化学学报 ›› 2013, Vol. 71 ›› Issue (03): 405-408.DOI: 10.6023/A12100848 上一篇    下一篇

研究论文

MoO2储锂性能及循环容量反常特性的第一性原理研究

吉晓, 刘雅雯, 余晓伟, 杨凯, 吴江滨, 缪灵, 江建军   

  1. 华中科技大学 光学与电子信息学院 武汉 430074
  • 投稿日期:2012-10-31 发布日期:2013-01-16
  • 通讯作者: 缪灵 E-mail:miaoling@hust.edu.cn

First Principles Study on the Li Storage Performance of MoO2

Ji Xiao, Liu Yawen, Yu Xiaowei, Yang Kai, Wu Jiangbin, Miao Ling, Jiang Jianjun   

  1. School of Optical and Electronic Information, HuaZhong University of Science and Technology, Wuhan 430074
  • Received:2012-10-31 Published:2013-01-16

基于第一性原理, 对MoO2作为电极材料的储锂性能进行了计算, 并探讨了其储锂容量在一定循环次数内呈上升的反常现象微观机理. 计算了MoO2材料中Li的单键能, 态密度(DOS)及其嵌锂电压, 结果表明MoO2中Li的吸附能较大, 储锂结构稳定. 嵌锂结构呈金属性, 嵌锂电压变化规律与文献实验结果一致. 针对循环容量反常特性, 计算了Mo的空位形成能, LiMoO2的差分电荷密度以及电荷布居情况, 计算结果表明Li的嵌入能为O提供电荷, 减弱了Mo—O键间的相互作用, 另一方面嵌入的Li能减弱Mo空位形成后的电荷极化作用, 从而大大降低Mo空位的形成能. 形成的Mo空位能为Li的嵌入提供了新的吸附位点, 提高了嵌锂的容量. 计算结果与实验符合得很好, 能为电极材料储锂性能的改善提供一定的理论指导.

关键词: 第一性原理, 锂电池, MoO2, 循环容量

Based on first principle calculations, MoO2 as electrode for lithium storage performance was calculated, and explored the microscopic mechanism of the anomaly phenmenon that the lithium storage capacity of MoO2 increase within a certain number of cycles. All of our calculations, including geometry and electronic structure calculation are performed by using density function theory on the basis of projector augmented wave (PAW) method implemented in the VASP package. Generalized gradient approximation (GGA) was employed to describe the exchange-correlation interactions. The kinetic energy cutoff of electron wave functions is 400 eV in the calculation. The structure relaxations were carried out until all the atomic forces in each ion were less than 0.02 eV/Å. We calculated average binding energy, density of states (DOS) and average cell voltage. We find that the binding energy is large which means the structure of MoO2 with Li is stable. And because the system is disordered by Li, the average binding energy decrease as the number of lithium increase. The average cell voltages show the same law with the experimental results, which show our calculation is reasonable. To explain the unusual characteristics of the circulating volume, Mo vacancy formation energy, LiMoO2 different charge density and charge distribution are calculated. The results show that the intercalation of Li weakened the Mo—O bond, on the other hand weakened the role of the charge polarization of the Mo vacancy, and thus greatly reduce the formation energy of Mo vacancy. What's more, the Mo vacancy provides new adsorption for Li, improve the capacity of lithium intercalation. In a word, the intercalation of lithium made the Mo vacancy form easily, and at the same time provides new volume for the lithium intercalation. The results are in good agreement with experimental, can provide some theoretical guidance for the improvement of the electrode materials for lithium storage.

Key words: first principle calculations, lithium ion battery, MoO2, unusual circulating volume