First-Principles Calculations on the LiMSO₄F/MSO₄F (M = Fe, Co, and Ni) Systems

Systematic first-principles calculations based on the density functional theory are carried out to discuss the crystal and electronic structures of the LiMSO 4 F/MSO 4 F (M = Fe, Co, and Ni) systems. It is shown that all of the LiMSO 4 F compounds are in a high spin antiferromagnetic ground state. However, they transform to different ground states with Li + extraction. LiFeSO 4 F is a typical Mott-Hubbard insulator and then transforms to a charge-transfer insulator with Li + extraction. The theoretical intercalation voltages of LiMSO 4 F are 3.54 (Fe), 4.73 (Co), and 5.16 V (Ni), respectively, which are close to corresponding LiMPO 4 phosphates. First-principles calculations show that a significant amount of electron-charge transfer takes place on the oxygen anions with Li + extraction, especially for LiCoSO 4 F and LiNiSO 4 F. This will lead to significant loss of oxygen from the material lattice which is an intrinsic drawback of LiMSO 4 F due to the concerns of structural and thermal stabilities.