the surface current density, which stems from surface irregularities arising from the morphology, defective nature of the SEI, and relative asymmetry in the deposition/stripping rates. Importantly, we find that the use of a stripping rate...

Electrodeposition of Indium from a Phosphonium-Based Ionic Liquid

Electrochemical deposition of indium metal from aqueous electrolytes is challenging as it occurs simultaneously with hydrogen evolution. The evolution of hydrogen can compromise cathodic current efficiency and can cause porosity of the deposited metal, but it can be avoided by using ionic liquid electrolytes. The high thermal stability of ionic liquids allows for high-temperature electrodeposition on a liquid cathode, offering several advantages over a solid electrode, such as easier separation of electrolysis products and the possibility to design a continuous electrowinning process. In this paper, the electrochemical behavior of indium in the ionic liquid trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101) was studied at 120 °C and 180 °C. Indium metal was electrodeposited on platinum and molybdenum substrates and on a liquid indium cathode at 180 °C. Impurities present in commercial Cyphos IL 101 interfered with the measurement of the electrochemical window, so that it had to be carefully purified. The electrochemistry of indium in Cyphos IL 101 was studied by cyclic voltammetry, QMCB, rotating disk and rotating ring disk voltammetry. InCl3 concentration between 10 and 400 mM in Cyphos IL 101 were used in this study. Therefore, the major indium(III) species in solution corresponds to the [InCl6]3– complex. Using the Levich equation, a diffusion coefficient of (7.5 ± 0.1) 10–12 m2 s–1 at 120 °C was calculated for [InCl6]3–. It was found that indium(III) is the most stable oxidation state in the ionic liquid. This ion is reduced via a two-step process, going from indium(III) to indium(I) and subsequently to indium(0). The disproportionation of indium(I) to indium(III) and indium(0) was clearly illustrated. During cyclic voltammograms, the anodic and cathodic peak potentials was found to depend on the scan rate. As the scan rate increases, the separation between the anodic and cathodic peaks becomes greater, indicating that the deposition of indium is irreversible or quasi-reversible. The indium electrodeposits were characterized by SEM-EDS. When depositing indium on molybdenum substrates, the deposition of spherical indium droplets was observed, even at temperatures substantially below the melting point of indium (see figure). The probable mechanism behind this deposition morphology will be explained. Figure 1

Thin Film Surface Coatings for Improved Lithium Metal Cycling Efficiency: A Combinatorial Approach

There is a continual push to improve the energy density of lithium-ion batteries, but this is becoming increasingly difficult as it is believed that many of the best electrode materials have been found and optimized. In order to achieve higher energy densities to meet future storage demands it may be necessary to move “beyond lithium-ion”. Recent research efforts have focused on reviving the lithium metal negative electrode as a potential path to higher energy density.[1] With its high theoretical capacity and lowest reduction potential among metals, using lithium as a negative electrode can certainly increase the energy density of a cell provided the large volume changes of the lithium electrode between the charged and discharged states can be handled. In addition, lithium metal anodes often demonstrate dendrite formation during electrodeposition instead of plating as a smooth film. Since conventional organic electrolytes are thermodynamically unstable to reduction by lithium, dendrite growth leads to continual loss of active lithium, resulting in poor cycling efficiencies (< 90%) and short cell lifetime.[2] These problems are exaggerated as the thickness of the plated lithium increases, making cells with industrially relevant material loadings a significant challenge. Recent studies have shown that the morphology and plating efficiency of lithium can be greatly improved with nanostructured surface coatings. [3],[4] Herein we report on the use of combinatorial materials analysis to investigate the effect of different nanostructured surface coatings on the electrochemical deposition of lithium metal. Custom 64-channel electrochemical cell plates were used along with a combinatorial electrochemical cell to provide an efficient means of screening different electrode coatings. Figure 1 shows a schematic of the 64-channel cell plate as well as the output cyclic voltammograms (CVs) from potentiodynamic lithium plating and stripping on 64 unmodified copper electrodes. All 64 channels show consistent output which was validated against conventional coin type lithium half cells. High throughput sputtering was used to make libraries of thin films with different composition, structure, and thickness. These sputtered libraries were deposited directly on the 64-channel cell plates and used to analyze the morphology and coulombic efficiency of lithium plating as a function of the 64 individual surface coatings. The influence of different electrolyte compositions with these surface coatings was also investigated. These results provide perspective regarding the value of different thin film anode surface coatings as part of a broad strategy for achieving high (>98 %) lithium metal cycling efficiencies. [1] X. Cheng et al., Toward safe lithium metal anode in rechargeable batteries: a review, Chemical reviews, 117 (2015), 10403-10473. [2] Q. Pang, et al. "An In Vivo Formed Solid Electrolyte Surface Layer Enables Stable Plating of Li Metal." Joule 1, (2017): 871-886. [3] Adam P. Cohn et al., Anode-Free Sodium Battery through in Situ plating of Sodium Metal, Nano Letters, 17, (2017) 1296-1301. [4] G. Zheng et al., Interconnected hollow carbon nanospheres for stable lithium metal anodes, Nature Nanotechnology 9, (2014), 618-623. Figure 1

