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Papers by Patrick Bottke

Research paper thumbnail of Ion Dynamics in Solid Electrolytes: NMR Reveals the Elementary Steps of Li + Hopping in the Garnet Li 6.5 La 3 Zr 1.75 Mo 0.25 O 12

Chemistry of Materials, 2015

Research paper thumbnail of Li ion dynamics in nanocrystalline and structurally disordered Li2TiO3

Zeitschrift für Physikalische Chemie, 2015

ABSTRACT The monoclinic polymorph of Li

Research paper thumbnail of A simple and straightforward mechanochemical synthesis of the far-from-equilibrium zinc aluminate, ZnAl2O4, and its response to thermal treatment

RSC Adv., 2015

Zinc aluminate (ZnAl 2 O 4 ) nanoparticles with an average size of about 10 nm are synthesized vi... more Zinc aluminate (ZnAl 2 O 4 ) nanoparticles with an average size of about 10 nm are synthesized via one-step mechanochemical processing of the ZnO : g-Al 2 O 3 stoichiometric mixture at ambient temperature. The mechanochemically induced formation of the phase is followed by XRD and 27 Al MAS NMR. Highresolution TEM studies reveal a non-uniform nanostructure of mechanosynthesized aluminate consisting of ordered grains surrounded or separated by disordered surface and interfacial regions. Due to the capability of 27 Al MAS NMR to probe the local environment of the Al cations, valuable insights into the short-range structure of ZnAl 2 O 4 on theÅngström length scale are provided. It is demonstrated that the as-prepared aluminate possesses a partly inverse spinel structure with a far-from equilibrium arrangement of cations and distorted polyhedra, which are spatially confined to the surface and interfacial regions with a volume fraction of ca. 50% and a thickness of ca. 1 nm. The response of the nanostructured ZnAl 2 O 4 to subsequent thermal treatment is further investigated. It turned out that the thermally induced grain growth is accompanied by a release of microstrain, by a shrinkage of the lattice parameter, as well as by a variation in the oxygen parameter and metal-oxygen bond lengths. Evidence is given of the thermally induced redistribution of cations approaching their equilibrium positions. Upon heating above 1100 K, mechanosynthesized ZnAl 2 O 4 relaxes towards a structural state that is similar to the bulk one.

Research paper thumbnail of Ex situ NMR Measurements of Li Dynamics in TiO2 Anodes with an Ordered Hierarchical Pore Structure

Research paper thumbnail of Towards a lattice-matching solid-state battery: synthesis of a new class of lithium-ion conductors with the spinel structure

Physical Chemistry Chemical Physics, 2013

Lithium ion batteries have conquered most of the portable electronics market and are now on the v... more Lithium ion batteries have conquered most of the portable electronics market and are now on the verge of deployment in large scale applications. To be competitive in the automotive and stationary sectors, however, they must be improved in the fields of safety and energy density (W h L À1 ). Solid-state batteries with a ceramic electrolyte offer the necessary advantages to significantly improve the current state-of-theart technology. The major limit towards realizing a practical solid-state lithium-ion battery lies in the lack of viable ceramic ionic conductors. Only a few candidate materials are available, each carrying a difficult balance between advantages and drawbacks. Here we introduce a new class of possible solid-state lithium-ion conductors with the spinel structure. Such compounds could be coupled with spinel-type electrode materials to obtain a ''lattice matching'' solid device where low interfacial resistance could be achieved. Powders were prepared by wet chemistry, their structure was studied by means of diffraction techniques and magic angle spinning NMR, and Li + self-diffusion was estimated by static NMR line shape measurements. Profound differences in the Li + diffusion properties were observed depending on the composition, lithium content and cationic distribution. Local Li + hopping in the spinel materials is accompanied by a low activation energy of circa 0.35 eV being comparable with that of, e.g., LLZO-type garnets, which represent the current benchmark in this field. We propose these novel materials as a building block for a lattice-matching all-spinel solid-state battery with low interfacial resistance. † Electronic supplementary information (ESI) available. See

