| HS Code | 979413 |
| Chemical Name | 4,5-Difluoro-1,3-dioxolan-2-one |
| Synonym | Difluoroethylene carbonate (DFEC) |
| Cas Number | 89149-80-4 |
| Molecular Formula | C3H2F2O3 |
| Molecular Weight | 124.04 g/mol |
| Appearance | Clear colorless liquid |
| Purity | ≥99.0% |
| Melting Point | -20 °C |
| Boiling Point | 110 °C at 15 mmHg |
| Flash Point | 55 °C |
| Density | 1.45 g/cm³ at 20 °C |
| Solubility | Soluble in organic solvents; low solubility in water |
| Water Content | ≤50 ppm |
| Refractive Index | 1.375 at 20 °C |
As an accredited Difluoroethylene Carbonate factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Difluoroethylene carbonate is packaged in sealed, inert, moisture-proof containers, typically 1 kg or 25 kg, ensuring purity and safety. |
| Container Loading (20′ FCL) | 20′ FCL: drums of Difluoroethylene Carbonate properly secured, labeled, segregated from incompatible materials, with adequate ventilation. |
| Shipping | Ship as **UN1993, Flammable Liquid, n.o.s. (Difluoroethylene Carbonate), Class 3, Packing Group II**. Use sealed, UN-approved containers under dry inert gas. Protect from moisture, heat, and ignition sources. Segregate from oxidizers and acids. Display flammable labels and follow IMDG, ADR, or IATA regulations for safe transport. |
| Storage | Store Difluoroethylene Carbonate in a tightly sealed container in a cool, dry, well-ventilated area, away from heat, open flames, and direct sunlight. Protect from moisture and humidity, as hydrolysis may occur. Keep incompatible materials, such as strong oxidizers, acids, and bases, separate. Use appropriate labeling and secondary containment to prevent leaks. |
| Shelf Life | Store in a cool, dry, inert atmosphere; proper handling ensures a shelf life of up to one year. |
A 1.5 wt% loading of difluoroethylene carbonate is introduced into a 1.0 mol/L LiPF₆ electrolyte only after the lithium salt has been fully dissolved and the base solvent water content has been confirmed below 15 mg/kg by Karl Fischer titration. In high-nickel NMC811/SiOx pouch cells, the addition ratio is held between 1.0 wt% and 2.5 wt% relative to total electrolyte mass because higher loadings raise viscosity and depress the −20°C discharge voltage. The base formulation is EC:EMC:DEC at 3:5:2 by volume with 1.0 wt% vinylene carbonate, a system used for automotive-grade 60–100 Ah pouch cells. The downstream production sequence includes electrolyte dripping under a dew point of −35°C, vacuum wetting at −0.095 MPa for 20–40 min, and a 45°C formation soak starting at 0.05C constant current to 4.35 V. The electrolyte is prepared in a closed blending vessel with final filtration through 0.1 µm PTFE membranes. The cell must pass UN 38.3 transport simulation, IEC 62660-1:2018 performance testing for traction batteries, and GB 38031-2020 safety requirements before module assembly. Terminal finished products are 400–800 V EV modules assembled from 60–100 Ah pouch cells. Process control is critical because residual moisture above 20 mg/kg in the electrolyte leads to LiPF₆ hydrolysis and HF generation, which consumes the fluorinated additive before formation and weakens the interfacial film. When a drum is opened, the remaining electrolyte should be used within 24 h or re-analyzed for moisture and HF content.