Corrosion Behavior of Aluminum Alloys Deposited from Ionic Liquids

Aluminum and its alloys have a wide range of applications due to their excellent properties, such as low density and high corrosion resistance. The electrochemical deposition of Al-based materials is not possible from aqueous solutions due to their rather negative Nernst potential (-1,66 V vs. SHE). There are few industrial processes for plating of aluminum, e.g. the SIGAL process. However, those processes usually are based on expensive, highly flammable and/or volatile substances, leading to high requirements regarding the technical equipment. The deposition from ionic liquids (ILs) opens new possibilities for industrial processes. The ILs have large electrochemical windows (> 3 V) and permit high solubility for metal salts, allowing the electrochemical deposition of base metals, like aluminum, and a considerable number of its alloys. Furthermore, there is no hydrogen embrittlement of steel substrates in ILs due to their aprotic character, and the deposition of Al-based films is possible at room temperature. Al-based materials are promising candidates for corrosion protection of steel and could replace environmentally harmful coatings, such as cadmium. ILs are still quite expensive, but their price continuously decreased during the last years, making an industrial process more interesting. This paper will discuss recent results from the authors’ lab on the deposition of aluminum alloys from imidazolium based ILs. Binary alloys of aluminum with Zn, Sn and Cr were deposited and investigated. The deposition process regarding precursor concentration, process parameters, properties of the deposits (composition, structure, morphology) and corrosion behaviour in aqueous sodium chloride solution will be discussed. Furthermore, it will be shown that the pre-treatment of the used steel substrates plays a crucial role to obtain well adhering layers.

An emulator for kinetic Monte Carlo simulations of kinetically controlled metal electrodeposition

In recent years there has been an increasing interest in developing models for atomistic-scale simulations of electrochemical metal deposition processes. One the most interesting and challenging features of such models is their capability to reproduce the physical evolution of the final deposition shape in a practical time scale. To date, most of the available models are limited to the simulation of a few nanoseconds of the physical phenomenon, for instance molecular dynamics, and there are very few methods, including kinetic Monte Carlo, that can reach to reproduce some seconds due to the requirement of an enormous computational cost. In this paper we present a surrogate-assisted kinetic Monte Carlo method based on Gaussian process emulation as a tool for predicting the final electrodeposition shape in a kinetically controlled copper electrodeposition on a gold substrate. The main advantage of this method is its ability to dramatically reduce the computational cost of the kinetic Monte Carlo simulation while yielding accurate results.

