First-Principles Studies on the Structural and Electronic Properties of α-Na2FePO4F with Strong Antisite Disorder,Inorganic Chemistry

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First-Principles Studies on the Structural and Electronic Properties of α-Na2FePO4F with Strong Antisite Disorder
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2023-09-07 , DOI: 10.1021/acs.inorgchem.3c02546
Jingjin Chen ₁ , Li-Hong Zhang ₁ , Zhishuo Li ₁ , Binpeng Hou ₁ , Xiaowen Shi ₂ , Zizhong Zhu _{1,

3}

Affiliation

Polyanionic Na₂FePO₄F is one of the most important cathode materials for sodium-ion batteries. The orthorhombic β-Na₂FePO₄F material has been studied extensively and intensively since it was proposed. In this article, a novel monoclinic sodium phosphate fluoride α-Na₂FePO₄F is concerned. Kirsanova’s experiment showed that Na and Fe ions in α-Na₂FePO₄F are prone to antisite, leading to strong antisite disorder. Through first-principle calculations, we show that the steric effect, the magnetic exchange and superexchange interactions between transition-metal cations are shown to be the main driving forces for Na⁺/Fe²⁺ antisite disorder. We first calculated the crystal structures, electronic properties, and cohesive energies of all the 10 antisite phases of α-Na₂FePO₄F and β-Na₂FePO₄F. Then, we compared the difference charge densities, magnetism, binding energies, and electrostatic potentials of α-Na₂FePO₄F and β-Na₂FePO₄F materials in the antisite and pristine phases. In α-Na₂FePO₄F, the binding energy of the antisite phase with the lowest binding energy is almost degenerate with that of the pristine phase. Moreover, only small differences of the electrostatic potential and the charge density distribution are found between the antisite (with lowest energy) and the pristine phases of α-Na₂FePO₄F, which also helped elaborate the facile formation of Na⁺/Fe²⁺ antisite in the α-Na₂FePO₄F material. Our research contributes to the understanding of the mechanism of Na⁺/Fe²⁺ antisite and the development of high-performance polyanionic cathode materials.

中文翻译：

强反位无序α-Na2FePO4F结构和电子性质的第一性原理研究

聚阴离子Na ₂ FePO ₄ F是钠离子电池最重要的正极材料之一。斜方晶系β-Na ₂ FePO ₄ F材料自提出以来得到了广泛而深入的研究。本文研究了一种新型单斜氟化磷酸钠α-Na ₂ FePO _{4 F。}Kirsanova的实验表明，α-Na ₂ FePO ₄ F中的Na和Fe离子容易发生反位，导致强反位无序。通过第一性原理计算，我们发现过渡金属阳离子之间的空间效应、磁交换和超交换相互作用是Na + /Fe 2+ 反位无序的^主要驱动^力。_{我们首先计算了α-Na 2} FePO ₄ F和β-Na ₂ FePO ₄ F的所有10个反位相的晶体结构、电子性质和内聚能。然后，我们比较了不同的电荷密度、磁性、结合能， α-Na ₂ FePO ₄ F 和 β-Na ₂ FePO ₄ F 材料在反位相和原始相的静电势。在α-Na ₂ FePO ₄ F中，结合能最低的反位相的结合能几乎与原始相的结合能简并。_{此外，在α-Na 2} FePO ₄ F的反位（能量最低）和原始相之间仅发现静电势和电荷密度分布的微小差异，这也有助于阐明Na ⁺ /Fe ^{2的容易形成+} α-Na ₂ FePO ₄ F 材料中的反位。^{我们的研究有助于理解Na +} /Fe ²⁺反位点机理以及高性能聚阴离子正极材料的开发。

更新日期：2023-09-07

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