When the upper cutoff voltage of a consumer LiCoO₂/graphite pouch cell is moved from 4.40 V to 4.48 V, oxidative decomposition of carbonate solvents at the cathode interface becomes the dominant calendar-life limitation. Difluoroethylene carbonate is introduced at 0.5–2.0 wt% of total electrolyte mass to modify the cathode electrolyte interphase and to restrict HF-catalyzed cobalt dissolution. The baseline electrolyte is 1.0 mol/L LiPF₆ in EC:EMC at 3:7 by volume, with vinylene carbonate optionally co-formulated at 1.0 wt%; the two additives together alter the gas composition during the first two formation cycles, so degassing timing must be adjusted after measuring pouch cell swelling. For ultra-thin smartphone cells, qualification requires IEC 62133-2:2017 for portable secondary cells, UL 2054 for household and commercial batteries, and UN 38.3 for transport. The production process uses an injection volume of 2.5–3.0 g/Ah, vacuum wetting at −0.095 MPa, and a stepped formation protocol of 0.05C to 4.48 V followed by 0.1C to full charge. After formation, the gas pocket is punctured, evacuated, and heat-sealed, which is standard for pouch cell finishing. Terminal products include 2.4–5.3 Ah LiCoO₂ pouch cells with nominal voltages of 3.87–3.88 V used in smartphones and tablets. The upper voltage boundary is not without trade-off: when DFEC exceeds 2.0 wt%, low-temperature discharge impedance tends to increase, and published data for this specific configuration is limited.
For 21700 cylindrical cells with a nominal capacity near 5,000 mAh, the electrolyte must fill the jelly roll without leaving dry electrode regions in the innermost windings. A DFEC loading of 1.5–3.0 wt% is used with a 1.0 mol/L LiPF₆ EC:DMC:EMC blend, and the upper addition limit is set by electrolyte viscosity measured on a Brookfield viscometer at 25°C; blends above approximately 8.0 mPa·s slow wetting and create batch-to-batch variation in formation impedance. The production process uses a high-precision injection pump with a dosing tolerance of ±0.05 g per cell, followed by vacuum wetting at −0.08 MPa and centrifugal wetting at 200–400 rpm for 3–5 min to distribute the liquid into the central mandrel region. Formation begins at 0.05C to 4.20 V and then to 4.35 V with a 45°C soak, and cells are aged for 7 days at 30°C before final internal resistance testing. Compliance for power tool, e-bike, and light EV cells is evaluated under IEC 62133-2:2017, UN 38.3, and UL 1642. The terminal product is a 4.8–5.0 Ah 21700 cylindrical cell with a maximum continuous discharge rating defined by cell temperature limits, commonly 10–15 A depending on cell design. At −20°C, cells containing more than 3.0 wt% DFEC may exhibit higher charge-transfer impedance, and published data for this specific configuration is limited.
When a downstream electrolyte blender supplies multiple cell makers with high-nickel cathode formulations, difluoroethylene carbonate is maintained as a concentrated additive solution in EMC at 10.0–20.0 wt% to reduce repeated handling of the pure fluorinated carbonate and to improve metering accuracy. The concentrated solution is added to the finished electrolyte in a closed 500–1,000 L stainless steel reactor whose residual moisture is held below 20 mg/kg and free acid below 50 mg/kg. The final electrolyte must comply with REACH (EC) No 1907/2006, CLP (EC) No 1272/2008, and IATA DG regulations for shipment; depending on the measured flash point, the blend may be classified as a flammable liquid, and the shipper must verify the applicable packing group. The addition ratio is calculated so that the final cell electrolyte contains 1.0–2.0 wt% DFEC; dilution is performed at 15–25°C with 60–120 rpm agitation for not less than 45 min. The blended electrolyte is filtered through 0.1 µm polytetrafluoroethylene membranes and transferred into 200 L stainless steel drums or 1,000 L ISO containers under nitrogen blanketing. The immediate downstream product is a high-voltage electrolyte solution, which is then used by cell makers to produce EV pouch cells, prismatic cells, and cylindrical cells; terminal finished products include traction battery packs and portable energy storage devices. The primary operational boundary is moisture ingress: once a drum is opened, the remaining electrolyte should be used within 24 h or re-analyzed for moisture and HF content before filling.
