Keywords: 
• LiMn204 /
• A1掺杂 /
• 电子结构 /
• 第一原理计算

Abstract: The structural and electronic properties of spinel LiMn204 and its A1 doping system LiAlo.125Mnl.s75Oa are investigated within the density functional theory in both the generalized gradient approximation (GGA) and the GGA with Hubbard U correc- tion (GGA+U). The results from the GGA method suggest that LiMn204 has a cubic structure and the valences of Mn ions are all +3.5, which is unable to explain the John-Teller distortions in the material. The band structure of LiMn204 predicted by the GGA method is also inconsistent with experimental result. With the GGA+U method, the low temperature structures of LiMn204 and its A1 doping system LiAlo.125Mnl.s7504 are shown to be orthogonal, the two different valence states of Mn, i.e., Mn3+/Mn4+ ions, are then determined, which is then able to explain the John-Teller distortion in octahedron Mna+O6 and the non-existence of distortion in octohedron Mn4+O6. These results are in good accordance with experimental data. Their band structures by GGA+U calculations are also consistent with experimental results. The GGA+U calculations on the LiAlo.125Mnl.s7504 indicate that with the replacement of an Mn by A1, the crystal structure and electronic properties are not significantly changed, but the John-Teller distortion in octahe- dron A13+O~ can be effectively eliminated, which could improve the performance of the anode materials based on LiMn204. The phenomenon is in consistent with the electrochemical experiments.