Germanium as a Sodium Ion Battery Material: In Situ TEM Reveals Fast Sodiation Kinetics with High Capacity
Germanium as a Sodium Ion Battery Material: In Situ TEM Reveals Fast Sodiation Kinetics with High Capacity
复制标题
DOI：
10.1021/acs.chemmater.6b00200
复制
发表时间：
2016-02-23
影响因子：
8.6
通讯作者：
Korgel, Brian A.
中科院分区：
文献类型：
--
作者：
Lu, Xiaotang;Adkins, Emily R.;Korgel, Brian A.
大量的研究正在进行，以创造超越锂离子电池的能量存储概念，并利用替代离子，如Na， Ca或Mg，仅举几例。这是一个挑战，因为能很好地储存锂的材料不一定能储存其他离子。晶体锗（Ge）就是这样一个例子：Li可以很容易地插入和提取，但Na却不能。然而，通过初始锂化步骤非晶化晶体锗纳米线，锗可以容易地和可逆地固化。在这里，我们使用实时原位透射电子显微镜（TEM）研究了锗纳米线中发生的钠化和脱钠过程。非晶锗（a- ge）纳米线在钠化作用下体积膨胀300%，相当于Na1.6Ge，这表明其存储Na的能力高于预期，即与NaGe相比。当纳米线脱水时，它们会形成孔隙。当纳米线再次凝固时，孔隙消失。纳米线在几个循环过程中保持其结构完整性。这些结果表明，a-Ge在钠离子电池中的应用潜力以前可能被低估了，而且，更普遍的是，对于一种类型的离子存储来说，电极材料可能看起来是惰性的，而通过预插入其他活性离子，电极材料可能会成为可能。
A significant amount of research is taking place to create energy storage concepts beyond the lithium ion battery and to utilize alternative ions, such as Na, Ca, or Mg, to name a few. This has been a challenge, as materials that work well to store lithium do not necessarily function for other ions. Crystalline germanium (Ge) represents such an example: Li can be readily inserted and extracted but not Na. However, by amorphizing the crystalline Ge nanowires with an initial lithiation step, Ge can be readily and reversibly sodiated. Here, we examine the sodiation and desodiation processes that occur in Ge nanowires using real-time in situ transmission electron microscopy (TEM). Amorphous germanium (a-Ge) nanowires exhibit a 300% expansion in volume upon sodiation, which corresponds approximately to Na1.6Ge, which indicates a higher than expected capacity to store Na, i.e., compared to NaGe. When the nanowires desodiate they form pores. The pores disappear when the nanowire is again sodiated. The nanowires retain their structural integrity over the course of several cycles. These results show that the potential of a-Ge for Na-ion battery applications may have been previously underestimated, and, more generally, electrode materials that might appear to be inert for one type of ion storage might be enabled by preinsertion of other active ions.