| HS Code | 436279 |
| Product Name | Electrolyte for Polyanionic Cathode/Hard Carbon Battery |
| Electrolyte Type | Sodium-ion battery electrolyte |
| Sodium Salt | NaPF6 |
| Salt Concentration | 1.0 M |
| Solvent Composition | EC:PC:DMC (1:1:1 by weight) |
| Additive | 2% FEC (fluoroethylene carbonate) |
| Ionic Conductivity | 6.5 mS/cm at 25°C |
| Electrochemical Stability Window | 1.0-4.5 V vs Na/Na+ |
| Operating Temperature Range | -20°C to 60°C |
| Water Content | <20 ppm |
| Free Acid Content | <50 ppm |
| Viscosity | 3.5 cP at 25°C |
| Density | 1.2 g/cm3 at 25°C |
| Sodium Ion Transference Number | 0.45 |
| Compatibility With Polyanionic Cathode | Stable, forms robust CEI layer |
| Compatibility With Hard Carbon Anode | Stable, forms efficient SEI layer |
As an accredited Electrolyte for Polyanionic Cathode/Hard Carbon Battery factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Sealed 1 L corrosion-resistant bottle under inert argon, with leak-proof cap, hazard labeling, and electrolyte specification sheet. |
| Container Loading (20′ FCL) | 20′ FCL safely loads drummed/non-hazardous battery electrolyte, secured with dunnage, labeled, and ventilated per shipping regulations. |
| Shipping | This electrolyte is shipped as a hazardous, flammable liquid. It must be packaged in leak-proof, UN-certified containers, with proper labeling and documentation. Transport requires compliance with IATA/IMDG/ADR regulations, avoiding extreme temperatures and direct sunlight. Ensure upright handling and secondary containment to prevent spills during transit. |
| Storage | Store in a cool, dry, well-ventilated area away from direct sunlight, heat, and ignition sources. Keep the container tightly sealed to prevent moisture absorption and contamination. Use compatible, corrosion-resistant materials. Store separately from oxidizing agents, acids, and bases. Ensure proper labeling and secondary containment to manage spills safely. |
| Shelf Life | Shelf life typically 6–12 months when sealed, stored cool, dry, and away from moisture or oxygen. |
In 20-foot containerised sodium-ion storage systems using NVPF-type polyanionic cathodes and hard carbon anodes, the electrolyte is formulated as a 1.0 mol/L NaPF6 solution in EC:DEC (1:1 v/v). The addition ratio is 5 wt% fluoroethylene carbonate, 1 wt% 1,3-propane sultone, and 0.5 wt% ethylene sulfate; total electrolyte fill is held at 3.2 ± 0.2 g/Ah, corresponding to 890–920 g per 280 Ah prismatic cell. Field data from production-scale dry rooms show that batch-to-batch hard carbon BET surface area variation from 3.2 m²/g to 5.8 m²/g translates into first-cycle Coulombic efficiency shifts of 1.2–2.4 percentage points, requiring electrolyte wetting time adjustment because un-wetted anode regions create local sodium plating during formation. Electrolyte viscosity at 25°C is specified within 6.8–7.4 mPa·s; at 10°C viscosity rises to 14–16 mPa·s, increasing filling line dwell time and reducing daily cell output.
Production for this segment uses NMP-based polyanionic cathode slurry and water-based hard carbon anode slurry on slot-die coating lines, with the anode calendered to 0.9–1.0 g/cm³ density. Measured anode porosity below 34% delays electrolyte wicking; typical anode pore volume is 0.12–0.15 cm³/g. Vacuum filling equipment maintains residual pressure below 5 kPa absolute for 12–18 h, followed by sealing and formation at 0.05C constant current to 4.00 V in a 45°C chamber to stabilize the NaF-rich interphase. On-line field failure data indicate dry-room dew point excursions above -40°C correlate with first-cycle capacity loss of 0.8–1.5%. Compliance is anchored to IEC 62619:2022 clause 7.2.2, GB/T 36276-2023 cell and module tests, UL 9540A:2019, and UN 38.3. Terminal products comprise 280 Ah prismatic cells assembled into 1P48S modules and installed in 20 ft containers rated at 5.0 MWh with 1,500 V DC bus architecture.
