Nanostructured Ceramics: Ionic Transport and Electrochemical Activity

Prutsch, Denise; Breuer, Stefan; Uitz, Marlena; Bottke, Patrick; Langer, Julia; Lunghammer, Sarah; Philipp, Martin; Posch, Patrick; Pregartner, Veronika; Stanje, Bernhard; Dunst, Andreas; Wohlmuth, Dominik; Brandstätter, Harald; Schmidt, Walter; Epp, Viktor; Chadwick, Alan V.; Hanzu, Ilie; Wilkening, Martin

doi:10.1515/zpch-2016-0924

“…For hexagonal, nanocrystalline LiBH 4 , that is, at temperatures higher than T trans. , ion dynamics in the bulk is rapid as well and has to be characterized by an activation energy of 0.52 (1) eV. This value is in line with earlier studies 15,19 and agrees with the activation energy from direct current (d.c.) conductivity measurements.…”

supporting

confidence: 90%

“…Nanostructured ceramics contain crystallites with at least one dimension in the nanometre regime. Many experiments into such compounds reveal enhanced ion dynamics as compared to the situation in the coarse-grained counterparts. − Also other properties, such as electrical and optical features, may benefit from shrinking the crystallite size. It is, however, not easy to identify the true origin of the changes or enhancements seen.…”

mentioning

confidence: 99%

Rapid Li Ion Dynamics in the Interfacial Regions of Nanocrystalline Solids

Breuer

¹

,

Uitz

²

,

Wilkening

³

2018

J. Phys. Chem. Lett.

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Diffusive processes are ubiquitous in nature. In solid state physics, metallurgy and materials science the diffusivity of ions govern the functionality of many devices such as sensors or batteries. Motional processes on surfaces, across interfaces or through membranes can be quite different to that in the bulk. A direct, quantitative description of such local diffusion processes is, however, rare. Here, we took advantage of Li longitudinal nuclear magnetic relaxation to study, on the atomic length scale, the diffusive motion of lithium spins in the interfacial regions of nanocrystalline, orthorhombic LiBH. Magnetization transients and free induction decays revealed a fast subset of Li ions having access to surface pathways that offer activation barriers (0.18 eV) much lower than those in the crystalline bulk regions (0.55 eV). These observations make orthorhombic borohydride a new nanostructured model system to study disorder-induced enhancements in interfacial diffusion processes.

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“…An exception is given for Li 7 Si 12 where Li cations are guided along the stacked Si 5 rings [34]. Besides these adjusting screws to manipulate macroscopic and microscopic ion dynamics, we have the possibility to take advantage of interfacial effects [35] in both single-phase and two-phase conductor:insulator or ion-conductor:electron-conductor composites [27,[36][37][38]. If the crystallite regions are reduced to nanometer-sized dimensions, a network of percolating diffusion pathways can be generated, which in the case of Li 2 O : Al 2 O 3 or LiF : Al 2 O 3 resulted in fast ion dynamics [39,40].…”

Section: Introductionmentioning

confidence: 99%

Fuzzy logic: about the origins of fast ion dynamics in crystalline solids

Gombotz

¹

,

Hogrefe

²

,

Zettl

³

et al. 2021

Phil. Trans. R. Soc. A.

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Nuclear magnetic resonance offers a wide range of tools to analyse ionic jump processes in crystalline and amorphous solids. Both high-resolution and time-domain 1 , 2 H , 6 , 7 Li , 19 F , 23 Na NMR helps throw light on the origins of rapid self-diffusion in materials being relevant for energy storage. It is well accepted that Li + ions are subjected to extremely slow exchange processes in compounds with strong site preferences. The loss of this site preference may lead to rapid cation diffusion, as is also well known for glassy materials. Further examples that benefit from this effect include, e.g. cation-mixed, high-entropy fluorides ( Ba, Ca) F 2 , Li-bearing garnets ( Li 7 La 3 Zr 2 O 12 ) and thiophosphates such as LiTi 2 ( PS 4 ) 3 . In non-equilibrium phases site disorder, polyhedra distortions, strain and the various types of defects will affect both the activation energy and the corresponding attempt frequencies. Whereas in ( Me, Ca ) F 2 ( Me = Ba , Pb ) cation mixing influences F anion dynamics, in Li 6 PS 5 X ( X = Br , Cl , I ) the potential landscape can be manipulated by anion site disorder. On the other hand, in the mixed conductor Li 4 + x Ti 5 O 12 cation-cation repulsions immediately lead to a boost in Li + diffusivity at the early stages of chemical lithiation. Finally, rapid diffusion is also expected for materials that are able to guide the ions along (macroscopic) pathways with confined (or low-dimensional) dimensions, as is the case in layer-structured RbSn 2 F 5 or MeSnF 4 . Diffusion on fractal systems complements this type of diffusion. This article is part of the Theo Murphy meeting issue ‘Understanding fast-ion conduction in solid electrolytes’.

