Complex Structures and Electrochemical Properties of Magnesium Electrolytes

Nakayama, Yasuo; Kudo, Yoshihisa; Oki, Hideki; Yamamoto, Kenta; Kitajima, Yoshinori; Noda, Kazuhiro

doi:10.1149/1.2956022

Cited by 46 publications

(50 citation statements)

References 16 publications

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“…However, contradictory results have been reported in the literature about the species present in solution and the exact solvation structure of Mg ions. Most experimental and simulation studies suggest hexa-coordinated Mg ions, whereas a few experimental studies using NEXAFS and Fouriertransformed extended X-ray absorption fine structure (EXAFS) and first-principlebased simulations reported a tetrahedral coordination for Mg 2+ ions [70,76]. A detailed study of the solvation structure of ionic species present in DCC solution was performed by Nakayama et al [70] using X-ray absorption fine structure (XAFS) and Fourier-transformed extended X-ray absorption fine structure (EXAFS).…”

Section: Organometallic Compounds (Complex Salts)mentioning

confidence: 99%

Elucidating Solvation Structures for Rational Design of Multivalent Electrolytes—A Review

Rajput

Seguin

Wood

et al. 2018

Topics in Current Chemistry Collections

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Fundamental molecular-level understanding of functional properties of liquid solutions provides an important basis for designing optimized electrolytes for numerous applications. In particular, exhaustive knowledge of solvation structure, stability, and transport properties is critical for developing stable electrolytes for fast-charging and high-energy-density next-generation energy storage systems. Accordingly, there is growing interest in the rational design of electrolytes for beyond lithium-ion systems by tuning the molecular-level interactions of solvate species present in the electrolytes. Here we present a review of the solvation structure of multivalent electrolytes and its impact on the electrochemical performance of these batteries. A direct correlation between solvate species present in the solution and macroscopic properties of electrolytes is sparse for multivalent electrolytes and contradictory results have been reported in the literature. This review aims to illustrate the current understanding, compare results, and highlight future needs and directions to enable the deep understanding needed for the rational design of improved multivalent electrolytes.

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Section: Organometallic Compounds (Complex Salts)mentioning

confidence: 99%

Elucidating Solvation Structures for Rational Design of Multivalent Electrolytes—A Review

Rajput

Seguin

Wood

et al. 2018

Topics in Current Chemistry Collections

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“…They aid the charge transfer of magnesium by changing ligands. 11,[13][14][15][16][17][18] Despite these advantages, the high reactivity of alkylmagnesium halides and anodic instability of ether solvent (typically tetrahydrofuran THF) prevents this ideal system from use in practical batteries.…”

Section: Introductionmentioning

confidence: 99%

Solution Structure and Magnesium Deposition Electrochemistry of Mixing Alkylmagnesium Halide with Magnesium Sulfonyl Amide/Glyme Solution

Egashira

Hiratsuka

2016

Electrochemistry

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To elucidate effective species and their quantitative requirements for reversible magnesium deposition, a triglyme solution of ethylmagnesium bromide (EtMgBr) complex was mixed with magnesium bis(trifluoromethanesulfonyl) amide/triglyme solution in various ratios. The mixed electrolyte characteristics have been assessed using electrochemical magnesium deposition tests, titration of methanol, and Raman spectroscopy. The existence of EtMgBr reduces the overpotential of magnesium deposition. The Coulombic efficiency of this process varies linearly with the EtMgBr content, although the active EtMgBr decreases more than expected from the mixing ratio. Raman spectra for the mixed electrolyte suggest a change in the structure of magnesium bromide species and coordination mode of magnesium by mixing of EtMgBr with magnesium sulfonylamide salt.

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“…55,56 Aqueous solutions of Mg(ClO 4 ) 2 , Mg(SO 4 ) 2 , Mg(NO 3 ) 2 , MgCl 2 are also known to show ion pair formation at high concentrations ( > 2 M), however Mg(OAc) 2 shows ion pair formation at lower concentrations ( >1 M). 57,58Previous experimental studies using X-ray absorption fine structures (XAFS) on Mg salts such as Mg(AlCl 2 EtBu)/THF have observed the formation of complex salt-solvent structures (Mg 2 Cl 2 THF 4 ) 2+ in the solution 59. Furthermore, the All Phenyl Complex (APC) type electrolytes exhibit a strong tendency for Mg complex formation 60.…”

mentioning

confidence: 99%

The Coupling between Stability and Ion Pair Formation in Magnesium Electrolytes from First-Principles Quantum Mechanics and Classical Molecular Dynamics

et al. 2015

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In this work we uncover a novel effect between concentration dependent ion pair formation and anion stability at reducing potentials, e.g., at the metal anode. Through comprehensive calculations using both first-principles as well as well-benchmarked classical molecular dynamics over a matrix of electrolytes, covering solvents and salt anions with a broad range in chemistry, we elucidate systematic correlations between molecular level interactions and composite electrolyte properties, such as electrochemical stability, solvation structure, and dynamics. We find that Mg electrolytes are highly prone to ion pair formation, even at modest concentrations, for a wide range of solvents with different dielectric constants, which have implications for dynamics as well as charge transfer. Specifically, we observe that, at Mg metal potentials, the ion pair undergoes partial reduction at the Mg cation center (Mg(2+) → Mg(+)), which competes with the charge transfer mechanism and can activate the anion to render it susceptible to decomposition. Specifically, TFSI(-) exhibits a significant bond weakening while paired with the transient, partially reduced Mg(+). In contrast, BH4(-) and BF4(-) are shown to be chemically stable in a reduced ion pair configuration. Furthermore, we observe that higher order glymes as well as DMSO improve the solubility of Mg salts, but only the longer glyme chains reduce the dynamics of the ions in solution. This information provides critical design metrics for future electrolytes as it elucidates a close connection between bulk solvation and cathodic stability as well as the dynamics of the salt.

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Complex Structures and Electrochemical Properties of Magnesium Electrolytes

Cited by 46 publications

References 16 publications

Elucidating Solvation Structures for Rational Design of Multivalent Electrolytes—A Review

Elucidating Solvation Structures for Rational Design of Multivalent Electrolytes—A Review

Solution Structure and Magnesium Deposition Electrochemistry of Mixing Alkylmagnesium Halide with Magnesium Sulfonyl Amide/Glyme Solution

The Coupling between Stability and Ion Pair Formation in Magnesium Electrolytes from First-Principles Quantum Mechanics and Classical Molecular Dynamics

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