Theoretical Study of the Structural Evolution of a Na2FeMn(CN)6 Cathode upon Na Intercalation
Theoretical Study of the Structural Evolution of a Na2FeMn(CN)6 Cathode upon Na Intercalation
复制标题
DOI：
10.1021/acs.chemmater.5b01132
复制
发表时间：
2015-05-26
影响因子：
8.6
通讯作者：
Henkelman, Graeme
中科院分区：
文献类型：
--
作者：
Xiao, Penghao;Song, Jie;Henkelman, Graeme
普鲁士蓝类似物NaxFeMn（CN）（6）是一种潜在的新型钠离子电池正极材料。在Na嵌入过程中，脱水材料表现出单斜晶系到菱面体的相变，而水合材料保持在单斜晶系相。通过密度泛函理论计算，我们用库仑吸引力、泡利排斥力和d-pi共价键之间的竞争来解释相变。间隙Na阳离子对主体材料中的N阴离子具有强的库仑吸引力，这倾向于使Mn-N键弯曲并减小结构的体积。晶格H2O的存在增强了泡利排斥，从而抑制了体积减小。计算的体积变化，因为它取决于晶格H2O的存在下，是与实验测量相一致。此外，预测了新的LiFeMn（CN）（6）相，其中MnN 6八面体分解成LiN 4和MnN 4共边四面体。
The Prussian Blue analog, NaxFeMn(CN)(6), is a potential new cathode material for Na-ion batteries. During Na intercalation, the dehydrated material exhibits a monoclinic to rhombohedral phase transition, while the hydrated material remains in the monoclinic phase. With density functional theory calculations, the phase transition is explained in terms of a competition between Coulomb attraction, Pauli repulsion, and d-pi covalent bonding. The interstitial Na cations have a strong Coulomb attraction to the N anions in the host material, which tend to bend the Mn-N bonds and reduce the volume of the structure. The presence of lattice H2O enhances the Pauli repulsion so that the volume reduction is suppressed. The calculated volume change, as it depends upon the presence of lattice H2O, is consistent with experimental measurements. Additionally, a new LiFeMn(CN)(6) phase is predicted where MnN6 octahedra decompose into LiN4 and MnN4 edge-sharing tetrahedra.