Hydrothermal synthesis of LiMnPO₄-C(sp²) hybrids, conductive channels, and enhanced dielectric permittivity: a modulated ionic conductor

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• 作者：S. K. Sharma ; P. V. Rajeswari ; B. Tiwari ; S. Ram
• 关键词：Cathode materials ; Hydrothermal synthesis ; Nanorods ; Dielectric properties
• 刊名：Ionics
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：23
• 期：1
• 页码：43-53
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Electrochemistry; Renewable and Green Energy; Optical and Electronic Materials; Condensed Matter Physics; Energy Storage;
• 出版者：Springer Berlin Heidelberg
• ISSN：1862-0760
• 卷排序：23

文摘

A nanohybrid C-LiMnPO₄ is important to tailor its electrochemical properties useful for Li+-ion batteries and photo-catalysis. In this article, we report a simple in situ C-LiMnPO₄ synthesis, wherein the LiMnPO₄ grows from a supersaturated solution LiOH·H₂O, MnSO₄·H₂O, and H₃PO₄ in water at 200 °C in an autoclave in a hydrothermal reaction and bonds in situ to nascent carbon of a surface layer on a surface reaction with a long chain hydrocarbon used during the reaction. A phase pure C-LiMnPO₄ is formed in a shape of nanorods (Pnma orthorhombic crystal structure), with 100–150 nm diameters, 150–800 nm lengths, and 2–3 nm thickness of a co-bonded C-sp2 surface layer. The LiMnPO₄ rigidly co-bonds to C-sp2 via O2− in the PO₄3− polygons in a joint surface layer that a single molecular bonding extends well up to 600 °C, with a due mass loss on an extended heating in air. The sample contains fine pores with an average 3.0 nm diameter and a 9.0 m2/g surface area. At room temperature, it develops a huge dielectric permittivity ε_r~1.9 × 105 near 1 Hz frequencies, which on raising the frequency decays progressively to a fairly steady ε_r~1.5 × 103 at ≥1 kHz. Bare LiMnPO₄ is a low dielectric phase, ε_r < 10. A non-Debye type of dielectric relaxation is shown in the modulus plots. As frequency approaches to 105 Hz, nearly three orders of larger ac conductivity, 2.5 × 10−5 Scm−1 at 106 Hz, develop over a carbon-free LiMnPO₄ value useful for the applications.