Acta Chimica Sinica ›› 2021, Vol. 79 ›› Issue (8): 1058-1064.DOI: 10.6023/A21050213 Previous Articles     Next Articles

Article

LiMn2O4尖晶石氧化物的低指数表面结构优化及表面能的第一性原理研究

陆远1,2, 王继芬1,2,*(), 谢华清1,2   

  1. 上海第二工业大学理学院 上海先进热功能材料工程技术研究中心 上海 201209
  • 投稿日期:2021-05-14 发布日期:2021-06-02
  • 通讯作者: 王继芬
  • 基金资助:
    国家自然科学基金(51776116); 国家自然科学基金重大项目(51590902)

First-principles Study on Low Index Surface Structure Optimization and Surface Energy of LiMn2O4 Spinel Oxides

Yuan Lu1,2, Jifen Wang1,2(), Huaqing Xie1,2   

  1. School of Sciences, Shanghai Polytechnic University; Shanghai Engineering Research Center of Advanced Thermal Functional Materials, Shanghai 201209, China
  • Received:2021-05-14 Published:2021-06-02
  • Contact: Jifen Wang
  • Supported by:
    National Natural Science Foundation of China(51776116); Major Project of National Natural Science Foundation of China(51590902)

The first principles density functional calculation method was used to calculate the index of low surface properties of LiMn2O4 spinel. Comparing with the bulk phase structures of LiMn2O4 crystals calculated by generalized gradient approximation (GGA) and generalized gradient approximation+on-site coulombic (GGA+U), it is found that the lattice parameters are obviously larger when the effective U value for the d orbital of Mn. However, the structural parameters of charge order and Jahn-Teller distortion are not found in own calculation. The results show that the Li terminal surface energy is lower when the (001), (010) and (100) surfaces of LiMn2O4 spinel in the state of lacking Li. The surface energy of (110) Mn/O terminal is lower than that of Li/Mn/O terminal in the state of lacking Li. The surface energy of (111) is the lowest in the low index surfaces. The surface energy of (111) after surface reconstruction is as low as 0.270 J/m2, which is the most stable section of spinel structure in this work. Considering antiferromagnetism, the surface energies of Mn/O terminal on (110) surface are lower than those of Li/Mn/O terminal, which Mn/O terminal surface energies are 1.050 J/m2 in the [↑↑↓↓] magnetic order and 1.061 J/m2 in [↑↓↑↓] magnetic order, respectively. The antiferromagnetic (110) surface is more stable in the spin configuration than in the magnetic order. We found that the structure of undercoordinated manganese ions on the surface are more stable by position exchange with the fully coordinated lithium ions by the observation of the surface reconstruction of (111). The Jahn-Teller effect is reduced when the average manganese oxidation state of the reconstructed surface is reduced. Except for (111) surface, the surface energies of other surfaces in the ferromagnetic state are similar to those in the antiferromagnetic state. Among them, the surface structures of (001)T3, (100)T1, (110)T1 and (111)T2 have the least surface energy among their own different surface terminals. This study provides theoretical calculation reference for understanding the capacity attenuation problem of LiMn2O4 materials and related experiments. It is also helpful to promote the research of high-performance lithium battery materials.

Key words: LiMn2O4 spinel oxide, first principle, Jahn-Teller effect, low exponent surface, surface reconstruction