期刊
CHEMISTRY OF MATERIALS
卷 23, 期 8, 页码 2278-2284出版社
AMER CHEMICAL SOC
DOI: 10.1021/cm200683n
关键词
Li-ion battery; lithium iron fluorosulfate; sodium iron fluorosulfate; atomistic modeling; ion transport; lithium ion conductor; sodium ion conductor
资金
- NSERC
- EPSRC Supergen
- EPSRC [EP/H019596/1] Funding Source: UKRI
- Engineering and Physical Sciences Research Council [EP/H019596/1] Funding Source: researchfish
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.
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