Microstructural Evolution of Tin Nanoparticles during In Situ Sodium Insertion and Extraction

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• 作者：Jiang Wei Wang ; Xiao Hua Liu ; Scott X. Mao ; Jian Yu Huang
• 刊名：Nano Letters
• 出版年：2012
• 出版时间：November 14, 2012
• 年：2012
• 卷：12
• 期：11
• 页码：5897-5902
• 全文大小：403K
• 年卷期：v.12,no.11(November 14, 2012)
• ISSN：1530-6992

文摘

The microstructural changes and phase transformations of tin nanoparticles during electrochemical sodiation were studied with a nanosized sodium ion battery using in situ transmission electron microscopy. It was found that the first sodiation process occurred in two steps; that is, the crystalline Sn nanoparticles were initially sodiated via a two-phase mechanism with a migrating phase boundary to form a Na-poor, amorphous Na_xSn alloy (x 0.5), which was further sodiated to several Na-rich amorphous phases and finally to the crystallized Na₁₅Sn₄ (x = 3.75) via a single-phase mechanism. The volumetric expansion was about 60% in the first step and 420% after the second step. However, despite the huge expansion, cracking or fracture was not observed, which is attributed to the second step of the single-phase sodiation that accommodates large portion of the sodiation-induced stress over the entire particle. Excellent cyclability was also observed during the reversible sodiation/desodiation cycles, showing great potential of Sn nanoparticles as a robust electrode material for rechargeable batteries.

Keywords:

Tin nanoparticles; sodiation; amorphous Na_xSn alloy; Na₁₅Sn₄; sodium ion battery; in situ transmission electron microscopy