For low-speed electric vehicle packs operating at 72–144 V and 8–15 kWh total energy, the polyanionic cathode/hard carbon cell requires an electrolyte that forms a stable SEI during first charge without excessive carbonate decomposition at 4.00 V. The selected formulation uses 1.0 M NaPF6 in EC:DMC:EMC (1:1:1 v/v/v) with 3–5 wt% FEC, 1 wt% vinylene carbonate, and 0.5 wt% DTD; fill ratio is 3.0 g/Ah for 50–100 Ah prismatic cells. On high-speed filling lines, injection accuracy is maintained at ±0.5 wt%, and pre-wetting uses a nitrogen pressure pulse of 0.4–0.6 MPa for 30–60 s after initial vacuum below 8 kPa. Formation launches at 0.05C to 3.90 V, then 0.1C to 4.05 V; the polyanionic cathode first-cycle efficiency is 92–95%, while hard carbon anode first-cycle efficiency lies near 82–88%, so the electrolyte additive package must consume surface oxygen groups without excessive gas generation.
| Formulation variable | Low-power urban quadricycle | High-power LSEV |
|---|---|---|
| NaPF6 concentration | 0.9 mol/L | 1.0 mol/L |
| EC:DMC:EMC volume ratio | 1:2:1 | 1:1:1 |
| FEC addition | 3 wt% | 5 wt% |
| DTD addition | 0.3 wt% | 0.5 wt% |
| Target viscosity at 25°C | 5.8–6.5 mPa·s | 4.8–5.6 mPa·s |
| Fill ratio | 3.2 g/Ah | 3.0 g/Ah |
Low-speed EV production demands continuous tab welding and hard carbon anode compression at 0.8–1.1 g/cm³; the electrolyte must tolerate residual moisture below 20 ppm without forming HF. Compliance testing follows UN/ECE R100.02 Annex 8, GB 38031-2020, ISO 12405-3:2014, and UN 38.3. Terminal products include 72 V 100 Ah and 96 V 80 Ah battery packs installed in urban micro-EVs and quadricycles, with pack-level energy of 7.2–10 kWh.
In telecom backup and uninterruptible power standby installations, long float intervals at high state of charge make oxidative electrolyte stability at the polyanionic cathode more critical than low-temperature rate capability. The specified electrolyte uses 0.8 mol/L NaPF6 in EC:PC:DEC (3:1:4 v/v/v), with 2 wt% FEC, 0.5 wt% vinyl ethylene carbonate, and total fill ratio 3.5 g/Ah. Production-scale 100 Ah prismatic cells are assembled with 0.1–0.2 MPa external compression; the filling line performs vacuum injection at -95 kPa gauge and then holds cells for 18–24 h before sealing. Formation protocol charges at 0.05C to 3.95 V and then ages at 45°C for 72 h to stabilize the NaF-rich interphase. Published data for float aging beyond 10 years in sodium-ion telecom cells remain limited; manufacturers typically interpolate from accelerated 60°C storage data. Compliance is anchored to Telcordia GR-3150-CORE, UL 1973:2018, IEC 62619:2022, and IEC 62485-2:2010. Terminal products comprise 48 V 100 Ah rack-mounted modules and 19-inch indoor cabinets rated for 10 kW per string.
Industrial motive power for automated guided vehicles, pallet movers, and small forklifts requires discharge and regen pulses exceeding 3C for 10–30 s, pushing the electrolyte toward higher linear carbonate content and lower viscosity. The selected sodium-ion electrolyte uses 1.0 M NaPF6 in EC:DMC (3:7 v/v) with 4 wt% FEC, 1 wt% 1,3-propane sultone, and 0.5 wt% ethylene sulfate. Total fill is maintained at 3.0 g/Ah; conductivity at 25°C is specified above 8.5 mS/cm. Cell production uses 100 Ah prismatic cells with laser-welded aluminum tabs; electrolyte injection equipment applies a two-step pressure-swing sequence from 5 kPa absolute to 0.6 MPa nitrogen for 45 s, then returns to 8 kPa for 10 min. Formation at 0.1C to 4.0 V is followed by 0.5C cycling for three cycles to condition hard carbon SEI. Compliance references EN 1175:2020 for industrial truck electrical systems, UL 2580:2019, and IEC 62619:2022 clause 7.2.3. Terminal products include 24 V 200 Ah and 48 V 300 Ah packs mounted in AGV frames; the lower PC content reduces anodic intercalation exfoliation at hard carbon surfaces during high-rate charge.
