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Metal hydride formation and hydrogen storage in Al-Li alloys IRI Symposium May 22, 2003

Metal hydride formation and hydrogen storage in Al-Li alloys IRI Symposium May 22, 2003. A. Rivera Defects in Materials, IRI, TUDelft Work supported by the Delft Institute for Sustainable Energy (DISE) Contributors at DM:

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Metal hydride formation and hydrogen storage in Al-Li alloys IRI Symposium May 22, 2003

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  1. Metal hydride formation and hydrogen storage in Al-Li alloysIRI SymposiumMay 22, 2003 A. Rivera Defects in Materials, IRI, TUDelft Work supported by the Delft Institute for Sustainable Energy (DISE) Contributors at DM: A. van Veen (head), F. Labohm, J. de Roode, W.J. Legerstee, K.T. Westerduin, S.W.H. Eijt, H. Schut. External contributors (Materials Science Faculty, TUDelft): R. Delhez, N. van der Pers

  2. World energy consumption To reduce oil dependency  Hydrogen

  3. A 1000 kg car consumes 5-6 kg fuel/100 km The same car would consume 2 kg H2/100 km in combustion mode or 1 kg H2 /100 km in fuel cell mode However, at room temperature and atmospheric pressure 1 kg H2 occupies 11 m3 Storage: Pressurised vessels Liquified H2 Sorbed at surface or bulk materials How to store hydrogen?

  4. Contents • Material requirements • Examples • Non-transition light metal hydrides • Experimental developments • Al-Li materials • Conclusions and further work

  5. Material requirements • Storage capacity > 5 wt. % • Fast reaction kinetics • H2 release: 100 kPa at T < 200 ºC • Reversibility in the range 0 – 200 ºC • Resistance to degradation • Cost • Safety

  6. Hysteresis between absorption and desorption Hydride stability Limited kinetics Poor heat conduction Small diffusion constant Surface reactions Necessity for initial hydriding activation Sensitivity to air, impurities or other gases Volume expansion Decrepitation into fine powder Sources of inefficiencies

  7. Hydrogen in solution: α-phase Hydrogen in hydride: β-phase Formation of hydride: α & β M + ½xH2 MHx + ΔQ Isotherm flat More plateaux can appear Storage and release • Desorption isotherm is lower due to stress • This is undesired for hydrogen storage • Formation enthalpy can be obtained

  8. E.g. MgH2 at 600 K Slow diffusion Kinetics 1 μm / s

  9. Hydrogen storage materials

  10. Key properties

  11. LiAlH4, NaAlH4 (in water  irreversible full H2 release) High capacities (10 and 5 wt.%, respectively) No reversible due to decomposition 3 LiAlH4Li3AlH6 + 2 Al + 3 H2[150-175 oC] Li3AlH6 + 2 Al 3 LiH + 3 Al + 1.5 H2[180-220 oC] 3 LiH + 3 Al  3 AlLi + 1.5 H2[387-425 oC] Slow kinetics Catalysts, as Fe, Ti and Zr Make some steps reversible Improve the kinetics Non-transition light metal hydrides

  12. Our approach • Objective: to develop nanostructured light weight alloys for hydrogen storage • Choice:Al-Li compounds • Preparation • Sputtering of Al-Li alloy or LiAlH4 • Laser ablation of Al-Li alloy or LiAlH4 • Cathodic charge, ion implantation gas or plasma exposure + annealing • Characterisation • Volumetric analyses, Permeation, TDS, XRD, NDP, PBA • Occasionally ERDA, SEM, TEM

  13. Gas analysis techniques • Hydra • Hydrogen absorption and desorption experiments • Desorption detection limits 1013 - 1022 H2 molecules • Dynamic measurements give direct information on kinetics • Appropriate for thin films • Permeation • of solved molecules or electrochemically introduced atoms • in situ after sputtering will become available soon • Sensitive thermal desorption spectrometry • Detection limit as low as 1011 H2 molecules • Significantly lower for D2

  14. Hydra

  15. Hydra Expansion volume M1 10-2-10 Pa M2 10-105 Pa M0 0.1-6 MPa Mix volume Gas inlet To pumps Pd filter Mass analyser Cell (90-900 K)

  16. Hydra (static) M1 1015-1017 H2 M2 1017-1022 H2 Expansion volume M0 0.1-6 MPa Mix volume Gas inlet To pumps Pd filter Mass analyser Cell (90-900 K)

  17. Hydra (dynamic) Expansion volume M1 M2 M0 0.1-6 MPa Mix volume Gas inlet To pumps Pd filter Mass analyser 1012-1015 H2/s 1013-1016 H2 Cell (90-900 K)

  18. Hydra software

  19. Desorption of LiAlH4 • 0.4 mg LiAlH4, 0.1 K/s • Total H2: 1.5x1022 g-1 • Total gas: 3.9x1022 g-1 • 0: Hydroxide • 1: LiAlH4 • 2: Li3AlH6 • 3: LiH

  20. Sputter deposited Al-Li: SEM • SEM evidences the formation of columnar structures in the nm range, size increases with distance from substrate ~1 µm sputter deposited Pd layer Pd ~1 µm sputter deposited Al-Li at room temperature, the layer contains 5at.%Li (NDP) Al Li

  21. Sputter deposited Al-Li: Hydrogen • Dynamic measurements: • High sensitivity • Easy background estimation • Peaks indicate kinetics processes • Around 0.5 at.H% • Recharging results in low T peak of 0.3 at.H%

  22. Conclusions and further work • Effort to fulfil material requirements • Successful H2 detection techniques • Successful creation of samples by • Sputtering • Laser ablation • Currently: • High Li content samples from LiAlH4 targets • Study of samples with high porosity • Fundamental study of Li nanocrystals in c-Al

  23. Further information • Contact • A. Rivera: Rivera@iri.tudelft.nl • A. van Veen: AvVeen@iri.tudelft.nl

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