Structure Stability of LiFeSO_4F Cathode Material as Lithium-ion Battery

摘要

The theoretical calculation predicts a voltage of about 3.5 V for Li/LiFeS_4F half cell, which is well consistent with experiments. The oxygen and fluorine with negative charge is anion, while sulfur and iron with positive charge are cations. The electron density difference around sulfur ions showed typical sp~3 characteristics, while those around O and Fe ions displayed explicit p and d orbital characteristics. The resultsonfirmed that O_(2p) states can effectively overlap with the orbitals of S and Fe ions and then form covalent bonds. Moreover, as the electron (charge) redistribution around O and S spheres is more obvious than that around O and Fe ones, S-O bonds are thus much stronger than that of Fe-0 ones. Therefore, the excellent structural stability of LiFeSO_4F can be attributed to the strong S-O and Fe-O covalent bonds.