成果報告書詳細
管理番号20150000000236
タイトル*平成26年度中間年報 革新型蓄電池先端科学基礎研究事業 革新型蓄電池先端科学基礎研究開発 (8)
公開日2015/5/26
報告書年度2014 - 2014
委託先名国立大学法人東京工業大学
プロジェクト番号P09012
部署名スマートコミュニティ部
和文要約
英文要約In this fiscal year, we developed lithium-rich layered rock-salt cathodes with high charge/discharge capacities as the material innovation group subject. Lix(Mn,Co,Ni)yO2 phases with an excess amount of lithium (1.2 < x < 1.6, 0.7 < y < 1.0) were successfully synthesized under different partial pressures of oxygen using high-pressure synthesis, and their structures, compositions, electrochemical properties were systematically investigated. Rietveld analyses using neutron diffraction data confirmed that the excess lithium was introduced to a tetrahedral site as well as octahedral sites in the transition metal layer. A structural distortion caused by the introduction of the tetrahedral lithium affected significantly the initial charge/discharge reactions, which could be a key factor to make an electrochemical active phase with high capacity. Furthermore, the Lix(Mn,Co,Ni)yO2 synthesized under a high oxygen pressure showed much higher discharge capacities than those synthesized under a low oxygen pressure. Detailed reaction mechanisms of the lithium-rich layered rock-salt cathodes were investigated using epitaxial-film model electrodes of Li1.90MnO2.95. The charge/discharge capacities increased with the decrease in the film thickness, which demonstrates that the surface region is actively reconstructed to generate a high-capacity phase. As the advanced analysis group subject, we demonstrated that operand neutron diffraction methods enable us to observe directly the structural changes of cathode and anode materials in a commercial 18650-type lithium secondary battery. The neutron diffraction experimental setup successfully provided the specific information of the large size cell under a practical battery-operation condition from low to high current drains; (i) changes in the reaction mechanism and non-uniform reactions of anode material caused by non-equilibrium state, and (ii) decrease in lattice volume change of cathode material with uniform reactions. Furthermore, automatic data analysis procedure has been developed to deal with the big data that are produced from a sequential charge-discharge reaction. The automatic structure analysis clarified the crystal structural changes of cathode and anode materials during the battery reactions.
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