Understanding the Mechanism of Stress Mitigation in Selenium-Doped Germanium Electrodes
Understanding the Mechanism of Stress Mitigation in Selenium-Doped Germanium Electrodes
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DOI：
10.1149/2.1091902jes
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发表时间：
2019-10
影响因子：
3.9
通讯作者：
X. Wang;C. Yenusah;K. Tantratian;M. Meyerson;A. Guo;C. Mullins;L. Zhu;L. Chen
中科院分区：
文献类型：
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作者：
X. Wang;C. Yenusah;K. Tantratian;M. Meyerson;A. Guo;C. Mullins;L. Zhu;L. Chen
本文旨在研究微米级(μm)硒(Se)掺杂锗(Ge)电极的应力缓解机理，该电极包括包裹多个纳米晶Ge(c-Ge)颗粒的自形成的非活性Li-Ge-Se网络。考虑到电极体系中含有多个活性粒子，基于单粒子的模型不能完全理解难以捉摸的托换机理。因此，采用相场模型研究了Li-Ge-Se网络对粒子-粒子相互作用的影响，以及电极的应力变化对锂离子的影响。非晶态Li-Ge-Se网络为颗粒间扩散提供了有效的Li扩散路径，减小了相邻颗粒表面之间的应力差。此外，相邻粒子之间的约束在反应前沿产生了较高的压应力，阻碍了锂离子在锂离子中的移动插入。Ge 0.9Se 0.1微米颗粒中的c-Ge纳米颗粒虽然被锂化得很快，但在其中心处产生了压应力，以达到应力平衡，产生更大的迟滞效应。同时，相邻颗粒之间的尺寸差异增加了非活性Li-Ge-Se中的主应力和剪应力，这可能导致非晶态网络的机械破坏和脱粘。我们相信，这一研究结果可以为电极的优化设计提供一些启示。
This paper aims to investigate the mechanism of stress mitigation in micrometer (μm) sized Selenium (Se)-doped Germanium (Ge) electrode, which includes a self-forming inactive Li-Ge-Se network enveloping multiple nanometer-sized crystalline Ge (c-Ge) particles. Considering the electrode system contains multiply active particles, models based on single-particle are unable to fully understand elusive underpinning mechanism. Hence, a phase-field model is employed to investigate the effect of the Li-Ge-Se network on the particle-particle interaction, and the stress variation of the electrode upon lithiation. The amorphous Li-Ge-Se network provides an effective Li diffusion path for inter-particle diffusion, reducing stress difference between the surfaces of neighboring particles. Furthermore, the constraint between the adjacent particles induces a higher compressive stress at the reaction front impeding the mobile Li insertion during lithiation. Though small c-Ge nano-particle in the Ge 0.9 Se 0.1 microparticle is lithiated quickly, the compressive stress is generated at its center for stress equilibrim causing more retardation effect. Meanwhile, the size difference between adjacent particles increases the principle and shear stresses in the inactive Li-Ge-Se, which could potentially lead to mechanical failure and debonding of the amorphous network. We believe that the results of this investigation can shed some light on the optimization design of electrodes.