Insights into morphological evolution and cycling behaviour of lithium metal anode under mechanical pressure

Dendritic Li formation is one of the critical reasons for the failure of Li batteries. In order to improve the lithium metal anode performance, a better understanding of the growth mechanisms of Li dendrites is necessary. Due to the malleable nature of lithium metal, mechanical pressure should play an important role in determining the morphology and cycling behaviour of Li anode. Here we investigated the effect of an applied external pressure on the electrochemical deposition of lithium metal. Instead of a highly porous, wire-like Li growth in the absence of pressure, a much more compact Li deposition can be achieved when a pressure is applied to the batteries in the charge/discharge processes. The improved Li deposition/stripping behaviour in the pressed cells yields a 5% higher Coulombic efficiency (~90%) and more than 5-fold longer cycling life than the cells without pressure at a current density of 2 mA/cm2. The use of pressure in shaping Li metal is an effective approach to address the Li metal problem and advance Li technologies in the future.

Surface Layer Effects Synergism with Electrolytes for Li Nucleation and Growth

Li metal has been considered the “holy grail” anode materials. Li metal has the most negative potential with an extremely high theoretical specific capacity of 3860 mA h g−1.[1] It is, however, plagued with multiple challenges which need solutions before the realization of this material. Li metal has two main failure mechanisms, one is the random growth of detrimental dendrites, which can lead to rapid thermal runoff, i.e. Galaxy Note 7.[2] The other issue that arises upon cycling is pulverization of lithium metal through none uniform plating, leading to an increase in solid electrolyte formation(SEI) and thereby the increase in voltage polarization within the cell.[3] Both Li failure mechanisms are rooted in the uneven distribution of SEI layers whose properties vary depending on the location of SEI formed.[4] The initial surface chemistry on Li metal influences SEI formation in the very beginning. In this work, electrochemical deposition of Li metal on different substrates with bare oxides has been performed to understand the nucleation and growth of Li crystals. Electrolyte and surface modification give rise to differing SEI properties/composition which leads to improved Li deposition morphology. The fundamental mechanisms that dictates the smooth Li deposition will be discussed.

Modeling of local maskless electrochemical deposition of metal microcolumns

The work deals with the problem of fabricating new materials for modern devices of microelectromechanics, microelectronics, biomimetics, etc. using the local electrodeposition of metals. The mathematical model is developed for the formation of 3D microstructures (microcolumns) by the local electrochemical deposition of metal using a moving disk microanode. The numerical solution of the mathematical problem is performed using the finite element method on the irregular grid. The grid is deformed and adaptively remeshed during modeling of deposit growth. Evolution of deposit surface is calculated for various exchange current densities, transfer coefficients, interelectrode distances and various dependences of the current efficiency on the current density.The results of modeling allow one to determine the relationships between the parameters of electrodeposition and the shape and dimensions of formed microstructures. These data can be used to predict the results of local electrodeposition of metal and to optimize the operation conditions.

A study on the effect of inter-electrode gap and pulse voltage on current density in electrochemical additive manufacturing

Electrochemical Additive Manufacturing—a novel non-thermal metal additive manufacturing process offers some advantages over traditional energy beam-based layered manufacturing processes, which have several inherent limitations such as thermal damages, residual stress, and part size restrictions. In this process, the principle of localized electrochemical deposition of metals is combined with the additive manufacturing procedure to manufacture metal parts at room temperature directly from computer-aided design files. The focus of research work presented in this paper is on the modeling of the current density produced in the electrochemical deposition system based on the Fick’s law of diffusion and electrode kinetics using the Butler–Volmer equation. The current densities involved in the micro-electrochemical additive manufacturing on nickel have been found to be several orders of magnitude higher than the standard electroplating studies, making it a very high overpotential deposition. The model developed in this work was used to study the effects of applied potential, pulse duty cycle, inter-electrode gap, and concentration on the current density and the transient diffusion layer thickness. The model predicted that lower inter-electrode gaps facilitated higher current density leading to faster deposition rates. The pulse voltage was found to produce higher current densities during the pulse-on time. The modeled current density values were validated with experimental results using the in-house-built electrochemical additive manufacturing setup.

