Decomposition behavior of unmilled and ball milled lithium alanate (LiAlH4) including long-term storage and moisture effects

Varin, R.A.; Zbroniec, L.

doi:10.1016/j.jallcom.2010.05.059

Cited by 57 publications

(72 citation statements)

References 22 publications

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“…In general, it is well-known in the literature [2,[11][12][13] that the dehydrogenation of LiAlH 4 in solid state occurs in three stages as shown below:…”

Section: Resultsmentioning

confidence: 99%

“…The hydride powder mixtures with the ball-to-powder weight ratio R = 132 were subsequently processed by controlled ball milling for selected time durations in the magneto-mill Uni-Ball-Mill 5 under IMP68 mode. This is a high impact energy mode with two very strong Nd-Fe-B magnets at the 6 and 8 o'clock positions and 4 steel balls (each 25 mm in diameter) in the vial [2,[11][12][13][14][15]. The pressure of high purity hydrogen (purity 99.999%: O 2 < 2 ppm; H 2 O < 3 ppm; CO 2 < 1 ppm; N 2 < 6 ppm; CO < 1 ppm; THC < 1 ppm) in the vial was kept constant at ~600 kPa during the entire milling process.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The XRD pattern for the n = 1 composite (Figure 2a) shows that after 2 min of milling the diffraction peaks of both constituents LiAlH 4 and LiNH 2 are still clearly observed. There is also a peak of Al which is an impurity in as received LiAlH 4 [11,12]. After 15 min of ball milling, the principal peaks of Li 3 AlH 6 appear and the principal Al peak becomes stronger, indicating that more Al is formed during milling.…”

Section: Experimental Methodsmentioning

confidence: 99%

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Mechanical and Thermal Dehydrogenation of Lithium Alanate (LiAlH4) and Lithium Amide (LiNH2) Hydride Composites

Varin

Zbroniec

2012

Crystals

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Hydrogen storage properties of the (nLiAlH 4 + LiNH 2 ) hydride composite where n = 1, 3, 11.5 and 30, synthesized by high energy ball milling have been investigated. The composite with the molar ratio n = 1 releases large quantities of H 2 (up to ~5 wt.%) during ball milling up to 100-150 min. The quantity of released H 2 rapidly decreases for the molar ratio n = 3 and is not observed for n = 11.5 and 30. The XRD studies indicate that the H 2 release is a result of a solid state decomposition of LiAlH 4 into (1/3)Li 3 AlH 6 + (2/3)Al + H 2 and subsequently decomposition of (1/3)Li 3 AlH 6 into LiH + (1/3)Al + 0.5H 2 . Apparently, LiAlH 4 is profoundly destabilized during ball milling by the presence of a large quantity of LiNH 2 (37.7 wt.%) in the n = 1 composite. The rate of dehydrogenation at 100-170 °C (at 1 bar H 2 ) is adversely affected by insufficient microstructural refinement, as observed for the n = 1 composite, which was milled for only 2 min to avoid H 2 discharge during milling. XRD studies show that isothermal dehydrogenation of (nLiAlH 4 + LiNH 2 ) occurs by the same LiAlH 4 decomposition reactions as those found during ball milling. The ball milled n = 1 composite stored under Ar at 80 °C slowly discharges large quantities of H 2 approaching 3.5 wt.% after 8 days of storage.

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“…In general, it is well-known in the literature [2,[11][12][13] that the dehydrogenation of LiAlH 4 in solid state occurs in three stages as shown below:…”

Section: Resultsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Mechanical and Thermal Dehydrogenation of Lithium Alanate (LiAlH4) and Lithium Amide (LiNH2) Hydride Composites

Varin

Zbroniec

2012

Crystals

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“…Once the remaining LiBH 4 has decomposed, it is not reformed under the applied hydriding conditions, thus it is not observed during the second desorption. Based on the in situ SR-PXD on the bulk sample, the compounds that are not regenerated under the applied temperatures and hydrogen pressures are possibly LiAlH 4 and/or Li 3 AlH 6 [37].…”

