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Lithium-ion battery (LiB) operation remains challenging, particularly in terms of safety, cycling stability, capacity rates and high-voltage applications. Although the electrolytes of LiBs account for 10-15% of the total battery weight, they are still an underestimated part. Data suggest that the composition of electrolytes offers great potential to deal with all these issues. In particular, fluorinated electrolyte solvents or even fluorinated additives offer several advantages due to the strength of the C-F bond, providing chemical and oxidative stability and increased electronegativity, exhibiting flame retardant properties and facilitating anode-mediated degradation, resulting in a LiF-rich and more stable solid electrolyte interphase (SEI), enabling more efficient surface passivation. Therefore, studies suggest that fluorinated equivalents, as well as entirely new compounds, are promising for solving battery-related problems.
But what happens to fluorinated organic compounds (FOCs) during usage? And what are the new potential risks associated with their release into the environment? The environmental and application-specific fate of FOCs is investigated by a selection of different fluorinated electrolytes, the application of various simulation methods, including the TOP (Total Oxidizable Precursor) Assay, electrochemistry, photo-induced degradation, and cycling of FOC-prepared self-assembled coin cells.
Gas chromatography and liquid chromatography coupled with high resolution mass spectrometry (GC/LC-HRMS) are used to identify transformation products (TP).
Fluorinated organic compounds (FOCs) are a type of man-made chemicals characterized by their robust carbon-fluorine bonds, which contribute to their chemical stability and resistance to degradation. This durability makes them valuable in various applications, such as lithium-ion batteries (LiBs) [1-3], could have a significant impact on the environment, but this potential has not yet been fully considered.
This study examines the environmental impact of two fluorinated aromatics, tris(pentafluorophenyl)borane (TPFPB) and tris(pentafluorophenyl)phosphine (TPFPP), given their role in enhancing the performance of LiBs[4, 5]. In order to achieve this, a number of laboratory simulation methods were employed, including total oxidizable precursor assay, electrochemistry (EC), Fenton reaction, UV-C irradiation, and hydrolysis. Liquid chromatography and gas chromatography coupled with high-resolution mass spectrometry were employed for the identification of transformation products (TPs) and the prediction of their molecular formulae. Notwithstanding their structural similarities, TPFPB and TPFPP exhibited distinct differences in their electrochemical behavior and degradation pathways. TPFPB was readily transformed via hydroxylation and hydrolysis, resulting in a diverse range of 49 TPs. In total, 28 TPs were newly identified, including oligomers and highly toxic dioxins. In contrast, TPFPP degraded only under extreme conditions, highlighting the need to develop new conditioning protocols for EC. Overall, the simulation experiments produced 9 structurally unique compounds, including 7 previously unidentified partially defluorinated byproducts. This study emphasizes the potential hazards linked to the use of FOCs in lithium-ion batteries and enhances our understanding of the complex environmental interactions of these compounds.
AbstractFluorinated organic compounds (FOCs) represent a class of synthetic chemicals distinguished by their resilient carbon–fluorine bonds, which demonstrate an ability to withstand environmental degradation over an extended period. The integration of FOCs into cutting-edge applications, including lithium-ion batteries (LiBs), presents considerable potential for environmental harm that has not yet been sufficiently addressed. This study focuses on the environmental fate of two fluorinated aromatics, tris(pentafluorophenyl)borane (TPFPB) and tris(pentafluorophenyl)phosphine (TPFPP), given their important role in improving the performance of LiBs. To achieve this, laboratory simulation methods including total oxidizable precursor assay, electrochemistry (EC), Fenton reaction, UV-C irradiation, and hydrolysis were employed. Liquid chromatography and gas chromatography coupled with high-resolution mass spectrometry were used for identification of transformation products (TPs) and prediction of their molecular formulae. Despite the structural similarity between TPFPB and TPFPP, distinct differences in electrochemical behavior and degradation pathways were observed. TPFPB readily underwent hydroxylation and hydrolysis, resulting in a wide range of 49 TPs. A total of 28 TPs were newly identified, including oligomers and highly toxic dioxins. In contrast, TPFPP degraded exclusively under harsh conditions, requiring the development of innovative conditioning protocols for EC. In total, the simulation experiments yielded nine structurally different compounds, including seven previously undescribed, partially defluorinated TPs. This study highlights the potential risks associated with the use of FOCs in LiBs and provides insight into the complex environmental behavior of FOCs.
