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Trimetallic borohydride Li3MZn5(BH4)15 (M = Mg, Mn) containing two weakly interconnected frameworks
Radovan Černý1, Pascal Schouwink, Yolanda Sadikin
1Laboratory of Crystallography, University of Geneva, 24-quai Ernest-Ansermet, CH-1211 Geneva, Switzerland. radovan.cerny@unige.ch
Inorganic Chemistry
|August 24, 2013
Summary
The first trimetallic borohydrides, Li3MZn5(BH4)15 (M=Mg, Mn), were synthesized and structurally characterized. These new materials show potential as solid-state electrolytes but have limited hydrogen storage applications.
Area of Science:
- Solid-state chemistry
- Materials science
- Inorganic chemistry
Background:
- Borohydrides are critical materials for energy storage and ionic conductivity.
- The development of novel complex borohydrides is essential for advancing battery technology and hydrogen storage.
- Trimetallic borohydrides offer unique structural and electrochemical properties.
Purpose of the Study:
- To synthesize and characterize novel trimetallic borohydrides of the formula Li3MZn5(BH4)15, where M = Mg and Mn.
- To elucidate the crystal structure and bonding characteristics of these new compounds.
- To evaluate their potential applications as solid-state electrolytes and for hydrogen storage.
Main Methods:
- Mechanochemical synthesis using LiBH4, MCl2/M(BH4)2, and ZnCl2.
- In situ synchrotron radiation powder X-ray and neutron diffraction for structural analysis.
- Density Functional Theory (DFT) calculations for optimizing local atomic arrangements and understanding bonding.
Main Results:
- Successful synthesis of Li3MZn5(BH4)15 (M = Mg, Mn) as the first trimetallic borohydrides and new cationic solid solutions.
- Isostructural compounds characterized by hexagonal average structure (diffraction) and suggested orthorhombic ordered models (DFT).
- A novel framework structure containing channels built from face-sharing (BH4)6 octahedra, with DFT favoring lithium within shared triangular faces forming interpenetrated mco-nets.
Conclusions:
- Li3MZn5(BH4)15 compounds represent a new class of trimetallic borohydrides with a unique structural framework.
- Potential for solid-state electrolyte applications exists, contingent on improving lithium mobility through heterovalent substitution.
- Limited suitability for hydrogen storage due to decomposition into known metal borohydrides.
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