The dominant process conflict in high-rate AGV cells is anode wetting during rapid charge. At a 3C regen pulse, the effective sodium ion flux at the hard carbon anode reaches 1.5–2.0 mA/cm², and unwetted regions become high local current density sites. Electrolyte viscosity must remain below 5 mPa·s at 25°C and below 12 mPa·s at -10°C; the DMC-rich solvent achieves this but reduces flash point to below 25°C, placing bulk electrolyte transport and storage under UN 1993 flammable liquid classification. Twin-screw mixing and high-shear dispersion ensure NaPF6 dissolution exotherm does not exceed 35°C, preventing thermal degradation of FEC. Field data show improper pressure-swing filling causes 3–5% capacity deficit after formation and increases DC internal resistance by 12–18% at 50% SOC.
Daily cycling of residential storage from 20% to 90% SOC at 0.3C to 0.5C creates a narrow window where gas evolution at the polyanionic cathode is minimal but the hard carbon anode must sustain continuous sodium ion insertion without metal plating. The electrolyte is formulated as 1.0 M NaPF6 in EC:DMC:PC (2:1:1 v/v/v) with 3 wt% FEC and 0.3 wt% DTD; fill ratio is 3.1 g/Ah. In production, 100 Ah prismatic cells are filled using peristaltic dosing pumps with ±0.5 wt% dispense accuracy, then sealed under -80 kPa gauge. Formation includes 0.05C charge to 3.90 V, a 12 h rest at 45°C, and a second 0.1C charge to 4.00 V. Compliance testing follows IEC 62619:2022 clause 7.2.1, UL 9540:2020, and VDE-AR-E 2510-50. Terminal products are 51.2 V 100 Ah modules in 5.12 kWh rack units, commonly grouped into 10.24 kWh residential installations. The operating boundary is set by calendar aging at 50°C where carbonate transesterification can raise internal pressure; published data for this specific residential sodium-ion configuration are limited beyond 6,000 cycles.
Across light electric two-wheeler assembly lines, polyanionic cathode/hard carbon cells are assembled around cylindrical formats because of their mechanical abuse tolerance and high-volume winding infrastructure. The electrolyte uses 1.1 M NaPF6 in EC:EMC (3:7 v/v) with 5 wt% FEC, 1 wt% 1,3-propane sultone, and 0.5 wt% DTD; fill ratio is 2.8 g/Ah, lower than prismatic cells because cylinder headspace is tighter. High-speed electrolyte injection on 21700 lines applies vacuum below 10 kPa absolute, followed by centrifugal wetting at 800–1,200 rpm for 60 s; this sequence prevents un-wetted hard carbon anode regions that would otherwise form sodium dendrites. Formation uses 0.05C to 3.95 V, then 0.2C to 4.05 V with 10% capacity verification. Compliance is determined by UN 38.3, UL 2271:2018, EN 50604-1:2016, and UN/ECE R136 where vehicle integration applies. Terminal products are 48 V 30 Ah and 60 V 20 Ah removable packs, with 2.0–3.5 kWh pack energy. Overcharge and nail-penetration testing at 100% SOC are standard production lot controls because the high FEC content lowers onset temperature of thermal runaway mitigation through NaF interphase formation but does not eliminate all pack-level venting risks.
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NPEC-102-HC is formulated as a non-aqueous sodium-ion electrolyte for cells that combine polyanionic positive electrodes—principally Na₃V₂(PO₄)₃ and Na₄Fe₃(PO₄)₂P₂O₇—with hard carbon negative electrodes. The liquid uses NaPF6 at a nominal concentration of 1.0 mol dm⁻³ in ethylene carbonate and diethyl carbonate at a 1:1 volume ratio; fluoroethylene carbonate is present at 2.0 wt% as the primary solid-electrolyte-interphase additive. Production release limits include water at ≤20 mg kg⁻¹ by ISO 760, free acid as HF at ≤50 mg kg⁻¹ by acid-base titration, density of 1.27–1.29 g cm⁻³ at 25 °C by ISO 12185, and dynamic viscosity of 4.0–4.5 mPa·s at 25 °C by ISO 3104. Conductivity is specified as ≥8.0 mS cm⁻¹ at 25 °C. The product is filtered through a 0.2 µm polytetrafluoroethylene membrane and filled under dry air with a dew point below -50 °C.
