The Experts below are selected from a list of 5706 Experts worldwide ranked by ideXlab platform
Martin Wilkening - One of the best experts on this subject based on the ideXlab platform.
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synthesis crystal structure and stability of cubic li7 xla3zr2 xbixo12
Inorganic Chemistry, 2016Co-Authors: Reinhard Wagner, Martin Wilkening, Daniel Rettenwander, Gunther J Redhammer, Gerold Tippelt, Gebhard Sabathi, Maurizio Musso, Bernhard Stanje, E Suard, Georg AmthauerAbstract:Li oxide garnets are among the most promising candidates for solid-state electrolytes in novel Li ion and Li metal based battery concepts. Cubic Li7La3Zr2O12 stabilized by a partial substitution of Zr4+ by Bi5+ has not been the focus of research yet, despite the fact that Bi5+ would be a cost-effective alternative to other stabilizing cations such as Nb5+ and Ta5+. In this study, Li7–xLa3Zr2–xBixO12 (x = 0.10, 0.20, ..., 1.00) was prepared by a low-temperature solid-state synthesis route. The samples have been characterized by a rich portfolio of techniques, including scanning electron microscopy, X-ray powder diffraction, neutron powder diffraction, Raman Spectroscopy, and 7Li NMR Spectroscopy. Pure-phase cubic garnet samples were obtained for x ≥ 0.20. The introduction of Bi5+ leads to an increase in the unit-cell parameters. Samples are sensitive to air, which causes the formation of LiOH and Li2CO3 and the protonation of the garnet phase, leading to a further increase in the unit-cell parameters. The ...
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fast li self diffusion in amorphous li si electrochemically prepared from semiconductor grade monocrystalline silicon insights from spin locking nuclear magnetic relaxometry
Journal of Physical Chemistry C, 2015Co-Authors: Andreas Dunst, Michael Sternad, Martin WilkeningAbstract:Silicon is one of the most promising anode materials for lithium-based rechargeable batteries. Provided the volume changes during Li uptake can be brought under control, Li ion diffusivity is expected to crucially determine the performance of such next-generation energy storage systems. Therefore, studying diffusion properties in e.g. amorphous Li–Si underpins applied research that is being directed toward the development of powerful storage devices. So far, only little information is available on Li+ self-diffusion in amorphous Si. Here, we used 7Li NMR Spectroscopy to precisely quantify microscopic activation energies and Li jump rates in amorphous Li–Si which is primarily formed if monocrystalline Si is lithiated electrochemically. Surprisingly, our results reveal relatively fast Li ion diffusivity with low activation energies for localized Li+ motions being in agreement with results from theory. The average activation energy for long-range ion transport is as high as ca. 0.65 eV; jump rates turn out t...
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short range li diffusion vs long range ionic conduction in nanocrystalline lithium peroxide li2o2 the discharge product in lithium air batteries
Energy and Environmental Science, 2014Co-Authors: Andreas Dunst, Ilie Hanzu, Stefan A Freunberger, Martin WilkeningAbstract:Understanding charge carrier transport in Li2O2, the storage material in the non-aqueous Li-O2 battery, is key to the development of this high-energy battery. Here, we studied ionic transport properties and Li self-diffusion in nanocrystalline Li2O2 by conductivity and temperature variable 7Li NMR Spectroscopy. Nanostructured Li2O2, characterized by a mean crystallite size of less than 50 nm as estimated from X-ray diffraction peak broadening, was prepared by high-energy ball milling of microcrystalline lithium peroxide with μm sized crystallites. At room temperature the overall conductivity σ of the microcrystalline reference sample turned out to be very low (3.4 × 10−13 S cm−1) which is in agreement with results from temperature-variable 7Li NMR line shape measurements. Ball-milling, however, leads to an increase of σ by approximately two orders of magnitude (1.1 × 10−10 S cm−1); correspondingly, the activation energy decreases from 0.89 eV to 0.82 eV. The electronic contribution σeon, however, is in the order of 9 × 10−12 S cm−1 which makes less than 10% of the total value. Interestingly, 7Li NMR lines of nano-Li2O2 undergo pronounced heterogeneous motional narrowing which manifests in a two-component line shape emerging with increasing temperatures. Most likely, the enhancement in σ can be traced back to the generation of a spin reservoir with highly mobile Li ions; these are expected to reside in the nearest neighbourhood of defects generated or near the structurally disordered and defect-rich interfacial regions formed during mechanical treatment.