Carbon Nanotube Fiber Pretreatments for Electrodeposition of Copper

There is increasing interest towards developing carbon nanotube‐copper (CNT‐Cu) composites due to potentially improved properties. Carbon nanotube macroscopic materials typically exhibit high resistivity, low electrochemical reactivity, and the presence of impurities, which impede its use as a substrate for electrochemical deposition of metals. In this research, different CNT fiber pretreatment methods, such as heat treatment, immersion in Watts bath, anodization, and exposure to boric acid (H3BO3), were investigated to improve the electrochemical response for copper deposition. It was shown that these treatments affect the surface activity of CNTs, including electrical resistivity, polarization resistance, and active surface area, which influence the electrodeposition process of copper. Properties of CNT structures and CNT‐Cu composites were researched by electrochemical impedance spectroscopy (EIS), galvanostatic copper deposition, scanning electron microscope (SEM), and four‐point electrical resistance measurements. Heat treatment, Watts bath, anodization, and boric acid treatments were shown to be effective for modifying the CNT surface reactivity for subsequent electrochemical deposition of copper.

Formation of Micrometer Scale Metal Structures on Glass by Selective Electroless Plating on Photopatterned Titanium and Copper Containing Films.

A procedure for formation of catalytic SiO2 substrate adhesive layer patterns and selective electrochemical metal deposition on the catalyst images was investigated. A photoreactive solution containing a diazonaphthoquinone sulfonate ester and Ti and Cu complexes was developed to deposit Cu catalyst-TiO2 adhesive layer latent images on glass. Sub-micrometer/micrometer scale positive tone photoactive TiCu complex film patterns were formed using a conventional photolithography technique. The Cu ions in 40-50 nm thick Ti and Cu oxide layers formed by pyrolysis of the TiCu complex films were reduced, residual Cu displaced with Pd then the porous Ti oxide structure filled and plated with Cu by selective electroless then electrolytic plating. Annealing the Cu plating filled TiO2 layers on glass resulted in formation of a smooth Ti3+/Cu1+ oxide interface that enabled formation of 20 μm thick Cu deposits on glass substrate with up to 1 kN/m adhesion strength. The adhesion strength was attributed to chemical bonding of Ti3+ and Cu1+ oxides to the glass and Ti4+ oxide to the Cu plating that was formed upon annealing the Cu filled TiO2 interlayer. Furthermore, a dip coating procedure was adapted that allowed copper film deposition on the entire surface of a 300 μm thick glass substrate with 50 μm in diameter holes enabling formation of electrically conductive through glass substrate interconnects.

Voltage-dependent cluster expansion for electrified solid-liquid interfaces: Application to the electrochemical deposition of transition metals

The detailed atomistic modeling of electrochemically deposited metal monolayers is challenging due to the complex structure of the metal-solution interface and the critical effects of surface elec- trification during electrode polarization. Accurate models of interfacial electrochemical equilibria are further challenged by the need to include entropic effects to obtain accurate surface chemical potentials. We present an embedded quantum-continuum model of the interfacial environment that addresses each of these challenges and study the underpotential deposition of silver on the gold (100) surface. We leverage these results to parameterize a cluster expansion of the electrified in- terface and show through grand canonical Monte Carlo calculations the crucial need to account for variations in the interfacial dipole when modeling electrodeposited metals under finite-temperature electrochemical conditions.

The use of electrochemical deposition of metals at the surface microstructuring by laser ablation in liquids

Micron, submicron, surface-periodic and nanostructures were obtained by laser ablation in a liquid method on the titanium plate surface and the nickel foil surface. Electrochemical deposition of the nickel in the modified region of the titanium leads to the formation of conical structures 6 μm in height and filamentary nanostructures on the separated film. During deposition on the laser-modified nickel target, the separable film retains the period of the structures from which it is removed. The component titanium target coated with a nickel film was also irradiated. After separation of the nickel film, perforations with an average diameter of 1 μm and holes up to 50 μm in diameter were detected.

