Probing molecular dynamics of metal borohydrides on the surface of mesoporous scaffolds by multinuclear high resolution solid state NMR

Lithium Conductivity and Ions Dynamics in LiBH4/SiO2 Solid Electrolytes Studied by Solid-State NMR and Quasi-Elastic Neutron Scattering and Applied in Lithium–Sulfur Batteries

“…Such a peak has been attributed to impurities or to H 2 gas trapped inside of solid LiBH 4 as similar peak was observed in the case of H 2 trapped in AlH 3 . Hwang et al performed NMR measurements while heating a mixture of LiBH 4 and SiO 2 and observed this “H 2 peak” and proposed a reaction (eq ) between the hydroxyl groups present at the surface of SiO 2 and LiBH 4 , releasing hydrogen at about 373 K. Hwang et al also noted the disappearance of the silanol peak (at 1.8 ppm) during heating of the mixture LiBH 4 and SiO 2 . One can note that no peak is visible at 1.8 ppm in Figure for the composite spectrum.…”

“…Such a peak has been attributed to impurities 75 or to H 2 gas trapped inside of solid LiBH 4 as similar peak was observed in the case of H 2 trapped in AlH 3 . 76 Hwang et al 73 performed NMR measurements while heating a mixture of LiBH 4 and SiO 2 and observed this "H 2 peak" and proposed a reaction (eq 6) between the hydroxyl groups present at the surface of SiO 2 and LiBH 4 , releasing hydrogen at about 373 K. One can note that no peak is visible at 1.8 ppm in Figure 10 for the composite spectrum. The existence of O−B bonds, supporting the existence of a reaction between the hydroxyl groups and LiBH 4 , was reported by Choi et al 46 for LiBH 4 ball-milled with Al 2 O 3 .…”

“…At 341 K, two components are seen at −40.97 and −41.93 ppm for the composite, whereas the spectrum for LiBH 4 (at 294 K) shows a single resonance at −41.50 ppm. Hwang et al observed the splitting of the central resonance in the 11 B spectrum for LiBH 4 in mesoporous silicates at temperatures above 373 K, i.e., when LiBH 4 is in the hexagonal crystal structure. Verkuijlen et al also observed a similar splitting for the 11 B resonance, both with and without 1 H decoupling, for LiBH 4 nanoconfined in mesoporous silica but at lower temperatures as low as 283 K. Their presented pattern without 1 H decoupling is similar to the one given by Shane et al for molten LiBH 4 at 558 K. Unreported so far is the presence of a third component at −41.50 ppm observed herein at 294 K for the composite.…”

“…Such a peak has been attributed to impurities 75 or to H2 gas trapped inside of solid LiBH4 as similar peak was observed in the case of H2 trapped in AlH3. 76 Hwang et al, 73 performing NMR measurements while heating a mixture of LiBH4 and SiO2, observed this "H2 peak" and proposed a reaction ( Eq. 6) between the hydroxyl groups present at the surface of SiO2 and LiBH4, releasing hydrogen and occurring at about 373 K.…”

“…At 341 K, two components are seen at -40.97 ppm and -41.93 ppm for the composite while the spectrum for LiBH4 (at 294 K) shows a single resonance at -41.50 ppm. Hwang et al73 have observed the splitting of the central resonance in the 11 B spectrum for LiBH4 in mesoporous silicates at temperatures above 373 K, i.e., when LiBH4 is in the hexagonal crystal structure. Verkuijlen et al71 have also observed a similar splitting for the11 B…”