Fluoroethylene Carbonate (FEC) Storage & Tank Compatibility

Storing Fluoroethylene Carbonate (FEC)? Start Here

Fluoroethylene carbonate (FEC) is a colorless cyclic carbonate ester (CAS 114435-02-8) used as a high-value electrolyte solvent and film-forming additive in lithium-ion and lithium-metal batteries. It is rarely a single-component bulk fluid in the field: it is shipped battery-grade (typically 99%+) and then blended into carbonate electrolytes alongside ethylene carbonate, EMC, and DMC, where it builds a thin, stable solid-electrolyte interphase (SEI) on silicon and graphite anodes. Because FEC is a polar aprotic organic solvent — not a water-based salt solution — material of construction (MOC) is driven by solvent attack and chemistry control, not by salinity. The dominant failure modes are swelling and stress-cracking of unsuitable plastics, and slow hydrolysis to release hydrofluoric acid (HF) if moisture or heat is present. Choosing the right tank, lining, and seal materials — and keeping the product dry and cool — protects both the asset and the demanding purity spec the battery market requires.

Is Polyethylene (HDPE / XLPE) Safe for Fluoroethylene Carbonate?

No — polyethylene is not recommended for FEC. FEC is a polar aprotic cyclic carbonate ester, and ester/ketone-class organic solvents are a known weakness of polyethylene: they are absorbed into the polymer, causing swelling, softening, and environmental stress-cracking over time, even though FEC's high boiling point and >102°C flash point make it relatively non-volatile. General polyethylene chemical-resistance charts rate esters and ketones as poor-to-unsuitable for continuous storage, and that behavior carries to carbonate esters like FEC. Equally important, FEC's battery-grade purity (ppm water, ppm HF) must be preserved; a permeable, leachable plastic wall works against that spec. Use stainless steel (316 preferred), a solvent-rated lined steel tank, or a resin-verified FRP, with PTFE/PFA/FKM seals. If any polyethylene is unavoidable in a transfer line, treat it as short-contact only and verify against your supplier's SDS and a chemical-resistance chart for ester/carbonate solvents.

Material compatibility at a glance

FEC is a polar aprotic cyclic carbonate solvent, not an aqueous brine, so polyethylene is the wrong material — carbonate esters swell and stress-crack HDPE/XLPE much like ketones and esters do. Specify stainless steel (316 where trace HF/moisture is possible), a solvent-rated lined steel tank, or a resin-verified FRP, with PTFE/PFA/FKM seals. Keep FEC dry; water and heat drive HF formation and hydrolysis.

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

• Harmful if swallowed (H302); causes skin and serious eye irritation (H315, H319) — wear chemical goggles and gloves.
• Skin sensitizer (H317) — repeated exposure may trigger an allergic reaction; avoid all skin contact.
• Combustible liquid (flash point >102°C); keep away from heat, sparks, and open flame and store cool.
• Hydrolyzes slowly in the presence of water and heat to release hydrofluoric acid (HF); keep containers sealed and dry.
• Thermal decomposition can yield HF and carbon oxides — provide ventilation and avoid overheating.
• Always follow the specific supplier SDS; battery-grade impurity limits and hazard details vary by lot and grade.

Common questions

Can I store fluoroethylene carbonate in an HDPE or XLPE poly tank?

No. FEC is a polar carbonate-ester solvent that swells and stress-cracks polyethylene over time, and a plastic wall can also compromise the ppm-level purity the battery market needs. Use stainless steel, solvent-rated lined steel, or resin-verified FRP instead.

Is FEC flammable?

It is combustible, not flammable. Its flash point is above 102°C (roughly 216°F), so it will not ignite at ordinary temperatures, but it must still be kept away from heat and ignition sources and stored cool.

Why does FEC need to be kept dry?

Water and heat drive hydrolysis of the carbonate ring, which can release hydrofluoric acid (HF) and degrade the product. Sealed, dry, cool storage protects both safety and the battery-grade purity spec.

What seal and gasket materials work with FEC?

PTFE, PFA, and FKM (fluoroelastomer) seals are recommended. Avoid EPDM and nitrile (Buna-N), which are attacked by polar organic solvents like FEC.