Research paper thumbnail of Li ion dynamics in TiO2 anode materials with an ordered hierarchical pore structure – insights from ex situ NMR

Physical Chemistry Chemical Physics, 2014

Ex situ Nuclear Magnetic Resonance (NMR) measurements were carried out to study lithium ion dynam... more Ex situ Nuclear Magnetic Resonance (NMR) measurements were carried out to study lithium ion dynamics in lithium intercalated mesoporous anatase (Li x TiO 2 ) serving as an anode material for rechargeable lithiumion batteries. As has been shown recently, hierarchically ordered TiO 2 shows excellent cycling performance and ensures a high lithium storage capacity. 7 Li spin-lattice relaxation NMR and stimulated echo NMR serve as a powerful combination to shed light on the Li hopping processes from an atomic-scale point of view.

Research paper thumbnail of Structure and dynamics of the fast lithium ion conductor “Li7La3Zr2O12”

Physical Chemistry Chemical Physics, 2011

The solid lithium-ion electrolyte &am... more The solid lithium-ion electrolyte "Li(7)La(3)Zr(2)O(12)" (LLZO) with a garnet-type structure has been prepared in the cubic and tetragonal modification following conventional ceramic syntheses routes. Without aluminium doping tetragonal LLZO was obtained, which shows a two orders of magnitude lower room temperature conductivity than the cubic modification. Small concentrations of Al in the order of 1 wt% were sufficient to stabilize the cubic phase, which is known as a fast lithium-ion conductor. The structure and ion dynamics of Al-doped cubic LLZO were studied by impedance spectroscopy, dc conductivity measurements, (6)Li and (7)Li NMR, XRD, neutron powder diffraction, and TEM precession electron diffraction. From the results we conclude that aluminium is incorporated in the garnet lattice on the tetrahedral 24d Li site, thus stabilizing the cubic LLZO modification. Simulations based on diffraction data show that even at the low temperature of 4 K the Li ions are blurred over various crystallographic sites. This strong Li ion disorder in cubic Al-stabilized LLZO contributes to the high conductivity observed. The Li jump rates and the activation energy probed by NMR are in very good agreement with the transport parameters obtained from electrical conductivity measurements. The activation energy E(a) characterizing long-range ion transport in the Al-stabilized cubic LLZO amounts to 0.34 eV. Total electric conductivities determined by ac impedance and a four point dc technique also agree very well and range from 1 × 10(-4) Scm(-1) to 4 × 10(-4) Scm(-1) depending on the Al content of the samples. The room temperature conductivity of Al-free tetragonal LLZO is about two orders of magnitude lower (2 × 10(-6) Scm(-1), E(a) = 0.49 eV activation energy). The electronic partial conductivity of cubic LLZO was measured using the Hebb-Wagner polarization technique. The electronic transference number t(e-) is of the order of 10(-7). Thus, cubic LLZO is an almost exclusive lithium ion conductor at ambient temperature.

Research paper thumbnail of Synthesis of ternary transition metal fluorides Li3MF6via a sol–gel route as candidates for cathode materials in lithium-ion batteries

Journal of Materials Chemistry, 2012

A sol-gel route for ternary lithium fluorides of transition metals (M) is presented allowing the ... more A sol-gel route for ternary lithium fluorides of transition metals (M) is presented allowing the synthesis of Li 3 MF 6 -type and Li 2 MF 5 -type compounds. It is based on a fluorolytic process using transition metal acetylacetonates as precursors. The domain size of the obtained powders can be controlled by modifying the conditions of synthesis. 6 Li and 7 Li magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy is used to study local environments of the Li ions in orthorhombic and monoclinic Li 3 VF 6 as well as Li 2 MnF 5 . The number of magnetically inequivalent Li sites found by MAS NMR is in agreement with the respective crystal structure of the compounds studied. Quantum chemical calculations show that all materials have high de-lithiation energies making them suitable candidates to be used as high-voltage battery cathode materials.

