Conductor-Insulator Interfaces in Solid Electrolytes: A Design Strategy to Enhance Li-Ion Dynamics in Nanoconfined LiBH4/Al2O3

Roman Zettl; Katharina Hogrefe; Bernhard Gadermaier; Ilie Hanzu; Peter Ngene; Petra E. De Jongh; H. Martin R. Wilkening

doi:10.1021/acs.jpcc.1c03789

Conductor-Insulator Interfaces in Solid Electrolytes: A Design Strategy to Enhance Li-Ion Dynamics in Nanoconfined LiBH₄/Al₂O₃

Roman Zettl
, Katharina Hogrefe
, Bernhard Gadermaier
, Ilie Hanzu
, Peter Ngene
, Petra E. De Jongh
, H. Martin R. Wilkening^*

^*Corresponding author for this work

Graz University of Technology
Institute for Chemistry and Technology of Materials, Christian-Doppler-Laboratory for Lithium Batteries, Graz University of Technology (NAWI Graz), Stremayrgasse 9, 8010 Graz, Austria

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

Synthesizing Li-ion-conducting solid electrolytes with application-relevant properties for new energy storage devices is a challenging task that relies on a few design principles to tune ionic conductivity. When starting with originally poor ionic compounds, in many cases, a combination of several strategies, such as doping or substitution, is needed to achieve sufficiently high ionic conductivities. For nanostructured materials, the introduction of conductor-insulator interfacial regions represents another important design strategy. Unfortunately, for most of the two-phase nanostructured ceramics studied so far, the lower limiting conductivity values needed for applications could not be reached. Here, we show that in nanoconfined LiBH4/Al2O3 prepared by melt infiltration, a percolating network of fast conductor-insulator Li+ diffusion pathways could be realized. These heterocontacts provide regions with extremely rapid 7Li NMR spin fluctuations giving direct evidence for very fast Li+ jump processes in both nanoconfined LiBH4/Al2O3 and LiBH4-LiI/Al2O3. Compared to the nanocrystalline, Al2O3-free reference system LiBH4-LiI, nanoconfinement leads to a strongly enhanced recovery of the 7Li NMR longitudinal magnetization. The fact that almost no difference is seen between LiBH4-LiI/Al2O3 and LiBH4/Al2O3 unequivocally reveals that the overall 7Li NMR spin-lattice relaxation rates are solely controlled by the spin fluctuations near or in the conductor-insulator interfacial regions. Thus, the conductor-insulator nanoeffect, which in the ideal case relies on a percolation network of space charge regions, is independent of the choice of the bulk crystal structure of LiBH4, either being orthorhombic (LiBH4/Al2O3) or hexagonal (LiBH4-LiI/Al2O3). 7Li (and 1H) NMR shows that rapid local interfacial Li-ion dynamics is corroborated by rather small activation energies on the order of only 0.1 eV. In addition, the LiI-stabilized layer-structured form of LiBH4 guarantees fast two-dimensional (2D) bulk ion dynamics and contributes to facilitating fast long-range ion transport.

Original language	English
Pages (from-to)	15052-15060
Number of pages	9
Journal	Journal of Physical Chemistry C
Volume	125
Issue number	27
DOIs	https://doi.org/10.1021/acs.jpcc.1c03789
Publication status	Published - 15 Jul 2021

Bibliographical note

Funding Information:
H.M.R.W. thanks the German Science Foundation (Deutsche Forschungsgemeinschaft (DFG)) for financial support (research unit FOR1277). In addition, P.E.d.J. and P.N. acknowledge financial support by the Dutch Research Council (Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NOW)), ECHO grant 712.015.005, as well as by the NWO materials for sustainability (Mat4Sus-739.017.009) grant. Moreover, further financial support by the Austrian Federal Ministry of Science, Research and Economy (BMWFW) and the National Foundation for Research, Technology and Development (CD-Laboratory of Lithium Batteries: Ageing Effects, Technology and New Materials) is gratefully acknowledged. This work also received funding from the European H2020 Framework program, no. 769929, and from the FFG comet project safe battery.

Publisher Copyright:
© 2021 The Authors. Published by American Chemical Society.

Funding

H.M.R.W. thanks the German Science Foundation (Deutsche Forschungsgemeinschaft (DFG)) for financial support (research unit FOR1277). In addition, P.E.d.J. and P.N. acknowledge financial support by the Dutch Research Council (Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NOW)), ECHO grant 712.015.005, as well as by the NWO materials for sustainability (Mat4Sus-739.017.009) grant. Moreover, further financial support by the Austrian Federal Ministry of Science, Research and Economy (BMWFW) and the National Foundation for Research, Technology and Development (CD-Laboratory of Lithium Batteries: Ageing Effects, Technology and New Materials) is gratefully acknowledged. This work also received funding from the European H2020 Framework program, no. 769929, and from the FFG comet project safe battery.

