[ACIE] 我室杨勇教授发表论文:Identifying the Structural Evolution of the Na‐ion Battery Na₂FePO₄F Cathode

我室杨勇教授在 ACIE 上发表论文:Identifying the Structural Evolution of the Na‐ion Battery Na₂FePO₄F Cathode

文章链接:https://onlinelibrary.wiley.com/doi/10.1002/anie.201805555

摘要:

Na₂FePO₄F is a promising cathode material for Na‐ion batteries due to its relatively high discharge voltage and excellent cycling performance. Here, the long‐ and short‐range structural evolution of Na₂FePO₄F during the cycling is studied through in‐situ high energy X‐ray diffraction (XRD), ex‐situ solid‐state nuclear magnetic resonance (NMR) and first‐principles DFT calculations. DFT calculations suggest that the intermediate phase, Na₁.₅FePO₄F, adopts a space group P2₁/c, which is a subgroup (P2₁/b11, No. 14) of Pbcn (No. 60) of the space group of the starting phase, Na₂FePO₄F, and this space group provides a good fit to the experimental XRD and NMR results. The two crystallographically unique Na sites in the structure of Na₂FePO₄F behave differently during the cycling, where the Na ions on the Na2 site are electrochemically active while those on the Na1 site are inert. This study determines the structural evolution and the electrochemical reaction mechanisms of Na₂FePO₄F in a Na‐ion battery.