Abstract The capacity loss and cycling aging of lithium-ion batteries at high (dis)charging rate (C-rate) hinders the development of emerging technologies. To improve the performance of Li-ion batteries, it is important to understand the coupling effect of the mechanical behaviors and the electrochemical response of electrodes, as the capacity loss and cycling aging are related to the mechanics of electrodes during (dis)charging. Many studies have formulated the distribution of stress, strain and lithium-ion fraction of electrodes during lithiation/delithiation. However, few of them reported a self-consistent formulation that contains mechanical-diffusional-electrochemical coupling effects, solid viscosity, and diffusion-induced creep for an electrode with large deformation under non-equilibrium process. This paper considers the electrode of a Li-ion battery as a solid solution system. Based on continuum mechanics, non-equilibrium thermodynamics and variational theory, we develop a generalized theory to describe the variations of stress distribution, electrode material deformation and lithium-ion fractions of the solid solution system over a non-equilibrium process. The finite deformation, mass transfer, phase transformation, chemical reaction and electrical potential of the system are coupled with each other in a fully self-consistent formulation. We apply the developed theory to numerically simulate a Sn anode particle using the finite difference method. Our results compare the influences of different C-rates on the non-equilibrium process of the anode particle. Higher C-rate corresponds to stronger dissipation effects including faster plastic deformation, larger viscous stress, more polarization in the electrical potential, longer relaxation time and less electrical energy. With the formulation and simulation of the non-equilibrium process, this study refines our understanding of the mechanical-diffusional-electrochemical coupling effect in Li-ion batteries with high C-rate.

中文翻译：

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锂离子电池连续固溶系统非平衡过程建模与仿真

摘要 锂离子电池在高（放电）倍率（C-rate）下的容量损失和循环老化阻碍了新兴技术的发展。为了提高锂离子电池的性能，了解机械行为和电极电化学响应的耦合效应非常重要，因为容量损失和循环老化与（放电）过程中电极的力学有关。许多研究已经制定了锂化/脱锂过程中电极的应力、应变和锂离子分数的分布。然而，他们中很少有人报道了一种自洽公式，该公式包含机械-扩散-电化学耦合效应、固体粘度和非平衡过程下大变形电极的扩散诱导蠕变。本文将锂离子电池的电极视为固溶体系统。基于连续介质力学、非平衡热力学和变分理论，我们开发了一种广义理论来描述非平衡过程中固溶体系统的应力分布、电极材料变形和锂离子分数的变化。系统的有限变形、传质、相变、化学反应和电势以完全自洽的公式相互耦合。我们应用开发的理论使用有限差分方法对 Sn 阳极颗粒进行数值模拟。我们的结果比较了不同 C 速率对阳极颗粒非平衡过程的影响。更高的 C 率对应于更强的耗散效应，包括更快的塑性变形、更大的粘性应力、更多的电位极化、更长的弛豫时间和更少的电能。通过对非平衡过程的制定和模拟，本研究完善了我们对高 C 倍率锂离子电池中机械-扩散-电化学耦合效应的理解。