成果報告書詳細
管理番号20110000000690
タイトル*平成22年度中間年報 次世代自動車用高性能蓄電システム技術開発 次世代技術開発 イオン液体電解液を用いたリチウム二次電池の研究開発(1)
公開日2012/4/6
報告書年度2010 - 2010
委託先名学校法人慶應義塾
プロジェクト番号P07001
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. 研究開発の内容及び成果等 1-1 背景 難揮発性・難燃性のイオン液体をリチウム二次電池の電解液として用いることによって、リチウム二次電池の安全性の大幅な向上が期待される。しかしながら、イオン液体の多くはイオン伝導率が低く、また、正極および負極における電極反応速度が遅いことが実用化への障害となっている。また、従来の炭素より比容量の大きな合金系負極を用いることで、リチウム二次電池のエネルギー密度の向上が期待されるが、イオン液体電解液中での合金負極の反応について検討された例は少ない。本研究開発では、1~ブチルー1~メチルピロリジニウム・ビス(トリフルオロメチルスルフォニル)アミド(BMPTFSA)イオン液体にリチウムイオン源としてLiTFSA を加えたものを電解液として用い、スズおよびケイ素負極に対するリチウムのドープ・脱ドープ反応における各種添加剤の効果について検討を行った。
英文要約Development of High-performance Battery System for Next-generation Vehicles
Next-generation Technology Development
Development of Rechargeable Lithium Batteries with Ionic Liquid Electrolytes
Takashi Miura, Keio University
Not only high energy density and high power density but also a high-level safety is strictly required for rechargeable lithium batteries employed in practical electric vehicles. By use of non-flammable electrolytes possible, dangerous accidents such as combustion and explosion can be avoided to some extent. Ionic liquids have attracted much attention recently as a promising candidate of non-flammable electrolytes for rechargeable lithium batteries. However, the ionic conductivity of most ionic liquids remains lower than that of conventional organic solvent electrolytes. Moreover, the resistance at the electrode-electrolyte interface is often high in ionic liquids compared with that in organic electrolytes. We have so far found that the interfacial resistance at the Sn electrode can be drastically reduced by addition of a kind of glymes into an ionic liquid electrolyte, 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)amide (BMP-TFSA) containing LiTFSA. In the present studies, the effects of the additives, namely, ethylene carbonate (EC) and vinylene carbonate (VC), on the charge-discharge performance of a tin and silicon thin film electrode have been investigated in 1 M LiTFSA / BMPTFSA.
Reversible charge-discharge for a tin thin film anode was possible in 1 M LiTFSA / BMPTFSA containing 1 M EC or VC at room-temperature. The interfacial resistance in 1 M LiTFSA / BMPTFSA / 1 M EC or VC was much smaller than that in 1 M LiTFSA / BMPTFSA. Formation of surface film was confirmed by attenuated total reflection Fourier transformation infrared (ATR-FTIR) spectroscopy for the surface of the sample electrodes after the charge-discharge experiments. A decrease in the interfacial resistance may be ascribed to the existence of oxygen atoms in lithium carbonate or carbonate in the surface film. On the other hand, the cycle performance in 1 M LiTFSA / BMPTFSA / 1 M VC was superior to that in 1 M LiTFSA / BMPTFSA / 1 M EC, suggesting the composition of the surface film derived from VC is different from that derived from EC.
Charge-discharge for a silicon thin film anode was impossible in 1 M LiTFSA / BMPTFSA. Passivation of the anode surface with some compounds containing TFSA– is considered to inhibit the anode reaction. When 1 M EC or 1 M VC was added to 1 M LiTFSA / BMPTFSA, reversible charge-discharge became possible. The ATR-FTIR spectra of the sample electrodes showed formation of a surface film similar to those obtained in an organic electrolyte (1 M LiClO4 / EC+DMC). Thus, the surface film derived from EC or VC is essential for using silicon anodes in the ionic liquid electrolytes. The cycle performance of the silicon thin film anode in 1 M LiTFSA / BMPTFSA / 1 M VC was again better than that in 1 M LiTFSA / BMPTFSA / 1 M EC. Since the absorption corresponding to carbonate in the surface film derived from VC was stronger than that derived from EC, carbonate is expected to play an important role in enhancement of cycle performance of the silicon anode.
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