Impact of electrolyte solvent and additive choices on high voltage Li-ion pouch cells

The effects that various electrolyte solvents and electrolyte additives had on both LaPO4-coated LiNi0.4Mn0.4Co0.2O2 and uncoated LiNi0.4Mn0.4Co0.2O2/graphite pouch cells were studied using automated storage, electrochemical impedance spectroscopy, gas production and long-term cycling experiments. S...

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Bibliographic Details
Published in:Journal of power sources 2016-10, Vol.329, p.387-397
Main Authors: Xia, Jian, Nelson, K.J., Lu, Zhonghua, Dahn, J.R.
Format: Article
Language:English
Subjects:
Electrolyte additives
Fluorinated solvents
High temperature cycling
High voltage Li-ion cells
LaPO4 coating
Sulfolane
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Summary:The effects that various electrolyte solvents and electrolyte additives had on both LaPO4-coated LiNi0.4Mn0.4Co0.2O2 and uncoated LiNi0.4Mn0.4Co0.2O2/graphite pouch cells were studied using automated storage, electrochemical impedance spectroscopy, gas production and long-term cycling experiments. Storage experiments showed that the voltage drop during storage at 4.3 or 4.4 V for both coated and uncoated cells was very similar for the same electrolyte choice. At 4.5 V or above, the LaPO4-coated cells had a significantly smaller voltage drop than the uncoated cells except when fluorinated electrolytes were used. Automated charge discharge cycling/impedance spectroscopy testing of cells held at 4.5 V for 24 h every cycle showed that all cells containing ethylene carbonate:ethyl methyl carbonate electrolyte or sulfolane:ethyl methyl carbonate electrolyte exhibited severe capacity fade. By contrast, cells containing fluorinated electrolytes had the best capacity retention and smallest impedance growth during these aggressive cycling/hold tests. Long-term cycling experiments to 4.5 V confirmed that cells containing fluorinated electrolyte had the best cycling performance in the uncoated LiNi0.4Mn0.4Co0.2O2/graphite cells while cells containing sulfolane:ethyl methyl carbonate electrolyte had the best cycling performance in coated LiNi0.4Mn0.4Co0.2O2/graphite cells. •A LaPO4-coating showed benefits above 4.5 V but not at 4.3 V or 4.4 V.•LaPO4-coated NMC442/graphite cells containing TAP performed best at 4.5 V.•Uncoated NMC442/graphite cells with FEC:TFEC performed best at 4.5 V.
ISSN:0378-7753
1873-2755
DOI:10.1016/j.jpowsour.2016.08.100