Clare P. Grey - One of the best experts on this subject based on the ideXlab platform.
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characterizing the structure and phase transition of li2ruo3 using variable temperature 17o and 7Li NMR Spectroscopy
Chemistry of Materials, 2019Co-Authors: Philip J Reeves, Ieuan D. Seymour, Kent J. Griffith, Clare P. GreyAbstract:Li-excess lithium-ion battery cathode materials and the role that reversible anionic redox may play in their high capacities have generated significant interest, motivating studies of the oxygen lo...
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Characterizing the Structure and Phase Transition of Li2RuO3 Using Variable-Temperature 17O and 7Li NMR Spectroscopy
2019Co-Authors: Philip J. Reeves, Ieuan D. Seymour, Kent J. Griffith, Clare P. GreyAbstract:Li-excess lithium-ion battery cathode materials and the role that reversible anionic redox may play in their high capacities have generated significant interest, motivating studies of the oxygen local structure. Li2RuO3 is an intriguing Li-excess model compound, which is studied here by local (7Li and 17O MAS NMR) and long-range (X-ray and neutron diffraction) structural probes. Li2RuO3 is often reported as adopting the C2/m or the C/2c space group, which ignores the important role that Ru–Ru dimerization plays in controlling its properties. 17O NMR reveals four oxygen sites confirming the room-temperature P21/m structure proposed by Miura, Y.; Yasui, Y.; Sato, M.; Igawa, N.; Kakurai, K. J. Phys. Soc. Japan 2007, 76, 033705. Through the rationalization of the 17O NMR shifts, at room temperature and through the phase transition (>260 °C), detailed information concerning the electronic structure and locations of the unpaired electrons in this compound is revealed
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mechanism of the delithiation lithiation process in life0 4mn0 6po4 in situ and ex situ investigations on long range and local structures
Journal of Physical Chemistry C, 2015Co-Authors: Ilham Bezza, Ralf Heinzmann, Clare P. Grey, Maximilian Kaus, Murat Yavuz, Michael Knapp, Stefan Mangold, Stephen Doyle, Helmut Ehrenberg, Sylvio IndrisAbstract:LiFe0.4Mn0.6PO4 olivine was prepared by a sol–gel route, using citric acid as a chelating agent and NH4H2PO4 as a phosphorus source. Sucrose was used as the source for the carbon-coating of the particles. The correlation between the physicochemical and the electrochemical properties of this positive electrode material was investigated. The electrochemical tests showed an initial discharge capacity of 121 mAh/g at a C/20 rate with a good reversibility of the lithiation/delithiation reactions. In situ XRD on LixFe0.4Mn0.6PO4 reveals the occurrence of new phases upon cycling, which disappeared again at the end of discharge. The single phase observed after one complete cycle is identical to the pristine one. In situ XAS Spectroscopy in combination with 57Fe Mossbauer and 7Li NMR Spectroscopy were used to investigate the changes in the local structure and the oxidation states of the transition metals and thus to complete the overall characterization of the lithiation/delithiation mechanism. All results reveal ...
Thomas F Fassler - One of the best experts on this subject based on the ideXlab platform.
