Alkali-ion conduction paths in LiFeSO4F and NaFeSO4F tavorite-type cathode materials

R Tripathi, Grahame R Gardiner, M Saiful Islam, L F Nazar

Research output: Contribution to journalArticlepeer-review

155 Citations (SciVal)


A new family of fluorosulfates has attracted considerable attention as alternative positive electrode materials for rechargeable lithium batteries. However, an atomic-scale understanding of the ion conduction paths in these systems is still lacking, and this is important for developing strategies for optimization of the electrochemical properties. Here, the alkali-ion transport behavior of both LiFeSO4F and NaFeSO4F are investigated by atomistic modeling methods. Activation energies for numerous ion migration paths through the complex structures are calculated. The results indicate that LiFeSO4F is effectively a three-dimensional (3D) lithium-ion conductor with an activation energy of similar to 0.4 eV for long-range diffusion, which involve a combination of zigzag paths through [100], [010], and [111] tunnels in the open tavorite lattice. In contrast, for the related NaFeSO4F, only one direction ([101]) is found to have a relatively low activation energy (0.6 eV). This leads to a diffusion coefficient that is more than 6 orders of magnitude lower than any other direction, suggesting that NaFeSO4F is a one-dimensional (1D) Na-ion conductor.
Original languageEnglish
Pages (from-to)2278-2284
Number of pages7
JournalChemistry of Materials
Issue number8
Publication statusPublished - 26 Apr 2011


  • sodium ion conductor
  • lithium iron fluorosulfate
  • Li-ion battery
  • atomistic modeling
  • ion transport
  • sodium iron fluorosulfate
  • lithium ion conductor


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