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摘要
Cation doping could be adopted as an effective method to optimize the electrochemical performance of Li-ion battery cathode materials. However, there is still major controversy regarding the site occupation behavior in the lattice following cation doping. To determine the preferred dopant sites in LiFePO4 and the general relation with ionic charge and/or size, density functional theory (DFT) was adopted to calculate the models of a range of dopants with charges varying from +1 to +6 doped at the Fe site or Li site of LiFePO4. As a result, it was found that cations preferentially occupy the Fe sites in a thermodynamically spontaneous process due to the stronger covalent interaction between dopants and adjacent 0 atoms; ionic charge is the dominant factor affecting the doping site occupation behavior, and ionic size is secondary. In addition, the doping of Fe sites preferentially favors the doping of high-valence ions, while the Li sites are more susceptible to low-valent ion dopants. From an energy standpoint, cation doping is more favorable with non-transition metal ions than with transition metal ions in both Fe and Li sites. The calculation results are consistent with the related experimental results.
- 出版日期2018-11
- 单位中南大学; 长江师范学院
