Electrochemical Cycling of Sodium-Filled Silicon Clathrate
Electrochemical Cycling of Sodium-Filled Silicon Clathrate
复制标题
钠填充硅笼形物的电化学循环
DOI：
10.1002/celc.201300104
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发表时间：
2014
期刊：
影响因子：
4
通讯作者：
Chan, Candace K.
中科院分区：
文献类型：
--
作者：
Wagner, Nicholas A.;Raghavan, Rahul;Zhao, Ran;Wei, Qun;Peng, Xihong;Chan, Candace K.
由于其高电荷存储容量（即> 3000 mA hg/m2），在高能量密度锂离子电池的硅基阳极开发方面有很多研究活动。近年来，人们对理解金刚石立方（c-Si）和非晶硅（a-Si）在与锂反应下的电化学、[1，2]结构、[3-5]和机械性质[6-8]产生了极大的兴趣。最近研究了笼形或笼状结构的硅作为潜在阳极，Langer等人进行了理论[9]和实验验证。[10]锂化可行。由于先前对硅笼形物的研究主要集中在其超导[11-18]和热电[19-24]特性上，因此这是这类材料的潜在新的和令人兴奋的应用。M8 Si 46形式的I型包合物，其中M是插入结构中的客体原子，每个晶胞由两个五边形十二面体（Si 20）笼和六个四面体（Si 24笼）组成，并在Pm 3 n空间群中结晶（图1a）。MxSi 136（0< x< 24）的II型笼形物[25]，每个晶胞由16个五边形十二面体和8个六边形十二面体（Si 28笼）组成，并在Fd 3 m空间群中结晶（图1b）。详细的X射线衍射（XRD）和核磁共振（NMR）研究锂化过程，得到几乎无客体的II型包合物Na 1。3Si 136 [10]表明，笼形结构可以保持，直到每个分子式单元插入24个Li。在插入更多的Li时，笼形物结构变成非晶的并且最终转变成结晶的Li 15 Si 4（c-Li 15 Si 4），非常像在c-Si的锂化期间观察到的。然而，在该先前的工作中没有显示脱锂行为，并且没有显示延长的循环数据。为此，我们对钠填充硅包合物进行了扩展的电化学，结构和理论研究，以更好地了解其作为锂离子电池阳极的性能。以Zintl相NaSi为原料，通过热分解制备了钠填充硅笼形物。[26-28]本品的XRD图谱
Due to their high charge-storage capacity(ie> 3000 mA hg À1), there has been much research activity in the development of silicon-based anodes for high-energy-density lithium-ion batteries. In recent years, there has been immense interest in understanding the electrochemical,[1, 2] structural,[3–5] and mechanical properties [6–8] of both diamond cubic (c-Si) and amorphous silicon (a-Si) under reaction with lithium. Silicon with a clathrate or cage-like structure has been recently investigated as a potential anode, with both theoretical [9] and experimental verification by Langer et al.[10] that lithiation is feasible. Since prior studies on silicon clathrates have focused predominately on their superconducting [11–18] and thermoelectric [19–24] properties, this is a potentially new and exciting application for this class of materials. Type-I clathrates of the form M8Si46, where M is a guest atom intercalated into the structure, are made of two pentagonal dodecahedra (Si20) cages and six tetrakaidecahedra (Si24 cages) per unit cell and crystallize in the Pm 3n space group (Figure 1a). Type-II clathrates [25] of the form MxSi136 (0< x< 24), are made of sixteen pentagonal dodecahedra plus eight hexakaidecahedra (Si28 cages) per unit cell and crystallize in the Fd 3m space group (Figure 1b). Detailed X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) studies of the lithiation process into practically guest free type-II clathrate Na1. 3Si136 [10] showed that the clathrate structure could be maintained until insertion of 24 Li per formula unit. Upon insertion of more Li, the clathrate structure became amorphous and eventually transformed into crystalline Li15Si4 (c-Li15Si4), much like is observed during lithiation of c-Si. However, no delithiation behavior was shown in this previous work, and no extended cycling data were shown. To this end, we have conducted an extended electrochemical, structural, and theoretical study of sodium-filled silicon clathrate to better understand its properties as an anode for lithium-ion batteries. Sodium-filled silicon clathrate was synthesized from the decomposition of Zintl phase NaSi.[26–28] XRD patterns of the as-