A phase-field model integrating reaction-diffusion kinetics and elasto-plastic deformation with application to lithiated selenium-doped germanium electrodes
A phase-field model integrating reaction-diffusion kinetics and elasto-plastic deformation with application to lithiated selenium-doped germanium electrodes
复制标题
反应扩散动力学和弹塑性变形相场模型及其在锂化掺硒锗电极中的应用
DOI：
10.1016/j.ijmecsci.2018.05.040
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发表时间：
2018-08
影响因子：
7.3
通讯作者：
X. Wang;Bing Wang;M. Meyerson;C. Mullins;Yongzhu Fu;Likun Zhu;Lei Chen
中科院分区：
文献类型：
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作者：
X. Wang;Bing Wang;M. Meyerson;C. Mullins;Yongzhu Fu;Likun Zhu;Lei Chen
最近的实验表明，形成非活性相（Li-Ge-Se）网络的微米（μm）尺寸的硒（Se）掺杂的锗（Ge）颗粒在循环稳定性和容量方面比未掺杂的Ge颗粒具有上级性能。因此，基于两个状态的锂（一个扩散和另一个合金化反应），相场模型（PFM）的发展，包括化学反应和锂扩散研究其余难以捉摸的托换机制。反应-扩散PFM使我们能够直接确定锂化过程受扩散和/或反应控制的条件。此外，耦合的弹塑性变形，该模型允许我们调查的非活性相的形态和应力变化的掺硒锗电极锂化后的作用。数值计算结果表明，由于非活性Li-Ge-Se相的柔软性，颗粒表面的拉伸环向应力被显著抑制，这与实验观察到的表面无裂纹行为一致。此外，我们发现软Li-Ge-Se相降低了反应前沿的平均压应力，从而减轻了对锂化动力学的应力阻滞效应。
Recent experiments revealed micrometer (µm)-sized selenium (Se)-doped germanium (Ge) particles forming a network of inactive phase (Li–Ge–Se) bring superior performance in cycling stability and capacity over un-doped Ge particles. Therefore, based on two states of Li (one for diffusion and another for alloyed reaction), a phase-field model (PFM) is developed incorporating both chemical reaction and Li diffusion to investigate remaining elusive underpinning mechanism. The reaction-diffusion PFM enables us to directly determine the conditions under which the lithiation process is diffusion- and/or reaction-controlled. Moreover, coupling the elasto-plastic deformation, the model allows us to investigate the role of the inactive phase in morphology and stress variation of Se-doped Ge electrode upon lithiation. The numerical results reveal that the tensile hoop stress at the surface of the particles is significantly suppressed due to softness of the inactive Li–Ge–Se phase, in line with the experimental observation of surface fracture-free behavior. Further, we find that the soft Li–Ge–Se phase reduces a compressive mean stress at the reaction front, thus alleviating the stress retardation effect on the lithiation kinetics.