Crystal structure analysis and first principle investigation of F doping in LiFePO4

Fluoro-polyanionic Compounds

“…Such fluorine doping closes the gap in the electronic structure, which results in a finite density of states at the Fermi level. Enhanced high rate performance and improved cycle stability of F-doped olivine-phosphate was also reported in more recent studies [46][47][48]. C-LiFePO 3.98 F 0.02 composite delivered the capacity of 164 mAh g À1 at C/10 rate.…”

“…C-LiFePO 3.98 F 0.02 composite delivered the capacity of 164 mAh g À1 at C/10 rate. The first principles computational results indicate that electronic properties, the lithium insertion voltage, and general electrochemical behavior, are very sensitive to the placement of fluorine ions in the structure of this compound [48]. It was suggested that LiVSiO 4 F and Li 0.5 FePO 3.5 F 0.5 lithium deinsertion causes a too large M-F distance (indicative of M-F bond breaking), being the predicted lithium insertion voltage about 0.3 V lower than that of the parent compound.…”

“…LiFe (PO 4 ) 1Àx F 3x /C (x ¼ 0.01, 0.05, 0.1, 0.2) was synthesized by a solid-state carbothermal reduction route at 650 C using NH 4 F as dopant. F-doped LiFePO 4 /C nanoparticles were prepared either via a low-temperature hydrothermal reaction followed by high-temperature treatment at 850 C for 5 h under Ar atmosphere [45,46] or via sol-gel process using LiF [48]. Nanostructured C-LiFePO 3.98 F 0.02 composite was synthesized by an aqueous precipitation of precursor material in molten stearic acid [48].…”

“…F-doped LiFePO 4 /C nanoparticles were prepared either via a low-temperature hydrothermal reaction followed by high-temperature treatment at 850 C for 5 h under Ar atmosphere [45,46] or via sol-gel process using LiF [48]. Nanostructured C-LiFePO 3.98 F 0.02 composite was synthesized by an aqueous precipitation of precursor material in molten stearic acid [48]. The excessively F-substituted LiFe(PO 4 ) 0.9 F 0.3 /C composite showed the most attractive high rate performance and the cycling life at high temperatures (T > 50 C) due to the fact that the more ionic Fe-F bond stabilizes the energy of the antibonding 3d orbitals of the transition-metal ion.…”

F-doped O3-NaNi1/3Fe1/3Mn1/3O2 as high-performance cathode materials for sodium-ion batteries

“…As can be seen from Fig. 1c, the lattice parameter is first observed to decrease as a function of increased F-doping as the radius of F − (1.33 Å) is smaller than that of O 2− (1.40 Å) [22] when the doping amount is less than 1%. However, further increasing the F-doping levels above 1% results in a lattice parameter increase, which is attributed to an elevated proportion of Mn 3+ /Mn 4+ and the larger ion radius of Mn 3+ (0.645 Å) than Mn 4+ (0.53 Å) [23].…”