Solid-State Electrochemical Synthesis of Silicon Clathrates Using a Sodium-Sulfur Battery Inspired Approach
Solid-State Electrochemical Synthesis of Silicon Clathrates Using a Sodium-Sulfur Battery Inspired Approach
复制标题
DOI：
10.1149/1945-7111/abdfe5
复制
发表时间：
2021-02-01
影响因子：
3.9
通讯作者：
Chan, Candace K.
中科院分区：
文献类型：
--
作者：
Dopilka, Andrew;Childs, Amanda;Chan, Candace K.
Tetrel元素（Si、Ge、Sn）的包合物由于其在电池和其它应用中的潜在用途而引起了人们的兴趣。钠填充的硅笼形物通常通过Zintl前体Na 4Si 4的热分解来合成，但是产物的相选择性通常难以实现。在此，我们报告了在450 ℃和550 ℃下使用电化学氧化选择性形成I型包合物Na 8 Si 46。采用受高温钠-硫电池启发的双电极电池设计，使用Na 4Si 4作为工作电极，Na β“-氧化铝固体电解质和由熔融Na或Sn组成的对电极。采用恒电流间歇滴定法研究了Na_4Si_4和Na_8Si_46的氧化特性，结果表明在准平衡条件下，Na_4Si_4和Na_8Si_46发生了两相反应。我们进一步证明，可以通过调节反应温度和Na蒸气压来改变产物的选择和形态。首次评价了合成的Na 8 Si 46的室温锂化，显示出与II型包合物Na 24 Si 136中的那些类似的电化学特性。结果表明，Zintl相在高温下的固态电化学氧化可以导致更多的控制晶体生长和更深入地了解金属间化合物的形成过程的机会。
Clathrates of Tetrel elements (Si, Ge, Sn) have attracted interest for their potential use in batteries and other applications. Sodium-filled silicon clathrates are conventionally synthesized through thermal decomposition of the Zintl precursor Na4Si4, but phase selectivity of the product is often difficult to achieve. Herein, we report the selective formation of the type I clathrate Na8Si46 using electrochemical oxidation at 450 degrees C and 550 degrees C. A two-electrode cell design inspired by high-temperature sodium-sulfur batteries is employed, using Na4Si4 as working electrode, Na beta ''-alumina solid electrolyte, and counter electrode consisting of molten Na or Sn. Galvanostatic intermittent titration is implemented to observe the oxidation characteristics and reveals a relatively constant cell potential under quasi-equilibrium conditions, indicating a two-phase reaction between Na4Si4 and Na8Si46. We further demonstrate that the product selection and morphology can be altered by tuning the reaction temperature and Na vapor pressure. Room temperature lithiation of the synthesized Na8Si46 is evaluated for the first time, showing similar electrochemical characteristics to those in the type II clathrate Na24Si136. The results show that solid-state electrochemical oxidation of Zintl phases at high temperatures can lead to opportunities for more controlled crystal growth and a deeper understanding of the formation processes of intermetallic clathrates.