Water-based vs. organic solvent-based processing of NVP/C cathodes for sodium-ion batteries toward higher processing rates

Sodium-ion batteries are treated as a drop-in technology to complement lithium-ion batteries in applications such as entry-level cars and stationary storage. This study compares water-based processing of the sodium-ion battery active material sodium vanadium phosphate (NVP/C) with processing using slurries based on the organic solvent NMP. By utilizing CMC/SBR as a binder, the adhesion strength, flexibility, electrical resistance, and rate capability were improved. These superior properties could be maintained at increasing the drying rate by a factor of 8. However, electrodes processed with the water-based binder system also suffered from binder migration at higher drying rates. To enable high-throughput processing, a strategy involving simultaneous multilayer coating of a primer and electrode slurry was explored. This approach helped mitigate the negative effects of binder migration.