| Parameter | Release specification | Test method |
|---|---|---|
| NaPF6 concentration | 1.0 ± 0.05 mol dm⁻³ | ion chromatography / ICP-OES |
| Ethylene carbonate : diethyl carbonate volume ratio | 1:1 ± 0.02 | gas chromatography |
| Fluoroethylene carbonate content | 2.0 ± 0.2 wt% | GC-FID |
| Water content | ≤20 mg kg⁻¹ | ISO 760 |
| Free acid as HF | ≤50 mg kg⁻¹ | acid-base titration |
| Density at 25 °C | 1.27–1.29 g cm⁻³ | ISO 12185 |
| Dynamic viscosity at 25 °C | 4.0–4.5 mPa·s | ISO 3104 |
| Conductivity at 25 °C | ≥8.0 mS cm⁻¹ | impedance spectroscopy |
On a production electrode line the dominant bottleneck is not bulk conductivity but the formation of a stable hard carbon SEI. Hard carbon electrodes with specific surface area above 1,500 m² g⁻¹ consume electrolyte during first charge; the 2.0 wt% FEC addition is intentionally set below 3.0 wt% to limit gas evolution while still generating sufficient NaF. In cells with 18650 geometry and an electrode stack wound to 0.35 mm mandrel tension, formation at 0.05 C to 0.1 C reduces the first-cycle capacity loss to 10–15% after a 4–8 h pre-soak.
Hard carbon in sodium-ion cells does not follow the graphite intercalation mechanism; the low-voltage plateau below 0.1 V vs Na/Na⁺ is assigned to sodium filling in closed nanopores, while the sloping region above 0.1 V involves adsorption at defects and edges. Carbonate solvents that are problematic for graphite are less prone to exfoliation in hard carbon, but simple NaPF6 in EC:DEC still forms a sodium-alkyl-carbonate-rich SEI that dissolves partially and exposes fresh surface. FEC is reduced at approximately 1.4 V vs Na/Na⁺ to yield NaF and poly(vinylene carbonate), producing a denser interphase. Public half-cell data for comparable formulations show first-cycle Coulombic efficiency of hard carbon rises from 78% without FEC to 85–88% with 2.0 wt% FEC at 20 mA g⁻¹; increasing FEC to 5.0 wt% improves this by less than 2 percentage points but increases formation gas volume by approximately 40%.
On the positive side, polyanionic cathodes are selected for stable phosphate frameworks, but the carbon black additive network can catalyze carbonate oxidation. The upper operating voltage is therefore controlled at 3.95–4.05 V vs Na/Na⁺ for Na₃V₂(PO₄)₃ and Na₄Fe₃(PO₄)₂P₂O₇. NaPF6 passivates the aluminum current collector through AlF₃ formation above 3.8 V; sulfonimide salts such as NaFSI or NaTFSI are excluded from this product because they induce aluminum pitting at 4.0–4.2 V unless concentrations exceed 3.0 mol dm⁻³. The trade-off is lower conductivity than sulfonimide formulations: 8.0–8.5 mS cm⁻¹ compared with 9.0–10.0 mS cm⁻¹ for equivalent NaFSI blends. The lower conductivity is accepted because the hard carbon anode permits a wider processing window than lithium metal and does not require ether-based SEI chemistry.
Transition-metal dissolution from polyanionic cathodes is lower than from layered oxides, but phosphate cathodes can still release vanadium or iron species when cells are held above 4.2 V for more than 100 h. These species migrate to the hard carbon and can catalyze electrolyte reduction. The product’s free-acid limit of ≤50 mg kg⁻¹ reduces phosphate framework protonation. In contrast, NaFSI-based electrolytes may show lower free acid but higher aluminum dissolution; the trade-off is managed by selecting NaPF6 for polyanionic cathode chemistries operating above 3.8 V.
Hard carbons from coconut shell or phenolic resin precursors contain oxygen functional groups at edge sites that influence FEC reduction. Surface oxygen content between 2–5 at% promotes NaF deposition; below 1 at%, wetting by the electrolyte is poor. The electrolyte cannot compensate for a hard carbon with surface oxygen below 1 at% except by increasing FEC to 3.0 wt%, which then raises gas evolution during formation.
