成果報告書詳細
管理番号20140000000195
タイトル*平成25年度中間年報 革新型蓄電池先端科学基礎研究事業 革新型蓄電池先端科学基礎研究開発 (3)
公開日2014/5/17
報告書年度2013 - 2013
委託先名学校法人立命館大学
プロジェクト番号P09012
部署名スマートコミュニティ部
和文要約
英文要約Development of innovative analytical methods for secondary batteries using soft X-ray synchrotron radiation

In the SR center of Ritsumeikan University, two soft X-ray XAFS beamlines (BL-2 and 10) and three hard X-ray XAFS beamlines (BL-3, 4 and 5) are devoted to the studies of secondary batteries. In addition, one beamline (BL-13) for soft X-ray spectroscopy has been newly developed and constructed for in situ XAFS experiments. Several developments and improvements have been performed in the fiscal year, 2013.

(1) Depth-profiling XAFS study on the effect of an electrolyte additive on the electrode surface
The depth-profiling XAFS method was applied to study the effect of an electrolyte additive, lithium bis(oxalate) borate (LiBOB) on the SEI formed on a model LiCoO2 electrode. XAFS analysis revealed that some of the Co ions at the electrode surface were reduced to Co(II) during the charge-discharge reactions, but this reaction could be suppressed by the addition of LiBOB.

(2) Operando S K-XAFS measurements of the thiophene derived SEI formation process by using the in situ XAFS cell
By using a unique cell for in situ XAFS measurement, S K-XAFS spectra has been measured during the first charging cycle of a cell composed of LiCoO2/0.1wt% thiophene added LiClO4/Li metal. Above 4.3 V charging, the peak at 2473 eV suddenly gained intensity, indicating the poly-thiophene formation on the electrode. This demonstrates the usefulness of the operando measurements to reveal the SEI formation in the charging and discharging processes of batteries.

(3) Upsizing of the 2D imaging XAFS and its application to spatial distribution analysis in the cathode reactions.
The 2D imaging area was upsized from 3 x 4 mm2 to 4 x 13 mm2. This enables us to observe reaction distribution of a coin-type cell (13 mm in diameter) of the electrode at one time. This 2D imaging XAFS system was applied to observe the reaction distributions of LiNiO2, LiMn2O4, as well as LiFePO4 in the charging/discharging cycles. Distinct non-uniform charging was observed in the electrode of LiNiO2, similar to that of LiFePO4, but the discharging proceeds preferentially at the area where the charging proceeded least preferentially. This tendency is just opposite to the case of LiFePO4.

(4) Preliminary test of the 1D imaging DXAFS method
A new unique method to obtain quick 1D imaging XAFS method has been designed and constructed. This is a combination of the imaging XAFS and wavelength dispersive XAFS (DXAFS) techniques, where the former is in the horizontal direction and the latter is in the vertical one. Preliminary test was performed for a Ni foil and confirmed that the EXAFS spectra could be obtained by increasing the curvature of the bent crystal, even if we adopt the vertical dispersion. This will open the route to the space-resolved and time resolved XAFS.
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