For high-precision slot-die coating, a high-pressure syringe pump is the standard delivery system. Unlike a doctor blade where thickness is controlled by a mechanical gap, slot-die coating is a pre-metered process—the wet film thickness is directly proportional to the pump's flow rate and inversely proportional to the coating speed.

To achieve a uniform, streak-free coating, the syringe pump should meet these technical criteria: (1) Pulse-Free Flow: The motor must have high micro-stepping resolution. Any "pulsing" in the flow will result in visible transverse "ribbing" or waves in your dried electrode. (2) High Torque/Linear Force: Battery and CDI slurries are often highly viscous ("peanut butter" consistency). Standard medical syringe pumps will often "stall" or "slip." You need a laboratory-grade pump with at least 20–40 lbs (9–18 kg) of linear force. (3) Chemical Compatibility: The syringe itself should be stainless steel or glass with a PTFE-tipped plunger. Plastic syringes can swell or leach when used with solvents like NMP (N-Methyl-2-pyrrolidone).

References:

H. Lee, et al., Design and Assembly of a Thin-Film-Based Micro Pump for a Micro-slot Die, International Journal of Precision Engineering and Manufacturing, 2020, 21, 2335–2344

X. Ding, et al., A review of the operating limits in slot die coating processes, AICHE J., 2016, 62, 2508-2524.