Magnesium Ethylenediamine Borohydride as Solid-State Electrolyte for Magnesium Batteries

Roedern, Elsa; Kühnel, Ruben‐Simon; Remhof, Arndt; Battaglia, Corsin

doi:10.1038/srep46189

Cited by 128 publications

(177 citation statements)

References 26 publications

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“…Mg(BH 4 )(NH 2 ), on the other hand, exhibits a Mg 2+ conductivity of 1.0 × 10 −6 S cm −1 at 150 °C, which is about 3 orders of magnitude higher than that of Mg(BH 4 ) 2 under the same condition . Complexation of organic ligand NH 2 CH 2 CH 2 NH 2 (EDA) to Mg(BH 4 ) 2 forming crystalline Mg(EDA) 1 (BH 4 ) 2 also led to higher Mg 2+ conductivity compared with the neat Mg(BH 4 ) 2 …”

Section: Complex Hydrides As Solid‐state Electrolytementioning

confidence: 99%

Complex Hydrides for Energy Storage, Conversion, and Utilization

2019

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functionalities and exhibit great potentials for the applications in the energy transfer chain (Figure 1).In chemistry, a hydride is a compound having negatively charged hydrogen anion. [2] Nowadays, however, hydrogenous compounds having hydrogen bonded to metals or nonmetal in ionic, metallic or covalent manner are collectively referred as hydrides. [3] Complex hydride is such a class of compound having a general formula of M(XH n ) m , where M is usually a metal cation and X is a metal or nonmetal element which sets up covalent or ionocovalent bonding with H. [4] The M[XH n ] m is H-rich and can decompose selectively to H 2 allowing complex hydrides of light-weight elements potential hydrogen storage media. As a matter of fact, since the pioneering work of Ti-catalyzed NaAlH 4 in 1997, [5] extensive investigations on hydrogen storage over alanates, [6] amide-hydride composites, [7] borohydrides, [8] amidoboranes [9] as well as metallorganic hydrides [10] were carried out and tremendous progress has been made (Figure 2). [1,4a] The break and setup of XH bonding would be endergonic and exergonic, respectively. The energy input and output in hydrogen desorption and reabsorption over a complex hydride depends strongly on its thermodynamic stability, which also offers an opportunity of using complex hydrides as thermal energy storage materials to cope up with the intermittent, fluctuating and unstable supply of renewable energies. Owning to their exclusive advantages of diversity, high energy densities and tunability, complex hydrides have been actively pursued for this application since year 2000. [11] Solid electrolytes with fast conduction of Li, Na, or Mg ions are highly demanded for all-solid-state batteries with high energy density and safety. Coincidentally, complex hydrides are composed of those cations and a relatively large sized [XH n ] anion. The coordination flexibility of the large anion with alkali or alkaline earth cation would create some favorable structural features, such as defects and/or low-barrier diffusion channels, to facilitate cation migration within the lattice of complex hydrides. [12] Starting from the finding of high Li-ion conduction in the high-temperature-phase LiBH 4 , [13] a variety of complex hydrides has been developed, some of which show superior ion conductivity to their nonhydride peers. [14] Hydrogen storage over complex hydride would undergo dihydrogen dissociation into surface H atoms followed by H Functional materials are the key enabling factor in the development of clean energy technologies. Materials of particular interest, which are reviewed herein, are a class of hydrogenous compound having the general formula of M(XH n ) m , where M is usually a metal cation and X can be Al, B, C, N, O, transition metal (TM), or a mixture of them, which sets up an iono-covalent or covalent bonding with H. M(XH n ) m is generally termed as a complex hydride by the hydrogen storage community. The rich chemistry between H and B/C/N/O/Al/TM allows complex hydrides of diverse compo...

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Section: Complex Hydrides As Solid‐state Electrolytementioning

confidence: 99%

Complex Hydrides for Energy Storage, Conversion, and Utilization

2019

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“…The ionic conductivity reached upon oxidation of Mg(BH 4 ) 2 is the highest reported so far. To date, the best possible ionic conductivity has been reported upon the modification of Mg(BH 4 ) 2 with ethylenediamine leading to an ionic conductivity of 5 × 10 −8 S cm −1 at 30 °C 42. Modification with ammonia enabled an ionic conductivity of 3 × 10 −6 S cm −1 at 100 °C 21.…”

Section: Resultsmentioning

confidence: 99%

“…To date, the best possible ionic conductivity has been reported upon the modification of Mg(BH 4 ) 2 with ethylenediamine leading to an ionic conductivity of 5 × 10 −8 S cm −1 at 30 °C. [42] Modification with ammonia enabled an ionic conductivity of 3 × 10 −6 S cm −1 at 100 °C. [21] The very low conductivity of pristine Mg(BH 4 ) 2 is attributed to its structure in which the Mg 2+ ions are seating in firm tetrahedral cages composed of four BH 4 − units with strong coulombic interaction.…”

