成果報告書詳細
管理番号20150000000235
タイトル*平成26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 (7)
公開日2015/5/26
報告書年度2014 - 2014
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
英文要約1)Development of advanced techniques with X-ray synchrotron radiation sources
We developed operando evaluation technique to understand the mechanism of reaction distribution formation in an LIB composite electrode.
A model electrode was prepared by setting the kapton film on the LiCoO2 composite layer. Since the ionic path was limited to along the in-plane direction in this model electrode, the reaction distribution was expected to be formed along the in-plane direction if ionic diffusion in the liquid in the composite electrode was insufficient. The reaction distribution during charge was observed by operando 2-dimentional XAFS measurements at Co K-edge. The state of charge (SOC) at a certain position was estimated from the peak top energy of Co K-edge XANES spectra obtained at the same position.
It was clearly observed that the SOC near the surface of the electrode changed and the charged area expanded gradually with the progress of charge. The effect of the salt concentration on the reaction distribution formation was evaluated. The reaction distribution becomes narrower as the salt concentration increases. This is because low concentration electrolyte can accept more Li from the active material than high concentration electrolyte can during the charge process.

2)Development of advanced analysis techniques with nuclear magnetic resonance and differential interference contrast microscope (LCM-DIM)
We developed motion detectable technique by MRI to understand migration flow in lithium ion battery during charging and discharging. Convection flow was observed when charging and discharging by 1H MRI. The convectional mode is dependent on applied current and viscosity of electrolytes. The mode appears in low viscous electrolytes dominantly, it causes inhomogeneous density distribution between electrolyte and electrode. It may arise decrement of battery performance. The generation mechanism and quantification of the mode were discussed.
Diffusion coefficients of electrolyte in carbon black were studied by PFG-NMR. Diffusion coefficient of 19F of 1M LiPF6+ EC + DMC electrolyte in carbon black was dominantly decreased with increasing diffusion time. It suggests strong interaction is existing between PF6- and terminal of carbon black.
We used laser confocal microscopy with the differential interference microscopy technique (LCM-DIM) to evaluate Zn deposition and dissolution processes with atomic height resolution in order to solve a serious problem of the formation of dendrite. It is found that some additives are needed to avoid the formation of dendrite. After our examinations using many additives, some simple organic molecules were found to be very effective to avoid the formation of dendrite. It is important note that bright Zn surfaces were continuously observed after 300 charging/discharging cycles. It is concluded that Zn electrodes can be used for an advanced battery under our finding conditions.
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