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Storage Stability of LiFePO 4 /C in Humid‐hot Air
Author(s) -
Guo Xiangfeng,
Zuo Jun,
Zhan Hui,
Zhou Yunhong
Publication year - 2011
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.201180400
Subject(s) - chemistry , faraday efficiency , calcination , chemical engineering , graphite , moisture , electrochemistry , ion , lithium (medication) , homogeneity (statistics) , electrode , organic chemistry , medicine , engineering , endocrinology , catalysis , statistics , mathematics
Storage stabilities of LiFePO 4 /C composite at different conditions are investigated in terms of structural and electrochemical evolutions. The results from different aging tests indicate that moisture and temperature are the key factors that have the most profound effects on the structure homogeneity which in turn influences the electrochemical performance of LiFePO 4 /C. Although the storage in a humid‐hot environment, such as saturated humidity air at 50°C, does not greatly influence the discharging capacity of LiFePO 4 /C, it does reduce the initial charging capacity, thus the amount of reversible Li + ions in a practical LiFePO 4 /graphite cell decreases. This impact is explained by the lithium extraction during the storage, forming olivine FePO 4 and associated Li 3 PO 4 . Elevated storage temperature also favors the delithiation process. The degree of delithiation increases from about 6% at 50°C to 18% at 80°C. It is also found that re‐calcination at 650°C effectively resolves the problem of the structural heterogeneity of the stored LiFePO 4 /C. Therefore both the initial charging capacity and coulombic efficiency of the stored sample in the first cycle revert to the original value of the fresh one.