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“…The scaffolds of the nanoconfined complex hydrides are ionic insulators. In such conductor/insulator composites, − enhanced ion transport along the heterointerfaces can occur due to both structural disorder − and/or space charge effects. ,− …”

Section: Introductionmentioning

confidence: 99%

Li-Ion Diffusion in Nanoconfined LiBH₄-LiI/Al₂O₃: From 2D Bulk Transport to 3D Long-Range Interfacial Dynamics

Zettl

¹

,

Gombotz

²

,

Clarkson

³

et al. 2020

ACS Appl. Mater. Interfaces

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Solid electrolytes based on LiBH 4 receive much attention because of their high ionic conductivity, electrochemical robustness, and low interfacial resistance against Li metal. The highly conductive hexagonal modification of LiBH 4 can be stabilized via the incorporation of LiI. If the resulting LiBH 4 -LiI is confined to the nanopores of an oxide, such as Al 2 O 3 , interface-engineered LiBH 4 -LiI/Al 2 O 3 is obtained that revealed promising properties as a solid electrolyte. The underlying principles of Li + conduction in such a nanocomposite are, however, far from being understood completely. Here, we used broadband conductivity spectroscopy and 1 H, 6 Li, 7 Li, 11 B, and 27 Al nuclear magnetic resonance (NMR) to study structural and dynamic features of nanoconfined LiBH 4 -LiI/Al 2 O 3 . In particular, diffusion-induced 1 H, 7 Li, and 11 B NMR spin–lattice relaxation measurements and 7 Li-pulsed field gradient (PFG) NMR experiments were used to extract activation energies and diffusion coefficients. 27 Al magic angle spinning NMR revealed surface interactions of LiBH 4 -LiI with pentacoordinated Al sites, and two-component 1 H NMR line shapes clearly revealed heterogeneous dynamic processes. These results show that interfacial regions have a determining influence on overall ionic transport (0.1 mS cm –1 at 293 K). Importantly, electrical relaxation in the LiBH 4 -LiI regions turned out to be fully homogenous. This view is supported by 7 Li NMR results, which can be interpreted with an overall (averaged) spin ensemble subjected to uniform dipolar magnetic and quadrupolar electric interactions. Finally, broadband conductivity spectroscopy gives strong evidence for 2D ionic transport in the LiBH 4 -LiI bulk regions which we observed over a dynamic range of 8 orders of magnitude. Macroscopic diffusion coefficients from PFG NMR agree with those estimated from measurements of ionic conductivity and nuclear spin relaxation. The resulting 3D ionic transport in nanoconfined LiBH 4 -LiI/Al 2 O 3 is characterized by an activation energy of 0.43 eV.

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Nanostructured Ceramics: Ionic Transport and Electrochemical Activity

Cited by 27 publications

References 108 publications

Rapid Li Ion Dynamics in the Interfacial Regions of Nanocrystalline Solids

Rapid Li Ion Dynamics in the Interfacial Regions of Nanocrystalline Solids

Fuzzy logic: about the origins of fast ion dynamics in crystalline solids

Li-Ion Diffusion in Nanoconfined LiBH₄-LiI/Al₂O₃: From 2D Bulk Transport to 3D Long-Range Interfacial Dynamics

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Nanostructured Ceramics: Ionic Transport and Electrochemical Activity

Cited by 27 publications

References 108 publications

Rapid Li Ion Dynamics in the Interfacial Regions of Nanocrystalline Solids

Rapid Li Ion Dynamics in the Interfacial Regions of Nanocrystalline Solids

Fuzzy logic: about the origins of fast ion dynamics in crystalline solids

Li-Ion Diffusion in Nanoconfined LiBH4-LiI/Al2O3: From 2D Bulk Transport to 3D Long-Range Interfacial Dynamics

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Product

Resources

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Li-Ion Diffusion in Nanoconfined LiBH₄-LiI/Al₂O₃: From 2D Bulk Transport to 3D Long-Range Interfacial Dynamics