1. Lithium-Amide Systems for Hydrogen Storage: cation/anion substitution
L. Fernández Albanesi, G. Amica, N. Gamba,
P. Arneodo Larochette and F. C. Gennari
Physical-Chemistry Department – CAB – CNEA (National Commision of Atomic Energy)
Bariloche - Argentina
Lithium-Amide Systems for Hydrogen Storage: cation/anion substitution

2. LiNH2 crystal structure
Li-N-H System
The Li-N-H system has received special attention since 2002 with the report of Chen et al.
LiNH2(s) + LiH(s) ↔ Li2NH(s) + H2(g)
(6.5 wt% H) ΔH = 44.5 kJ/mol
Li-N-H is a reversible storage system through the breaking and formation of N-H bonds
LiNH2 crystal structure
P. Chen, Z. Xiong, J. Luo, J. Lin, K.L. Tan, Nature 420 (2002) 302–304
Hydrogen Days Prague, Czech Republic; 13 to 15 June 2018

3. excess of LiH to avoid the NH3 formation and emission
Destabilization
It is necessary to lower the operation temperature
excess of LiH to avoid the NH3 formation and emission
LiNH LiH
Addition of different compounds to the Li-N-H system during ball milling process:
AlCl3
looking for replacing the Li+ by Al3+ ions to produce vacancies
MgH2 / CaH2 / TiH2
because metal hydrides offer a possible way to modify its thermodynamic properties
MgCl2
to understand the behaviour of the halides on the properties of Li-Mg-N-H system
Hydrogen Days Prague, Czech Republic; 13 to 15 June 2018

4. Improvement of the dehydrogenation and hydrogenation kinetics
AlCl3
LiNH LiH AlCl3
AlCl3
AlCl3
Improvement of the dehydrogenation and hydrogenation kinetics
Hydrogen Days Prague, Czech Republic; 13 to 15 June 2018

5. The addition of AlCl3 modifies the system thermodynamics
L-N-Al-H-Cl system
The addition of AlCl3 modifies the system thermodynamics
Hydrogen Days Prague, Czech Republic; 13 to 15 June 2018

6. Thermal treatment at 300 ºC under 7 bar of H2 pressure
L-N-Al-H-Cl systems
Thermal treatment at 300 ºC under 7 bar of H2 pressure
cubic I213
AlCl3 BM
AlCl3 TT
New phases in the Li-Al-N-H-Cl system, isostructural with the cubic and hexagonal type-Li4(NH2)3Cl(*)
hexagonal R-3 and cubic I213
AlCl3 BM
AlCl3 TT
Intensity (a.u.)
hexagonal R-3
AlCl3 BM
AlCl3 TT
AlCl3 BM
LiNH LiH
For low amount addition of AlCl3 Al3+ is incorporated in the LiNH2 lattice
(*) A.A. Anderson, P.A. Chater, D.R. Hewett, P.R. Slater, Faraday Discuss 151 (2011)
L. Fernández Albanesi, S. Garroni, S. Enzo, F.C.Gennari, Dalton Trans. 45 (2016)
Hydrogen Days Prague, Czech Republic; 13 to 15 June 2018

7. MgH2 / CaH2 / TiH2 LiNH2 + 1.6 LiH + 0.2 MgH2
The H2 release finishes at 290 ºC
LiNH LiH CaH2
Improvement in the H2 desorption rate
+ 0.2 TiH2
No modification was observed by TiH2 addition
Hydrogen Days Prague, Czech Republic; 13 to 15 June 2018

8. Reactions at 300 ºC under 7 bar of H2 pressure
L-N-Mg-H and L-N-Ca-H systems
Reactions at 300 ºC under 7 bar of H2 pressure
2LiNH2 + MgH2 ↔ Mg(NH2)2 + 2LiH
Mg(NH2)2 + 2LiH ↔ Li2Mg(NH)2 + 2H2
4LiNH2 + 3CaH CaNH-Ca(NH2)2 + 4LiH + 2H2
2LiNH2 + 4LiH + 2CaNH-Ca(NH2)2 ↔ 3Li2NH + 3CaNH + 4H2
G. Amica, P. Arneodo Larochette, F.C.Gennari, Int. J. Hydrogen Energy 40 (2015)
Hydrogen Days Prague, Czech Republic; 13 to 15 June 2018

9. Thermal treatment at 200 ºC under 60 bar of H2 pressure
MgCl2
2 LiNH2 + MgCl Mg(NH2)2 + 2 LiCl
Mg(NH2)2–2LiCl–2LiH
Thermal treatment at 200 ºC under 60 bar of H2 pressure
Mg(NH2)2
Li4(NH2)3Cl
3LiNH2 + LiCl Li4(NH2)3Cl
Li2Mg2(NH)3
Hydrogen Days Prague, Czech Republic; 13 to 15 June 2018

10. Mg(NH2)2– 2LiCl–2LiH 2Mg(NH2)2 + 3LiH ↔ Li2Mg2(NH3) + LiNH2 + 3H2
Li2Mg2(NH3) + LiNH2 + LiH ↔ 2Li2Mg(NH)2 + H2
Thermal decomposition of Li4(NH2)3Cl
H2 desorption from Mg(NH2)2-2LiH-2LiCl
and thermal decomposition of Li4(NH2)3Cl
H2 desorption from Mg(NH2)2-2LiH-2LiCl
N. Gamba, P. Arneodo Larochette, F.C.Gennari, RSC Adv. 5 (2015)
Hydrogen Days Prague, Czech Republic; 13 to 15 June 2018

11. Conclusions
The Mg(NH2)2–2LiH was synthesized by metathesis reaction between LiNH2 and MgCl2
The as milled Mg(NH2)2–2LiCl–2LiH material shows good dehydrogenation rate and high H2 storage capacity at 200 ºC
The formation of Li4(NH2)3Cl was favored during H2 cycling, deteriorating the storage properties

12. Conclusions
Dehydrogenation behaviour shows that CaH2 and MgH2 were the best additives under de experimental conditions studied, without positive effect of TiH2
Dehydrogenation rate of Li-N-Ca-H system at 300 ºC was, at least, three times faster than Li-N-H pristine system
The hydrogen storage reversibility involves the formation of 2CaNH-Ca(NH2)2 solid solution in the hydrogenated state and the Li2NH–CaNH mixture in the dehydrogenated state
A clear thermodynamic destabilization was only observed for LiNH2-LiH with MgH2 added, with minor effect in the case of CaH2

13. Conclusions The Li-N-H system stores hydrogen reversibly
When AlCl3 is added the kinetic properties are improved
The addition of AlCl3 modifies the system thermodynamics
Combination of XPRD and FTIR studies demonstrate that the formation of lithium aluminum amide-chloride new compound occurs by combination of milling and thermal treatment
This new phases are able to release and uptake hydrogen reversibly
In these systems, the effect of anion/cation substitution promotes N-H bond destabilization and induces structural defects into LiNH2 lattice improving the Li+ mobility
The Mg(NH2)2–2LiH was synthesized by metathesis reaction between LiNH2 and MgCl2
The as milled Mg(NH2)2–2LiCl–2LiH material shows good dehydrogenation rate and high H2 storage capacity at 200 ºC
The formation of Li4(NH2)3Cl is favoured during H2 cycling, deterioring the storage properties

14. Who we are...
Hydrogen Days Prague, Czech Republic; 13 to 15 June 2018

15. Where we are…
Hydrogen Days Prague, Czech Republic; 13 to 15 June 2018

16. Argentina
Bariloche
Hydrogen Days Prague, Czech Republic; 13 to 15 June 2018

17. Thank you very much!