Devices and methods for preparing a slurry and coating a substrate with a slurry

Abstract

Devices and methods for preparing a slurry for coating onto a substrate. The devices and methods of the present disclosure relate to providing a slurry in a closed volume with at least one passage. The slurry includes a solvent, a powder, and a binder. The slurry can also include a dispersion agent. The slurry is forced repeatedly under high pressure through the at least one passage in a first flow direction and then back through the at least one passage in a second flow direction, opposite the first flow direction. The forcing homogenously disperses the powder and the binder within the solvent. Both sides of the substrate are then coated simultaneously with the slurry extruded from the closed volume after the forcing. Curing of the coated slurry includes freeze drying to preserve the porosity of the slurry on the substrate.

What is claimed is: 
     
         1 . A system comprising:
 a first cylinder assembly having a first cylinder and a first piston, the first piston being configured to reciprocally move within the first cylinder;   a second cylinder assembly having a second cylinder and a second piston, the second piston being configured to reciprocally move within the second cylinder; and   a passage interconnecting the first cylinder assembly to the second cylinder assembly, the first cylinder, the second cylinder and the passage forming a closed volume;   wherein, in operation, the first cylinder assembly and the second cylinder assembly are configured to alternatingly and repeatedly apply compression and suction under high pressure to a slurry within the first cylinder and the second cylinder to cause the slurry to flow through the passage in a first flow direction and then back again through the passage in a second flow direction that is opposite the first flow direction, in response to a reciprocal actuation of the first and second pistons of the first and second cylinders, the slurry including a solvent, a powder, a binder, and a dispersion agent selected for forming a battery cell electrode applied to a substrate, the reciprocal actuation homogenously dispersing the powder and the binder within the solvent.   
     
     
         2 . The system of  claim 1 , further comprising:
 a die assembly connected to the first cylinder assembly and having two sub-die parts,   wherein each sub-die part has an inlet passage for receiving the slurry from the first cylinder assembly and an outlet configured to extrude the slurry onto a substrate passing through the die assembly.   
     
     
         3 . The system of  claim 1 , wherein the two sub-die parts assembled form a passage for a substrate to pass through for extruding the slurry onto both sides of the substrate simultaneously. 
     
     
         4 . The system of  claim 1 , wherein a ratio of the binder to the powder is about 0.02:1 to about 0.1:1 by weight. 
     
     
         5 . The system of  claim 1 , wherein the powder is a carbon black powder, and a ratio of the solvent to the carbon black powder is about 4.5:1 to about 8:1 by weight. 
     
     
         6 . The system of  claim 1 , wherein the slurry is about 0.01-2 wt % of the dispersion agent. 
     
     
         7 . The system of  claim 1 , wherein about 10 to 15 kWh of energy per kilogram of solid powder is required to form the dispersion of the powder and the binder in the slurry. 
     
     
         8 . The system of  claim 1 , wherein a cross section in the first flow direction of the passage is smaller than cross sections of the cylinders in stroke directions of the two pistons. 
     
     
         9 . The system of  claim 8 , wherein a diameter of the passage is 1/16 inch to ½ inch. 
     
     
         10 . The system of  claim 1 , wherein the slurry lacks n-methyl-2-pyrrolidone. 
     
     
         11 . The system of  claim 1 , wherein the solvent is water. 
     
     
         12 . The system of  claim 1 , wherein the binder is a polytetrafluoroethylene emulsion. 
     
     
         13 . The system of  claim 1 , wherein the dispersion agent is an alcohol. 
     
     
         14 . The system of  claim 1 ,
 wherein a ratio of the binder to the powder is about 0.02:1 to about 0.1:1 by weight,   wherein the powder is a carbon black powder, and a ratio of the solvent to the carbon black powder is about 4.5:1 to about 8:1 by weight,   wherein the slurry is about 0.01-2 wt % of the dispersion agent, and   wherein about 10 to 15 kWh of energy per kilogram of solid powder is required to form the dispersion of the powder and the binder in the slurry.   
     
     
         15 . The system of  claim 1 , wherein a diameter of the passage is 1/16 inch to ½ inch.