成果報告書詳細
管理番号20110000001370
タイトル*平成22年度中間年報 次世代自動車用高性能蓄電システム技術開発 次世代技術開発 リチウムイオン2次電池の過剰な負荷条件下における電極界面の原子・分子レベル解析技術開発
公開日2012/6/27
報告書年度2010 - 2010
委託先名国立大学法人東北大学学際科学国際高等研究センター
プロジェクト番号P07001
部署名スマートコミュニティ部
和文要約和文要約等以下本編抜粋:
1. 研究開発の内容及び成果等
1.1 本事業の目的と概要
当該研究開発テーマは,本研究開発課題では,電池が過剰な負荷状態に置かれた状態をラボレベルで再現し,その状態についてその場分光法を用い,分子の振動状態より電極界面の原子・分子レベル解析を遂行している.過剰な負荷条件下におけるガス発生,電極表面界面生成物,電極界面近傍の電解液状態を原子・分子レベルにて追跡している.その解析を基に,リチウム2次電池の重量エネルギー密度500Wh/kgの実現に向けた高電位領域や高温条件下における電池構成要素である電解液,リチウム塩,電極材料に関する高エネルギー密度化と安全性向上の指針を得ることを最終的な目標としている。
英文要約Title:Fundamental Research Projects for In Situ Spectroelectrochemistry with Atomic- Molecular Level on Over Loaded Battery Active Materials (FY2009-FY2011) FY2010 Annual Report In situ FT Raman spectroscopy with the near infrared laser beam was conducted on composite electrodes of highly polarized LiCoO2 cathode active materials with the PVdF binder in the mixture of EC+DEC solvents with 1M LiPF6 salts. The reason of using the near infrared laser beam is to avoid florescence on in situ Raman spectra of composite electrodes in EC+DEC with 1M LiPF6. For the first step of FT Raman experiments, we carried out FT Raman spectra for the PVdF binder and the mixture of EC+DEC solvents with 1M LiPF6. When we use the visible laser beam as taking normal Raman spectra, we can hardly distinguish between Raman lines and florescence from sample. When we applied the near infrared laser beam instead of the visible laser beam, observed Raman spectra became clear shapes. These spectra suggest that FT Raman spectroscopy is powerful tool to remove florescence in Raman spectra for battery active materials. Subsequently, to explore highly polarized LiCoO2 cathode active materials with the PVdF binder in EC+DEC with 1M LiPF6 salts, we constructed specially designed air-tight electrochemical cell equipped with optical window and three electrode holders. The in situ FT Raman spectra under potentiostatic conditions were measured at various potentials with insertion/ extraction of lithium. Firstly, in situ FT Raman spectra of the composite electrode of LiCoO2 at open circuit potential (OCP: 3.5V) were measured. That in situ FT Raman spectrum at OCP clearly indicated Raman lines for LiCoO2 for cathode at 485cm-1 and 597cm-1, carbon black for additive around 1300cm-1 and 1600cm-1, the electrolyte solution and the PVdF binders. Since the effect of the florescence was quite low in this FT Raman spectrum, we can measure in situ FT Raman spectra of this composite electrode at various potentials with insertion/ extraction of lithium. Finally, we succeeded to measure the variation of the in situ FT Raman spectra for the composite electrodes of LiCoO2. With increasing and decreasing potentials, we note characteristic feature of the Raman spectra in the in situ FT Raman spectra of the composite electrode of LiCoO2. The Raman intensity for LiCoO2 was decreased with increasing potential. This result suggests the reduction of the optical skin depth due to the conductivity change of LiCoO2. Above higher potential between 4.2 V and 5.0V, some Raman lines for PVdF had potential dependence. Compared with the in situ FT Raman spectra before and after potential cycles, the Raman intensity of C-H vibration was increased in composite electrodes after potential cycling. This increased Raman intensity is ascribed to the formation of an organic film on composite electrodes of LiCoO2.
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