Lithium Bis(trifluoromethanesulphonyl)imide: Applications in Battery Technologies and Toxicity

General Description

Lithium bis(trifluoromethanesulphonyl)imide plays a crucial role in enhancing the performance and efficiency of lithium-sulfur batteries by stabilizing the interface and preventing the diffusion of polysulfides, ultimately leading to higher charge-storage capacities and extended cycle lives. However, studies have shown that Lithium bis(trifluoromethanesulphonyl)imide, part of the PFAS group, exhibits dose-dependent cytotoxic effects on human renal carcinoma and hepatoma cells, impacting gene expression related to kidney injury, methylation, lipid metabolism, and apoptosis. Further research is needed to understand the toxicity mechanisms of this emerging contaminant better.

Figure 1. Lithium bis(trifluoromethanesulphonyl)imide

Applications in Battery Technologies

Lithium bis(trifluoromethanesulphonyl)imide is a pivotal component in advanced battery technologies, particularly in lithium-sulfur batteries, which are noted for their high energy density and potential for large-scale energy storage applications. The compound, Lithium bis(trifluoromethanesulphonyl)imide, acts primarily as an electrolyte salt in these batteries, contributing significantly to their performance and efficiency. The key issue in lithium-sulfur batteries is the dissolution and relocation of polysulfides, which are liquid-state active materials. These materials tend to migrate from the cathode to the anode, leading to rapid capacity fading and decreased Coulombic efficiency. The innovative use of Lithium bis(trifluoromethanesulphonyl)imide in a poly(ethylene oxide) coated polypropylene membrane aims to address this challenge. The presence of Lithium bis(trifluoromethanesulphonyl)imide in the membrane facilitates the formation of a stable interface that significantly slows the diffusion of polysulfides. This results in enhanced stabilization of these active materials within the cathode region, ensuring that the lithium ions can move smoothly, which is crucial for maintaining the battery's capacity and extending its lifecycle. The inclusion of Lithium bis(trifluoromethanesulphonyl)imide in the composite structure of the battery's functional membrane not only improves its physical properties but also enhances its electrochemical stability. This is evidenced in batteries where Lithium bis(trifluoromethanesulphonyl)imide is used; they exhibit substantially higher charge-storage capacities and longer cycle lives compared to those without it. For instance, batteries incorporating this compound demonstrate capacities as high as 1212 mA∙h g-1 and maintain a high reversible capacity even after multiple cycles, highlighting the compound's effectiveness in blocking the irreversible diffusion of polysulfides and maintaining stable electrochemical performance. Furthermore, Lithium bis(trifluoromethanesulphonyl)imide enables a more uniform and controlled ionic conductivity across the electrolyte, reducing the typical degradation seen in lithium-sulfur batteries. This enhanced control and stability offered by Lithium bis(trifluoromethanesulphonyl)imide are instrumental in pushing the boundaries of lithium-sulfur battery technology, making it a key material for the future of energy storage systems. ¹

Toxicity

Lithium Bis(trifluoromethanesulphonyl)imide, a novel compound found in lithium-ion batteries and a member of the Per and Polyfluoroalkyl Substances (PFAS) group, has been the subject of investigation regarding its toxicity on human renal carcinoma cells (A498) and hepatoma cells (HepG2). Studies utilizing the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay revealed that both Lithium Bis(trifluoromethanesulphonyl)imide and Perfluorooctane sulfonate (PFOS) exhibit dose-dependent cytotoxic effects on A498 and HepG2 cells, with Lithium Bis(trifluoromethanesulphonyl)imide demonstrating lower toxicity compared to PFOS. Evaluation of intracellular redox conditions using microplate readers and confocal microscopy demonstrated a notable decrease in Reactive Oxygen Species (ROS) levels and an increase in Superoxide dismutase (SOD) content in response to Lithium Bis(trifluoromethanesulphonyl)imide exposure in both cell lines. Moreover, Lithium Bis(trifluoromethanesulphonyl)imide exposure promoted cell apoptosis, particularly in HepG2 cells. Quantitative analysis of mRNA expression levels revealed significant alterations in gene expression associated with kidney injury, methylation, lipid metabolism, and transportation upon exposure to Lithium Bis(trifluoromethanesulphonyl)imide. Notably, Lithium Bis(trifluoromethanesulphonyl)imide exposure downregulated smooth muscle alpha-actin (Acta2) and upregulated transforming growth factor beta 1 (Tgfb1), B-cell lymphoma 2-like 1 (Bcl2l1), hepatitis A virus cellular receptor 1 (Harvcr1), nuclear factor erythroid 2-like 2 (Nfe2l2), and hairy and enhancer of split 1 (Hes1) expression, impacting kidney function. Furthermore, Lithium Bis(trifluoromethanesulphonyl)imide exposure influenced DNA methylation processes by modulating the expression of ten-eleven translocation (TET) and DNA methyltransferase (DNMT) genes. Additionally, Lithium Bis(trifluoromethanesulphonyl)imide exposure led to alterations in lipid metabolism, promoting lipid anabolism and affecting lipid catabolism in HepG2 cells. These findings shed light on the potential regulatory role of Lithium Bis(trifluoromethanesulphonyl)imide in oxidative stress, apoptosis, and methylation processes in human renal carcinoma and hepatoma cells, highlighting the need for further research into the toxicity mechanisms of this emerging contaminant. ²

Reference

1. Chiu LL, Chung SH. A Poly(ethylene oxide)/Lithium bis(trifluoromethanesulfonyl)imide-Coated Polypropylene Membrane for a High-Loading Lithium-Sulfur Battery. Polymers (Basel). 2021; 13(4): 535.

2. Zhang X, Sands M, Lin M, Guelfo J, Irudayaraj J. In vitro toxicity of Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) on Human Renal and Hepatoma Cells. Toxicol Rep. 2024; 12: 280-288.

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