3-Methyl-2-oxazolidinone (JEFFSOL® MEOX) as a Substitute Solvent for NMP in Battery Manufacturing

This work presents 3-Methyl-2-oxazolidinone (JEFFSOL® MEOX) as a substitute solvent for N-methyl-2-pyrrolidone (NMP) in the manufacture of Li-ion batteries. NMP is a good solvent for polyvinylidene difluoride (PVDF, a common binder material), and also has a high boiling point (202 °C), allowing for gradual drying of electrode slurries to form homogeneous coatings. However, NMP has a reprotoxic effect and its use is attracting increasing legislative pressure; it would be advantageous to the battery-making industry to find a more benign alternative. Of the few other solvents that will readily dissolve PVDF, examples such as dimethylformamide are also significantly toxic, so further investigation is necessary to find a credible alternative solvent system. We show that JEFFSOL® MEOX (boiling point 225 °C) is capable of dissolving PVDF at accessible temperatures (40 °C–50 °C), and that at a similar ratio of active material:binder:solvent, both JEFFSOL® MEOX and NMP produce electrode slurries with a viscosity of 5–6 Pa.s at 25 °C and at a shear rate of 10 s−1. Cells formed using JEFFSOL® MEOX-made and NMP-made cathode coatings showed comparable electrochemical performance.