Structural, electronic and Li diffusion properties of LiFeSO4F

The structural, electronic and Li diffusion properties of LiFeSO 4 F were analyzed by first-principles calculation under the DFT + U framework. The difference of the calculated lattice parameters and the reported data is within 3%. The redox potential of Fe 2+ /Fe 3+ versus Li metal is 3.7 V, and phase separation of LiFeSO 4 F and FeSO 4 F is expected during Li extraction. Pure LiFeSO 4 F is an insulator with a band gap of 3.6 eV, while the band gap in the partially delithiated form Li 1 − x FeSO 4 F is obviously smaller. A very low Li migration energy of 0.3 eV is required in the partially delithiated form Li 1 − x FeSO 4 F, and the diffusion coefficient is estimated to be about 1.6 ⁎ 10 − 7 cm 2 s − 1 .