Research paper thumbnail of DFT Study of the Role of Al 3+ in the Fast Ion-Conductor Li 7–3 x Al 3+ x La 3 Zr 2 O 12 Garnet

Chemistry of Materials, 2014

We investigate theoretically the site occupancy of Al 3+ in the fast-ion-conducting cubic-garnet ... more We investigate theoretically the site occupancy of Al 3+ in the fast-ion-conducting cubic-garnet Li 7−3x Al 3+

Research paper thumbnail of Novel amino propyl substituted organo tin compounds

Canadian Journal of Chemistry, 2014

ABSTRACT In this work, a new synthetic pathway yielding unprotected amino propyl tin compounds is... more ABSTRACT In this work, a new synthetic pathway yielding unprotected amino propyl tin compounds is described. For this purpose, mono stannanes with different substitution patterns are used. In a first step, tin hydrides are deprotonated using lithium diisopropyl amide and mixed with an electrophile containing a protected amine in the ω-position. After deprotection via acidic hydrolysis, the desired amino propyl tin compounds are obtained in high yield and purity. The thermal reaction behavior of the amino propyl tin hydrohalide intermediates containing one aromatic residue at the central tin atom is also investigated. For this purpose, amino propyl tin hydrohalides are heated under vacuum until the aromatic hydrocarbon is liberated. This thermal treatment leads to so far unknown tin halides containing an amino propyl side chain. For all of these substances detailed liquid 1H, 13C, and 119Sn-nuclear magnetic resonance (NMR) data were obtained, and in one case solid state NMR is also conducted. Regarding solids, single crystal X-ray analysis is performed. Some derivatization reactions with these new substances are demonstrated, especially the synthesis of an amino propyl tin carboxylate, which might be very interesting for biological, pharmaceutical, or technical processes.

Research paper thumbnail of Low temperature synthesis, characterization and substrate-dependent photocatalytic activity of nanocrystalline TiO2 with tailor-made rutile to anatase ratio

Applied Catalysis A: General, 2008

... In phenol decomposition the samples' photocatalytic performance gradually and significan... more ... In phenol decomposition the samples' photocatalytic performance gradually and significantly increases with their anatase content: photocatalysts containing only anatase as crystalline phase were up to three times more efficient than rutile ones. ...

Research paper thumbnail of Small Change—Great Effect: Steep Increase of Li Ion Dynamics in Li 4 Ti 5 O 12 at the Early Stages of Chemical Li Insertion

Chemistry of Materials, 2015

Lithium titanate (LTO) is one of the most promising anode materials for large-scale stationary el... more Lithium titanate (LTO) is one of the most promising anode materials for large-scale stationary electrochemical storage of energy produced from renewable sources. Besides many other aspects, such as negligible formation of passivation layers and no volume expansion during lithiation, the success of LTO is mainly based on its ability to easily accommodate and release Li ions in a fully reversible way. This feature is tightly connected with Li self-diffusion. As yet, little information is available about microscopic Li diffusion properties and elementary steps of Li hopping at low intercalation levels, i.e., at values of x being significantly smaller than 1. Here, we used 7 Li spin-locking NMR relaxometry to probe absolute hopping rates of LTO (homogeneous) solid solutions in quasi-thermodynamic equilibrium. As a result, the largest increase of Li diffusivity is observed when small amounts of Li are inserted. Strong Coulomb repulsions caused by the simultaneous occupation of neighboring 8a and 16c sites serve as an explanation for the enhanced Li diffusivity found. At even larger values of x, Li mobility slows down but is still much faster than in the host material with x = 0. Our results experimentally corroborate the outcome of recently published calculations on the DFT level focusing on both dynamic and structural aspects. The findings favor the formation of LTO solid solutions upon chemical lithiation; the steep increase in Li diffusivity found might also help with understanding the flat insertion potential observed.

