Growth Manner of Octahedral-Shaped Li(Ni1/3Co1/3Mn1/3)O2 Single Crystals in Molten Na2SO4

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• 作者：Takeshi Kimijima ; Nobuyuki Zettsu ; Katsuya Teshima
• 刊名：Crystal Growth & Design
• 出版年：2016
• 出版时间：May 4, 2016
• 年：2016
• 卷：16
• 期：5
• 页码：2618-2623
• 全文大小：352K
• 年卷期：0
• ISSN：1528-7505

文摘

The synthesis of shape-controlled crystals has been a highly attractive research topic in modern materials chemistry. In this work, the growth of Li(Ni_1/3Co_1/3Mn_1/3)O₂ (NCM) crystals in molten sulfate or carbonate salts (flux) at 1000 °C was systematically studied under various conditions. In situ X-ray diffraction during the growth and thermogravimetry-differential thermal analysis revealed that the growth of NCM crystals in the flux was controlled by liquid-phase sintering according to the Ostwald ripening principle. We studied the effect of Na⁺ in the flux on the crystal shapes and found that Na⁺ was critical in forming octahedral crystals with well-developed facets. Single crystals with well-developed facets were obtained homogeneously from Na₂SO₄, while truncated polyhedral crystals of smaller size were obtained from Li₂SO₄. The shape-controlled NCM crystals showed discharge capacities approaching 160 mAh g^–1 in the operating voltage range of 2.8–4.4 V vs Li/Li⁺ under a low current density of 0.1 C, independent of flux composition. This suggests that the Li⁺ and transition-metal ions in the individual NCM crystals were highly ordered into hexagonal arrangements belonging to the R3̅m space group, without cation mixing.