The electrolyte solution inside a battery plays a crucial role in both performance and longevity. Its volatile nature and limited quantity make it difficult to examine—especially in heavily aged commercial cells. This method focuses on such cells but is designed to be broadly compatible with other formats and future battery types.

To analyze the electrolyte, it must first be extracted in sufficient quantity. While chemical solvent extraction serves as a reference, the main approach uses mechanical extraction via centrifuge. Each cell is fully discharged and opened under inert gas to avoid contamination. A specially designed, additively manufactured multi-part construction secures cell and vial in the centrifuge tube. This ensures safe and repeatable extraction across different battery types.

The setup is leak-proof, chemically resistant, and allows visual volume control without opening the gas-tight tube. It’s compatible with cylindrical formats like 18650 and 21700, as well as pouch cells. The method yields ample electrolyte, even from aged cells—except in a few extreme cases.

The undiluted electrolyte is ready for storage or analysis. Small samples suffice for chemical characterization, but larger volumes enable conductivity or diffusion testing. It can even be reused in coin cells for electrical testing.

Multiple analytical methods such as GC-MS, FID, and ICP-OES reveal the electrolyte’s full composition. Most major components are identifiable, though some proprietary additives remain unknown.

The technique shows how aging affects electrolyte quantity and composition. While solvent structures remain stable, additive depletion and decomposition products increase—especially under heat and cycling. Comparing aged with pristine samples helps assess a battery’s condition.