Advances in Li-ion batteries for energy storage have facilitated the success of mobile electronic equipment. In particular, high power densities in combination with low-price materials may also make Li-ion batteries attractive for more heavy-duty automotive applications. To facilitate such developments it is essential to understand the material properties that are responsible for the kinetic performance of Li-ion-battery electrodes. In general it is believed that two-phase reactions in electrode materials, responsible for the flat potential upon (dis)charging, lead to relatively low (dis)charge rates, hence limiting the power density. In this context, spinel Li 4 -Ti 5 O 12 [1][2][3][4][5] is very interesting because it has the unusual combination of fast (dis)charge rates [6] and an extremely flat potential, [3,7] the latter being due to the two-phase reaction be- [8] respectively). As a result the twophase reaction will not lead to substantial structural strain, a favorable property because lattice strains upon cycling are among the main causes of capacity loss in lithium battery electrodes. Although it is established in the literature that at room temperature the (dis)charging in Li 4+x Ti 5 O 12 proceeds through a two-phase equilibrium, [3,8] which is responsible for the very flat potential for 0.09 < x < 2.91, the absence of strain and the observation of partial 16c occupation at room temperature [9] and at elevated temperatures [10] indicate that solid-solution behavior could occur close to room temperature. The aim of this contribution is to study the Li 4+x Ti 5 O 12 structure in detail to gain more understanding of its performance as a battery electrode. The unexpected results completely change our understanding of this material. In contrast to common knowledge, Li 4+x Ti 5 O 12 as a two-phase system (consisting of the end members Li 4 Ti 5 O 12 and Li 7 Ti 5 O 12 ) appears to be unstable at room temperature, and relaxes to a homogeneous solid-solution phase for the whole concentration range. True two-phase separation in equilibrium is only observed below 100 K. The relaxation towards equilibrium takes place on the timescale of spontaneous Li-ion diffusion (in absence of an applied gradient), and reveals that faster Li insertion will lead to a kinetically induced effective two-phase reaction, which is commonly observed for Li 4 Ti 5 O 12 . However, unlike previous assumptions, the present results demonstrate that this is actually a nonequilibrium situation. The solid-solution-induced disorder, resulting from the mixed 8a/16c occupation, is most likely responsible for the high rate-capabilities in Li 4+x Ti 5 O 12 .Room-temperature neutron diffraction of chemically lithiated materials, given in Figure 1a, show that only subtle changes take place in the spinel structure upon lithiation. Although hardly visible in Figure 1a, the high intensity and large d-spacing range probed by neutron diffraction on the General Materials Diffractometer (GEM, ISIS, Didcot, UK), lead to a large number of resolved reflectio...

Upon lithium insertion in the pristine TiO2 anatase phase the theoretical maximum of LiTiO2 can be reached in crystallite sizes less than approximately 10 nm, whereas bulk compositions appear limited to Li(x) approximately 0.6TiO2 at room temperature. Both X-ray absorption spectroscopy (XAS) and ab initio calculations have been applied to probe the electronic structure of the newly formed LiTiO2 phase. These results indicate that a large majority of the Li-2s electrons reside at the Ti-3d(t2g)/4s hybridized site. About 10% of these electrons are transferred to non-localized states which makes this compound a good electronic conductor. Ionic conductivity is probed by nuclear magnetic resonance (NMR) relaxation experiments indicating relatively small hopping rates between the Li-ion sites in LiTiO2. Formation of the poor ionic-conducting LiTiO2 at the surface of the particles explains why micro-anatase Li(x)TiO2 is not able to reach the theoretical maximum capacity at room temperature, and why this theoretical maximum capacity reached in nano-sized materials cannot be (dis)charged at high rates.