Synergistic Effects from Substrate and Electrolytes on Li Deposition

Li metal has been considered the “holy grail” anode materials. Li metal has the most negative potential with an extremely high theoretical specific capacity of 3860 mA h g−1.[1] It is, however, plagued with multiple challenges which need solutions before the realization of this material. Li metal has two main failure mechanisms, one is the random growth of detrimental dendrites, which can lead to rapid thermal runoff, i.e. Galaxy Note 7.[2] The other issue that arises upon cycling is pulverization of lithium metal through none uniform plating, leading to an increase in solid electrolyte formation(SEI) and thereby the increase in voltage polarization within the cell.[3] Both Li failure mechanisms are rooted in the uneven distribution of SEI layers whose properties vary depending on the location of SEI formed.[4] The initial surface chemistry on Li metal influences SEI formation in the very beginning. In this work, electrochemical deposition of Li metal on specific substrate has been performed to understand the nucleation and growth of Li crystals. Electrolyte and substrate have been identified to have synergistic effects on the morphology and efficiency of deposited Li. The fundamental mechanisms that dictates the smooth Li deposition will be discussed.

Interfacial Insight from Operando XAS/TEM for Magnesium Metal Deposition with Borohydride Electrolytes

Operando soft X-ray absorption spectroscopy (sXAS) and transmission electron microscopy (TEM) of the electrochemical deposition of magnesium metal from borohydride electrolytes is presented. The analysis identifies the active component for the deposition of magnesium metal as the contact-ion pair [Mg(μ-H)2BH2]+. Additionally, the formation of boron clusters accompanied by H2 -gas formation accompany the deposition of Mg metal, and play a vital role in the formation of a solid-electrolyte interphase (SEI) on the surface. To use Mg metal as a viable anode for future battery systems, understanding the interfacial components and chemistry is key.

(Invited) Pulsed Current Deposition: From Nano-Crystalline to Multi-Functional Coatings

The electrochemical deposition of metals and alloys using alternating uni- and bipolar current profiles, in short Pulse Plating technologies, has found the interest of both researchers and companies worldwide in recent years. The use of a modulated current deposition opens a wide field of new possibilities in electrochemical surface finishing as has been discussed at many occasions such as the biannual international conference “European Pulse Plating Seminar” and the Interfinish 2012. While the starting point often has been the aim for nano-crystallinity of deposited coatings, being still one major advantage of pulse plating in the technical awareness of the users, there are nowadays different approaches enabling a combined functionality beyond the nano-crystallinity. Any pulsed electrodeposition process should be based on a fundamental knowledge of the deposition mechanisms and thus requires for the initial set up a profound study of electro kinetics, mass transport limitations and electro-crystallization effects. Electrochemical measurements at laboratory scale and structural analysis of the electrodeposits in dependence on the plating parameters applied will enable the definition of suitable pulse plating sequences. This presentation will discuss the possibilities and applications of generating multi functional layer systems based on the concept of depositing nano-crystalline layers via pulse plating techniques. The electrochemical parameters and concepts for achieving nano-crystalline layers will be explained supported by electrochemical fundamentals. Advantages and limitations of such nano-crystalline coatings will be briefly discussed. Using the results of several (international) fundamental and applied research projects, funded by the European Union strategic research programs, more sophisticated benefits of pulse plated metal alloy coatings will be presented. This will include the incorporation of nano-particles in the metal coating (nano-dispersion coatings), alloy deposition and surface property adjustment. Beside electrochemical experiments for gaining a profound knowledge of the electrolyte properties and the reaction mechanisms, the only way to quantify field line distribution and potential fields, even in a local resolution, are numerical simulation tools. Based on the characteristic electrode kinetics, possible resistive effects at the electrode surface, the general plating conditions (e.g., electrolyte temperature) and the electrolyte properties (e.g., conductivity) a numerical simulation software tool has been used, allowing the exact calculation of current field line distribution and potential fields between two electrodes. Pulse plating with its numerous possibilities to control electrochemical conditions directly at the (substrate) surface, will allow to precisely control the alloy composition of deposited binary and ternary alloys just by adjustment of the pulse parameters. Thermal, electrical properties as well as magnetic properties of the resulting coatings can be adjusted by this method. The underlying nano-crystallinity will additionally increase the resulting layer hardness. The incorporation of particles to form a (nano) dispersion coating will provide hardness and wear resistance better and more stable than pure nano-crystalline coatings. This presentation will be complemented by several examples of the industrial use of pulse plating for high-tech components and mass production parts.

