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Role of phase transformation processes in determining the discharge behavior of electrodes in lithium ion battery.

机译：相变过程在确定锂离子电池中电极放电行为中的作用。

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摘要

Although the performance of Li-ion batteries has improved dramatically in last ten years, Li-ion batteries cannot be directly used in hybrid-electric vehicles and electric vehicles, as they are limited by low pulse power, abuse tolerance, calendar and cycle life, and high cost. In this context, the newly-developed phase transformation cathode materials such as LiFePO4 make the Li-ion batteries, a promising candidate for vehicular applications, as LiFePO 4 exhibits high power density, high electrochemical and thermal stability, and relative inexpensive and less toxic nature compared to conventional insertion electrodes. However, the commercial applications of LiFePO4 in Li-ion batteries were limited due to its poor rate capability. In order to improve the rate capability of LiFePO4 cathode materials or to develop new phase transformation electrode materials with high rate capability, it is essential to understand the electrochemical kinetics and rate-controlling mechanisms involved in the charge/discharge process. To date, the shrinking core model (SCM) is the only mathematical model available in the literature, that is applicable to phase transformation electrodes. Currently, LiFePO 4 is available from different manufacturers and all of them exhibit different rate capabilities. The difference in rate capabilities of these samples cannot be explained by the shrinking core model. Also a large discrepancy can be observed between the experimental discharge curves and discharge curves obtained from shrinking core model.;In this doctoral dissertation, the reasons for the discrepancy between experimental results and the results obtained from shrinking core model are identified by experimental techniques and mathematical modeling. From these results, it is found that the diffusion is not the only controlling mechanism for the discharge process of LiFePO4 and the discrepancy between the experimental and SCM results is due to the assumptions used in the SCM. Based on these results and also by assuming that the discharge process is controlled by both diffusion and rate of phase transformation, the shrinking core model is modified. The modified SCM is validated by predicting the discharge behavior of three commercially-available LiFePO4 samples. Using the modified shrinking core model as a tool, the effects of chemical diffusion, rate of phase transformation, solid solution range, volume change, and particle size on discharge rate capability of LiFePO4 are determined. The modified SCM developed in this contribution is applicable to any phase transformation electrode such as Li4Ti5O12 in Li-ion battery and metal hydride electrode in Nickel metal hydride battery, thus making it a useful tool for practitioners in the field.
机译：尽管近十年来锂离子电池的性能有了显着提高，但是锂离子电池由于其低脉冲功率，耐滥用性，日历和循环寿命而受到限制，因此不能直接用于混合动力汽车和电动汽车。和高成本。在这种情况下，由于LiFePO 4具有高功率密度，高电化学和热稳定性以及相对便宜和低毒性的特性，因此新开发的相变阴极材料（例如LiFePO4）使锂离子电池成为车载应用的有希望的候选者。与传统的插入电极相比。但是，LiFePO 4在锂离子电池中的商业应用由于其差的速率能力而受到限制。为了提高LiFePO4正极材料的倍率能力或开发具有高倍率能力的新型相变电极材料，必须了解充电/放电过程中涉及的电化学动力学和倍率控制机制。迄今为止，收缩芯模型（SCM）是文献中唯一可用的数学模型，适用于相变电极。当前，LiFePO 4可从不同的制造商处获得，并且它们都具有不同的速率功能。这些样本在速率能力上的差异无法通过缩小的核心模型来解释。实验放电曲线与收缩核心模型获得的放电曲线之间也存在较大差异。本博士论文通过实验技术和数学方法确定了实验结果与收缩核心模型获得的结果之间存在差异的原因。造型。从这些结果中发现，扩散不是LiFePO4放电过程的唯一控制机制，并且实验结果和SCM结果之间的差异是由于SCM中使用的假设造成的。基于这些结果，并还假设放电过程受扩散和相变速率的控制，对收缩核模型进行了修改。通过预测三种市售的LiFePO4样品的放电行为，可以验证改进的SCM。使用改进的收缩核模型作为工具，确定了化学扩散，相变速率，固溶范围，体积变化和粒径对LiFePO4放电速率能力的影响。此贡献开发的改进型SCM适用于任何相变电极，例如锂离子电池中的Li4Ti5O12和镍金属氢化物电池中的金属氢化物电极，因此使其成为本领域从业人员的有用工具。

著录项

  • 作者

    Kasavajjula, Uday S.;

  • 作者单位

    Tennessee Technological University.;

  • 授予单位 Tennessee Technological University.;
  • 学科 Engineering Chemical.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 182 p.
  • 总页数 182
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 化工过程（物理过程及物理化学过程）;
  • 关键词

  • 入库时间 2022-08-17 11:38:29

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