The Impact of Initial SEI Formation Conditions on Strain‐Induced Capacity Losses in Silicon Electrodes
The Impact of Initial SEI Formation Conditions on Strain‐Induced Capacity Losses in Silicon Electrodes
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DOI：
10.1002/aenm.201803066
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发表时间：
2018-12
影响因子：
27.8
通讯作者：
W. Zhang;Truong H. Cai;B. Sheldon
中科院分区：
文献类型：
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作者：
W. Zhang;Truong H. Cai;B. Sheldon
钝化锂离子电池中硅表面的固体电解质中间相（SEI）在电化学循环过程中会受到极大的机械应变。由此产生的这些 SEI 膜的降解是限制硅基电极循环寿命的一个关键问题。由于传统多孔电极具有复杂的多相微观结构，无法直接测量这些应变对 SEI 形成和容量损失的影响。为了克服这一限制，提出了一种新的原位方法，用于在电化学循环过程中对 SEI 施加受控机械应变。这种方法使用具有不同尺寸岛的图案化硅膜作为模型电极颗粒。在锂化/脱锂过程中，岛边缘的横向膨胀/收缩以平面应变的形式施加到SEI。然后，对岛尺寸效应的详细分析提供了应变对不同电位范围内发生的过剩容量损失的影响的定量测量。一项重要发现是，施加的应变仅在锂化过程中（在所有循环期间）导致大量容量损失。此外，采用快速和慢速 SEI 形成（第一个循环）会导致后续循环期间发生的应变引起的损失存在很大差异。
The solid electrolyte interphase (SEI) that passivates silicon surfaces in Li ion batteries is subjected to extremely large mechanical strains during electrochemical cycling. The resulting degradation of these SEI films is a critical problem that limits the cycle life of silicon‐based electrodes. With the complex multiphase microstructure in conventional porous electrodes, it is not possible to directly measure the impact of these strains on SEI formation and capacity loss. To overcome this limitation a new in situ method is presented for applying controlled mechanical strains to SEI during electrochemical cycling. This approach uses patterned silicon films with different sized islands that act as model electrode particles. During lithiation/delithiation, the lateral expansion/contraction of the island edges applies in plane strains to the SEI. Detailed analysis of the island size effect then provides quantitative measurements of the impact of strain on the excess capacity losses that occur in different potential ranges. One key finding is that the applied strains lead to large capacity losses during lithiation only (during all cycles). Also, employing fast and slow SEI formation (first cycle) leads to large differences in the strain‐induced losses that occur during subsequent cycling.