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Atomic Structure and Kinetics of NASICON Na x V 2 (PO 4 ) 3 Cathode for Sodium‐Ion Batteries
Author(s) -
Jian Zelang,
Yuan Chenchen,
Han Wenze,
Lu Xia,
Gu Lin,
Xi Xuekui,
Hu YongSheng,
Li Hong,
Chen Wen,
Chen Dongfeng,
Ikuhara Yuichi,
Chen Liquan
Publication year - 2014
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201400173
Subject(s) - sodium , materials science , ion , crystal structure , crystallography , cathode , formula unit , fast ion conductor , phase (matter) , electrochemistry , analytical chemistry (journal) , chemistry , electrode , electrolyte , metallurgy , organic chemistry , chromatography
Na 3 V 2 (PO 4 ) 3 is one of the most important cathode materials for sodium‐ion batteries, delivering about two Na extraction/insertion from/into the unit structure. To understand the mechanism of sodium storage, a detailed structure of rhombohedral Na 3 V 2 (PO 4 ) 3 and its sodium extracted phase of NaV 2 (PO 4 ) 3 are investigated at the atomic scale using a variety of advanced techniques. It is found that two different Na sites (6b, M1 and 18e, M2) with different coordination environments co‐exist in Na 3 V 2 (PO 4 ) 3 , whereas only one Na site (6b, M1) exists in NaV 2 (PO 4 ) 3 . When Na is extracted from Na 3 V 2 (PO 4 ) 3 to form NaV 2 (PO 4 ) 3 , Na + occupying the M2 site (CN = 8) is extracted and the rest of the Na remains at M1 site (CN = 6). In addition, the Na atoms are not randomly distributed, possibly with an ordered arrangement in M2 sites locally for Na 3 V 2 (PO 4 ) 3 . Na + ions at the M1 sites in Na 3 V 2 (PO 4 ) 3 tend to remain immobilized, suggesting a direct M2‐to‐M2 conduction pathway. Only Na occupying the M2 sites can be extracted, suggesting about two Na atoms able to be extracted from the Na 3 V 2 (PO 4 ) 3 structure.