| Standard or test method | Scope | Typical acceptance criterion |
|---|---|---|
| UN 38.3 | Transport simulation for cells and batteries | No fire, no explosion, no leakage |
| IEC 62619:2022 | Industrial secondary lithium cells and batteries | Pass thermal, electrical, and mechanical safety tests |
| IEC 62660-1:2018 | Traction cell performance | Capacity, energy, and power per specification |
| GB 38031-2020 | Electric vehicle traction battery safety | No fire or explosion within specified post-test period |
| UL 9540A | Thermal runaway propagation at module and pack level | No propagation beyond target cell |
In prismatic cells with a laser-welded aluminum square shell and a nominal capacity above 150 Ah, the substitution of a fraction of EMC by DFEC changes not only the interfacial film composition but also the gas generation profile during formation and thermal abuse. The electrolyte formulation under evaluation uses 1.0 mol/L LiPF₆ in EC:DMC:EMC with 1.0 wt% vinylene carbonate and 1.5–2.5 wt% DFEC. Because the cell breathes under charge and discharge, a clamp fixture applying 3–5 kN is used during formation, and the swelling force is recorded as a batch-to-batch quality metric; a rise above 5 kN during the first formation cycle triggers rejection because it indicates excessive gas generation or insufficient wetting. The production process includes electrolyte injection at 4.0–4.5 g/Ah, vacuum wetting at room temperature, and a 45°C formation protocol with 0.05C constant current to 4.35 V for high-nickel cathode systems. Compliance testing for traction applications follows GB 38031-2020; module-level propagation performance is assessed under UL 9540A, and transport simulation follows UN 38.3. Thermal runaway onset is measured by adiabatic rate calorimetry using a heat-wait-search method from 50°C at 0.02°C/min; the self-heating temperature is influenced by the LiF-rich anode interphase and cathode surface stabilization, although published cell-level data for this specific fluorinated carbonate is limited. The terminal product is a 150–300 Ah prismatic EV cell assembled into 400 V or 800 V automotive battery packs. Process incompatibility must be noted: DFEC should not be combined with strongly basic or amine-based electrolyte additives at elevated temperature because nucleophilic attack can open the cyclic carbonate ring and release fluoride species.
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4,5-Difluoro-1,3-dioxolan-2-one, CAS RN 87189-24-6, is supplied as a fluorinated cyclic carbonate for lithium-ion electrolyte formulation. The molecule has the formula C3H2F2O3 and a molar mass of 124.04 g mol⁻¹; the two fluorine substituents occupy the 4- and 5-positions of the dioxolanone ring. Commercial documentation may list the product as difluoroethylene carbonate, DFEC, or battery-grade fluorinated cyclic carbonate, but no universal product model code is assigned. Because no single ISO product standard exists, purchase orders are written against the CAS RN, molecular formula, gas-chromatographic purity, moisture content, free fluoride, chloride, and packaging configuration. The compound is not a drop-in replacement for ethylene carbonate or fluoroethylene carbonate; its function is evaluated as an additive or co-solvent in high-voltage and silicon-containing lithium-ion systems. The accepted commercial specification is therefore the certificate of analysis rather than a nominal grade name. Suppliers commonly report purity by capillary gas chromatography with flame ionization detection, moisture by Karl Fischer coulometry aligned to ASTM E203, and density by oscillating U-tube methods aligned to ASTM D4052. Lot-to-lot consistency is managed under ISO 9001:2015, Clause 8.5.6, with change control for raw-material sources and purification conditions. Published data for a unified physical-property specification across all suppliers is limited; values such as density, refractive index, and boiling range should be read from the lot-specific certificate rather than generic literature.
Electrolyte blending operations introduce DFEC after the base carbonate mixture has been dried to a moisture content of 10 mg kg⁻¹ or lower in 316L stainless-steel vessels. The vessel is inerted with nitrogen and fitted with a magnetically coupled agitator; the additive is transferred through a sealed feed line to prevent headspace moisture ingress. Because the material is sensitive to hydrolysis, the surrounding dry-room dew point is maintained at -40°C or below. At addition levels of 0.5–3.0 wt%, the low mass fraction does not dominate bulk conductivity, but localized concentration gradients near the feed nozzle can produce transient viscosity differences and uneven wetting of the separator in downstream cell filling. Metering is therefore performed at a controlled rate with in-line static mixers of 20–30 elements, followed by low-shear recirculation. Vessel-specific validation is required because published data for this exact configuration is limited.
