第一性原理研究:Mg2+掺杂尖晶石型LiMn2O4的电子结构

尖晶石 LiMn₂O₄ 正极材料是在原有锂电池正极材料 LiCoO₂ 、LiNiO₂ 、LiMnO₂ 的基础上研发出来的优选 正极材料, 它相较于 LiCoO₂ 材料价格更加低廉热稳定性加强且安全性能有所提高。采用 Mg²⁺ 掺杂 LiMn₂O₄正极 材料, 利用基于密度泛函理论的第一性原理对 LiMg_0.5Mn_1.5O₄ 晶格常数与能带结构、态密度进行计算与分析。结 果表明: 新材料 LiMg_0.5Mn_1.5O₄ 的空间群为 F4332, 掺杂后晶胞参数 a 明显减小, 晶胞体积收缩; 掺杂量为 0.5 时明 显比掺杂量 0.125 时 Fermi 能量和能量密度高。Mg ²⁺ 掺杂能影响 LiMn₂O₄ 的晶体结构, 形成更加稳定的共价键。 掺杂量会改变 LiMn₂O₄ 的空间群影响到结构稳定性, 所以掺杂量不宜过大。

First-Principles Study: the Electron Structure of Mg 2+ Doped Spinel LiMn2O4

Spinel LiMn₂O₄ cathode material is a preferred cathode material developed on the basis of the original lithium battery cathode materialsLiCoO₂, LiNiO₂ and LiMnO₂. Compared with LiCoO₂ material, it has lower price, better thermal stability and better safety performance. Mg²⁺ doped LiMn₂O₄ anode material is used. Based on the first principle of density functional theory, the lattice constant, energy band structure and state density of LiMg_0.5Mn_1.5O₄ are calculated and analyzed. The results show that the space group of new material LiMg_0.5Mn_1.5O₄ is F4332. After doping, it is found that cell parameter a decreases and cell volume decreases. When the doping amount is 0.5, the Fermi energy and energy density are significantly higher than when the doping amount is 0.125. Mg²⁺ doping can affect the crystal structure of LiMn₂O₄ and form a more stable covalent bond. The doping amount change the spatial group of LiMn₂O₄ and affect the structural stability. So the amount of doping should not be too much.