Extracting the redox orbitals in Li battery materials with high-resolution x-ray compton scattering spectroscopy.

We present an incisive spectroscopic technique for directly probing redox orbitals based on bulk electron momentum density measurements via high-resolution x-ray Compton scattering. Application of our method to spinel Li_{x}Mn_{2}O_{4}, a lithium ion battery cathode material, is discussed. The orbital involved in the lithium insertion and extraction process is shown to mainly be the oxygen 2p orbital. Moreover, the manganese 3d states are shown to experience spatial delocalization involving 0.16±0.05 electrons per Mn site during the battery operation. Our analysis provides a clear understanding of the fundamental redox process involved in the working of a lithium ion battery.

RISING beamline (BL28XU) for rechargeable battery analysis.

The newly installed BL28XU beamline at SPring-8 is dedicated to in situ structural and electronic analysis of rechargeable batteries. It supports the time range (1 ms to 100 s) and spatial range (1 µm to 1 mm) needed for battery analysis. Electrochemical apparatus for battery charging and discharging are available in experimental hutches and in a preparation room. Battery analysis can be carried out efficiently and effectively using X-ray diffraction, X-ray absorption fine-structure analysis and hard X-ray photoelectron spectroscopy. Here, the design and performance of the beamline are described, and preliminary results are presented.

EXAFS study of crystal structures of (Ba1-xLax)2In2O5+x and their oxide ion conductivity.

Crystal structures of(Ba1-xLax)2In2O5+x (x=0.00, 0.20, 0.30, 0.40, 0.50) were analyzed by EXAFS and the powder X-ray Rietveld method. A Fourier transform of In K-edge EXAFS data from (Ba1-xLax)2In2O5+x showed a peak between 1.2 and 2.0 A attributed to the nearest oxide ions around In3+ cation. The peak as back-Fourier transformed, and the structural parameters were refined by the least square fitting. The coordination number of In3+ cation increases with increasing La3+ cation) content. This means oxygen is introduced at interstitial site by keeping an electroneutrality. As a result of the oxygen distribution, the oxide ion vacancies distribute randomly. The electrical conductivities of (Ba1-xLax)2In2O5 rapidly increased above 1203 K due to the order-disorder transition of oxygen vacancy. On the other hand, the electrical conductivities of (Ba1-xLax)2In2O5+x (x=0.20, 0.30, 0.35. 0.40, 0.45, 0.50) did not show the sharp discontinuity in the conductivity because the disorder phase of defective perovskite type structure was stabilized by doping La3+ cations at A-site even at low temperature.

Changes in electronic structure by Li ion deintercalation in LiCoO2 from cobalt L-edge and oxygen K-edge XANES.

Cobalt L-edge and oxygen K-edge X-ray Absorption Near Edge Structure (XANES) investigated change in electronic structure by electrochemical lithium ion de-intercalation in LiCoO2. The Co L-edge XANES of Li(1-x)CoO2 did not show any chemical shift even at high x value. The oxygen K-edge XANES of Li(1-x)CoO2 indicated that the holes compensating the lithium ion deintercalation are located primarily in the oxygen 2p states rather than in the Co 3d states.