In lithium-ion electrolytes, the most consequential impurities in fluorinated cyclic carbonates are water, free fluoride, chloride, and high-boiling organic residues. Water reacts with LiPF6 to form HF and PF5; the resulting acid attack degrades carbonate solvents, dissolves transition metals from the cathode, and increases cell impedance. Free fluoride from incomplete purification or storage hydrolysis attacks the surface of nickel-rich cathode particles and can induce pitting in aluminum current collectors at high potential. Chloride limits are enforced because chloride accelerates aluminum corrosion and can participate in parasitic redox shuttles. Gas-chromatographic purity alone does not capture these risks; a 99.5% area purity may still contain 0.5% of a surface-active impurity that raises first-cycle irreversible capacity. For this reason, procurement specifications frequently add orthogonal limits: moisture ≤50 mg kg⁻¹, free fluoride ≤20 mg kg⁻¹, chloride ≤5 mg kg⁻¹, and color below 20 APHA. These values are representative battery-grade supply limits, not universal legal limits, and must be confirmed in the purchase contract and the supplier quality agreement.
| Parameter | Method/Instrument | Representative limit | Process risk |
|---|---|---|---|
| Gas-chromatographic purity | GC-FID, capillary column | ≥99.5 area % | unresolved organic impurities |
| Moisture | ASTM E203 Karl Fischer coulometry | ≤50 mg kg⁻¹ | LiPF6 hydrolysis and HF generation |
| Free fluoride | Ion chromatography | ≤20 mg kg⁻¹ | aluminum current-collector corrosion |
| Chloride | Ion chromatography | ≤5 mg kg⁻¹ | pitting and redox shuttle formation |
| Color | APHA visual or spectrophotometric | ≤20 APHA | oxidized impurity indicator |
When the additive is sampled from drums or intermediate bulk containers, the sampling procedure should be performed under a dry nitrogen curtain. A 200 L drum opened for 10 min in a room at 40% RH can absorb enough water to exceed the 50 mg kg⁻¹ limit depending on headspace movement and air exchange. This is why electrolyte manufacturers require re-verification of moisture after any abnormal storage event or after partial container use. A second failure mode is residue formation when DFEC is mixed with amine-containing impurities or strongly basic desiccants; nucleophilic attack opens the carbonate ring and generates glycol-type by-products that raise the acid number and may clog microporous separator channels. Contact with amines and strongly basic materials is therefore avoided.
Fluoroethylene carbonate is established as a reference additive because the single fluorine substituent leads to a LiF-rich solid electrolyte interphase that accommodates volume change in silicon–graphite anodes. FEC has the formula C3H3FO3 and a molar mass of 106.05 g mol⁻¹; it is commonly evaluated at 2–10 wt% in carbonate electrolytes. DFEC introduces a second fluorine at the 5-position, raising the molar mass to 124.04 g mol⁻¹ and changing the reduction pathway. In a graphite or silicon–graphite anode, the additional fluorine can produce a more heavily fluorinated SEI; however, higher fluorine content does not directly translate into lower impedance. The SEI also contains polymeric and organic carbonate decomposition products that are controlled by salt concentration, solvent ratio, formation current density, and temperature. Substitution of FEC with DFEC at equal mass percentage is not stoichiometrically equivalent because the molar fluorine content and reduction products differ. A formulation containing 2 wt% FEC and a formulation containing 2 wt% DFEC cannot be assumed to have the same SEI thickness, first-cycle loss, gas evolution, or high-temperature storage behavior. Cell-level comparisons are therefore run with constant anion and carbonate composition using IEC 62660-1 or equivalent internal cell-test protocols. Published data for this specific configuration is limited; batch-specific validation is required.
| Parameter | Ethylene carbonate | Fluoroethylene carbonate | Difluoroethylene carbonate |
|---|---|---|---|
| CAS RN | 96-49-1 | 114435-02-8 | 87189-24-6 |
| Molecular formula | C3H4O3 | C3H3FO3 | C3H2F2O3 |
| Molar mass | 88.06 g mol⁻¹ | 106.05 g mol⁻¹ | 124.04 g mol⁻¹ |
| Fluorine substitution | none | 4-position | 4,5-positions |
| Electrolyte role | primary solvent | SEI additive or co-solvent | high-voltage additive or co-solvent |
In high-voltage NMC811 or lithium manganese nickel oxide systems, DFEC is used as an additive or co-solvent to alter the cathode electrolyte interphase. The electron-withdrawing effect of the second fluorine lowers the HOMO energy relative to unsubstituted ethylene carbonate, which may improve oxidation tolerance under high-voltage cycling. This effect is not independent of the cathode surface; transition-metal sites and conductive carbon can catalyze carbonate oxidation even when the additive is present. High-voltage compatibility testing is typically performed in pouch or coin cells with a polyethylene or polypropylene separator, a 1 M LiPF6 electrolyte in carbonate solvents, and a voltage window of 2.8–4.35 V or 3.0–4.5 V depending on cathode chemistry. The dosage is adjusted in 0.5 wt% steps, and the response is measured by Coulombic efficiency, DC internal resistance, and capacity retention after storage at 45–60°C. No universal additive concentration can be specified without defining the cathode, anode, formation protocol, and test standard.
