成果報告書詳細
管理番号20110000000980
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 電極作製にガスデポジション法を利用したリチウム二次電池の研究開発
公開日2012/6/27
報告書年度2010 - 2010
委託先名国立大学法人鳥取大学
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:
[記載項目]
1. 研究開発の内容及び成果等
研究・開発の目的
現在のリチウム二次電池の負極には黒鉛が用いられているが,さらなる高容量化のために,代替材料として金属・合金系および酸化物系活物質が提案されている.しかしながら,これらには充放電第1サイクルにおける容量可逆性が低く,またサイクル寿命が短いなどの課題がある.他方,正極においても活物質利用率の向上や一層高い出力密度を達成するための電極作製法の導入が必要である.
英文要約(FY2007-FY2011) FY2010 Annual Report
Title: Development of High-performance Battery System for Next-generation Vehicles/Next-generation technology development/Development of Lithium Secondary Batteries with Electrodes Produced by Gas-Deposition
Hiroki Sakaguchi, Tottori University
Abstract
To overcome a problem of Si as anode materials for next-generation Li-ion batteries, we have proposed composite thick-film electrodes consisted of Si-based materials prepared by a gas-deposition (GD) method. In our previous studies, we have fabricated the thick-film electrodes consisted of Si particles coated with transition metals (Ru, Cu, and Ni) by using an electroless deposition (ELD) method, and found that these electrodes exhibited better cycling performances. In particular, it has been revealed that the thick-film electrode of Si coated with Ni-P exhibited a higher elastic modulus and excellent performance even though the coating amount was very small. We consider that the coated layers play a role as a buffer layer to relax a stress induced by the volumetric changes of Si during the charge-discharge processes. These results indicate that Ni-P is a very suitable composite material for our composite thick-film electrodes. In this fiscal year, in order to investigate the influence of Ni-P as the composite material on the anode properties of Si-based thick-film electrodes, we evaluated the electrode performance of composite thick-film electrodes prepared by GD for a mixture of Si particles and Ni-P particles synthesized by the ELD method. On the other hand, to enhance a reversibility of charge-discharge capacities of thick-film electrodes, we studied an applicability of ionic liquid electrolyte instead of conventional organic solvent electrolytes.
Ni-P particles were synthesized by the ELD method and the particles were supplied by a company. A mixture of commercial Si particles and the Ni-P particles were used as source material powder of GD. By a gas-deposition using Ar carrier gas, thick film electrodes were formed on Cu foil substrates. Electrochemical measurements were carried out using a beaker-type three-electrode cell with the obtained thick film electrodes as a working electrode and Li plates as counter and reference electrodes in 1 M LiClO4-propylene carbonate. A charge-discharge test was performed under a constant current of 1.0 A g-1 at 303K with potential range of 0.005?3.400 V vs. Li/Li+. As an evaluation of ionic liquid electrolytes, we assembled 2032-type coin cells consisted of Si thick-film electrodes (working electrode), Li sheets (counter electrode), and ionic liquids (electrolyte), and investigated anode properties of the Si electrodes. The ionic liquids used in this study have a common anion, bis(trifluoromethanesulfonyl)amide [TFSA?]. The cations were 1-methoxyethoxymethyl(tri-n-butyl)phosphonium [MEMBu3P+], N-methyl-N-propylpiperidinium [PP13+], 1-ethyl-3-methyl imidazolium [EMI+], 1-buthyl-3-methyl imidazolium [BMI+]. The charge-discharge test was performed at 0.4 A g-1 (~0.1 C) at 303K with potential range of 0.005?2.000 V vs. Li/Li+.
Figure 1 shows dependence of discharge capacities on charge-discharge cycling numbers for the composite thick-film electrodes consisted of Si and Ni-P particles with different Ni-P amounts. In case of the composite electrode containing 20 wt.% of Ni-P, the significant capacity decay was observed for the initial several ten cycles though the discharge (Li-extraction) capacity of 2340 mA h g-1 at the first cycle was much larger in comparison with other electrodes. In contrast, for the composite electrode containing 60 wt.% Ni-P, the capacity decay was remarkably suppressed.
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