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 method of coating a substrate comprising the steps of:
 providing a slurry in a closed volume with at least one passage, the slurry including a solvent, a powder, a binder, and a dispersion agent;   forcing the slurry 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, to homogenously disperse the powder and the binder within the solvent; and   coating both sides of the substrate simultaneously with the slurry extruded from the closed volume after the forcing.   
     
     
         2 . The method of  claim 1 , wherein a ratio of the binder to the powder is about 0.02:1 to about 0.1:1 by weight. 
     
     
         3 . The method of  claim 1 , wherein a ratio of the solvent to the non-carbon powder is about 0.6:1 to about 1.25:1 by weight. 
     
     
         4 . The method of  claim 1 , where the slurry is about 0.01-2 wt % of the dispersion agent. 
     
     
         5 . The method of  claim 1 , wherein the ratio of the solvent to the carbon powder is about 4.5:1 to about 8:1 by weight. 
     
     
         6 . The method of  claim 1 , wherein the closed volume comprises two cylinders connected by the at least one passage, and wherein each of the two cylinders includes a piston, and a reciprocal actuation of the two pistons forces the slurry to flow in the first flow direction and the second flow direction. 
     
     
         7 . The method of  claim 6 , wherein a cross section in the first flow direction of each of the at least one passage is smaller than cross sections of the cylinders in stroke directions of the two pistons. 
     
     
         8 . The method of clam  7 , wherein a diameter of each of the at least one passage is 1/16 inch to ½ inch. 
     
     
         9 . The method 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. 
     
     
         10 . The method of  claim 1 , wherein the slurry lacks n-methyl-2-pyrrolidone. 
     
     
         11 . The method of  claim 1 , wherein the solvent is water. 
     
     
         12 . The method of  claim 11 , wherein the powder is carbon black powder. 
     
     
         13 . The method of  claim 12 , wherein the binder is a polytetrafluoroethylene emulsion. 
     
     
         14 . The method of  claim 13 , wherein the dispersion agent is an alcohol. 
     
     
         15 . The method of  claim 1 , further comprising applying a vacuum to the closed volume prior to the coating to remove gas from the slurry. 
     
     
         16 . An electrode that is coated according to the method of  claim 1 . 
     
     
         17 . A battery having an electrode that is coated according to the method of  claim 1 . 
     
     
         18 . A battery system having a plurality of battery cells, each of the battery cells having an electrode that is coated according to the method of  claim 1 . 
     
     
         19 . A method of curing a coated substrate comprising the steps of:
 providing a substrate coated on both sides with a slurry, the slurry including a solvent, a powder, a binder, and a dispersion agent;   freezing at least the solvent and the dispersion agent coated on the substrate;   sublimating at least the solvent and the dispersion agent frozen on the substrate;   heating the substrate after the sublimating under vacuum to above the standard freezing points of the at least one solvent and the dispersion agent; and   calendering the substrate after the heating.   
     
     
         20 . The method of  claim 19 , wherein the calendering comprises cold calendering the substrate to stabilize the coating on the substrate followed by hot rolling of the substrate. 
     
     
         21 . The method of  claim 19 , wherein the solvent is water. 
     
     
         22 . The method of  claim 19 , wherein the powder is carbon black powder and the substrate forms an electrode for a battery cell. 
     
     
         23 . The method of  claim 19 , wherein the binder is polytetrafluoroethylene emulsion. 
     
     
         24 . The method of  claim 19 , wherein the dispersion agent is an alcohol. 
     
     
         25 . The method of  claim 19 , wherein the slurry lacks n-methyl-2-pyrrolidone. 
     
     
         26 . 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 connecting the first cylinder assembly to the second cylinder assembly,   wherein, in operation, the first cylinder assembly and the second cylinder assembly are configured to alternatingly apply compression and suction to a slurry within the first cylinder and the second cylinder to cause the slurry to reciprocally move through the passage.   
     
     
         27 . The system of  claim 26 , 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.   
     
     
         28 . The system of  claim 26 , 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.