Electrolyte Effects on Spinel Dissolution and Cathodic Capacity Losses in 4 V U/LiJvIn2O4 Rechargeable Cells

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Jang, Dong H.; Oh, Seung M.
Issue Date
Electrochemical Society
J. Electrochem. Soc., 144, 3342 (1997)
Spinel dissolution and cathodic capacity losses in 4 V Li/LiMn204 secondary cells were examined in various electrolyte
solutions comprising different solvents and Li salts. It was found that spinel dissolution is induced by acids that
are generated as a result of electrochemical oxidation of solvent molecules on composite cathodes. Among various organic
solvents, ethers such as tetrahydrofuran and dimethoxyethane were readily oxidized to produce acids whereas carbonates
(ethylene carbonate, propylene carbonate, diethylcarbonate) were relatively inert. Consequently, when a spinelloaded
composite cathode was charge/discharge cycled in the potential range of 3.6 to 4.3 V (vs. Li/Li), both the acid
concentration and the extent of spinel dissolution was much higher in the ether-containing electrolytes as compared to
the carbonates. The results, obtained from the chemical analysis on acid-attacked spinel powders and from the open-circuit
potential measurement of composite cathodes, indicated that Li and Mn ion extraction is dominant in the earlier
stage of acid attack. As the spinel dissolution further continues, however, oxygen losses from the lattice become more
important. The combined feature of solvent oxidation and spinel dissolution was also affected by the nature of lithium
salts added. Generally, the solvent-derived acid generation was not significant in those electrolytes containing fluorinated
salts (LiPF5, LiBF4, and LiA5F6), yet the spinel dissolution in these electrolytes was still appreciable because acids were
generated via another pathway; a reaction between the F-containing anions and impurity water.
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College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of Chemical and Biological Engineering (화학생물공학부)Journal Papers (저널논문_화학생물공학부)
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