Battery electrolytes: Characteristics
Why a few drops of water can ruin a battery
What this tab covers The physical and chemical properties that set its grade, price and uses, with the commercial grades and the standards that define them.Electrolytes are sold on purity and formulation. Water and acid (HF) content must be in single-digit or low double-digit ppm, metals in ppb. Each cell maker has its own additive package, so electrolyte is semi-custom and switching suppliers needs requalification.
Properties that matter commercially
| Property | Value / specification | Why it matters | Source |
|---|---|---|---|
| Salt concentration | about 1.0-1.2 mol/L LiPF6 (about 11-13% by weight) (indicative) | Sets ionic conductivity | Indicative; 11% derived from HKEX shipments |
| Water content | under about 20 ppm (indicative) | Water hydrolyses LiPF6 to HF, damaging cells | Indicative |
| Free acid (as HF) | under about 50 ppm (indicative) | Acid attacks cathode and SEI | Indicative |
| Solvent purity | battery grade above 99.99% (indicative) | Impurities cause gassing | Indicative |
Commercial grades
- LFP storage electrolyte (long life)
- High-nickel EV electrolyte (high voltage, FEC/LiFSI additives)
- Fast-charge electrolyte (LiFSI-rich)
- LCO high-voltage consumer electrolyte
- Sodium-ion (NaPF6) electrolyte
- Semi-solid and solid electrolytes