Effect of lithium intercalation on the structural and electronic properties of layered LiFeSO4OH and layered FeSO4OH using first-principle calculations

[Display omitted] •First-principle method (using DFT) was carried out on the L-LiFeSO4OH and L-FeSO4OH.•SO42− polyanion has a strong S–O bond co-joined with the highly covalent Fe–O bond.•Introducing sulfur as the counter cation improves the cathode material voltage.•L-LiFeSO4OH can be classified as a Moth Hubbard insulator.•L-FeSO4OH can be classified as a charge-transfer insulator. The effect of lithium intercalation on the structural and electronic properties of layered LiFeSO4OH and layered FeSO4OH cathode material is investigated using first-principle calculations. Results of Mulliken analysis, band gap, density of state, and charge density before and after intercalation are discussed. The importance of the strong covalent character of S–O and Fe–O bonds in high charge/discharge cycles and thermodynamic stabilities is confirmed. Analysis of the partial density of state reveals that the main contributor to the strong S–O covalent bond is the hybridization between the S 3s, S 3p electron state and the O 2p electron state. The Fe 3d orbital also plays an important role in cathode performance because it dominates the conduction and valence bands and radically changes upon the removal and insertion of lithium ion inside the cathode materials. The charge density elucidates the ionic and covalent characters of the bond inside the cathode.