Consequences of Electrolyte Degradation for the Electrochemical Performance of Li1+x(NiaCobMn1-a-b)1-xO2. Issue 13 (7th August 2015)

• Record Type: Journal Article
• Authors: Peng, H.-J.; Urbonaite, S.; Villevieille, C.; Wolf, H.; Leitner, K.; Novák, P.
• Is Part Of: Journal of the Electrochemical Society. Volume 162:Issue 13(2015)
• Page Start: A7072
• Page End: A7077
• Publication Date: 2015-08-07
• Subjects: Alkoxide formation -- Cycling stability -- Electrolyte analysis -- Electrolyte Degradation -- Lithium-nickel-cobalt-manganese-oxide cathodes -- SEI effect -- Trans-esterification reaction; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0061513jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : In lithium-ion batteries, the stability of the electrolyte during cycling is among the key parameters that govern cycle life and specific-charge retention. For the case of carbonate-based electrolytes, one of the main reduction products is the alkoxide anion. Here, we report a study of the parameters influencing the formation of these anions during cycling and of the effects that this process has on cycling performance. To this end, conventional and overlithiated lithium-nickel-cobalt-manganese-oxide cathodes were studied in combination with an electrolyte containing ethyl methyl carbonate. The extent of trans-esterification reaction within the electrolyte, serving as an indicator for the alkoxide-anion formation, was estimated based on gas-chromatography results. An analysis of the electrolyte extracted from cells after testing them at different cycling rates revealed a crucial role of anode passivation in the process of alkoxide-anion formation. The upper cutoff potential was found to be inversely proportional to the extent of trans-esterification. Further analysis of the electrolyte extracted from the full-cells containing Li1.05 (Ni0.33 Co0.33 Mn0.33 )0.95 O2 suggested that electrolyte instability toward the anode can cause a surface layer buildup on the cathode side, which in turn deteriorates the overall cell performance.