Capturing metastable structures during high-rate cycling of LiFePO4 nanoparticle electrodes
Capturing metastable structures during high-rate cycling of LiFePO4 nanoparticle electrodes
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DOI：
10.1126/science.1252817
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发表时间：
2014-06-27
期刊：
影响因子：
56.9
通讯作者：
Grey, Clare P.
中科院分区：
文献类型：
--
作者：
Liu, Hao;Strobridge, Fiona C.;Grey, Clare P.
不存在涉及大量结构重排和大体积变化的相变通常被认为是支撑任何电池电极材料高倍率能力的关键特征。在明显的矛盾，纳米颗粒LiFePO4，商业上重要的阴极材料，显示异常高的速率，而其锂组成相图表明，它应该通过动力学限制，两相成核和生长过程反应。因此，有关平衡相的知识是不够的，需要直接研究动态过程。利用时间分辨原位X射线粉末衍射，我们揭示了在快速锂提取和插入过程中存在连续的亚稳固溶体相。这种非平衡易相变路线提供了一种机制，用于实现高速率的能力，通过两相反应操作的电极材料。
The absence of a phase transformation involving substantial structural rearrangements and large volume changes is generally considered to be a key characteristic underpinning the high-rate capability of any battery electrode material. In apparent contradiction, nanoparticulate LiFePO4, a commercially important cathode material, displays exceptionally high rates, whereas its lithium-composition phase diagram indicates that it should react via a kinetically limited, two-phase nucleation and growth process. Knowledge concerning the equilibrium phases is therefore insufficient, and direct investigation of the dynamic process is required. Using time-resolved in situ x-ray powder diffraction, we reveal the existence of a continuous metastable solid solution phase during rapid lithium extraction and insertion. This nonequilibrium facile phase transformation route provides a mechanism for realizing high-rate capability of electrode materials that operate via two-phase reactions.