The hard X-ray beamline BL8 at the superconducting asymmetric wiggler at the 1.5 GeV Dortmund Electron Accelerator DELTA is described. This beamline is dedicated to X-ray studies in the spectral range from approximately 1 keV to approximately 25 keV photon energy. The monochromator as well as the other optical components of the beamline are optimized accordingly. The endstation comprises a six-axis diffractometer that is capable of carrying heavy loads related to non-ambient sample environments such as, for example, ultrahigh-vacuum systems, high-pressure cells or liquid-helium cryostats. X-ray absorption spectra from several reference compounds illustrate the performance. Besides transmission measurements, fluorescence detection for dilute sample systems as well as surface-sensitive reflection-mode experiments have been performed. The results show that high-quality EXAFS data can be obtained in the quick-scanning EXAFS mode within a few seconds of acquisition time, enabling time-resolved in situ experiments using standard beamline equipment that is permanently available. The performance of the new beamline, especially in terms of the photon flux and energy resolution, is competitive with other insertion-device beamlines worldwide, and several sophisticated experiments including surface-sensitive EXAFS experiments are feasible.

Electric properties D 8000The Electronic Structure and Ionic Diffusion of Nanoscale LiTiO2 Anatase. -Upon lithium insertion in the pristine TiO 2 anatase phase the theoretical maximum LiTiO2 is reached only for crystallite sizes <10 nm. The electronic structure of the newly formed LiTiO2 phase is characterized by XAS and ab initio DFT calculations. LiTiO2 shows improved electronic conductivity but very poor Li ion mobility. The favorable increase in Li storage capacity with decreasing particle size in anatase TiO2 is obtained at the expense of reduced Li + ion dynamics. During charging, the formation of the LiTiO2 phase will limit the charge rate whereas during discharge the LiTiO2 phase is removed first allowing easier diffusion through the Li poor phases. -(BORGHOLS, W. J. H.; LUETZENKIRCHER-HECHT, D.; HAAKE, U.; VAN ECK, E. R. H.; MULDER, F. M.; WAGEMAKER*, M.; Phys.

The design of a miniaturized sputter deposition chamber for the in situ study of thin film growth processes with x rays is reported. X-ray diffraction experiments, grazing incidence x-ray reflectometry, as well as x-ray fluorescence analysis are possible. Due to its compact design and low weight, the chamber can be used in conjunction with conventional x-ray reflectometers and laboratory x-ray diffractometers as well, i.e., very detailed in situ studies of reactive and nonreactive sputtering processes and the resulting film properties are possible. The construction of the chamber is described in detail and first results obtained in situ with different techniques are presented, indicating that experiments that were previously restricted to synchrotron radiation facilities are now possible even with laboratory equipment.

Lithium intercalation and de-intercalation in amorphous MoO 3 electrodes were investigated using electrochemical techniques and in situ grazing incidence reflection mode X-ray absorption spectroscopy. A new electrochemical cell suited for in situ investigations with X-rays under grazing incidence in a protective He atmosphere was built. A Kapton sealed electrolyte compartment, the bottom of which was the amorphous MoO 3 working electrode, was placed in this steel container so that a well-defined electrochemistry analysis was possible in parallel to the X-ray investigations. We present the results of potentiodynamic polarization experiments, as well as potentiostatic current transients, in close connection to surface-sensitive in situ X-ray absorption spectra. The results show that the Mo 6+ ions of the amorphous oxide electrode are reduced by electrochemical lithiation, leading to a formal Mo 5+ oxidation state. Angledependent experiments reveal that the intercalation is not complete for the applied conditions, i.e. the Li ions are not homogeneously distributed in the entire volume of the amorphous working electrode. In addition, a certain amount of Li remains in the Mo oxide electrode after a complete intercalation/deintercalation cycle. The results suggest that Li ions are accumulated at the electrode/electrolyte interface during both intercalation and de-intercalation.

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In spring 2005 the worldwide first cold-bore superconductive undulator was installed in the storage ring ANKA. In this paper the obtained results concerning the measured spectra and the heat load from the beam are described. Future developments in the field on superconductive undulators at ANKA are summarized.