成果報告書詳細
管理番号20140000000023
タイトル*平成24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 (6)
公開日2014/1/22
報告書年度2012 - 2012
委託先名学校法人早稲田大学
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This research aims at the R & D Initiative for Scientific Innovation of Next Generation Battery / Durability Analysis of Li-Ion Batteries (LIB) using in-situ Impedance Method. Using ac impedance analysis for LIB, we research analysis of the status of the LIB. Moreover, we evaluate the trend of the change in the condition of the electrode, electrolyte, and separator during the degradation of the LIB. Our research is establishment of method for the analysis method of status of degradation of the LIB by Ac impedance analysis.
The purposes of the research in FY2012 were to evaluate impedance response of LIBs, which are composed of ionic resistance of electrolyte and solid electrolyte interphase (SEI), and charge transfer resistance, combining comparison with state variation of each anode and cathode due to LIB degradation. For further understanding, the impedance response was analyzed by using proper equivalent circuit. The parameter variation calculated by the analysis was discussed from the standpoint of physical variation in the LIB. Also, novel anode of Si-O-C composite, which is expected to be an electrode for next generation LIB, was evaluated by means of ac impedance measurement.
(1) Symmetric cells composed of anodes or cathodes were evaluated for precise separation of impedance response, as expansion of impedance analysis of LIB with reference electrode. We have started to collaborate with the group for technology development of advanced analysis from FY2012. The symmetric cell composed of Ni-Mn based cathodes fabricated by the group was evaluated by means of impedance measurement with wider frequency range to 1 mHz. With considering RC parallel circuit whose time constant is less than 10-5 sec, the impedance increase was observed with increase of surrounding temperature. This phenomenon considered being due to electron conduction between current collector and active material or inter-active materials, which is needed further investigation.
(2) A commercially available LIB was evaluated on variation of impedance response and physical state of the electrodes. The LIBs were cycled under room temperature or 60 oC. From the comparison of impedance before and after charge-discharge cycles, the impedance increased both in the case of under room temperature and 60 oC. The impedance of the LIB cycled under 60 oC dominantly increased. These LIBs were disassembled and then their electrodes were evaluated by means of micro FT-IR. On the anodes cycled under room temperature or 60 oC, the peaks attribute to lithium alkyl carbonate and lithium carbonate which would be decomposed products of electrolyte were confirmed, which corresponds to the increase of impedance.
(3) A fabrication process of LIB was optimized to improve the charge-discharge property of the LIB. Higher precision coater was employed for special treatment of current collector. Also, mixer was employed for more effective fabrication process. The mixer enables to shorten the preparation time of slurry from about 1 day to 3hours. These improvements of the fabrication process have achieved LIBs with higher performance and shorter fabrication time. In addition, LIB operation with other active materials was confirmed.
(4) A LIB with a micro reference electrode fabricated in our laboratory was also evaluated before and after charge-discharge cycles. In the case of the LIB fabricated in our laboratory, the impedance of LIB also increased with charge-discharge cycles. These electrodes were evaluated by means of XPS. The results suggested that the compounds derived from SEI increased on the anode and LiF increased on the cathode with increase of impedance after charge-discharge cycles.
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