First-Principles Studies Of Cathode Material LiFePO₄ Of Lithium Ion Batteries

The first-principles USPP pseudopotential method within the generalized gradient approximation(GGA) based on the density functional theory(DFT) is employed to investigate mainly the following three questions.1:The geometry and electronic structure of the bulk cathode material LiFePO4 have been studied by first principles calculations. The total density of states, partial density of states, band structure and valence electron charge density contours has been shown. On one hand, we want to obtain the theory lattice constant and electronic structure; on the other hand, the USPP+GGA method will be justifed by comparing with results attained by other theoretical or experimental methods. It is found that the results obtained by our calculations are in good agreement with other theoretical results and experimental datas.2:The local and electronic structures of the doped materials LiMxFe1-xPO4 have been studies in details. The total density of states and partial density of states have also been studied in details. The result show that the electronic conductivity of the doped materials can be improved to certain extent.3:The first-principle calculations based on the denstiy functional theory also employed to investigate the LiFePO4 (100), (010) and (001) surfaces. And the electronic structures of surfaces have been studied in details. The result show that (010) is the most stable termination and the magnetic moments of Fe atoms at (or close to) the surface is also different comparing to the bulk.