Fast sodium ionic conduction in Na2B10H10-Na2B12H12 pseudo-binary complex hydride and application to a bulk-type all-solid-state battery
Fast sodium ionic conduction in Na2B10H10-Na2B12H12 pseudo-binary complex hydride and application to a bulk-type all-solid-state battery
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DOI：
10.1063/1.4977885
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发表时间：
2017-03-06
影响因子：
4
通讯作者：
Orimo, Shin-ichi
中科院分区：
文献类型：
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作者：
Yoshida, Koji;Sato, Toyoto;Orimo, Shin-ichi
在本工作中，我们通过机械球磨纯Na2B10H10和Na2B12H12组分的混合物，制备了高钠离子导电性的Na2B10H10-Na2B12H12准二元络合物氢化物。这两种组分在室温下都表现为单斜相，但球磨混合物部分稳定了高离子导电性的无序立方相，其含量和有利的结构对称性(体心立方或面心立方)取决于机械球磨条件和组分化合物的摩尔比。第一性原理分子动力学模拟表明，密闭硼烷混合物和纯物质的总能量相当接近，这有助于解释观察到的混合化合物的稳定性。当Na2B10H10：Na2B12H12=1：3时，密闭硼烷混合物的离子电导率与体心立方相的比例有关，在摩尔比为1：3时出现最大值。在303K时，该摩尔比的电导率高达log(sigma/S cm(-1))=-3.5，比纯材料的电导率高出约2-3个数量级。采用密闭硼烷混合电解液、钠-金属负极和TiS2正电极的块状全固态钠离子电池具有较高的比容量，接近NaTiS2形成的理论值，且至少循环11次稳定放电/充电，第二次循环的高放电容量保持率超过91%。
In the present work, we developed highly sodium-ion conductive Na2B10H10-Na2B12H12 pseudobinary complex hydride via mechanically ball-milling admixtures of the pure Na2B10H10 and Na2B12H12 components. Both of these components show a monoclinic phase at room temperature, but ball-milled mixtures partially stabilized highly ion-conductive, disordered cubic phases, whose fraction and favored structural symmetry (body-centered cubic or face-centered cubic) depended on the conditions of mechanical ball-milling and molar ratio of the component compounds. First-principles molecular-dynamics simulations demonstrated that the total energy of the closo-borane mixtures and pure materials is quite close, helping to explain the observed stabilization of the mixed compounds. The ionic conductivity of the closo-borane mixtures appeared to be correlated with the fraction of the body-centered-cubic phase, exhibiting a maximum at a molar ratio of Na2B10H10:Na2B12H12 = 1:3. A conductivity as high as log(sigma/S cm(-1)) = -3.5 was observed for the above ratio at 303 K, being approximately 2-3 orders of magnitude higher than that of either pure material. A bulk-type all-solid-state sodium-ion battery with a closo-borane-mixture electrolyte, sodium-metal negative-electrode, and TiS2 positive-electrode demonstrated a high specific capacity, close to the theoretical value of NaTiS2 formation and a stable discharge/charge cycling for at least eleven cycles, with a high discharge capacity retention ratio above 91% from the second cycle.