β-SnSb for Sodium Ion Battery Anodes: Phase Transformations Responsible for Enhanced Cycling Stability Revealed by In Situ TEM,ACS Energy Letters

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β-SnSb for Sodium Ion Battery Anodes: Phase Transformations Responsible for Enhanced Cycling Stability Revealed by In Situ TEM
ACS Energy Letters ( IF 19.3 ) Pub Date : 2018-06-19 00:00:00 , DOI: 10.1021/acsenergylett.8b00762
Hezhen Xie _{1,

2} , Xuehai Tan ₃ , Erik J. Luber _{1,

2} , Brian C. Olsen _{1,

2} , W. Peter Kalisvaart _{1,

2} , Katherine L. Jungjohann ₄ , David Mitlin ₅ , Jillian M. Buriak _{1,

2}

Affiliation

β-SnSb is known to be a highly stable anode for sodium ion batteries during cycling, but its sodiation–desodiation alloying reactions are poorly understood. Combining in situ TEM with electroanalytical methods, we demonstrate that β-SnSb forms Na₃Sb and Na₁₅Sn₄ in sequence upon sodiation and re-forms as β-SnSb upon desodiation. The negative enthalpy of mixing for Sn and Sb is sufficient to cause sequentially deposited bilayers of Sn/Sb to transform into β-SnSb, resulting in comparable cycling stability. The good cycling stability of β-SnSb results from the complex two-phase amorphous–nanocrystalline microstructure in the partially charged–discharged states, as well as the intrinsic mechanical toughness of the β phase. Per the in situ TEM results, the sequential phase transformation shows minimal fracturing of the β-SnSb, indicating facile buffering of stresses. Extensively cycled specimens eventually show crystalline Sn phase segregation, which may be the source of the ultimate capacity fade in the alloy and bilayers.

中文翻译：

用于钠离子电池阳极的β-SnSb：通过原位TEM揭示了增强循环稳定性的相变

众所周知，β-SnSb是钠离子电池在循环过程中高度稳定的阳极，但其对钠盐-钠盐的合金化反应知之甚少。将原位TEM与电分析方法相结合，我们证明β-SnSb形成Na ₃ Sb和Na ₁₅ Sn ₄在糖化过程中顺序排列，在糖化过程中重新形成β-SnSb。Sn和Sb的混合负焓足以引起顺序沉积的Sn / Sb双层转变为β-SnSb，从而具有相当的循环稳定性。β-SnSb的良好循环稳定性来自于部分充放电状态下复杂的两相非晶-纳米晶体微观结构以及β相的固有机械韧性。根据原位TEM结果，顺序相变显示β-SnSb的断裂最小，表明应力的缓冲很容易。大量循环的样本最终显示出结晶的Sn相偏析，这可能是合金和双层中最终容量衰减的来源。

更新日期：2018-06-19

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