Bublil Shaul, Sharabani Tali, Turgeman Meital, Grinblat Judith, Elias Yuval, Noked Malachi, Greenstein Miryam Fayena, Aurbach Doron
Chemistry Department, Bar Ilan Institute for Nanotechnology and Advanced Materials , Bar-Ilan University , Ramat-Gan 5290002 , Israel.
Langmuir. 2019 Sep 10;35(36):11670-11678. doi: 10.1021/acs.langmuir.9b02141. Epub 2019 Aug 30.
Disordered carbons are promising anode materials for sodium ion batteries. However, a major drawback of these materials is their low coulombic efficiency in the first cycles, which indicates parasitic reactions. Such reactions can be suppressed by alumina coating on the surface of the anodic materials; more ions are then available for electrochemical activity, and less electrolyte solution is lost. On the other hand, some pores and surface edge sites are passivated by the coating and are no longer available for reversible reaction with sodium ions; hence, their contribution is eliminated, leading to reduction in specific capacity. We show herein that electrochemical insertion of sodium ions into carbon anodes prior to alumina coating has a double positive effect on anode perfomances, meaning preventing passivation and maintaining high specific capacity. We show that the artificial layer still prevented parasitic reactions, while the pores and surface edge sites retained electrochemical activity. The capacity values were thus restored and even became higher as a result of preventing the development of a surface layer. Ultraviolet photoelectron spectroscopy measurements assessed the energetic states of the electrodes and confirmed that the alumina coating forms a barrier for interfacial electron transfer from the electrode to the solution at any polarization stage.
无序碳是钠离子电池很有前景的负极材料。然而，这些材料的一个主要缺点是其在首个循环中的库仑效率较低，这表明存在寄生反应。这种反应可通过在负极材料表面包覆氧化铝来抑制；这样一来，更多离子可用于电化学反应，且电解液损失更少。另一方面，一些孔隙和表面边缘位点会被涂层钝化，不再能与钠离子发生可逆反应；因此，它们的贡献被消除，导致比容量降低。我们在此表明，在包覆氧化铝之前将钠离子电化学插入碳负极对负极性能有双重积极作用，即防止钝化并保持高比容量。我们发现人工层仍能防止寄生反应，而孔隙和表面边缘位点保留了电化学反应活性。由于防止了表面层的形成，容量值因此得以恢复甚至变得更高。紫外光电子能谱测量评估了电极的能态，并证实氧化铝涂层在任何极化阶段都形成了从电极到溶液的界面电子转移屏障。