Electrode drying is external to the electrolyte, but batch variance in residual moisture changes the acid number during cell formation. Electrodes dried to 200 mg kg⁻¹ residual water or lower are acceptable; a hard carbon electrode with 800 mg kg⁻¹ residual water consumes the FEC additive through hydrolysis and produces HF. Battery manufacturers typically dry hard carbon anodes at 120–150 °C under vacuum for 12 h, and polyanionic cathode electrodes at 100–120 °C under vacuum for 8–12 h.
Compared with EC:PC-based grades, this product retains higher conductivity at room temperature because diethyl carbonate has lower viscosity than propylene carbonate; published values for 1 M NaPF6 in EC:PC are commonly 6.8–7.5 mS cm⁻¹ at 25 °C. The EC:PC system has better low-temperature liquid range but can increase interfacial resistance on hard carbon unless sulfite or sultone additives are introduced. Compared with EC:DMC-based grades, this product has higher boiling point and flash point but slightly lower conductivity; dimethyl carbonate-containing electrolytes may reach 9.5 mS cm⁻¹ at 25 °C but their flash point can fall below 20 °C, complicating vacuum filling and transport classification. The present formulation has a flash point of 31 °C and is classified as UN 1993, Class 3, Packing Group III. Compared with NaFSI or NaTFSI carbonate grades, this product sacrifices some conductivity for aluminum current-collector compatibility and lower sulfonimide-induced anode corrosion; sulfonimide electrolytes are reserved for cells with lower upper voltage or for high-concentration formulations above 3.0 mol dm⁻³.
| Formulation | Conductivity at 25 °C | Flash point | Hard carbon first-cycle Coulombic efficiency | Aluminum pitting potential |
|---|---|---|---|---|
| NPEC-102-HC, 1 M NaPF6 EC:DEC 1:1 + 2 wt% FEC | 8.0–8.5 mS cm⁻¹ | 31 °C | 85–88% | >4.2 V |
| 1 M NaPF6 EC:PC 1:1 + 2 wt% FEC | 6.8–7.5 mS cm⁻¹ | 28 °C | 82–85% | >4.2 V |
| 1 M NaPF6 EC:DMC 1:1 + 2 wt% FEC | 9.5–10.0 mS cm⁻¹ | 18 °C | 84–87% | >4.2 V |
| 1 M NaFSI EC:DEC 1:1, no additive | 9.0–9.5 mS cm⁻¹ | 30 °C | 78–82% | 3.8–4.0 V |
Operational limits in full cells are shaped by the negative-to-positive capacity ratio. A ratio below 1.05 can drive the hard carbon anode below 0 V during constant-current charging, producing sodium plating on the anode surface and rapid capacity fade. A ratio above 1.20 reduces energy density without improving cycle life. The recommended negative-to-positive capacity ratio is 1.10–1.15. Under these conditions and with the upper voltage held at 3.95 V, public data for comparable Na₃V₂(PO₄)₃/hard carbon cells report 80% capacity retention after 1,000 cycles at 1 C; published data for this exact product are limited.
Compatibility boundaries are narrow in open production environments. Water ingress above 30 mg kg⁻¹ converts NaPF6 to HF and PF₅; bare copper negative tabs corrode, and the resulting HF attacks the phosphate cathode surface. The product must be transferred through closed stainless-steel or fluoropolymer circuits with FFKM seals; silicone, EPDM, and nitrile wetted parts swell in the carbonate solvent. Open-vessel exposure at relative humidity above 10% for more than 30 min is outside the defined process envelope. Mixing with lithium salts is not permitted because mixed alkali hexafluorophosphate precipitates can form. Contact with amine-based additives or urethane adhesives may accelerate carbonate transesterification and is to be avoided.
Electrolyte filling is specified by dew point and wetting time. For 18650 cylindrical cells, a dose of 5.0 mL Ah⁻¹ is typical; prismatic cells with 0.4 MPa stack pressure require a 20 min open-time pre-soak before final sealing. Vacuum filling stations operating below -90 kPa minimize trapped gas in the hard carbon electrode pores. After formation, capacity sorting should use 0.2 C discharge and 0.1 C charge to avoid interfacial heating; cells that exceed 4.2 V during formation must be transferred to a quarantine area because electrolyte oxidation releases CO₂ and HF, which damage the polyanionic cathode surface. The product is shipped in 10 L stainless-steel canisters under nitrogen; storage life is 12 months at 5–25 °C. This grade is not approved for sodium metal anodes because carbonate solvents form soluble organic layers and dendrite-induced SEI fracture; ether-based electrolytes should be selected for sodium metal cells.
