Nanocomposite polymer electrolyte for rechargeable magnesium batteries

Shao, Yuyan; Rajput, Nav Nidhi; Hu, Jianzhi; Hu, Mary Y.; Liu, Tianbiao; Wei, Zhehao; Gu, Meng; Deng, Xuchu; Xu, Song; Han, Kee Sung; Wang, Jiulin; Nie, Zimin; Li, Guosheng; Zavadil, Kevin R.; Xiao, Jie; Wang, Chongmin; Henderson, Wesley A.; Zhang, Ji Guang; Wang, Yong; Mueller, Karl T.; Persson, Kristin A.; Li, Jun

doi:10.1016/j.nanoen.2014.12.028

Cited by 138 publications

(136 citation statements)

References 94 publications

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“…However, despite the calculated difference in the 11 B signals between neutral and singly charged species in Table IV, experimental spectra only contain a single quintet located from −40 to −43 ppm. 13,19,20 Infrared spectroscopy has confirmed, 19,20,23,53 for Mg(BH 4 ) 2 in ethereal solvents, the existence of two separate bands in the B-H stretching region. Bremer reported 53 that solvates of Mg(BH 4 ) 2 in diethyl ether exhibit four B-H stretching bands.…”

Section: Resultsmentioning

confidence: 89%

“…Regardless of the solvent, the formation of +2 charged clusters is prohibitive, which is generally agreed upon. 19,23 The high free energy of BH 4 − dissociation may partially explain low conductivity 20 of Mg(BH 4 ) 2 in ethereal solvent. The free energies to generate singly or doubly charged clusters are lower in G1 (5.1 and 12.2 kcal/mol) than in THF (11.5 and 22.2 kcal/mol).…”

Section: Discussionmentioning

confidence: 99%

“…This marked the discovery of the first stable, halide-free electrolyte for magnesium batteries. Since then, there have been a number of experimental 13,[20][21][22][23][24][25] and theoretical 12,23,26 studies aimed at improving battery performance. Presently, there are some problems with this electrolyte, including low ionic conductivity and solubility.…”

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confidence: 99%

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Exploring the Liquid Structure and Ion Formation in Magnesium Borohydride Electrolyte Using Density Functional Theory

Deetz¹,

Cao²,

Wang³

et al. 2018

J. Electrochem. Soc.

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Rechargeable magnesium batteries have attracted much interest due their high volumetric capacity, potential for safe operation, and the natural abundance of magnesium. However, the development of magnesium batteries for practical applications has been obstructed by the lack of understanding of the liquid structure of electrolytes. Herein, we use quantum density functional theory coupled with a continuum solvation model to investigate the structure of Mg(BH 4 ) 2 in two ethereal solvents: tetrahydrofuran (THF), and monoglyme (G1). The most energetically favorable clusters of Mg(BH 4 ) 2 , MgBH 4 + , and Mg 2+ , with associated solvent molecule ligands, are determined. The free energy required to generate monovalent ions in the electrolyte is positive and the formation of divalent complexes is prohibitive. Singly and doubly charged complexes are more stable in G1 than THF, which is consistent with experimental findings. From the standpoint of free energy, clusters containing multiple magnesium atoms are not favored. Theoretical 25 Mg-NMR, 11 B-NMR spectra, and infrared vibrational modes of borohydride were calculated for each cluster. The relationships between cluster charge and the signals of each spectrum are determined. These analytical descriptors could be useful to characterize the degree of ion dissociation in the electrolyte. For rechargeable batteries to become widespread in electric vehicle and grid energy storage applications, it is imperative that they are safe and low cost.1,2 These challenges have motivated researchers in recent years to consider alternatives to lithium-ion batteries, such as sodium 3,4 and multivalent 5,6 battery chemistries. Ever since the first prototypes were developed, 7,8 magnesium batteries have attracted much interest from the research community. Compared with lithiumion batteries, magnesium batteries have several advantages, such as their high volumetric capacity (3832 mAh/cm 3 ), which is a result of the divalency of magnesium. Additionally, the cycling of plating/stripping of Mg 2+ onto the magnesium metal anode does not produce dendrites, which alleviates one of safety concerns of lithium batteries. 9,10 However, magnesium batteries face crucial challenges before they can succeed in practical applications.11 In particular, the choice of the electrolyte is critical to their performance. 12,13 There are only a handful of electrolytes known to be stable 14 during battery cycling, due to the reactivity of the Mg anode. that an electrolyte consisting of magnesium borohydride in an ethereal solvent, such as tetrahydrofuran or monoglyme, could reversibly plate/strip Mg 2+ onto a magnesium metal anode. X-ray photoelectron spectroscopy 13 has shown that a Mg anode using this electrolyte did not yield signals for boron or carbon, implying that the electrolyte is electrochemically stable during charge and discharge cycles. This marked the discovery of the first stable, halide-free electrolyte for magnesium batteries. Since then, there have been a number of experimental 13,[20][21][22...

