Solid-state magnesium electrolytes may pave the way for novel types of rechargeable, sustainable, and cheap batteries with high volumetric and gravimetric capacities. There are, however, currently no solid-state magnesium electrolytes that fulfill the requirements for solid-state battery applications. Here, we present the synthesis, structure, and properties of six new methylamine magnesium borohydride compounds, α- and β-Mg(BH₄)₂·6CH₃NH₂, Mg(BH₄)₂·3CH₃NH₂, and α-, α′- and β-Mg(BH₄)₂·CH₃NH₂. The β-Mg(BH₄)₂·CH₃NH₂ polymorph displays a record high Mg²⁺ ionic conductivity of σ(Mg²⁺) = 1.50 × 10^–4 S cm^–1 at room temperature. The high Mg²⁺ conductivity of β-Mg(BH₄)·CH₃NH₂ is facilitated by a one-dimensional chain-like structure interconnected by weak dihydrogen bonds and dispersion interactions, forming a migration pathway across the chains. The oxidative stability of Mg(BH₄)₂·CH₃NH₂ is ∼1.2 V vs Mg/Mg²⁺, and the reversible plating and stripping were confirmed by cyclic voltammetry and symmetric cell cycling, revealing high stability toward magnesium electrodes for at least 50 cycles at 60 °C.

中文翻译：

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甲胺硼氢化镁作为全固态镁电池的电解质

固态镁电解质可能为具有高体积和重量容量的新型可充电、可持续且廉价的电池铺平道路。然而，目前还没有满足固态电池应用要求的固态镁电解质。在这里，我们介绍了六种新的甲胺硼氢化镁化合物 α- 和 β-Mg(BH ₄ ) ₂ ·6CH ₃ NH ₂、Mg(BH ₄ ) ₂ ·3CH ₃ NH ₂和 α的合成、结构和性质-、α'-和β-Mg(BH ₄ ) ₂ ·CH ₃ NH ₂。β-Mg(BH ₄) ₂ ·CH ₃ NH ₂多晶型物在室温下显示出最高的 Mg ²⁺离子电导率 σ(Mg ²⁺ ) = 1.50 × 10 ^–4 S cm ^{–1 。}β-Mg(BH ₄ )·CH ₃ NH ₂的高Mg ²⁺电导率是由一维链状结构促进的，该结构通过弱双氢键和色散相互作用相互连接，形成跨链的迁移路径。_{Mg(BH 4} ) ₂ ·CH ₃ NH ₂的氧化稳定性为~1.2 V vs Mg/Mg ²⁺，并且通过循环伏安法和对称电池循环证实了可逆的电镀和剥离，显示出在 60 °C 下对镁电极至少 50 个循环的高稳定性。