成果報告書詳細
管理番号20110000000040
タイトル*平成21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/構造規制型新規金属負極の研究開発
公開日2012/6/27
報告書年度2009 - 2009
委託先名公立大学法人首都大学東京 大学院
プロジェクト番号P07001
部署名スマートコミュニティ部
和文要約本研究提案の内容は構造を規制した電極を作製することにより、リチウム金属負極および合成系負極のサイクル安定性を向上させ、本来これらの負極材料が有している高いエネルギー密度をリチウム二次電池に応用可能にする点にある。本年度は、リチウム金属負極および合成系負極に関して下記項目について重点的に研究を行った。
英文要約In order to realize high energy density batteries, new anode and cathode materials should be developed w/practical cycle life. Both Li metal and alloy anodes have higher energy density than that of graphite electrode. However, both electrodes have serious problem which is a very low cycleability. In the project, we proposed the tech. of 3-dimensionally ordered electrodes for Li metal and alloy anode. We have focused on (1)3-dimensionally ordered macroporous(3DOM) separators for Li metal anode and (2) a micro-domain structure for Sn-Ni alloy anode. (1) 3DOM separators for Li metal anode: The cycleability of Li metal anode is highly limited by a formation of Li dendrite. Therefore, Li dendrite formation has to be suppressed for the practical application of Li metal anode. We have revealed in FY2008 that a Li-tolerant polymer w/3-dimensionally ordered macroporous(3DOM)structure,i.e.,3DOM separator, effectively suppressed the growth of Li dendrite and provided good cycleability over 300 cycles to Li metal anode. In FY2009, 3DOM separator was prepared from polyimide having mechanical stability, chemical stability, and thermal stability. 3DOM polyimide separators with different pore-sizes were prepared by colloidal crystal templating method. The galvanostatic charge/discharge test was conducted to examine cycleability of Li metal anode with 3DOM polyimide separator, in which the beaker type cell composed of a copper sheet electrode, a 3DOM polyimide separator, a Li foil counter electrode in 1 mol dm-3LiPF6/ethylene carbonate was used. 0.65mg (2.5mAh) of Li metal was deposited on the copper sheet electrode, and then 0.16mg(0.63mAh) of the deposited Li metal was consumed(dissolved) in discharge process, corresponding to DOD 25% of the deposited Li metal, and the same amt of Li metal was recovered(deposited) in the charge process. The charge/discharge test was still continued over 1000cycles with 100% efficiency. The Li metal anode showed better cycleability by using the 3DOM polyimide with smaller pore-size. In addition, the cycleability of Li metal anode was influenced by a kind of electrolyte. SEM observation revealed that the morphology of deposited Li metal through the 3DOM polyimide separator was grain-like shape and not influenced by the pore size of 3DOM polyimide separator, and any Li dendrite was not formed.(2) micro-domain structure for Sn-Ni alloy anode: The problem of Sn-Ni alloy is a poor cycleability due to the large vol change of during charge and discharge processes. In FY2008, we prepared 3DOM Sn-Ni alloy electrode and revealed that it exhibited better cycleability than conventional plate-type Sn-Ni alloy electrode. However, 3DOM Sn-Ni alloy was fragmented to 20~50 ?m pieces and its capacity was drastically dropped over 50cycles. In FY2009, we introduced a micro-domain structure into 3DOM Sn-Nialloy electrode for inhibition of fragmentation. 3DOM Sn-Ni w/micro-domain structure was prepared by using a photoresist pattern with ordered cylindrical pores (diameter: 20?m, depth: 30?m). 3DOM Sn-Ni alloy w/cylindrical domain structure showed 650 mAh g-1 in 1st charge/discharge cycle, and its capacity was maintained at 100% after 200 cycles under the condition of DOD77%(500mA h g-1). This good cycleability was ascribed to suppression of fragmentation by introduction of the micro-domain structure. The full cell composed of 3DOM Sn-Ni alloy anode with cylindrical domain structure and LiFePO4 cathode, exhibited 142.6Wh L-1. For practical use, we prepared Sn-Ni alloy anode with micro-domain structure on flexible Cu foil substrate as well. However, the capacity was lower than that on SiO2 substrate because of poor contact w/substrate. In order to obtain better contact w/the flexible substrate, both heat treatment of the Sn-Ni anode on Cu foil and exploration of another Sn-based alloy anode such as Sn-Cu are going on now. We already succeeded on provision of some Sn alloys and evaluation of the Sn-based alloys is underway.
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