成果報告書詳細
管理番号20110000000659
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 活物質・カーボンナノ複合構造制御による高出力・大容量Liイオン二次電池の研究開発2
公開日2012/6/27
報告書年度2010 - 2010
委託先名国立大学法人東北大学
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1.研究開発の内容及び成果
ナノ結晶活物質の新規合成法に基づく高容量型正極材料の開発を行った。
a. 超臨界流体を利用したナノ結晶活物質の合成
有望なリチウム電極活物質材料においてナノサイズ化することにより高容量・高出力特性を発現することが明らかになるにつれ、より低コストで量産的かつ各種の活物質に対して適応可能な汎用的合成法が要求されている。本研究開発では、格段に低い400℃以下の低温プロセスを用いても様々なナノ結晶活物質が高速合成できる超臨界流体合成プロセスを開発した。
英文要約Annual Report of FY2010 NEDO Advanced battery program for new generation vehicles

“Development of High Power and High Energy Li-ion Secondary Battery by Nanofabrication of Li-host/Carbon Composites”

Dr. Itaru Honma, professor of IMRAM, TOHOKU University,
Katahira 2-1-1 Aoba-ku, Sendai, Miyagi,

Lithium ion battery materials based on the polyoxianionic structures such as olivine structure lithium metal phosphates (LiMPO4 M= Fe, Mn, Co, Ni) and lithium metal silicates (LiMSiO4 M=Fe,Mn,Co, Ni) have recently been proposed as potential candidates for high energy and high rate applications such as hybrid electric vehicles and electric vehicles. The ability to control the homogeneity in size, shape, composition, crystal structure and surface structure of the NCs is crucial for overcoming their intrinsic problems. Many efforts have been made to control the LiMPO4 nanocrystal size, morphology and crystal structure via wet chemistry routes such as polyol and solvothermal methods. However, these methods resulted in the formation of 50–300 nm range NCs and some of these methods require a long reaction time (16 h) to obtain highly crystalline product. In spite of this progress, the difficulty in producing the LiMPO4 NCs below 40 nm is hampering the realization of the critical size for these cathode materials, where the nanosize effect will be significant. Therefore, tuning the particle size to the desired range is the key factor for studying the critical size and its effect on the LiMPO4 nanoelectrodes. On the other hand the LiMSiO4 have a potential ability to facilitate the insertion/extraction of two lithium ions per formula unit with a capacity of ~333mAh/g as per theoretical capacity. However, so far reversible two lithium ion capacity has not been achieved due to the structural instability caused by the John-Teller distortion and the subsequent amorphisation that was observed during the charge-discharge studies. Recent efforts made to achieve full capacity is also failed to register the two lithium ions capacity and stable cyclic performances. This has left an impression that no further dramatic improvement in the specific capacity is anticipated with silicate family despite the attractive 333mAh/g theoretical capacity. The reversible two lithium ion capacity with stable cyclic performance requires a cathode to be stable for structural and volume changes during battery operation. The ability to control the structural stability and volume changes is essential for breakthrough performance and subsequent development of silicate family cathodes to take their place in large-scale applications such as electric vehicles.
Supercritical fluids (SCFs) have been widely studied as a new kind of reaction media owing to their unique properties such as gas like diffusivity and viscosity with density closer to that of liquid. The surface tension completely vanishes above the critical point of the fluid; this is of particular interest in controlling surface and interface chemistries of the nanostructures. Furthermore, SCFs form homogeneous phase with gas or organic compounds, which makes it unique reaction medium for preparing organic-inorganic hybrid nanomaterials. In recent years, many inorganic nanostructures have been fabricated via SCFs process. This motivated us to have new possible route to address the challenges of fabricating low cost, high efficiency nano-energy materials. In this context we have developed novel supercritical fluid process for synthesis, size and morphology control and designing surface chemistry. In this NEDO report we have investigated novel synthetic processes of various nano-crystalline electrode materials and their Lithium electrode properties.
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