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lithium ion mobility in lithium phosphidosilicates crystal structure 7Li 29si and 31p mas NMR Spectroscopy and impedance Spectroscopy of li8sip4 and li2sip2
Chemistry: A European Journal, 2016Co-Authors: Lorenzo Toffoletti, Holger Kirchhain, Johannes Landesfeind, Wilhelm Klein, Leo Van Wullen, Hubert A Gasteiger, Thomas F FasslerAbstract:The need to improve electrodes and Li-ion conducting materials for rechargeable all-solid-state batteries has drawn enhanced attention to the investigation of lithium-rich compounds. The study of the ternary system Li-Si-P revealed a series of new compounds, two of which, Li8SiP4 and Li2SiP2, are presented. Both phases represent members of a new family of Li ion conductors that display Li ion conductivity in the range from 1.15(7)×10−6 Scm−1 at 0 °C to 1.2(2)×10−4 Scm−1 at 75 °C (Li8SiP4) and from 6.1(7)×10−8 Scm−1 at 0 °C to 6(1)×10−6 Scm−1 at 75 °C (Li2SiP2), as determined by impedance measurements. Temperature-dependent solid-state 7Li NMR Spectroscopy revealed low activation energies of about 36 kJ mol−1 for Li8SiP4 and about 47 kJ mol−1 for Li2SiP2. Both compounds were structurally characterized by X-ray diffraction analysis (single crystal and powder methods) and by 7Li, 29Si, and 31P MAS NMR Spectroscopy. Both phases consist of tetrahedral SiP4 anions and Li counterions. Li8SiP4 contains isolated SiP4 units surrounded by Li atoms, while Li2SiP2 comprises a three-dimensional network based on corner-sharing SiP4 tetrahedra, with the Li ions located in cavities and channels.
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substitution of lithium for magnesium zinc and aluminum in li15si4 crystal structures thermodynamic properties as well as 6li and 7Li NMR Spectroscopy of li15si4 and li15 xmxsi4 m mg zn and al
Chemistry: A European Journal, 2016Co-Authors: Volodymyr Baran, Leo Van Wullen, Thomas F FasslerAbstract:An investigation into the substitution effects in Li15 Si4 , which is discussed as metastable phase that forms during electrochemical charging and discharging cycles in silicon anode materials, is presented. The novel partial substitution of lithium by magnesium and zinc is reported and the results are compared to those obtained for aluminum substitution. The new lithium silicides Li14 MgSi4 (1) and Li14.05 Zn0.95 Si4 (2) were synthesized by high-temperature reactions and their crystal structures were determined from single-crystal data. The magnetic properties and thermodynamic stabilities were investigated and compared with those of Li14.25 Al0.75 Si4 (3). The substitution of a small amount of Li in metastable Li15 Si4 for more electron-rich metals, such as Mg, Zn, or Al, leads to a vast increase in the thermodynamic stability of the resulting ternary compounds. The (6,7) Li NMR chemical shift and spin relaxation time T1 -NMR Spectroscopy behavior at low temperatures indicate an increasing contribution of the conduction electrons to these NMR Spectroscopy parameters in the series for 1-3. However, the increasing thermal stability of the new ternary phases is accompanied by a decrease in Li diffusivity, with 2 exhibiting the lowest activation energy for Li mobility with values of 56, 60, and 62 kJ mol(-1) for 2, Li14.25 Al0.75 Si14 , and 1, respectively. The influence of the metastable property of Li15 Si4 on NMR Spectroscopy experiments is highlighted.
Andreas Dunst - One of the best experts on this subject based on the ideXlab platform.
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fast li self diffusion in amorphous li si electrochemically prepared from semiconductor grade monocrystalline silicon insights from spin locking nuclear magnetic relaxometry
Journal of Physical Chemistry C, 2015Co-Authors: Andreas Dunst, Michael Sternad, Martin WilkeningAbstract:Silicon is one of the most promising anode materials for lithium-based rechargeable batteries. Provided the volume changes during Li uptake can be brought under control, Li ion diffusivity is expected to crucially determine the performance of such next-generation energy storage systems. Therefore, studying diffusion properties in e.g. amorphous Li–Si underpins applied research that is being directed toward the development of powerful storage devices. So far, only little information is available on Li+ self-diffusion in amorphous Si. Here, we used 7Li NMR Spectroscopy to precisely quantify microscopic activation energies and Li jump rates in amorphous Li–Si which is primarily formed if monocrystalline Si is lithiated electrochemically. Surprisingly, our results reveal relatively fast Li ion diffusivity with low activation energies for localized Li+ motions being in agreement with results from theory. The average activation energy for long-range ion transport is as high as ca. 0.65 eV; jump rates turn out t...