High-speed Cu electrodeposition and its solderability

The effects of the plating current density (j) on the electroplated Cu microstructure, impurity distribution, and the solderability of the electroplated Cu were investigated. Analyses of electron backscatter diffraction and transmission electron microscopy showed that the Cu grain size (D) decreased from microscale to submicron-scale, and the predominant crystallographic orientation translated from [111]||ND+[101]||ND into [101]||ND (ND: Cu deposition direction) with increasing j. Time-of-flight secondary ion mass spectrometry analysis showed that the impurity content in the Cu platings (especially the Cl content) increased as a function of j. These investigations showed that j posed a significant influence on the characteristics of the electroplated Cu. Two intermetallic compound (IMC) species (η-Cu6Sn5 and Cu3Sn) accompanied with some material defects (e.g., nanovoids and microcracks) formed at the solder/Cu pillar interface after reflow. The IMC (Cu6Sn5) growth morphology and orientation, and the defect distribution were also strongly j-dependent. These j-dependent interfacial microstructures were closely related to different D and impurity contents of the Cu platings. The results of this study advanced our understanding of the effects of j on electrochemical metal deposition, and they were helpful in the development of the high-speed Cu electrodeposition technology.

Electrochemical Deposition and Dissolution Behavior of Magnesium Metal in Organosilicon-Containing Electrolyte Solutions

Introduction: Magnesium metal rechargeable batteries are expected as post lithium-ion batteries. One of the drawbacks of the development of magnesium metal rechargeable batteries is electrolyte. Research for electrolyte has been investigated extensively. We also reported the magnesium(II) bis(trifluoromethanesulfony)amide (Mg(TFSA)2)/triethylene glycol dimethyl ether (triglyme) that enabled magnesium metal to deposit/dissolve at ambient temperature[1]. However, low coulombic efficiency and large over potential should be overcome. In this study, fluoroorganosilicon compound (FOS) that has high electrochemical and thermal stability was used as co-solvent to overcome these issues. Electrochemical deposition and dissolution behavior of magnesium metal in the Mg(TFSA)2/ triglyme+FOS was investigated. Experimental: A three-electrode cell was used. Platinum plate was used as a working electrode and magnesium wires were used as a counter electrode and a quansi-reference electrode. 0.5 mol dm-3 Mg(TFSA)2/triglyme+FOS(various ratio) was used as electrolyte solutions. Cyclic voltammetry and chronopotentiometry measurement was carried out. X-ray diffraction (XRD) measurement and scanning electron microscope (SEM) observation were conducted. All operations and electrochemical measurements were carried out in Ar-filled glove box. Results and discussion: Figure 1 shows the cyclic voltammograms of the Pt electrode in Mg(TFSA)2/triglyme and Mg(TFSA)2/triglyme+FOS (1:2 by vol.) at the 5th cycle. Both reduction and oxidation currents were observed at the potential around - 2 V and 1 V, respectively. After chronopotentiometry, magnesium metal deposition was confirmed by XRD pattern and SEM image. Coulombic efficiency in triglyme+FOS was higher than that in triglyme. Based on this result, it is suggested that the addition of FOS is effective to magnesium metal deposition and dissolution reaction in triglyme. Reference: 1. T. Fukutsuka, K. Asaka, A. Inoo, R. Yasui, K. Miyazaki, T. Abe, K. Nishio and Y. Uchimoto, Chem. Lett., 11 (2014) 1788. Figure 1