**3. Conclusion**

58 Advanced Topics in Measurements

confirmed between the TEY and PFY spectrum. Meanwhile both experimental spectra of LiPF6 with air exposure have similar features to Li3PO4 and H3PO4, such as the white line at 2152.9 eV (black dashed line) and the broad peak around 2170 eV. This indicates most local structures of P atoms in LiPF6 changed the octahedral coordination with F atoms shown in fig. 15 (a) into the tetrahedral coordination with O atoms (i.e. phosphates). Hence we identified surface P atoms in LiPF6 without air exposure has been also changed into phosphates, because the energy position of the pre-edge peak of the TEY spectrum closes to that of the white line of phosphates. We think that only the surface of LiPF6 samples has been changed by negligible moisture in a glove box over the course of several weeks. About LiPF6 with air exposure, both the TEY and PFY spectrum shape are very similar to that of Li3PO4, but the shoulder peak at 2154.5 eV (red dashed line) can be seen only spectra of LiPF6 with air exposure. This origin is not clear yet, but may originate from POF3, POF2(OH)

or other materials generated by hydrolyzed LiPF6 [Kawamura et al., 2006].

Fig. 15. (a) Crystal structure of LiPF6 drawn by VESTA program [Momma & Izumi, 2008]. The crystal information is referred by [Röhr & Kniep, 1994]; (b) Simulated spectra of LiPF6 by FEFF program and experimental P K-XANES spectra of LiPF6 with and without air exposure. TEY spectra of Li3PO4 and H3PO4 are also shown as a reference sample. The self-

From these results, it is clearly indicated the efficiency of the vessel to carry the highly hydrolytic materials without changing the chemical condition. This transfer vessel system is using in many case, and especially in LIB materials, the system is absolutely essential.

absorption effect is not corrected in PFY spectra.

We developed the unique and efficient soft X-ray XAFS measurement system at BL-10 of the SR center, Ritsumeikan University. As well as being able to accept stable solid samples in the HV sample chamber, hygroscopic and hydrated compounds, which are changed the condition in vacuum, and liquid samples are also able to accept in the AP chamber with the vacuum-tight window of a thin Be foil and in He gas atmosphere. In the HV chamber, a multiple measurement combined with the TEY, PEY, and PFY methods can give us the depth profile of samples. This is very useful for chemical analysis of practical samples. In addition, the transfer vessel system is an efficient tool for carrying anaerobic samples without changing chemical conditions. These setups will satisfy with many demands for various sample conditions. We hope that this XAFS system will be used by many users and stimulate further soft X-ray XAFS studies.