Aufgrund ihrer Persistenz, Mobilität und Toxizität haben per- und polyfluorierte Alkylverbindungen (PFAS) zunehmend an Aufmerksamkeit und Relevanz gewonnen. Mit der PFAS-Belastung von Umweltmatrices ist auch der Bedarf an analytischen Methoden gestiegen. Trifluoressigsäure (TFA) gehört als kürzeste perfluorierte Carbonsäure zur Gruppe der PFAS und gilt als emerging pollutant, dessen Gehalte in der Umwelt zukünftig eine stärkere Überwachung erfordern. Im Vortrag wird zunächst auf die Entwicklung einer sensitiven Analysenmethode zur Bestimmung von TFA in Böden mittels HPLC-MS/MS eingegangen. Anschließend werden die TFA-Ergebnisse von 100 ausgewählten Acker- und Grünlandproben aus Deutschland vorgestellt und diskutiert.
In light of the emerging threat of environmental contamination from per- and polyfluoroalkyl substances (PFAS), there is a growing need for analytical techniques that can be applied to a range of environmental matrices, including water, air, plant, and soil samples. Trifluoroacetic acid (TFA) is a member of the PFAS class, representing the shortest perfluorinated carboxylic acid and is an emerging pollutant whose environmental levels are expected to increase in the future. Soil matrices represent the interface between plant and ecosystem uptake of TFA, but contamination is poorly understood, largely due to a lack of uniform TFA determination methods.
This study compares six ways of determining TFA in soils and highlights their limitations. We present a validated sample preparation method with high recoveries (104 %), low LOD (0.015 ng/g) and LOQ (0.045 ng/g). This approach includes isotope dilution analysis with hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry (HILIC-MS/MS) detection.
The method was applied to quantify the TFA content in 100 soil samples from grassland and farmland across Germany. The results indicate the ubiquity of TFA, accompanied by elevated contamination levels in certain locations. An analysis of variance revealed no correlation with collection site and designation purpose. However, a low correlation was observed with dry bulk density.
In this study, 77 end-of-life (EOL) commercial lithium-ion batteries (LIBs) of different formats were systematically analyzed to investigate electrolyte degradation mechanisms and the influence of pristine electrolyte composition on aging. Comprehensive chemical characterization employed targeted and non-targeted mass spectrometry (MS), combining liquid and gas chromatography (LC-MS/MS, GC-MS) with high-resolution MS (HRMS). This approach identified confirmed pristine components and complex degradation products. Commercial rechargeable pouch and cylindrical cells often deviated from conventional research model systems, using mixed lithium salt anions, ionic liquids (ILs), and high concentrations of triflates, triflimides, and bis(fluorosulfonyl)imide (FSI), functioning as solvents, salts, or additives. Specific IL degradation products and previously unreported pathways were proposed. A novel series of oligomerization products from propylene carbonate (PC) was also identified. In contrast, non-rechargeable coin cells showed prevalent use of per- and polyfluoroalkyl substances (PFAS) in their original electrolytes. Distinct PFAS degradation mechanisms were proposed for the first time. The absence of carbonate oligomers and lithium salt-derived products in coin cells, alongside standard carbonates, suggests lithium counterion coordination critically influences Lewis acid-catalyzed degradation. These findings provide new insight into real-world LIB aging, highlighting differences between commercial devices and model systems.