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Cite this

@article{ae10bbbce81444da8bb22784d5c8df79,

title = "Conductor-Insulator Interfaces in Solid Electrolytes: A Design Strategy to Enhance Li-Ion Dynamics in Nanoconfined LiBH4/Al2O3",

abstract = "Synthesizing Li-ion-conducting solid electrolytes with application-relevant properties for new energy storage devices is a challenging task that relies on a few design principles to tune ionic conductivity. When starting with originally poor ionic compounds, in many cases, a combination of several strategies, such as doping or substitution, is needed to achieve sufficiently high ionic conductivities. For nanostructured materials, the introduction of conductor-insulator interfacial regions represents another important design strategy. Unfortunately, for most of the two-phase nanostructured ceramics studied so far, the lower limiting conductivity values needed for applications could not be reached. Here, we show that in nanoconfined LiBH4/Al2O3 prepared by melt infiltration, a percolating network of fast conductor-insulator Li+ diffusion pathways could be realized. These heterocontacts provide regions with extremely rapid 7Li NMR spin fluctuations giving direct evidence for very fast Li+ jump processes in both nanoconfined LiBH4/Al2O3 and LiBH4-LiI/Al2O3. Compared to the nanocrystalline, Al2O3-free reference system LiBH4-LiI, nanoconfinement leads to a strongly enhanced recovery of the 7Li NMR longitudinal magnetization. The fact that almost no difference is seen between LiBH4-LiI/Al2O3 and LiBH4/Al2O3 unequivocally reveals that the overall 7Li NMR spin-lattice relaxation rates are solely controlled by the spin fluctuations near or in the conductor-insulator interfacial regions. Thus, the conductor-insulator nanoeffect, which in the ideal case relies on a percolation network of space charge regions, is independent of the choice of the bulk crystal structure of LiBH4, either being orthorhombic (LiBH4/Al2O3) or hexagonal (LiBH4-LiI/Al2O3). 7Li (and 1H) NMR shows that rapid local interfacial Li-ion dynamics is corroborated by rather small activation energies on the order of only 0.1 eV. In addition, the LiI-stabilized layer-structured form of LiBH4 guarantees fast two-dimensional (2D) bulk ion dynamics and contributes to facilitating fast long-range ion transport. ",

author = "Roman Zettl and Katharina Hogrefe and Bernhard Gadermaier and Ilie Hanzu and Peter Ngene and \{De Jongh\}, \{Petra E.\} and Wilkening, \{H. Martin R.\}",

note = "Funding Information: H.M.R.W. thanks the German Science Foundation (Deutsche Forschungsgemeinschaft (DFG)) for financial support (research unit FOR1277). In addition, P.E.d.J. and P.N. acknowledge financial support by the Dutch Research Council (Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NOW)), ECHO grant 712.015.005, as well as by the NWO materials for sustainability (Mat4Sus-739.017.009) grant. Moreover, further financial support by the Austrian Federal Ministry of Science, Research and Economy (BMWFW) and the National Foundation for Research, Technology and Development (CD-Laboratory of Lithium Batteries: Ageing Effects, Technology and New Materials) is gratefully acknowledged. This work also received funding from the European H2020 Framework program, no. 769929, and from the FFG comet project safe battery. Publisher Copyright: {\textcopyright} 2021 The Authors. Published by American Chemical Society.",

year = "2021",

month = jul,

day = "15",

doi = "10.1021/acs.jpcc.1c03789",

language = "English",

volume = "125",

pages = "15052--15060",

journal = "Journal of Physical Chemistry C",

issn = "1932-7447",

publisher = "American Chemical Society",

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TY - JOUR

T1 - Conductor-Insulator Interfaces in Solid Electrolytes

T2 - A Design Strategy to Enhance Li-Ion Dynamics in Nanoconfined LiBH4/Al2O3

AU - Zettl, Roman

AU - Hogrefe, Katharina

AU - Gadermaier, Bernhard

AU - Hanzu, Ilie

AU - Ngene, Peter

AU - De Jongh, Petra E.

AU - Wilkening, H. Martin R.