Section: Improving the Ionic Conductivity Of Other Borohydrides Throumentioning

confidence: 99%

Facile Self‐Forming Superionic Conductors Based on Complex Borohydride Surface Oxidation

Luo

Rawal

Cazorla

et al. 2020

Advanced Sustainable Systems

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Complex hydrides have attracted significant attention as better inorganic solid‐state electrolytes owing to their lightweight and good compatibility with metal anodes (Li, Na, and/or Mg) for all solid‐state batteries. However, high ionic conductivity is usually observed at high temperatures upon the stabilization of adequate crystalline phases enabling fast ionic mobility. Here, an extremely simple strategy to significantly increase the ionic conductivity of complex borohydrides is reported. By exposing complex borohydrides to oxygen, the rearrangement of surface atoms upon the oxidation of borohydride particles and the resulting defects lead to extremely high ionic conductivity. NaBH4 and LiBH4 exposed to 5% O2 show an ionic conductivity of ≈10−3 S cm−1 at 35 °C. Similarly, oxidized Mg(BH4)2 displays a conductivity of ≈10−6 S cm−1 at 25 °C instead of 9.63 × 10−13 S cm−1. To the best of the authors' knowledge, this is to date, the simplest approach to tune the properties of borohydrides toward high ionic conductivity at room temperature as it does not rely on the difficult synthesis of large cage boron based anions to substitute BH4− and allow better ionic conduction paths. Owing its simplicity, the finding has the potential to enable new avenues toward the realization of viable complex borohydride based solid‐state electrolytes.

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“…However, the conductivity of solid state Mg(BH 4 ) 2 is very low (<10 −12 S cm −1 at 30 • C) [182] but may be enhanced in double anion compounds, e.g., Mg(BH 4 )(NH 2 ) has a Mg 2+ conductivity of 1 × 10 −6 S cm −1 at T = 150 • C [183]. Recently, the addition of ethylene diamine, NH 2 (CH 2 ) 2 NH 2 (en), to Mg(BH 4 ) 2 resulted in the formation of cis-Mg(en)(BH 4 ) 2 which shows ion conductivity between 5 × 10 −8 and 6 × 10 −5 S cm −1 in the temperature range 30 to 70 • C, respectively [182]. So far, the most promising compounds are Na 2 B 10 H 10 and Na 2 B 12 H 12 , which show superionic conductivity in the high-temperature polymorphs (phase transition at 87 and 207 • C, respectively) with Na ion conductivity of~0.01 and 0.1 S cm −1 , respectively [184,185].…”

Section: Complex Metal Hydrides As Electrolytesmentioning

confidence: 99%

“…Reversible Mg stripping/plating has been demonstrated using Mg(BH 4 ) 2 as an electrolyte in THF and dimethoxyethane solutions [181]. However, the conductivity of solid state Mg(BH 4 ) 2 is very low (<10 −12 S cm −1 at 30 • C) [182] but may be enhanced in double anion compounds, e.g., Mg(BH 4 )(NH 2 ) has a Mg 2+ conductivity of 1 × 10 −6 S cm −1 at T = 150 • C [183]. Recently, the addition of ethylene diamine, NH 2 (CH 2 ) 2 NH 2 (en), to Mg(BH 4 ) 2 resulted in the formation of cis-Mg(en)(BH 4 ) 2 which shows ion conductivity between 5 × 10 −8 and 6 × 10 −5 S cm −1 in the temperature range 30 to 70 • C, respectively [182].…”

Section: Complex Metal Hydrides As Electrolytesmentioning

confidence: 99%

Complex Metal Hydrides for Hydrogen, Thermal and Electrochemical Energy Storage

et al. 2017

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Hydrogen has a very diverse chemistry and reacts with most other elements to form compounds, which have fascinating structures, compositions and properties. Complex metal hydrides are a rapidly expanding class of materials, approaching multi-functionality, in particular within the energy storage field. This review illustrates that complex metal hydrides may store hydrogen in the solid state, act as novel battery materials, both as electrolytes and electrode materials, or store solar heat in a more efficient manner as compared to traditional heat storage materials. Furthermore, it is highlighted how complex metal hydrides may act in an integrated setup with a fuel cell. This review focuses on the unique properties of light element complex metal hydrides mainly based on boron, nitrogen and aluminum, e.g., metal borohydrides and metal alanates. Our hope is that this review can provide new inspiration to solve the great challenge of our time: efficient conversion and large-scale storage of renewable energy.

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Magnesium Ethylenediamine Borohydride as Solid-State Electrolyte for Magnesium Batteries

Cited by 128 publications

References 26 publications

Complex Hydrides for Energy Storage, Conversion, and Utilization

Complex Hydrides for Energy Storage, Conversion, and Utilization

Facile Self‐Forming Superionic Conductors Based on Complex Borohydride Surface Oxidation

Complex Metal Hydrides for Hydrogen, Thermal and Electrochemical Energy Storage

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