Mesoporous Cr2O3 as negative electrode in lithium batteries:: TEM study of the texture effect on the polymeric layer formation
Mesoporous Cr2O3 as negative electrode in lithium batteries:: TEM study of the texture effect on the polymeric layer formation
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DOI：
10.1016/j.jpowsour.2007.09.084
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发表时间：
2008-01-03
影响因子：
9.2
通讯作者：
Tarascon, J. -M.
中科院分区：
文献类型：
--
作者：
Dupont, L.;Laruelle, S.;Tarascon, J. -M.
据报道，介孔单晶（PSC）氧化物在通过插层过程操作的锂离子电池中表现出比本体材料更高的电化学性能。在这里，我们将这项研究扩展到介孔Cr2 O3与Li+/Li-0的电化学行为。我们证实，Cr2 O3通过转化反应机制向Li反应，导致放电时形成大的金属铬纳米颗粒（10 nm）;后者嵌入到Li 2 O基质中，在这种特定情况下，大量的聚合物材料来自电解质降解，围绕颗粒，并填充孔隙。在接下来的充电过程中，纳米颗粒的再氧化发生，形成CrO 1-x，与块状Cr2 O3电极相比，主要区别在于在充电结束时保留聚合物层。我们认为，通过毛细管效应，材料的中孔性是这种差异的根源。这些电解质降解产物被证明有助于在大量的循环中保持材料的中孔性;有趣的是，它们在容量保持方面对电池性能无害，同时通过减少扩散长度，即对于Li+离子，在电荷转移方面呈现出很大的优势。插入反应中注意到的基于介孔材料的电极的积极属性可以扩展到转化反应电极，只要我们可以掌握它们的合成，同时通过软或硬模板技术控制它们的介孔性。(C)2007 Elsevier B. V.保留所有权利。
Mesoporous single crystal (PSC) oxides have been reported as presenting higher electrochemical performances than bulk materials in lithium ion batteries operating via intercalation processes. Here, we extend this study to the electrochemical behaviour of mesoporous Cr2O3 versus Li+/Li-0. We confirm that the Cr2O3 reacts towards Li through a conversion reaction mechanism leading, upon discharge, to the formation of large metallic chromium nanoparticles (10 nm); the latter are embedded into a Li2O matrix together with, in this specific case, a copious amount of polymeric materials coming from electrolyte degradation, surrounding the particles, and filling the pores. During the following charge, re-oxidation of the nanoparticles occurs with the formation of CrO1-x, with the main difference, as opposed to bulk Cr2O3 electrodes, being the preservation of the polymeric layer at the end of the charge. We believe the material mesoporosity, via capillary effects, to be at the origin of such a difference. These electrolyte degradation products are shown to help in maintaining the material mesoporosity for a great number of cycles; and interestingly they are not detrimental to the cell performance in terms of capacity retention while presenting great advantages in terms of charge transfer by reducing diffusion lengths, namely for Li+ ions. The positive attributes of mesoporous material-based electrodes noticed for insertion reactions can then be extended to conversion reaction electrodes as long as we can master their synthesis while controlling their mesoporosity through either soft or hard templating techniques. (C) 2007 Elsevier B.V. All rights reserved.