Research paper thumbnail of Ion Dynamics in Solid Electrolytes: NMR Reveals the Elementary Steps of Li + Hopping in the Garnet Li 6.5 La 3 Zr 1.75 Mo 0.25 O 12

Chemistry of Materials, 2015

Research paper thumbnail of Li ion dynamics in nanocrystalline and structurally disordered Li2TiO3

Zeitschrift für Physikalische Chemie, 2015

ABSTRACT The monoclinic polymorph of Li

Research paper thumbnail of A simple and straightforward mechanochemical synthesis of the far-from-equilibrium zinc aluminate, ZnAl2O4, and its response to thermal treatment

RSC Adv., 2015

Zinc aluminate (ZnAl 2 O 4 ) nanoparticles with an average size of about 10 nm are synthesized vi... more Zinc aluminate (ZnAl 2 O 4 ) nanoparticles with an average size of about 10 nm are synthesized via one-step mechanochemical processing of the ZnO : g-Al 2 O 3 stoichiometric mixture at ambient temperature. The mechanochemically induced formation of the phase is followed by XRD and 27 Al MAS NMR. Highresolution TEM studies reveal a non-uniform nanostructure of mechanosynthesized aluminate consisting of ordered grains surrounded or separated by disordered surface and interfacial regions. Due to the capability of 27 Al MAS NMR to probe the local environment of the Al cations, valuable insights into the short-range structure of ZnAl 2 O 4 on theÅngström length scale are provided. It is demonstrated that the as-prepared aluminate possesses a partly inverse spinel structure with a far-from equilibrium arrangement of cations and distorted polyhedra, which are spatially confined to the surface and interfacial regions with a volume fraction of ca. 50% and a thickness of ca. 1 nm. The response of the nanostructured ZnAl 2 O 4 to subsequent thermal treatment is further investigated. It turned out that the thermally induced grain growth is accompanied by a release of microstrain, by a shrinkage of the lattice parameter, as well as by a variation in the oxygen parameter and metal-oxygen bond lengths. Evidence is given of the thermally induced redistribution of cations approaching their equilibrium positions. Upon heating above 1100 K, mechanosynthesized ZnAl 2 O 4 relaxes towards a structural state that is similar to the bulk one.

Research paper thumbnail of Ex situ NMR Measurements of Li Dynamics in TiO2 Anodes with an Ordered Hierarchical Pore Structure

Research paper thumbnail of Towards a lattice-matching solid-state battery: synthesis of a new class of lithium-ion conductors with the spinel structure

Physical Chemistry Chemical Physics, 2013

Lithium ion batteries have conquered most of the portable electronics market and are now on the v... more Lithium ion batteries have conquered most of the portable electronics market and are now on the verge of deployment in large scale applications. To be competitive in the automotive and stationary sectors, however, they must be improved in the fields of safety and energy density (W h L À1 ). Solid-state batteries with a ceramic electrolyte offer the necessary advantages to significantly improve the current state-of-theart technology. The major limit towards realizing a practical solid-state lithium-ion battery lies in the lack of viable ceramic ionic conductors. Only a few candidate materials are available, each carrying a difficult balance between advantages and drawbacks. Here we introduce a new class of possible solid-state lithium-ion conductors with the spinel structure. Such compounds could be coupled with spinel-type electrode materials to obtain a ''lattice matching'' solid device where low interfacial resistance could be achieved. Powders were prepared by wet chemistry, their structure was studied by means of diffraction techniques and magic angle spinning NMR, and Li + self-diffusion was estimated by static NMR line shape measurements. Profound differences in the Li + diffusion properties were observed depending on the composition, lithium content and cationic distribution. Local Li + hopping in the spinel materials is accompanied by a low activation energy of circa 0.35 eV being comparable with that of, e.g., LLZO-type garnets, which represent the current benchmark in this field. We propose these novel materials as a building block for a lattice-matching all-spinel solid-state battery with low interfacial resistance. † Electronic supplementary information (ESI) available. See

