Urea Calcium Borohydrides as Ca2+ Solid-State Electrolytes

IF 7 2区材料科学 Q2 CHEMISTRY, PHYSICAL Chemistry of Materials Pub Date : 2025-01-17 DOI:10.1021/acs.chemmater.4c03098

Mads B. Amdisen, Torben R. Jensen

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Abstract

Solid-state calcium batteries can potentially contribute to future renewable energy storage systems, however the discovery of electrolytes with sufficiently high Ca²⁺ conductivity at ambient conditions is a challenge. Here we present mechanochemical synthesis and properties of five different urea calcium tetrahydridoborate compositions as well as three crystal structures, Ca(BH₄)₂·xCO(NH₂)₂, x = 2, 4, and 6. The orthorhombic structure of Ca(BH₄)₂·2CO(NH₂)₂ consists of dinuclear molecular units, [Ca₂(BH₄)₄(OC(NH₂)₂)₄], with the two Ca²⁺ ions bridged by three urea molecules. The low symmetry monoclinic structures of Ca(BH₄)₂·4CO(NH₂)₂ and Ca(BH₄)₂·6CO(NH₂)₂ consist of [Ca(BH₄)₂(OC(NH₂)₂)₄] and [Ca(OC(NH₂)₂)₆]²⁺ octahedra with BH₄^– counterions in the later, and all three structures are held together by dihydrogen bonds. The calcium ionic conductivity reaches a maximum of σ(Ca²⁺) = 2.46 × 10^–7 S cm^–1 for the composition Ca(BH₄)₂–3.30CO(NH₂)₂ at RT, and of σ(Ca²⁺) = 1.23 × 10^–4 S cm^–1 for Ca(BH₄)₂–6.52CO(NH₂)₂ at 70 °C. Activation energies in the range 0.5 < E_a < 2.4 eV depending on the urea content and heating or cooling during measurement of ionic conductivity and an ionic transport number of T_ion = 0.997 are also reported. The investigation of this series of compounds and their composites provides approaches for optimizing multiple physical phenomena that facilitate increased cationic conductivity.

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尿素硼氢化钙作为Ca2+固态电解质

固态钙电池可能有助于未来的可再生能源存储系统，然而，在环境条件下发现具有足够高的Ca2+导电性的电解质是一个挑战。本文介绍了五种不同尿素四氢硼酸钙组成的机械化学合成及其性质，以及Ca(BH4)2·xCO(NH2)2, x = 2, 4和6的三种晶体结构。Ca(BH4)2·2CO(NH2)2的正交结构由双核分子单元[Ca2(BH4)4(OC(NH2)2)4]组成，两个Ca2+离子由三个尿素分子桥接。Ca(BH4)2·4CO(NH2)2和Ca(BH4)2·6CO(NH2)2的低对称单斜结构由[Ca(BH4)2(OC(NH2)2)4]和[Ca(OC(NH2)2)6]2+八面体组成，后者为BH4 -反离子，三种结构通过二氢键结合在一起。Ca(BH4)2 - 3.30 co (NH2)2的钙离子电导率在室温下达到最大值σ(Ca2+) = 2.46 × 10-7 S cm-1, Ca(BH4)2 - 6.52 co (NH2)2的钙离子电导率在70℃时达到最大值σ(Ca2+) = 1.23 × 10-4 S cm-1。活化能在0.5 <范围；Ea & lt;2.4 eV取决于尿素含量和加热或冷却测量时的离子电导率和离子输运数= 0.997也被报道。这一系列化合物及其复合材料的研究为优化多种促进阳离子电导率增加的物理现象提供了方法。

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来源期刊

Chemistry of Materials 工程技术-材料科学：综合

CiteScore

14.10

自引率

5.80%

发文量

929

审稿时长

1.5 months

期刊介绍： The journal Chemistry of Materials focuses on publishing original research at the intersection of materials science and chemistry. The studies published in the journal involve chemistry as a prominent component and explore topics such as the design, synthesis, characterization, processing, understanding, and application of functional or potentially functional materials. The journal covers various areas of interest, including inorganic and organic solid-state chemistry, nanomaterials, biomaterials, thin films and polymers, and composite/hybrid materials. The journal particularly seeks papers that highlight the creation or development of innovative materials with novel optical, electrical, magnetic, catalytic, or mechanical properties. It is essential that manuscripts on these topics have a primary focus on the chemistry of materials and represent a significant advancement compared to prior research. Before external reviews are sought, submitted manuscripts undergo a review process by a minimum of two editors to ensure their appropriateness for the journal and the presence of sufficient evidence of a significant advance that will be of broad interest to the materials chemistry community.