Identifying the Structural Evolution of the Sodium Ion Battery Na2FePO4F Cathode. Issue 37 (19th August 2018)

• Record Type: Journal Article
• Authors: Li, Qi; Liu, Zigeng; Zheng, Feng; Liu, Rui; Lee, Jeongjae; Xu, Gui‐Liang; Zhong, Guiming; Hou, Xu; Fu, Riqiang; Chen, Zonghai; Amine, Khalil; Mi, Jinxiao; Wu, Shunqing; Grey, Clare P.; Yang, Yong
• Is Part Of: Angewandte Chemie international edition. Volume 57:Issue 37(2018)
• Page Start: 11918
• Page End: 11923
• Publication Date: 2018-08-19
• Subjects: density functional calculations -- electrochemistry -- Na2FePO4F -- NMR spectroscopy -- sodium-ion batteries; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201805555
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Na2 FePO4 F is a promising cathode material for Na‐ion batteries owing to its relatively high discharge voltage and excellent cycling performance. Now, the long‐ and short‐range structural evolution of Na2 FePO4 F during cycling is studied by 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, Na1.5 FePO4 F, adopts the space group of P 21 / c, which is a subgroup ( P 21 / b 11, No. 14) of Pbcn (No. 60), the space group of the starting phase, Na2 FePO4 F, 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 Na2 FePO4 F behave differently during 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 Na2 FePO4 F in a Na‐ion battery. Abstract : Revealing the structural evolution : Structural changes of the Na2 FePO4 F cathode for a sodium‐ion battery during the cycling are elucidated by tracking the local environment of the Na sites.