Research paper thumbnail of Li ion dynamics in TiO2 anode materials with an ordered hierarchical pore structure – insights from ex situ NMR

Physical Chemistry Chemical Physics, 2014

Ex situ Nuclear Magnetic Resonance (NMR) measurements were carried out to study lithium ion dynam... more Ex situ Nuclear Magnetic Resonance (NMR) measurements were carried out to study lithium ion dynamics in lithium intercalated mesoporous anatase (Li x TiO 2 ) serving as an anode material for rechargeable lithiumion batteries. As has been shown recently, hierarchically ordered TiO 2 shows excellent cycling performance and ensures a high lithium storage capacity. 7 Li spin-lattice relaxation NMR and stimulated echo NMR serve as a powerful combination to shed light on the Li hopping processes from an atomic-scale point of view.

Research paper thumbnail of Structure and dynamics of the fast lithium ion conductor “Li7La3Zr2O12”

Physical Chemistry Chemical Physics, 2011

The solid lithium-ion electrolyte &am... more The solid lithium-ion electrolyte "Li(7)La(3)Zr(2)O(12)" (LLZO) with a garnet-type structure has been prepared in the cubic and tetragonal modification following conventional ceramic syntheses routes. Without aluminium doping tetragonal LLZO was obtained, which shows a two orders of magnitude lower room temperature conductivity than the cubic modification. Small concentrations of Al in the order of 1 wt% were sufficient to stabilize the cubic phase, which is known as a fast lithium-ion conductor. The structure and ion dynamics of Al-doped cubic LLZO were studied by impedance spectroscopy, dc conductivity measurements, (6)Li and (7)Li NMR, XRD, neutron powder diffraction, and TEM precession electron diffraction. From the results we conclude that aluminium is incorporated in the garnet lattice on the tetrahedral 24d Li site, thus stabilizing the cubic LLZO modification. Simulations based on diffraction data show that even at the low temperature of 4 K the Li ions are blurred over various crystallographic sites. This strong Li ion disorder in cubic Al-stabilized LLZO contributes to the high conductivity observed. The Li jump rates and the activation energy probed by NMR are in very good agreement with the transport parameters obtained from electrical conductivity measurements. The activation energy E(a) characterizing long-range ion transport in the Al-stabilized cubic LLZO amounts to 0.34 eV. Total electric conductivities determined by ac impedance and a four point dc technique also agree very well and range from 1 × 10(-4) Scm(-1) to 4 × 10(-4) Scm(-1) depending on the Al content of the samples. The room temperature conductivity of Al-free tetragonal LLZO is about two orders of magnitude lower (2 × 10(-6) Scm(-1), E(a) = 0.49 eV activation energy). The electronic partial conductivity of cubic LLZO was measured using the Hebb-Wagner polarization technique. The electronic transference number t(e-) is of the order of 10(-7). Thus, cubic LLZO is an almost exclusive lithium ion conductor at ambient temperature.

Research paper thumbnail of Synthesis of ternary transition metal fluorides Li3MF6via a sol–gel route as candidates for cathode materials in lithium-ion batteries

Journal of Materials Chemistry, 2012

A sol-gel route for ternary lithium fluorides of transition metals (M) is presented allowing the ... more A sol-gel route for ternary lithium fluorides of transition metals (M) is presented allowing the synthesis of Li 3 MF 6 -type and Li 2 MF 5 -type compounds. It is based on a fluorolytic process using transition metal acetylacetonates as precursors. The domain size of the obtained powders can be controlled by modifying the conditions of synthesis. 6 Li and 7 Li magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy is used to study local environments of the Li ions in orthorhombic and monoclinic Li 3 VF 6 as well as Li 2 MnF 5 . The number of magnetically inequivalent Li sites found by MAS NMR is in agreement with the respective crystal structure of the compounds studied. Quantum chemical calculations show that all materials have high de-lithiation energies making them suitable candidates to be used as high-voltage battery cathode materials.

