成果報告書詳細
管理番号20150000000225
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 (2)
公開日2015/5/26
報告書年度2014 - 2014
委託先名国立大学法人九州大学
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Although olivine-type LiFePO4 is a promissing cathode candidate for the next-generation lithium rechargeable battery, the theoretical energy density is limited to 560 mWh/g. To overcome the upper limit, smaller and lighter anions such as fluorine is more suitable than PO4 polyanion. In addition, fluoride can generate high voltage against Li, because of the biggest electronegativity. Nevertherless, there are few reports about fluoride cathode, because it is difficult to synthesize.
In this research, we have proposed several novel fluoride cathodes such as rutile-type FeOF and perovskite-type FeF3. However, the conversion-type cathodes such as FeOF and FeF3 can not use as cathode against carbonaceous anode, because it has no Li in the initial composition. To overcome the drawback, reconversion reaction of the composite cathode of LiF and FeO was tried as follows;
LiF + FeO → FeOF + Li+ + e-
Then, among the iron-based cathodes, the highest energy density more than 700 mWh/g was able to be confirmed.
Moreover, in order to realize the larger composite cathode, the following researches are tried;
1)Investigation of the reconversion reaction in LiF and Fe composite thin film cathode obtained by vapor deposition method
2)Synthesis by the pyrolysis method using organoiron complexes.
3)Trial of Li halaides such as Li2O and LiCl as Li sources in conversion-type cathode

It is reported that Ca doped LaCoO3 shows high activity to oxygen reduction reaction (ORR), however overpotential at high current density is large because of small surface area. Effects of surface area on ORR activity were studied in details. Single phase of LCC perovskite oxide with mesoporous structure was successfully prepared. ORR and OER activity of mesoporous LCC and bulk one were measured with gas diffusion electrode (GDE). At low current density, bulk LCC shows a little smaller overpotential, however, with increasing current density, overpotential of mesoporous LCC became smaller than that of bulk LCC for ORR. Stability of LCC under ORR and OER was studied with cycle operation of current direction of 20mA/cm2. In case of bulk LCC, discharge as well as charge potential decreased and increased, respectively after 30 cycles, however, in case of mesoporous LCC, potential for ORR and OER were hardly changed over 60 cycles. Therefore, from stability, mesoporous LCC shows much superior property than that of bulk one. Optimization of Denka Black(DB) was performed and it was found that overpotential was drastically decreased with increasing DB amount. The optimized composition seems to exist at 1:1 weight ratio. By using the optimized composition, cycle stability of Zn-air battery was measured at 75 % utilization of Zn and 50mA/cm2, it was found that discharge capacity higher than 450 mA/cm2 was stably exhibited at ca. 1V over 100 cycles.
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