Temperature dependent magnetic structure of lithium delithiated LixFeSO4F (x = 0, 1) by Mössbauer spectroscopy

Abstract

Recently, lithium iron sulfate compounds have been highly considered for a positive electrode material for lithium ion batteries. In this work, LiFeSO4F and the fully delithiated FeSO4F were prepared by the ionothermal process and chemical oxidation reaction method. The LixFeSO4F (x = 0, 1) samples show the triclinic structure with P-1 space group. In the case of delithiated FeSO4F, changes in lattice parameters were observed due to the disappearance of the Li site while maintaining the triclinic structure. Temperature-dependent magnetic susceptibility curves show the antiferromagnetic (AFM) structure with the ordering temperature of 28 K for LiFeSO4F and 99 K for FeSO4F. Also, temperature-dependent Mössbauer spectra of LiFeSO4F below TN were fitted with two-sets of eight Lorentzian indicating the existence of two different types of Fe2+ ions due to the different hyperfine and electric quadrupole interactions. With the lithium delithiated, the Fe3+ iron ions in FeSO4F exhibit two-sets of six-line patterns due to the electron transfer in FeO4F2 site by lithium delithiation. These suggest that the different AFM ordering in LixFeSO4F can be originated from the Fe2+/Fe3+ magnetic ions with different charge distributions and spin contributions.

Review on Synthesis, Characterization, and Electrochemical Properties of Fluorinated Nickel‐Cobalt‐Manganese Cathode Active Materials for Lithium‐Ion Batteries

“…A further good next generation CAM class are the “Li‐ excess/Li‐rich/over‐lithiated” NCM electrode materials with a general formula of 0.35Li 2 MnO 3 ⋅ 0.65Li[Ni 0.35 Co 0.20 Mn 0.45 ]O 2 . In terms of good safety properties, the lithium metal phosphate (LiMPO 4 ‐M=Fe, Mn, Co, and Ni) and lithium iron fluorosulfate are good choices.…”

“…We note that, in addition, the fluorination of phosphate, vanadate and sulfate‐based CAMs was studied. The following non‐exhaustive list gives an impression on available reports: NaVPO 4 F, Na 3 V 2 (PO 4 ) 2 F 3 , Na 3 (VO 1‐ x PO 4 ) 2 F 1+2x , coated/doped/double treated Na 3 (VO 1‐x PO 4 ) 2 F 1+2x , Na 3‐x Li x V 2 (PO 4 ) 2 F 3 , Na 2 M 1 PO 4 F (M 1 =Co, Fe, Mn), LiVPO 4 F, coated/doped/treated LiVPO 4 F, Li 2 VPO 4 F, Li 3 V 2 (PO 4 ) 3‐z F z , Li 5 V(PO 4 ) 2 F 2 , xLi 3 V 2 (PO 4 ) 3‐y *LiVPO 4 F, LiFeSO 4 F, treated LiFeSO 4 F, LiVSiO 4 F, LiFePO 4 F, LiFePO 4 (OH) x F 1‐x , Li 2 FePO 4 F, Li 2 CoPO 4 F, Li 2 NiPO 4 F, and Li 2 MnPO 4 F …”