钠离子电池正极材料MoF6的第一性原理研究
郑炎亭,郑 锋,吴顺情*

(厦门大学物理科学与技术学院,福建 厦门 361005)

键价力场; MoF6; 钠离子电池; 正极材料; 结构预测

First-principles Study of Na-ion Battery Cathode MoF6
ZHENG Yanting,ZHENG Feng,WU Shunqing*

(College of Physical Science and Technology,Xiamen University,Xiamen 361005,China)

bond valence-based force field; MoF6; Na-ion battery; cathode; structure prediction

DOI: 10.6043/j.issn.0438-0479.201703016

备注

基于键价力场模型构造相互作用势,勘探材料结构中势能曲面以寻找适合钠离子嵌入的空间位置; 并结合第一性原理进行计算,探究了MoF6材料在钠离子嵌入过程中的结构演变及其内在机制.预测了不同钠离子含量下NaxMoF6-Im-3m和NaxMoF6-Pnma的晶体结构,并研究了不同钠离子含量下的中间相稳定性; 通过分析键长和键角的变化,揭示MoF6八面体形变、钠含量及结构稳定性等方面的关系.研究结果表明,MoF6八面体扭曲程度对结构稳定性有明显影响,扭曲程度越低,结构的能量也越低,稳定性越好; MoF6在嵌钠过程中体积变化程度小于15%,电压高于2.9 V,表明其具有成为钠离子电池正极材料的潜力.

Based on the Bond Valence-based force field model,we construct the interaction potentials and explore the potential energy surfaces in the MoF6 structures to find the suitable intercalation positions for the sodium ions.Combined with the first-principles calculations,the structural evolution and the corresponding mechanism of the material during the sodiation process are investigated.In two different MoF6 experimental structures(Im-3m,Pnma),NaxMoF6 structures with different Na contents are predicted.The relationship between the formation energy,the voltage and the Na content x is studied.Results show that MoF6 octahedra have significant effects on the stability of the structure.The structure with lower distortion shows higher stabilities energetically.Considering the relatively small volume change during the intercalation process and high voltage,MoF6 material can be a potential cathode material for sodium ion batteries.The investigation on the intercalation process of polyvalent metal fluoride MoF6 will provide important insights for the experimental and theoretical researches of polyvalent metal fluoride as cathode material.