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