Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published August 25, 2015 | Supplemental Material
Journal Article Open

Synthesis of a Bimetallic Dodecaborate LiNaB_(12)H_(12)with Outstanding Superionic Conductivity

Abstract

Metal dodecaborates M_2/_nB_(12)H_(12) (n denotes the valence of the metal M), containing icosahedral polyatomic anion [B_(12)H_(12)]^(2−), have been attracting increasing interest as potential energy materials, especially in the context of hydrogen storage and superionic conductivity. M_2/_nB_(12)H_(12) are commonly formed as dehydrogenation intermediates from metal borohydrides M(BH_4)_n, like LiBH_4 and Mg(BH_4)_2, which are well-known as potential high-density hydrogen storage materials. The strong B−B bond in the icosahedral [B_(12)H_(12)]^(2−), however, is regarded to be the key factor that prevents the rehydrogenation of dodecaborates. In order to elucidate the mechanism as well as to provide effective solutions to this problem, a novel solvent-free synthesis route of anhydrous M_2/nB_(12)H_(12) (here M means Li, Na, and K) has been developed. Thermal stability and transformations of the anhydrous single phase Li_2B_(12)H_(12) suggested the formation of the high temperature polymorph of Li_2B_(12)H_(12) during the dehydrogenation of LiBH_4, while concurrently emphasized the importance of further investigation on the decomposition mechanism of metal borohydrides and metal dodecaborates. The high stability of icosahedral [B_(12)H_(12)]^(2−), on the other hand, favors its potential application as solid electrolyte. Recently, Na^+ conductivity of Na_2B_(12)H_(12) was reported to be 0.1 S/cm above its order−disorder phase transition at ∼529 K, which is comparable to that of a polycrystalline β"-Al_2O_3 (0.24 S/cm at 573 K) solid state Na-electrolyte. Mechanistic understanding on the diffusion behavior of cation and further improvement of ionic conductivity at a lower temperature, however, are important in order to facilitate the practical application of metal dodecaborates as superionic conductors.

Additional Information

© 2015 American Chemical Society. Received: April 28, 2015; Revised: August 6, 2015; Published: August 7, 2015. Author Contributions: The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. This work was partly supported by Grants-in-Aid for Scientific Research No. 25709067, JSPS Invitation Fellowship for Research in Japan (Short-Term), the International Institute for Carbon Neutral Energy Research (WPI-I2CNER), sponsored by the Japanese Ministry of Education, Culture, Sports, Science and Technology of Japan, Fonds Spéciaux de Recherche and FNRS as well as SNBL (ESRF) for the beamtime, and the Swiss National Science Foundation. The NMR facility at Caltech was supported by the National Science Foundation (NSF) under Grant Number 9724240 and partially supported by the MRSEC Program of the NSF under Award Number DMR-520565. The authors declare no competing financial interest.

Attached Files

Supplemental Material - cm5b01568_si_001.pdf

Supplemental Material - cm5b01568_si_002.gif

Files

cm5b01568_si_001.pdf
Files (2.7 MB)
Name Size Download all
md5:7d6fe9c13972bda031fee25337395ae3
901.8 kB Preview Download
md5:9a8cb009aa34bc49fa5d937ec9c83c1f
1.8 MB Preview Download

Additional details

Created:
August 20, 2023
Modified:
October 24, 2023