成果報告書詳細
管理番号20120000000313
タイトル*平成23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 9
公開日2012/8/2
報告書年度2011 - 2011
委託先名国立大学法人東北大学
プロジェクト番号P09012
部署名スマートコミュニティ部
和文要約和文要約等以下本編抜粋:
核磁気共鳴(NMR)はリチウム電池中の7Li核をはじめ、電解質中の1H核(プロトン)、19F核などの様々な原子核スピンをプローブと して、電池材料の構造変化やイオン移動に関する情報を得る事ができる。とりわけ、最近のパルス磁場勾配技術の進歩により、リチウムイオンや溶媒分子の拡散係数測定や磁気共鳴イメージング(MRI)による電池反応進行時の蓄電池内の空間・時間情報を得ることが可能になった。本研究では、核スピンをプローブとするNMR・MRIの技術を材料革新、革新電池開発に役立てるため、既存のNMR・MRI技術の高感度化と多核化を進め、電池材料・電池システムの高度解析技術を開発する。
英文要約Title: Research & Development Initiative for Scientific Innovation of New Generation Batteries (FY2009-FY2013) FY2011 Annual Report

b. Development of high magnetic field (9.4T) NMR・MRI system

1. Estimation of damages and disaster recovery from the Japan Earthquake
In 11th March 2010, NMR instruments have suffered from massive earthquake happened in east Japan. The disaster planning for the earthquake in Tohoku University could avoid the worst situation of magnet quenching. However, due to supply stop of liquid nitrogen and liquid helium, NMR machine operation was suspended for over one month and shim coils for adjustment of magnetic linearity were damaged. The examination and corrective maintenance for NMR probes, control devices, were carried out for a few months. It took about three month after the big earthquake to be restored to its former state.

2. Development of quantitative analysis of MRI for rechargeable battery
We have developed new quantitative analysis for rechargeable battery. Image analysis software, ImageJ, manipulates images measured by in-situ MRI during charging and discharging. It takes several minutes to complete the calculation of thousands of images for one cycle. These calculated data is combined with charge and discharge electrochemical result, to be understood the degradation processes and charge-discharging mechanisms. We have revealed that various types of filters adopted in image calculation can select specific event such as elution of paramagnetic ions, magnetic change in cathode material etc.


3. Evaluation approaches for artifact MRI by paramagnetic material
Cathode materials for lithium ion battery are generally including paramagnetic atoms, such as Co, Fe, Mn, etc. These atoms in high magnetic field create extra magnetic field, which disturbs linear magnetic field applied by magnetic gradient coils. It causes MRI artifacts, distortions, changes in intensity etc. We treated these effects theoretically to derive the relationship between MRI distortion and extra magnetic field applied by paramagnetic atoms in cathode material in lithium ion battery. This technique is a new functional MRI (fMRI) which can detect magnetic change along with structural changes, elution of magnetic ions during charge and discharge in rechargeable battery.


c. Development of high magnetic MAS-NMR system for solid state cathode materials
We have developed high magnetic (14.7T) MAS-NMR system and local structure of nine kinds of LiCoO2 samples were investigated. The eight of them were commercial LiCoO2 and the other one was synthesized via a solid state reaction. XRD patterns show that the crystal structure of the LiCoO2 samples is clarified into the space group R3m with the layered α-NaFeO2-type structure. Raman spectra show nothing special except that one of the samples contains impurity. Meanwhile 7Li MAS NMR spectra of seven samples have additional side peaks due to the defects in Li-overstoichiometric materials (Li1+xCoO2), two samples have a single main peak. Moreover, other additional new peaks are observed. This experiment reveals high magnetic MAS-NMR is quite sensitive probes for detecting slight differences in 7Li local structure in cathode material. We explained these side peaks as resulting from cobalt d-orbital and Fermi contact interaction. The peak positions are qualitatively agrees with theoretical treatment, but more sophisticated treatment is necessary to understand quantitative analysis.
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