High Li+ and Na+ Conductivity in New Hybrid Solid Electrolytes based on the Porous MIL-121 Metal Organic Framework

Solid-state electrolytes (SSEs) can leapfrog the development of all-solid-state batteries (ASSBs), enabling them to power electric vehicles and to store renewable energy from intermittent sources. Here, a new hybrid Li+ and Na+ conducting SSE based on the MIL-121 metal-organic framework (MOF) structure is reported. Following synthesis and activation of the MOF, the free carboxylic units along the 1D pores are functionalized with Li+ or Na+ ions by ion exchange. Ion dynamics are investigated by broadband impedance spectroscopy and by Li-7 and Na-23 NMR spin-lattice relaxation. A crossover at 50 degrees C (Li+) and at 10 degrees C (Na+) from correlated to almost uncorrelated motion at higher temperature is observed, which is in line with Ngai\u27s coupling model. Alternatively, in accordance to the jump relaxation model of Funke, at low temperature only a fraction of the jump processes are successful as lattice rearrangement in the direct vicinity of Li+ (Na+) is slow. H-1 NMR unambiguously shows that Li+ is the main charge carrier. Conductivities reach 0.1 mS cm(-1) (298 K, Na+) while the activation energies are 0.28 eV (Li+) and 0.36 eV (Na+). The findings pave the way towards development of easily tunable and rationally adjustable high-performance MOF-based hybrid SSEs for ASSBs

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

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

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

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

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

Solid electrolytes based on LiBH4 receive much attention because of their high ionic conductivity, electrochemical robustness, and low interfacial resistance against Li metal. The highly conductive hexagonal modification of LiBH4 can be stabilized via the incorporation of LiI. If the resulting LiBH4-LiI is confined to the nanopores of an oxide, such as Al2O3, interface-engineered LiBH4-LiI/Al2O3 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 1H, 6Li, 7Li, 11B, and 27Al nuclear magnetic resonance (NMR) to study structural and dynamic features of nanoconfined LiBH4-LiI/Al2O3. In particular, diffusion-induced 1H, 7Li, and 11B NMR spin-lattice relaxation measurements and 7Li-pulsed field gradient (PFG) NMR experiments were used to extract activation energies and diffusion coefficients. 27Al magic angle spinning NMR revealed surface interactions of LiBH4-LiI with pentacoordinated Al sites, and two-component 1H 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 LiBH4-LiI regions turned out to be fully homogenous. This view is supported by 7Li 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 LiBH4-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 LiBH4-LiI/Al2O3 is characterized by an activation energy of 0.43 eV

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

Solid electrolytes based on LiBH4 receive much attention because of their high ionic conductivity, electrochemical robustness, and low interfacial resistance against Li metal. The highly conductive hexagonal modification of LiBH4 can be stabilized via the incorporation of LiI. If the resulting LiBH4-LiI is confined to the nanopores of an oxide, such as Al2O3, interface-engineered LiBH4-LiI/Al2O3 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 1H, 6Li, 7Li, 11B, and 27Al nuclear magnetic resonance (NMR) to study structural and dynamic features of nanoconfined LiBH4-LiI/Al2O3. In particular, diffusion-induced 1H, 7Li, and 11B NMR spin-lattice relaxation measurements and 7Li-pulsed field gradient (PFG) NMR experiments were used to extract activation energies and diffusion coefficients. 27Al magic angle spinning NMR revealed surface interactions of LiBH4-LiI with pentacoordinated Al sites, and two-component 1H 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 LiBH4-LiI regions turned out to be fully homogenous. This view is supported by 7Li 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 LiBH4-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 LiBH4-LiI/Al2O3 is characterized by an activation energy of 0.43 eV

Li-Ion Diffusion in Nanoconfined LiBH4LiI/Al2O3: From 2D Bulk Transport to 3D Long-Range Interfacial Dynamics

Solid electrolytes based on LiBH4 receive much attention because of their high ionic conductivity, electrochemical robustness, and low interfacial resistance against Li metal. The highly conductive hexagonal modification of LiBH4 can be stabilized via the incorporation of LiI. If the resulting LiBH4-LiI is confined to the nanopores of an oxide, such as Al2O3, interface-engineered LiBH4-LiI/Al2O3 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 1H, 6Li, 7Li, 11B, and 27Al nuclear magnetic resonance (NMR) to study structural and dynamic features of nanoconfined LiBH4-LiI/Al2O3. In particular, diffusion-induced 1H, 7Li, and 11B NMR spin-lattice relaxation measurements and 7Li-pulsed field gradient (PFG) NMR experiments were used to extract activation energies and diffusion coefficients. 27Al magic angle spinning NMR revealed surface interactions of LiBH4-LiI with pentacoordinated Al sites, and two-component 1H 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 LiBH4-LiI regions turned out to be fully homogenous. This view is supported by 7Li 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 LiBH4-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 LiBH4-LiI/Al2O3 is characterized by an activation energy of 0.43 eV

New Kids on the Woog - Ein kinderfreundliches Quartier für die neue Heinrich-Hoffmann Schule. Städtebaulicher Entwurf im Wintersemester 2018/19

In diesem städtebaulichen Entwurf wurden Konzepte gesucht, welche die stadträumliche Integration der Schule in die neue Nachbarschaft fördern. Studierende entwickelten a) ein Mobilitätskonzept, das eine sichere, möglichst autofreie An- und Abreise ermöglicht, b) ein Freiraumkonzept, welches das Schulgelände mit den umliegenden Freiräumen sowie Sport- und Kultureinrichtungen vernetzt und vertiefen c) einen Entwurf für die schuleigenen Freiräume, das ebenso die Bedarfe von Inklusions-Kindern berücksichtigt sowie ein Massenmodel für das neue Schulgebäude, welches die städtebaulichen Vor- und Nachteile einer Typologie, der Verteilung und Ausrichtung der Baumassen, sowie Erschließung erkennen lässt