Section: Cyclic Stabilitymentioning

confidence: 99%

Hydrogen Desorption Properties of Bulk and Nanoconfined LiBH4-NaAlH4

2016

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Nanoconfinement of 2LiBH 4 -NaAlH 4 into a mesoporous carbon aerogel scaffold with a pore size, BET surface area and total pore volume of D max = 30 nm, S BET = 689 m 2 /g and V tot = 1.21 mL/g, respectively is investigated. Nanoconfinement of 2LiBH 4 -NaAlH 4 facilitates a reduction in the temperature of the hydrogen release by 132˝C, compared to that of bulk 2LiBH 4 -NaAlH 4 and the onset of hydrogen release is below 100˝C. The reversible hydrogen storage capacity is also significantly improved for the nanoconfined sample, maintaining 83% of the initial hydrogen content after three cycles compared to 47% for that of the bulk sample. During nanoconfinement, LiBH 4 and NaAlH 4 reacts to form LiAlH 4 and NaBH 4 and the final dehydrogenation products, obtained at 481˝C are LiH, LiAl, AlB 2 and Al. After rehydrogenation of the nanoconfined sample at T = 400˝C and p(H 2 ) = 126 bar, amorphous NaBH 4 is recovered along with unreacted LiH, AlB 2 and Al and suggests that NaBH 4 is the main compound that can reversibly release and uptake hydrogen.

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“…A complementary in situ hydrogenation study of a slurry of LiH and Al(Ti) in THF was conducted in which the reaction was monitored by static 7 Li NMR spectroscopy (Varian 400 MHz NMR (9.4 T), 7 Li at 155.455 MHz, acquisition details are in the ESI †). The results of this study are depicted in Fig.…”

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confidence: 99%

In situ high pressure NMR study of the direct synthesis of LiAlH4

et al. 2013

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Li wide-line NMR spectroscopy incorporating a high pressure NMR apparatus has allowed the first in situ study of the solvent mediated, direct synthesis of an alanate, thus overcoming the dearth of analytical techniques available to study phenomena occurring in a pressurised slurry. In contrast to the decomposition reaction, the elucidated hydrogenation pathway does not proceed through the hexahydride intermediate.The practical utilisation of hydrogen as an energy carrier awaits the development of high-capacity, hydrogen storage materials that can be recharged under moderate conditions. A viable onboard hydrogen carrier must have: high gravimetric and volumetric hydrogen capacities; thermodynamic properties that are within rather stringent limits; and dehydrogenation and rehydrogenation kinetics that allow hydrogen cycling at moderate temperatures and pressures.1,2 Although no directly reversible hydrogen material has yet met all of these criteria, a great deal of progress as have been made towards harnessing the high storage capacity, relatively low desorption temperatures, and comparative ease of hydrogenation of sodium alanate (NaAlH 4 ) and lithium alanate (LiAlH 4 ). 3It is well established that the dehydrogenation of both undoped and Ti-doped LiAlH 4 (Al(Ti)) proceeds via Li 3 AlH 6 as an intermediate before decomposition into LiH and Al as seen in eqn (1) and (2). 4-73LiAlH 4 / Li 3 AlH 6 + 2Al + 2H 2 (1)The in situ decomposition of LiAlH 4 has been studied previously by DSC, 7,8 X-ray and neutron diffraction measurements 9 and NMR spectroscopy. 10 The direct re-hydrogenation of LiH and Al to LiAlH 4 is challenging as the reaction in eqn (1) While Ashby et al. 13 found that THF solvated LiAlH 4 could be obtained in 96% yield following 5 h or reaction at 393 K under 340 bar of H 2 .More recently, Wang et al. reported the utilisation of high pressure ball-milling to form crystalline LiAlH 4 with a desolvation step following the reaction.14 Graetz et al. subsequently demonstrated the reversibility of this material using PCT isotherms (eqn (3)).15 Hydrogenation was reported to occur at room temperature and 13 bar H 2 forming the LiAlH 4 $4THF adduct from a THF slurry of LiH and Al(Ti), with the removal of the adduct at 333 K in vacuo to form crystalline LiAlH 4 . In a nal development, the complication of a requisite side process to remove the adduct prior to dehydrogenation was eliminated by Liu et al. who reported a remarkably mild and simple process to generate LiAlH 4 from the dehydrogenation products (eqn (4)).

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Decomposition behavior of unmilled and ball milled lithium alanate (LiAlH4) including long-term storage and moisture effects

Cited by 57 publications

References 22 publications

Mechanical and Thermal Dehydrogenation of Lithium Alanate (LiAlH4) and Lithium Amide (LiNH2) Hydride Composites

Mechanical and Thermal Dehydrogenation of Lithium Alanate (LiAlH4) and Lithium Amide (LiNH2) Hydride Composites

Hydrogen Desorption Properties of Bulk and Nanoconfined LiBH4-NaAlH4

In situ high pressure NMR study of the direct synthesis of LiAlH4

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