N1 - Funding Information: H.M.R.W. thanks the German Science Foundation (Deutsche Forschungsgemeinschaft (DFG)) for financial support (research unit FOR1277). In addition, P.E.d.J. and P.N. acknowledge financial support by the Dutch Research Council (Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NOW)), ECHO grant 712.015.005, as well as by the NWO materials for sustainability (Mat4Sus-739.017.009) grant. Moreover, further financial support by the Austrian Federal Ministry of Science, Research and Economy (BMWFW) and the National Foundation for Research, Technology and Development (CD-Laboratory of Lithium Batteries: Ageing Effects, Technology and New Materials) is gratefully acknowledged. This work also received funding from the European H2020 Framework program, no. 769929, and from the FFG comet project safe battery. Publisher Copyright: © 2021 The Authors. Published by American Chemical Society.

PY - 2021/7/15

Y1 - 2021/7/15

N2 - Synthesizing Li-ion-conducting solid electrolytes with application-relevant properties for new energy storage devices is a challenging task that relies on a few design principles to tune ionic conductivity. When starting with originally poor ionic compounds, in many cases, a combination of several strategies, such as doping or substitution, is needed to achieve sufficiently high ionic conductivities. For nanostructured materials, the introduction of conductor-insulator interfacial regions represents another important design strategy. Unfortunately, for most of the two-phase nanostructured ceramics studied so far, the lower limiting conductivity values needed for applications could not be reached. Here, we show that in nanoconfined LiBH4/Al2O3 prepared by melt infiltration, a percolating network of fast conductor-insulator Li+ diffusion pathways could be realized. These heterocontacts provide regions with extremely rapid 7Li NMR spin fluctuations giving direct evidence for very fast Li+ jump processes in both nanoconfined LiBH4/Al2O3 and LiBH4-LiI/Al2O3. Compared to the nanocrystalline, Al2O3-free reference system LiBH4-LiI, nanoconfinement leads to a strongly enhanced recovery of the 7Li NMR longitudinal magnetization. The fact that almost no difference is seen between LiBH4-LiI/Al2O3 and LiBH4/Al2O3 unequivocally reveals that the overall 7Li NMR spin-lattice relaxation rates are solely controlled by the spin fluctuations near or in the conductor-insulator interfacial regions. Thus, the conductor-insulator nanoeffect, which in the ideal case relies on a percolation network of space charge regions, is independent of the choice of the bulk crystal structure of LiBH4, either being orthorhombic (LiBH4/Al2O3) or hexagonal (LiBH4-LiI/Al2O3). 7Li (and 1H) NMR shows that rapid local interfacial Li-ion dynamics is corroborated by rather small activation energies on the order of only 0.1 eV. In addition, the LiI-stabilized layer-structured form of LiBH4 guarantees fast two-dimensional (2D) bulk ion dynamics and contributes to facilitating fast long-range ion transport.

AB - Synthesizing Li-ion-conducting solid electrolytes with application-relevant properties for new energy storage devices is a challenging task that relies on a few design principles to tune ionic conductivity. When starting with originally poor ionic compounds, in many cases, a combination of several strategies, such as doping or substitution, is needed to achieve sufficiently high ionic conductivities. For nanostructured materials, the introduction of conductor-insulator interfacial regions represents another important design strategy. Unfortunately, for most of the two-phase nanostructured ceramics studied so far, the lower limiting conductivity values needed for applications could not be reached. Here, we show that in nanoconfined LiBH4/Al2O3 prepared by melt infiltration, a percolating network of fast conductor-insulator Li+ diffusion pathways could be realized. These heterocontacts provide regions with extremely rapid 7Li NMR spin fluctuations giving direct evidence for very fast Li+ jump processes in both nanoconfined LiBH4/Al2O3 and LiBH4-LiI/Al2O3. Compared to the nanocrystalline, Al2O3-free reference system LiBH4-LiI, nanoconfinement leads to a strongly enhanced recovery of the 7Li NMR longitudinal magnetization. The fact that almost no difference is seen between LiBH4-LiI/Al2O3 and LiBH4/Al2O3 unequivocally reveals that the overall 7Li NMR spin-lattice relaxation rates are solely controlled by the spin fluctuations near or in the conductor-insulator interfacial regions. Thus, the conductor-insulator nanoeffect, which in the ideal case relies on a percolation network of space charge regions, is independent of the choice of the bulk crystal structure of LiBH4, either being orthorhombic (LiBH4/Al2O3) or hexagonal (LiBH4-LiI/Al2O3). 7Li (and 1H) NMR shows that rapid local interfacial Li-ion dynamics is corroborated by rather small activation energies on the order of only 0.1 eV. In addition, the LiI-stabilized layer-structured form of LiBH4 guarantees fast two-dimensional (2D) bulk ion dynamics and contributes to facilitating fast long-range ion transport.

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