In this study, 77 end-of-life (EOL) commercial lithium-ion batteries (LIBs) of various formats were systematically analyzed to investigate electrolyte degradation and the influence of pristine electrolyte compositions on aging behavior. Comprehensive chemical characterization was conducted using targeted and non-targeted mass spectrometry (MS), employing LC-MS/MS, GC-MS, and high-resolution MS (HRMS). This integrated approach enabled the identification of confirmed pristine components and complex degradation products. The results show that rechargeable pouch and cylindrical cells often deviate from conventional model systems, containing mixed lithium salt anions, ionic liquids (ILs), and high concentrations of triflates, triflimides, and bis(fluorosulfonyl)imide (FSI). These function as solvents, salts, or safety-enhancing additives. Specific IL degradation products were identified, and hypotheses formulated on previously unreported pathways. Furthermore, a novel series of oligomerization products of propylene carbonate (PC) was detected. In contrast, non-rechargeable coin cells revealed widespread use of per- and polyfluoroalkyl substances (PFAS) in their original electrolytes. Based on ex situ analyses, hypothetical PFAS degradation mechanisms are proposed here for the first time. The absence of carbonate oligomers and lithium salt-derived products, alongside the presence of standard carbonates, indicates lithium counterion coordination as a key factor in Lewis acid-catalyzed degradation. This study offers valuable insights into real-world battery aging.
The use of per- and polyfluorinated alkyl substances (PFAS), which are very persistent and cannot be completely degraded in the environment, is a well-known problem worldwide. In contrast, fluorinated organic compounds used as electrolytes in lithium-based batteries (LiBs) have been less studied. Despite their increasing use in LiBs due to beneficial properties, such as improving safety, cycling performance, or even enabling high-voltage applications, there is little data on their distribution, transformation, and fate in the environment.
To fill this gap, fluorine-containing electrolyte components are studied in oxidative and reductive transformation processes. The identified transformation products (TP) will be determined in relevant environmental matrices and LiBs.
Lithium-based batteries (LiBs) have become increasingly important in modern society, as cutting-edge portable energy storage systems and as a crucial component in the energy revolution. However, they still face challenges such as safety concerns, capacity degradation, and the ever-growing demand for higher energy density. To address these issues, researchers have turned their attention to fluorinated organic compounds (FOCs) as part of LiBs electrolytes. These substances, closely related to per- and polyfluorinated alkyl substances (PFAS), have shown great potential in optimizing LiBs. Specifically, their strong fluorine-carbon bond offers enhanced oxidative and chemical resistance. Nevertheless, their environmental impact is a cause for concern. Fluorinated organics can persist in the environment or can lead to the formation of persistent end-products, which accumulate and contribute to global health problems.
To study the fate of fluorinated organic electrolytes in different environmental and application scenarios, a range of simulation methods are employed, including the TOP (Total Oxidizable Precursor) Assay, electrochemistry, photo-induced degradation, and cycling of self-assembled coin cells prepared with FOCs. Transformation products (TP) are identified using gas chromatography and liquid chromatography coupled with high resolution mass spectrometry (GC/LC-HRMS).
Fluorinated organic compounds (FOCs) are a category of anthropogenic chemicals distinguished by their resilient carbon-fluorine bonds, which confer significant chemical stability and resistance to degradation. This durability makes them valuable in various applications, particularly in lithium-ion batteries (LiBs) [1,2]. However, the environmental implications of these compounds have not been thoroughly investigated. This study focuses on the environmental impact of two fluorinated aromatic compounds: tris(pentafluorophenyl)borane (TPFPB) and tris(pentafluorophenyl)phosphine (TPFPP), specifically regarding their roles in enhancing LiB performance [3,4]. To assess their environmental fate, we employed a range of laboratory simulation techniques generating transformation products (TPs), including total oxidizable precursor assays, electrochemistry (EC), Fenton reactions, UV-C irradiation, and hydrolysis. We utilized liquid chromatography and gas chromatography coupled with high-resolution mass spectrometry to identify TPs and predict their molecular formulas. Despite their structural similarities, TPFPB and TPFPP displayed differences in electrochemical behavior and degradation pathways. TPFPB underwent significant transformation through hydroxylation and hydrolysis, yielding a diverse array of 49 TPs, including 28 newly identified compounds, including oligomers and minor levels of highly toxic dioxins. In contrast, TPFPP underwent degradation only at extreme conditions, highlighting the necessity for new conditioning protocols in electrochemistry. Overall, our simulation experiments revealed 9 structurally unique compounds, including 7 previously unidentified partially defluorinated byproducts. This study underscores the potential environmental hazards associated with the use of FOCs in lithium-ion batteries and enhances our understanding of the complex interactions these compounds have with the environment.
