成果報告書詳細
管理番号20120000000311
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 7
公開日2012/6/27
報告書年度2011 - 2011
委託先名独立行政法人産業技術総合研究所、日立マクセルエナジー株式会社、パナソニック株式会社、株式会社本田技術研究所
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:
1. 共同研究の内容及び成果等
本共同研究は、本事業の研究開発項目3「材料革新」について、当該研究開発項目担当の4法人が、リチウムイオン電池のエネルギー密度の向上並びに高耐久化・高度信頼性の同時達成のための電池材料の革新に資する指針の提案を目指すものである。
英文要約Title: Research and Development for Innovation of Materials for Lithium-ion and Lithium Batteries / Research and Development Initiative for Scientific Innovation of New Generation Batteries (RISING) (FY2009-FY2013) FY2011 Annual Report
The present study has been done in collaboration with AIST, Hitachi Maxell, Honda R&D Co., and Panasonic. The goal of this study is to indicate concepts for innovatively improving methods for positive and negative electrode materials in order to achieve breakthroughs of lithium-ion cell performance, durability and reliability. This study focused on the following subjects; (i) formation of highly durable interface between positive electrodes and electrolytes, (ii) high voltage positive electrodes and (iii) high capacity negative electrodes possessing longer cycle and storage life. In this fiscal year, 2011, we have studied the electrochemical properties of the surface-coated positive electrodes and characterized them, particularly focusing on the quantitative evaluation of the cycle degradation for the active materials, in order to achieve highly durable positive electrodes. In addition, electrode reaction and degradation mechanisms of high voltage positive electrodes and high capacity negative alloy electrodes have been investigated.
i) Formation of highly durable interface between positive electrodes and electrolytes:
As a dry process, mechanochemical coating of Al2O3 on LiNi1/3Mn1/3Co1/3O2 was investigated. The electrochemical tests of the cells cycled at 50oC showed higher capacity retention and lower electrode impedance, indicating that the cycle degradation of the electrode was suppressed by the Al2O3-coating. PES and XRD analyses indicated that there observed no clear relation between the cycle degradation of the cells and the amounts of the deposited by-products on the electrodes, nor the structural changes of the cathode active materials. On the other hand, there observed increased amounts of small cracks in the particles of the cathode active materials with cycling, which would be responsible mainly for the cycle degradation of the cells. Such cracks were much reduced in the Al2O3-coated active materials, indicating that the surface coating has an effect on suppressing the cracks in the active materials, which leads to the improved cell performances with cycling. As a wet process, we have established a new method of Al2O3-coating more homogeneously on LiNi1/3Mn1/3Co1/3O2, and observed similarly the suppression of the crack-formation in the active materials with cycling. Therefore, the coating has an effect on the improved cell performance with cycling via the suppression of the crack-formation, irrespective of the coating process.
ii) High voltage positive electrode materials:
In order to improve durability of LiNi0.5Mn1.5O4, Al2O3 was coated by the mechanochemical process. With increasing the amounts of Al2O3 coating, the initial electrode impedance was raised and the reversible capacity was decreased. The cycle performance was much improved by optimizing the electrolyte components. Further optimization of the coating conditions and analyses of the degraded electrodes will be carried out with the collaboration of other groups.
iii) High capacity negative electrode materials:
High capacity alloy electrodes show large volumetric changes for Li insertion / extraction reactions, which generate cracks in the active materials, leading to the drastic cycle degradation of the cells. In order to avoid cracking of alloy electrodes, we tried to prepare alloy electrodes with micro-porous structure by a self-assembly process. The prepared alloy electrodes showed increasing cycle capability and higher coulomb efficiency, but disadvantageously the preparation of thicker alloy electrodes, being necessary for higher energy density cells, was difficult. Then, we try to investigate another process to prepare thicker alloy electrodes with improved cycle performances.
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