Lithium Bis(trifluoromethanesulfonyl)imide (LiTFSI) Storage & Tank Compatibility

Storing Lithium Bis(trifluoromethanesulfonyl)imide (LiTFSI)? Start Here

Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, Li[N(SO₂CF₃)₂], empirical formula C₂F₆LiNO₄S₂) is a white, odorless, strongly hygroscopic crystalline lithium salt. It is widely used as a conducting salt in lithium-ion and lithium-metal battery electrolytes, where it is valued as a more thermally and hydrolytically stable alternative to lithium hexafluorophosphate. The delocalized, fluorinated sulfonimide anion gives the salt high solubility in both water and organic carbonate or ether solvents, plus good ionic conductivity. Despite its electrolyte stability, the dry salt is not benign: it is classified as acutely toxic by ingestion and skin contact, corrosive to skin and eyes, and a target-organ hazard on repeated exposure, and it can release fluoride and sulfur oxides if strongly overheated or mixed with strong acid. Because its solutions are essentially non-oxidizing and non-solvent toward polyolefins, polyethylene tanks are a standard, cost-effective containment choice for both the solid salt and its electrolyte solutions.

Is Lithium Bis(trifluoromethanesulfonyl)imide Safe in HDPE and XLPE Tanks?

Yes. As a fully dissociated ionic lithium salt, LiTFSI and its aqueous or carbonate-solvent electrolyte solutions do not swell, dissolve, or chemically attack high-density polyethylene (HDPE) or cross-linked polyethylene (XLPE). The dissolved salt is non-oxidizing and is not a hydrocarbon, aromatic, chlorinated, ketone, or ester solvent that would soften the polymer, so HDPE and XLPE are a Suitable (S) material of construction for storing the solid salt and its solutions. Polypropylene and PVDF are likewise suitable, and PVDF is a natural choice anywhere trace fluoride is a concern.

The practical risks are moisture management and toxicity rather than polymer attack. LiTFSI is strongly hygroscopic, so keep it sealed and dry to preserve electrolyte quality and to avoid forming pooled, corrosive liquid. Carbon steel is corroded by the salt solution and is rated Unsuitable; stainless steel, glass, and FRP are conditional and should be qualified against your specific concentration and temperature, since strong overheating or acid contact can liberate fluoride that etches glass and pits metals. Use polyethylene, polypropylene, or PVDF wetted parts and fluoride-compatible elastomers such as FKM (Viton), and confirm the rating against your exact solvent system before placing the tank in service.

Material compatibility at a glance

Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is a highly water-soluble, hygroscopic ionic lithium salt used as a conducting salt in battery electrolytes. Its aqueous and electrolyte solutions are well handled by polyethylene: HDPE and XLPE tanks are rated Suitable (S) for the solid and its solutions, as are polypropylene and PVDF. Carbon steel is Unsuitable (U); stainless steel, glass, and FRP are Conditional (C) depending on grade, temperature, and concentration. Keep the salt sealed and dry, since overheating or acid contact can liberate fluoride and sulfur oxides.

Ratings: S suitable · C conditional / limited · U unsuitable. Verify against the cited resistance charts and your concentration/temperature before specifying.

The safety that actually matters

• Acutely toxic: toxic if swallowed (H301), toxic in contact with skin (H311), and fatal in contact with skin (H310); use chemically resistant gloves and avoid all skin contact and dust ingestion.
• Corrosive (H314): causes severe skin burns and serious eye damage; wear splash goggles, a face shield, and protective clothing, and provide emergency eyewash and shower.
• Target-organ hazard on prolonged or repeated exposure (H372, H373); minimize and monitor exposure and use local exhaust ventilation to control dust.
• Hygroscopic solid: absorbs atmospheric moisture; store sealed in a cool, dry area to maintain quality and prevent pooling of corrosive liquid.
• Strong heating or contact with strong acids can release hydrogen fluoride, sulfur oxides, and nitrogen oxides; keep away from acids and ignition-temperature heat sources and keep fluoride-specific first aid available.
• Harmful to aquatic life with long-lasting effects (H412); contain spills and prevent release to drains and waterways.

Common questions

Can I store LiTFSI in an HDPE or XLPE tank?

Yes. The solid salt and its aqueous or electrolyte solutions are compatible (rated S) with high-density and cross-linked polyethylene. The dissolved salt is non-oxidizing and does not swell or dissolve polyethylene, so HDPE and XLPE are a standard containment choice. Keep the tank sealed and dry because the salt is hygroscopic.

Why is carbon steel not recommended for LiTFSI?

The ionic salt solution promotes pitting and corrosion of carbon steel, so it is rated Unsuitable (U). Stainless steel and glass are conditional: they are often used in dry, controlled battery processing, but trace fluoride from overheating or acid contact can pit metal and etch glass, so they should be qualified for your specific service.

Does LiTFSI release hydrofluoric acid?

Not under normal storage. LiTFSI is more hydrolytically and thermally stable than LiPF6, but strong overheating or contact with strong acid can decompose the fluorinated sulfonimide anion to release hydrogen fluoride, sulfur oxides, and nitrogen oxides. Store it sealed and dry, away from acids and high heat, and keep fluoride-specific first aid on hand.

Is LiTFSI flammable?

No. It is a non-combustible solid with an NFPA flammability rating of 0 and no flash point. Its primary hazards are acute toxicity, corrosivity, and target-organ effects rather than fire.