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short range li diffusion vs long range ionic conduction in nanocrystalline lithium peroxide li2o2 the discharge product in lithium air batteries
Energy and Environmental Science, 2014Co-Authors: Andreas Dunst, Ilie Hanzu, Stefan A Freunberger, Martin WilkeningAbstract:Understanding charge carrier transport in Li2O2, the storage material in the non-aqueous Li-O2 battery, is key to the development of this high-energy battery. Here, we studied ionic transport properties and Li self-diffusion in nanocrystalline Li2O2 by conductivity and temperature variable 7Li NMR Spectroscopy. Nanostructured Li2O2, characterized by a mean crystallite size of less than 50 nm as estimated from X-ray diffraction peak broadening, was prepared by high-energy ball milling of microcrystalline lithium peroxide with μm sized crystallites. At room temperature the overall conductivity σ of the microcrystalline reference sample turned out to be very low (3.4 × 10−13 S cm−1) which is in agreement with results from temperature-variable 7Li NMR line shape measurements. Ball-milling, however, leads to an increase of σ by approximately two orders of magnitude (1.1 × 10−10 S cm−1); correspondingly, the activation energy decreases from 0.89 eV to 0.82 eV. The electronic contribution σeon, however, is in the order of 9 × 10−12 S cm−1 which makes less than 10% of the total value. Interestingly, 7Li NMR lines of nano-Li2O2 undergo pronounced heterogeneous motional narrowing which manifests in a two-component line shape emerging with increasing temperatures. Most likely, the enhancement in σ can be traced back to the generation of a spin reservoir with highly mobile Li ions; these are expected to reside in the nearest neighbourhood of defects generated or near the structurally disordered and defect-rich interfacial regions formed during mechanical treatment.
Sylvio Indris - One of the best experts on this subject based on the ideXlab platform.
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mechanism of the delithiation lithiation process in life0 4mn0 6po4 in situ and ex situ investigations on long range and local structures
Journal of Physical Chemistry C, 2015Co-Authors: Ilham Bezza, Ralf Heinzmann, Clare P. Grey, Maximilian Kaus, Murat Yavuz, Michael Knapp, Stefan Mangold, Stephen Doyle, Helmut Ehrenberg, Sylvio IndrisAbstract:LiFe0.4Mn0.6PO4 olivine was prepared by a sol–gel route, using citric acid as a chelating agent and NH4H2PO4 as a phosphorus source. Sucrose was used as the source for the carbon-coating of the particles. The correlation between the physicochemical and the electrochemical properties of this positive electrode material was investigated. The electrochemical tests showed an initial discharge capacity of 121 mAh/g at a C/20 rate with a good reversibility of the lithiation/delithiation reactions. In situ XRD on LixFe0.4Mn0.6PO4 reveals the occurrence of new phases upon cycling, which disappeared again at the end of discharge. The single phase observed after one complete cycle is identical to the pristine one. In situ XAS Spectroscopy in combination with 57Fe Mossbauer and 7Li NMR Spectroscopy were used to investigate the changes in the local structure and the oxidation states of the transition metals and thus to complete the overall characterization of the lithiation/delithiation mechanism. All results reveal ...
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study of local structure and li dynamics in li4 xti5o12 0 x 5 using 6li and 7Li NMR Spectroscopy
Zeitschrift für anorganische und allgemeine Chemie, 2012Co-Authors: Holger Hain, Marco Scheuermann, Ralf Heinzmann, Linda Wunsche, Horst Hahn, Sylvio IndrisAbstract:Abstract We studied the local structure and the Li ion dynamics in electrochemically and chemically prepared Li 4 + x Ti 5 O 12 with x = 0 … 5 . We used magic-angle spinning 7Li NMR on samples with different Li contents to investigate the sites that are occupied/emptied during Li insertion/removal. While the electrochemical measurements show a lithium insertion in two steps, 1D MAS NMR as a function of the lithium content shows that the overall spectral evolution observed during lithium insertion is inverted during lithium removal. Thereby the second insertion step is associated with an increased structural disorder. For samples with x=0, 2, 3, and about 5, we performed temperature-dependent measurements of the 7Li NMR relaxation rates T 1 − 1 , T 2 − 1 , and T 1 ρ − 1 to study the dynamics of the Li ions. For the samples with x=0, 2, and 3, activation energies of (0.45±0.1) eV were obtained. The highest mobility of the Li ions is observed for the samples with x=2 and 3. Results from 6Li and 7Li 2D exchange MAS NMR Spectroscopy on samples with x=2 and 4 show that magnetization transfer for 7Li below 323 K is dominated by spin diffusion.
