Identification of Electrolyte-Soluble Organic Cross-Talk Species in a Lithium-Ion Battery via a Two-Compartment Cell

Abstract

Electrode cross-talk in lithium-ion batteries has been increasingly recognized in recent years as an explanation for several performance trends during cycling. However, little is known about the nature of such cross-talk species/reactions. In an attempt to further that understanding, we constructed a two-compartment lithium-ion cell using a solid-state lithium-ion conductor as the separator to block the movement of species generated at one electrode to the other. After a long-term hold at a high voltage, the electrolytes extracted from each side were analyzed via high-performance liquid chromatography coupled with electrospray ionization mass spectrometry and nuclear magnetic resonance spectroscopy. We compared these results with those from a coin cell made with a regular porous separator. Extra species were present in the coin cell, which were absent in both compartments of the two-compartment cell, and we identified them as cross-talk species. We propose chemical structures for such species and show that these species likely have carbon–carbon double bonds and fluorinated carbons. We also confirm that the organophosphate-type species proposed by several groups previously are indeed generated at the anode.

Clarification of Decomposition Pathways in a State‐of‐the‐Art Lithium Ion Battery Electrolyte through 13C‐Labeling of Electrolyte Components

“…In previous studies, a large variety of similar as well as different decomposition product species was identified in thermally/electrochemically aged samples …”

“…The decomposition of LiPF 6 ‐based electrolytes to organo(fluoro)phosphates (O(F)Ps) was investigated intensively . Subsequent studies addressed reductively and oxidatively generated products and evolving gases separately as well as the identification of further decomposition compounds …”

Analysis of Carbonate Decomposition During Solid Electrolyte Interphase Formation in Isotope‐Labeled Lithium Ion Battery Electrolytes: Extending the Knowledge about Electrolyte Soluble Species

“…in 1997 annotating dimethyl‐2,5‐dioxahexane carboxylate (DMDOHC), ethyl methyl‐2,5‐dioxahexane carboxylate (EMDOHC) and diethyl‐2,5‐dioxahexane carboxylate (DEDOHC) as EC decomposition products [24] . Among others, Laruelle and coworkers continued this process and identified a wide range of further decomposition species and discussed reactive species and the corresponding reaction products [25–34] …”

Clarification of Decomposition Pathways in a State‐of‐the‐Art Lithium Ion Battery Electrolyte through 13C‐Labeling of Electrolyte Components

“…In previous studies,alarge variety of similar as well as different decomposition product species was identified in thermally/electrochemically aged samples. [27][28][29]40] One representative LIB electrolyte formulation (( 13 C 3 -)EC/DEC,3 0/70 wt. %; 1mol L À1 LiPF 6 )w as investigated after thermal degradation in as ealed container or electrochemical aging consisting of three formation cycles and > 500 cycles.T od ecipher the molecular origin of electrolyte decomposition products,the exclusion of reaction products of labeled EC and unlabeled DEC solvent reagents during the respective decomposition was imperative.T herefore,gas chromatography-mass spectrometry (GC-MS) measurements were conducted and yielded unaltered 13 C 3 -EC and DEC species after both aging processes ( Figure S1 in the Supporting Information).…”

“…[19] Thed ecomposition of LiPF 6 -based electrolytes to organo(fluoro)phosphates (O(F)Ps) was investigated intensively. [22][23][24][25] Subsequent studies addressed reductively and oxidatively generated products and evolving gases separately [26,27] as well as the identification of further decomposition compounds. [28,29] Besides electrochemical decomposition, thermal stress at elevated temperatures (60-80 8 8C) is another reason for aring opening polymerization of ethylene carbonate (EC) and acomparable variety of species.…”