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首页> 外文会议>NATO Advanced Study Institute on New Trends in Intercalation Compounds for Energy Storage, Sep 22-Oct 2, 2001, Sozopol, Bulgaria >IMPEDANCE OF DIFFUSION OF INSERTED IONS SIMPLE AND ADVANCED MODELS
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IMPEDANCE OF DIFFUSION OF INSERTED IONS SIMPLE AND ADVANCED MODELS

机译：插入离子简单扩散模型和高级模型

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The kinetics and thermodynamics properties of insertion compounds for battery applications are investigated by means of several electrochemical methods. The impedance technique is particularly appealing, and it is used widely, because of two particular features. It is a small signal technique, which means that we may investigate the system at different steady states without affecting significantly the stationary potential. And it is a frequency-resolved technique, which enables one to separate the processes that occur at different time scales (from few mHz up to the kHz). In order to carry out the research of properties of an electrode material the impedance is measured after equilibration of the electrode potential at a steady state. The fundamental event in this type of experiment is lithium ion intercalation to (or deintercalation from) the working electrode. This overall process occurs in several steps, and it useful to distinguish two kinds of kinetics limitations. First are those that take place before the lithium ions enter the electrode: the ion transport through a passivation layer at the electrode surface, and the overcoming of a potential barrier at the electrode/electrolyte interface (interfacial charge-transfer). These processes usually appear as arcs in the high frequency wing of the impedance diagram, and will not be treated in detail in this report. When lithium ions in solution have in fact crossed the electrolyte/electrode interface, the spatial variation of the chemical potential provides a driving force for lithium ion transport throughout the electrode. We assume in this report that the electrode material is a good electronic conductor, so that the chemical potentials of the electronic species are essentially uniform throughout the material (Weppner, 1995) and only ion transport need be examined. Otherwise transport involves coupled displacement of ionic and electronic species driven both by electrostatic and chemical potential gradients, which requires a different approach (Vorotyntsev et al., 1994). The process of ion diffusion in the solid state will be analyzed in the following sections. We first overview the normal framework based on ordinary diffusion through a regular network of sites. Thereafter we describe kinetic effects associated to multiple types of the lithium intercalation sites.
机译：通过几种电化学方法研究了用于电池的插入化合物的动力学和热力学性质。阻抗技术特别吸引人，并且由于两个特殊功能而被广泛使用。这是一种小信号技术，这意味着我们可以在不影响稳态的情况下研究处于不同稳态的系统。这是一种频率分辨技术，使人们能够分离出在不同时标（从几mHz到kHz）发生的过程。为了进行电极材料性能的研究，在稳定状态下电极电位平衡之后测量阻抗。这种类型的实验中的基本事件是锂离子嵌入工作电极（或从工作电极脱嵌）。整个过程分几个步骤进行，有助于区分两种动力学限制。首先是那些在锂离子进入电极之前发生的离子：离子在电极表面通过钝化层的传输，以及在电极/电解质界面的势垒的克服（界面电荷转移）。这些过程通常在阻抗图的高频机翼中显示为弧形，因此在本报告中将不再详细介绍。当溶液中的锂离子实际上已经越过电解质/电极界面时，化学势的空间变化将为锂离子在整个电极中的运输提供驱动力。我们在这份报告中假设电极材料是一种良好的电子导体，因此电子物质的化学势在整个材料中基本上是均匀的（Weppner，1995），只需要检查离子传输。否则，运输涉及由静电和化学势梯度驱动的离子和电子物质的耦合位移，这需要不同的方法（Vorotyntsev等，1994）。以下各节将分析固态离子的扩散过程。我们首先概述基于通过常规站点网络进行常规传播的常规框架。此后，我们描述了与多种类型的锂嵌入位点相关的动力学效应。

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