Published data for sodium-ion and lithium metal electrolytes containing DFEC is limited. The additive’s reduction and oxidation behavior should not be extrapolated from lithium-ion graphite systems without half-cell, symmetric-cell, and full-cell testing. In lithium metal systems, the SEI composition and lithium deposition morphology are sensitive to current density, stack pressure, and electrolyte flow. The addition of a fluorinated cyclic carbonate may alter dendrite growth, but it may also increase interfacial resistance if the SEI becomes too resistive. In sodium-ion hard-carbon systems, passivation requirements differ because the sodium-ion radius and hard-carbon surface chemistry are not identical to lithium-ion graphite. Consequently, DFEC is assessed experimentally at 0.5–2.0 wt% in sodium-ion or lithium metal electrolytes, with cycling performance measured under IEC 62660-1 or academic coin-cell protocols. Published data for this specific configuration is limited; no substitution ratio can be inferred from lithium-ion graphite data alone.
In electrolyte manufacturing, the addition of DFEC is completed after the LiPF6 salt is fully dissolved and the bulk temperature has returned to 15–25°C. The reaction between water and LiPF6 is exothermic, and an additive containing free fluoride or residual moisture can initiate localized hydrolysis. Contact surfaces are constructed of 316L stainless steel or fluoropolymer-lined components because long contact with free fluoride can corrode unlined carbon steel. Inline static mixers are preferred over top-mounted high-shear dispersers for low-viscosity carbonate systems; the static mixer dilutes the additive without pulling air into the electrolyte. The batch is sampled at top, middle, and bottom ports and analyzed for moisture and acidity before filling. If moisture exceeds 15 mg kg⁻¹, the batch is reworked using molecular sieves acceptable to the cell manufacturer and re-analyzed. The exact rework loop is plant-specific and is documented in the process control plan.
Vinylene carbonate is an unsaturated cyclic carbonate that forms a polymeric anode SEI and is used at 1–5 wt%; its action differs from DFEC. The fluorinated dioxolanone does not contain vinyl unsaturation and therefore cannot polymerize by the same mechanism. VC is often consumed at the anode during formation, whereas DFEC may distribute between anode and cathode surfaces depending on voltage, transport, and cell design. In high-voltage cells, VC can contribute to cathode impedance at elevated temperature because the polymer layer may not be stable at high potential. DFEC is evaluated as a fluorinated cathode-surface modifier that does not rely on vinyl polymerization. The difference is verified by post-mortem X-ray photoelectron spectroscopy of the electrode surface and by electrical impedance spectroscopy with a 10 mV AC perturbation from 100 kHz to 10 mHz. No single additive is superior across all cell designs; selection is a formulation-specific trade-off among anode durability, cathode impedance, gas generation, and calendar life.
The additive is packaged in narrow-neck glass ampoules or fluoropolymer-lined containers under a dry nitrogen headspace. Moisture ingress after first opening is the primary degradation pathway. The container should be resealed immediately after sampling, and any product transferred into process equipment should be blanketed with nitrogen at 0.2–0.5 bar positive pressure. Storage at 2–8°C slows hydrolysis and impurity formation, although low temperature can increase viscosity and slow discharge from small-diameter feed lines. Before use, the liquid is warmed to room temperature in the sealed container to avoid condensation. Personnel exposure limits follow the safety data sheet for the specific supplier, and engineering controls are selected for fluorinated organic liquid handling. Free fluoride generated by decomposition requires waste streams to be segregated from acid-sensitive systems.
