成果報告書詳細
管理番号20130000000489
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 (2)
公開日2014/1/28
報告書年度2012 - 2012
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In this project, we have been investigated cryolite Li3MF6, trirutile-type Li2MF6, inverse spinel-type Li2MF4 and perovskite-type NaFeF3 as new fluoride cathodes. However, these cathodes allow mostly no more than one or two -electron transfer per formula unit and limit a full utilization of the oxidation states of the cathode materials. In this year we investigated cathode materials, which were expected to give a high redox voltage and large reversible capacity through the conversion reaction. In addition, thermal stability of FeOF was confirmed by TG-DSC measurements. The topics in this year can be summarized as follows;
1) LiF-Fe cathode material
The conversion reaction of LiF/Fe is known as follow;
FeF3 + 3Li+ + 3e- → 3LiF + Fe (1)
To obtain the theoretical capacity of 712 mAh/g, the LiF and Fe phases should be well dispersed. We developed a new vapor-deposition technique to increase contact surface areas of LiF and Fe and investigated their electrochemical properties. As a result, approximately 200 mAh/g of reversible capacity was confirmed with a plateau at around 3 V, and the cathode could work at room temperature.
(2) New florin based cathode material
In order to increase the energy density, we pursue studies for developing new synthesis methods of MnOF and investigate their electrochemical property.
(3) Thermal stability of FeOF
Thermal stability of FeOF was investigated and compeired with that of FeF3. We found a peak at 150 C, which was not seen in FeF3. The thermal stability of FeOF at the fully discharged state showed lower than that of FeF3 due to oxidative product during discharge.
 Air electrode activity of mesoporous metal oxide for Zn-air battery was studied in this year. Among MnO2 with various crystal structure, it was found that δ-type MnO2 shows the largest oxygen reduction reaction activity and suitable for air electrode of Zn-air electrode. Discharge property of Zn-air battery was also studied by using the test cell designed and discharge capacity of 20mAh/g-Zn was observed for the cell using δ-MnO2 air electrode. On the other hand, discharge capacity was slightly enlarged by addition of Pd, however, discharge capacity was slightly increased. Therefore, modification of δ-MnO2 with Pd seems not to be suitable for air electrode of Zn-air battery. On the other hand, effect of meso porous structure on discharge capacity was further studied by using β-MnO2 and it became clear that higher and flat discharge potential was observed on β-MnO2 with mesoporous structure comparing with that of bulk sample.
Effects of ethylene glycol on oxygen reduction activity were also studied by using δ-MnO2. It was found that oxidation peak of ethylene glycol was observed at 0.7 V vs. S.H.E. When 4 M KOH added with ethylene glycol was used for electrolyte, discharge potential decreased, however, discharge capacity was enlarged suggesting that ethylene glycol was oxidized.
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