成果報告書詳細
管理番号20110000000949
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 リチウム空気二次電池用リチウム~固体電解質複合負極の研究開発
公開日2012/4/6
報告書年度2010 - 2010
委託先名国立大学法人三重大学
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 リチウム空気電池の開発をするにあたり4つの研究課題を掲げた。それぞれの今年度の研究成果を報告する。
(1)安定なリチウム複合負極の開発と抵抗低減
複合負極において電極反応はリチウムと中間層の界面で進行する。従って、複合負極の電気化学特性はリチウム金属が接している中間層材料の性質に強く依存する。また、水溶液電解質の固有の現象として充放電時のpHの変化がある。これより最外層のLTAPは水に安定というだけでなく、充放電時のpH範囲において安定である事が求められる。本課題ではまず、複合負極で重要な中間層の抵抗低減~添加物の効果について検討した結果を報告する。
中間層として用いている有機系ポリマー電解質はホストポリマーとしてポリエチレンオキシド(PEO)にリチウム塩、たとえばLi(CF3SO2)2N(LiTFSI)を溶かしたものである。PEO18LiTFSIの組成の液体を冷却すると60°C付近で凝固が始まりPEOが結晶として析出する。
英文要約Title: Development of High Performance Battery System for Next-Generation Vehicles / Development of the composite anode for Li-Air rechargeable batteries (FY2007-FY2011) FY2010 Annual Report
In the study of Li-Air batteries, four research subjects were examined.
1) Preparation of stable composite anode and reduction of the resistance
The effect of ionic liquid addition to the polymer electrolyte on the lithium anode performances was studied. PP13TFSI (N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide) was used as additive to the PEO-based polymer electrolyte. On the symmetrical cell of Li/PEO18LiTFSI‐xPP13TFSI/Li, the change in the electric conductivity by amount x of PP13TFSI was measured. The electric conductivity at 25 °C is 7×10-5 S cm-1 at x=1.44 and the lithium ion transport number tends to decrease with x. This indicates that the anions are the main carrier in the ionic liquid added polymer electrolyte.
The chemical stability of the lithium and polymer electrolyte is significantly improved by the ionic liquid addition. The ionic liquid doesn't effect on the interfacial conductivity due to the low transference number of lithium, but is beneficial to stabilize the interface.
2) Study on lithium dissolution and deposition to improve cycling efficiency
The relation of the additive amount of PP13TFSI and the time required for the short-circuit was examined for the Li/PEO18LiTFSI‐xPP13TFSI/Li symmetrical cell. The time increases with x, but it turns to decrease when too much PP13TFSI is added. Time required for dendrite formation at x=1.44 is larger by a factor of about 1.5 compared to the acid-treated SiO2 addition. The amount of the lithium that can be deposited on copper current collector was 1270 mAh g-1 at 1.0 mA cm-2 and 2148 mAh g-1 at 0.1 mA cm-2. Charge and discharge cycle of the symmetrical cell at 0.3 mA cm-2 was examined and a steady polarization behavior was maintained during 30 cycles.
3) Development of a new water-stable solid electrolyte
Stability of solid electrolyte Li7La3Zr2O12 (LLZ) in aqueous solution was investigated. Two kinds of Li8.05La3Zr2O12.525 (LLZ-8) and Li7La3Zr2O12 (LLZ-7) were prepared by the sol-gel method. A single phase with a garnet structure in LLZ-8 was obtained as a result. The integrated conductivity including bulk and grain boundary was estimated to be 1.6×10-4 S cm-1. The activation energy is about 35 kJ mol-1. LLZ-8 was soaked in 1M LiOH, 0.1M HCl, and saturated LiCl solution. In the former two, the increase of the resistance was observed. On the other hand, no change in resistance was observed in the neutral LiCl solution.
4) Development of new reservoir system
The discharge product of aqueous Li-Air battery is LiOH. The basicity of the electrolyte solution becomes higher as the discharge continues. It is needed to protect LATP from such a strong base, since it decomposed into Li3PO4 and others. The dissociation equilibrium of LiOH is suppressed by large amount of lithium ions in the aqueous solution. The LATP was immersed in LiOH(1 M) + LiCl saturated (19 M) solution. It is revealed that LATP is stable in this solution. The data demonstrates that most Li+ and OH- ions are associated in LiCl-saturated solution.
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