Short answer: LiPF6 is the default salt for commercial lithium-ion cells with graphite anodes and aluminum cathode foils, because it gives good conductivity and passivates aluminum. LiTFSI is more thermally and chemically stable and does not form HF, which makes it the better choice for lithium-sulfur, lithium-metal, polymer and many solid-state systems, as long as the cathode stays below the voltage where LiTFSI corrodes aluminum.
What are LiPF6 and LiTFSI?
Lithium hexafluorophosphate (LiPF6, CAS 21324-40-3) is the conducting salt in almost every commercial lithium-ion electrolyte, usually at about 1 M in carbonate solvents such as EC/DMC or EC/EMC.
Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, CAS 90076-65-6) is an imide salt with a large, delocalized anion. It is widely used in research electrolytes, ionic liquids and polymer electrolytes; see our LiTFSI electrolyte solution.
Side-by-side comparison
| Property | LiPF6 | LiTFSI |
|---|---|---|
| Thermal stability | Decomposes from roughly 70-80 °C in solution | Stable to well above 300 °C as a salt |
| Moisture sensitivity | High: hydrolyzes and forms HF | Low: does not form HF |
| Aluminum current collector | Passivates aluminum | Can corrode aluminum above about 3.7-3.8 V vs Li unless additives or high concentration are used |
| Ionic conductivity (1 M, carbonates) | High | Similar or slightly lower, solvent dependent |
| Typical use | Commercial Li-ion (graphite / NMC, LFP, LCO) | Li-S, Li-metal, polymer and solid-state electrolytes, ionic liquids |
| Handling | Glovebox or dry room essential | Dry handling recommended; far more forgiving |
When should you choose LiPF6?
- Standard lithium-ion cells with an aluminum cathode foil and graphite anode.
- High-voltage cathodes (NMC, NCA, LCO, LNMO) where aluminum passivation matters.
- When results need to be comparable with commercial electrolytes.
When should you choose LiTFSI?
- Lithium-sulfur cells, usually in DOL/DME with LiNO3 as an additive.
- Lithium-metal anodes and “salt-in-solvent” high-concentration electrolytes.
- PEO-based polymer electrolytes and composite solid electrolytes.
- High-temperature testing, where LiPF6 would decompose.
Can you mix LiPF6 and LiTFSI?
Yes. Dual-salt electrolytes are common in research: a small amount of LiPF6 helps passivate aluminum while LiTFSI improves thermal stability. Related salts such as LiFSI, LiBF4 and lithium difluorophosphate are also used as additives. Browse our electrolyte materials.
Frequently asked questions
Is LiTFSI better than LiPF6?
Neither is better in every case. LiTFSI is more stable; LiPF6 protects the aluminum cathode foil. The right choice depends on your cell chemistry and voltage window.
Why does LiPF6 need a glovebox?
LiPF6 reacts with traces of water to form HF, which damages electrodes and gives poor, irreproducible results. Keep water below about 20 ppm.
Do you supply both salts?
Yes. NanoLithium supplies LiPF6 powder, LiTFSI electrolyte solution and other electrolyte salts, and ships to the USA, Canada, Europe, South Korea and worldwide. Contact us for a quote.
