成果報告書詳細
管理番号20120000000306
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 3
公開日2013/2/6
報告書年度2011 - 2011
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
和文要約和文要約等以下本編抜粋:1. 共同研究の内容及び成果等 次世代リチウム二次電池の正極材料として、現在、経済性及び安全性の観点から最も有力視されている材料としてオリビン系リン酸鉄が挙げられるが、560 Wh/kgの理論エネルギー密度限界がネックとなっている。
英文要約As a cathode active material of a next-generation lithium secondary battery, LiFePO4 has drawn much interest at a viewpoint of cost and safety. However, the theoretical energy density is limited to 560 Wh/kg. To overcome the theoretical energy density limit, the shortest route which attains the capacity which exceeds LiFePO4 is anion exchange of PO4 to the lighter anion. Among the anion candidates, fluoride which has the maximum electronegativity in an element is considered an ultimate anion candidate. Since the synthesis of fluorides were difficult, there were few reports about fluoride cathode, until now. In this project, we investigated cryolite Li3MF6, trirutile-type Li2MF6, inverse spinel-type Li2MF4 and perovskite-type NaFeF3 as new fluoride cathodes. In this year, we focused on oxyfluoride-type FeOF and perovskite-type NaCuF3. In addition, thermal stability of perovskite-type FeF3 was also confirmed by TG-DSC measurements. The topics in this year can be summarized as follows;
oxyfluoride-type FeOF: Until now, to synthesize FeOF, we have to induce high pressure more than 60 kbar. However, we found new synthesis condition using single-roll quenching machine under atmospheric pressure. The obrtained rutile-type FeOF with P42/mnm showed 450mAh/g reversible capacity between 1.3 and 4 V correnponding to 1.5 Li per FeOF.
perovskite-type NaCuF3: NaCuF3 with P-1 could be synthesized both by mechanical milling and single-roll quenching machine. The reversible capacity against Na anode was 240 mAh/g corresponding to 1.3 Na per NaCuF3.
Thermal stability of perovskite-type FeF3: After 3Li conversion reaction of FeF3, we detected Fe and LiF. This result is consistent with the conversion type reaction formula (FeF3+3Li -> 3LiF+Fe). The thermal stability of fully discharged state is better than electrolyte, because the main component LiF is thermally and chemically stable.
From now on, the cathode search range will be expanded also to other oxyfluorides. Furthermore, to find post-LiFePO4 cathode, the polyanionic cathode with fluorine such as Li3 V2(PO4) 2F3 will be investigated, in next financial year.
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