Electrolyte effects on spinel dissolution and cathodic capacity losses in 4 V Li/Li{sub x}Mn{sub 2}O{sub 4} rechargeable cells

Journal Article · Wed Oct 01 04:00:00 EDT 1997 · Journal of the Electrochemical Society

DOI:https://doi.org/10.1149/1.1838016· OSTI ID:562191

Jang, D H; Oh, S M ^[1]

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1. Seoul National Univ. (Korea, Republic of). Dept. of Chemical Technology

Spinel dissolution and cathodic capacity losses in 4 V Li/Li{sub x}Mn{sub 2}O{sub 4} 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 spinel-loaded composite cathode was charge/discharge cycled in the potential range of 3.6 to 4.3 V (vs Li/Li{sup +}), 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 (LiPF{sub 6}, LiBF{sub 4}, and LiAsF{sub 6}), 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.

• Sponsoring Organization: USDOE
• OSTI ID: 562191
• Journal Information: Journal of the Electrochemical Society, Journal Name: Journal of the Electrochemical Society Journal Issue: 10 Vol. 144; ISSN JESOAN; ISSN 0013-4651
• Country of Publication: United States
• Language: English

Related Subjects

25 ENERGY STORAGE
36 MATERIALS SCIENCE
BATTERY CHARGING
CARBONIC ACID ESTERS
CATHODES
DISSOLUTION
ELECTROLYTES
ENERGY LOSSES
LITHIUM
LITHIUM FLUORIDES
LITHIUM OXIDES
MANGANESE OXIDES
MATERIALS TESTING
METAL-NONMETAL BATTERIES
VOLTAGE DROP