Capturing the stress evolution in electrode materials that undergo phase transformations during electrochemical cycling
Capturing the stress evolution in electrode materials that undergo phase transformations during electrochemical cycling
复制标题
DOI：
10.1016/j.ijsolstr.2021.03.019
复制
发表时间：
2021-03
影响因子：
3.6
通讯作者：
Bo Wang;J. Réthoré;K. Aifantis
中科院分区：
文献类型：
--
作者：
Bo Wang;J. Réthoré;K. Aifantis
目前的工作揭示了在离子插入过程中经历相变的球形颗粒中产生的应力。为了解释电化学循环过程中发生的物理过程，所使用的模型是小变形模型，并考虑相变、化学机械耦合和浓度依赖性材料特性的影响。两相锂化通过 Cahn-Hilliard 方程进行建模。研究发现，DIS 是由锂浓度梯度引起的不均匀体积膨胀引起的，静水应力有利于锂离子在弹性变形下的扩散，而阻碍了塑料外壳中的扩散。当弹性模量减小时，扩散引起的应力的大小减小，但弹性变形下应变增加，而塑料情况则相反。此外，如果假设电极在塑性变形期间经历应变软化，则与假设应变硬化时相比，预计会出现更小的应力和更高的塑性应变。这项工作的新颖之处在于，所提出的模型强调了化学机械耦合效应、浓度依赖性材料特性和扩散引起的应力的塑性变形的重要性。这些发现为设计下一代机械稳定的相变电极材料提供了前瞻性的见解。
The present work sheds light on the stresses generated in a spherical particle subjected to phase transformations during ion-insertion. In order to account for the physical process that occurs during electrochemical cycling, the models used are those of small deformation and account for the effects of phase transformation, chemo-mechanical coupling and concentration-dependent material properties. The two-phase lithiation is modeled by the Cahn–Hilliard equation. It is found that the DISs arise from the inhomogeneous volume expansions resulting from Li concentration gradients and the hydrostatic stress facilitates the diffusion of Li-ions under elastic deformation while it hinders diffusion in the plastic case. When the elastic modulus is reduced the magnitude of the diffusion-induced stress decreases but the strain increases under elastic deformation whereas the opposite occurs for the plastic case. Furthermore, if the electrode is assumed to undergo strain softening during plastic deformation, smaller stresses and higher plastic strains are predicted than when strain hardening is assumed. The novelty of this work is that the proposed models highlight the importance of chemo-mechanical coupling effects, concentration-dependent material properties and plastic deformation on diffusion-induced stresses. These findings render prospective insights for designing next-generation mechanically stable phase transforming electrode materials.