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Section: Resultsmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Exploring the Liquid Structure and Ion Formation in Magnesium Borohydride Electrolyte Using Density Functional Theory

Deetz¹,

Cao²,

Wang³

et al. 2018

J. Electrochem. Soc.

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“…These systems provide a relatively facile delivery of Mg 2+ ions in a chloride-free electrolyte and an 28,30,48,49 in cells with a working Mg electrode. However, these electrolytes suffer from low (≤87%) CE, significant overpotential, destructive incompatibilities with Mg metal resulting in passivation of the anode surface, and parasitic loss of electrolyte due to the electrochemical decomposition of solvent (e.g., AN) mimicking Mg-plating/insertion.…”

Section: ■ Introductionmentioning

confidence: 99%

Exploration of the Detailed Conditions for Reductive Stability of Mg(TFSI)₂ in Diglyme: Implications for Multivalent Electrolytes

2016

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We reveal the general mechanisms of partial reduction of multivalent complex cations in conditions specific for the bulk solvent and in the vicinity of the electrified metal electrode surface and disclose the factors affecting the reductive stability of electrolytes for multivalent electrochemistry. Using a combination of ab initio techniques, we clarify the relation between the reductive stability of contact-ion pairs comprising a multivalent cation and a complex anion, their solvation structures, solvent dynamics, and the electrode overpotential. We found that for ion pairs with multiple configurations of the complex anion and the Mg cation whose available orbitals are partially delocalized over the molecular complex and have antibonding character, the primary factor of the reductive stability is the shape factor of the solvation sphere of the metal cation center and the degree of the convexity of a polyhedron formed by the metal cation and its coordinating atoms. We focused specifically on the details of Mg (II) bis(trifluoromethanesulfonyl)imide in diethylene glycol dimethyl ether (Mg(TFSI)2)/diglyme) and its singly charged ion pair, MgTFSI+. In particular, we found that both stable (MgTFSI)+ and (MgTFSI)0 ion pairs have the same TFSI configuration but drastically different solvation structures in the bulk solution. This implies that the MgTFSI/dyglyme reductive stability is ultimately determined by the relative time scale of the solvent dynamics and electron transfer at the Mg–anode interface. In the vicinity of the anode surface, steric factors and hindered solvent dynamics may increase the reductive stability of (MgTFSI)+ ion pairs at lower overpotential by reducing the metal cation coordination, in stark contrast to the reduction at high overpotential accompanied by TFSI decomposition. By examining other solute/solvent combinations, we conclude that the electrolytes with highly coordinated Mg cation centers are more prone to reductive instability due to the chemical decomposition of the anion or solvent molecules. The obtained findings disclose critical factors for stable electrolyte design and show the role of interfacial phenomena in reduction of multivalent ions.

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“…Studies on the magnesium based GPEs are interesting due to less reactivity of Mg metal in air compared to Li or Na which makes it safer to handle. It also has a significantly higher specific capacity (i.e., 3833 mA h cm À3 for Mg, 2061 mA h cm À3 for Li and 136 mA h cm À3 for Na) [26][27]. The use of Mg(CF 3 SO 3 ) 2 salt in polymer electrolytes was found to have higher ionic conductivity (s) ranging from $10 À4 to 10 À3 S cm À1 [28][29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Ionic liquid-based polymer gel electrolytes for symmetrical solid-state electrical double layer capacitor operated at different operating voltages

Syahidah

Majid

2015

Electrochimica Acta

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Nanocomposite polymer electrolyte for rechargeable magnesium batteries

Cited by 138 publications

References 94 publications

Exploring the Liquid Structure and Ion Formation in Magnesium Borohydride Electrolyte Using Density Functional Theory

Exploring the Liquid Structure and Ion Formation in Magnesium Borohydride Electrolyte Using Density Functional Theory

Exploration of the Detailed Conditions for Reductive Stability of Mg(TFSI)₂ in Diglyme: Implications for Multivalent Electrolytes

Ionic liquid-based polymer gel electrolytes for symmetrical solid-state electrical double layer capacitor operated at different operating voltages

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Nanocomposite polymer electrolyte for rechargeable magnesium batteries

Cited by 138 publications

References 94 publications

Exploring the Liquid Structure and Ion Formation in Magnesium Borohydride Electrolyte Using Density Functional Theory

Exploring the Liquid Structure and Ion Formation in Magnesium Borohydride Electrolyte Using Density Functional Theory

Exploration of the Detailed Conditions for Reductive Stability of Mg(TFSI)2 in Diglyme: Implications for Multivalent Electrolytes

Ionic liquid-based polymer gel electrolytes for symmetrical solid-state electrical double layer capacitor operated at different operating voltages

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Exploration of the Detailed Conditions for Reductive Stability of Mg(TFSI)₂ in Diglyme: Implications for Multivalent Electrolytes