Research paper thumbnail of DFT Study of the Role of Al 3+ in the Fast Ion-Conductor Li 7–3 x Al 3+ x La 3 Zr 2 O 12 Garnet

Chemistry of Materials, 2014

We investigate theoretically the site occupancy of Al 3+ in the fast-ion-conducting cubic-garnet ... more We investigate theoretically the site occupancy of Al 3+ in the fast-ion-conducting cubic-garnet Li 7−3x Al 3+

Research paper thumbnail of Novel amino propyl substituted organo tin compounds

Canadian Journal of Chemistry, 2014

ABSTRACT In this work, a new synthetic pathway yielding unprotected amino propyl tin compounds is... more ABSTRACT In this work, a new synthetic pathway yielding unprotected amino propyl tin compounds is described. For this purpose, mono stannanes with different substitution patterns are used. In a first step, tin hydrides are deprotonated using lithium diisopropyl amide and mixed with an electrophile containing a protected amine in the ω-position. After deprotection via acidic hydrolysis, the desired amino propyl tin compounds are obtained in high yield and purity. The thermal reaction behavior of the amino propyl tin hydrohalide intermediates containing one aromatic residue at the central tin atom is also investigated. For this purpose, amino propyl tin hydrohalides are heated under vacuum until the aromatic hydrocarbon is liberated. This thermal treatment leads to so far unknown tin halides containing an amino propyl side chain. For all of these substances detailed liquid 1H, 13C, and 119Sn-nuclear magnetic resonance (NMR) data were obtained, and in one case solid state NMR is also conducted. Regarding solids, single crystal X-ray analysis is performed. Some derivatization reactions with these new substances are demonstrated, especially the synthesis of an amino propyl tin carboxylate, which might be very interesting for biological, pharmaceutical, or technical processes.

Research paper thumbnail of Low temperature synthesis, characterization and substrate-dependent photocatalytic activity of nanocrystalline TiO2 with tailor-made rutile to anatase ratio

Applied Catalysis A: General, 2008

... In phenol decomposition the samples' photocatalytic performance gradually and significan... more ... In phenol decomposition the samples' photocatalytic performance gradually and significantly increases with their anatase content: photocatalysts containing only anatase as crystalline phase were up to three times more efficient than rutile ones. ...

Research paper thumbnail of Small Change—Great Effect: Steep Increase of Li Ion Dynamics in Li 4 Ti 5 O 12 at the Early Stages of Chemical Li Insertion

Chemistry of Materials, 2015

Lithium titanate (LTO) is one of the most promising anode materials for large-scale stationary el... more Lithium titanate (LTO) is one of the most promising anode materials for large-scale stationary electrochemical storage of energy produced from renewable sources. Besides many other aspects, such as negligible formation of passivation layers and no volume expansion during lithiation, the success of LTO is mainly based on its ability to easily accommodate and release Li ions in a fully reversible way. This feature is tightly connected with Li self-diffusion. As yet, little information is available about microscopic Li diffusion properties and elementary steps of Li hopping at low intercalation levels, i.e., at values of x being significantly smaller than 1. Here, we used 7 Li spin-locking NMR relaxometry to probe absolute hopping rates of LTO (homogeneous) solid solutions in quasi-thermodynamic equilibrium. As a result, the largest increase of Li diffusivity is observed when small amounts of Li are inserted. Strong Coulomb repulsions caused by the simultaneous occupation of neighboring 8a and 16c sites serve as an explanation for the enhanced Li diffusivity found. At even larger values of x, Li mobility slows down but is still much faster than in the host material with x = 0. Our results experimentally corroborate the outcome of recently published calculations on the DFT level focusing on both dynamic and structural aspects. The findings favor the formation of LTO solid solutions upon chemical lithiation; the steep increase in Li diffusivity found might also help with understanding the flat insertion potential observed.