Battery electrode coatings applied by waterborne electrodeposition

Abstract

The present invention is directed towards a method of coating a substrate comprising electrocoating an electrodepositable coating composition onto the substrate, the electrodepositable coating composition comprising a binder comprising a pH-dependent rheology modifier; an electrochemically active material and/or an electrically conductive agent; and an aqueous medium. Also disclosed are electrodepositable coating compositions, coated substrates and electrical storage devices.

We claim: 
     
         1 . A method of coating a substrate comprising:
 electrocoating an electrodepositable coating composition onto at least a portion of the substrate, wherein the electrodepositable coating composition comprises:   a binder comprising a pH-dependent rheology modifier;   an electrochemically active material and/or an electrically conductive agent; and   an aqueous medium.   
     
     
         2 . The method of  claim 1 , wherein the pH-dependent rheology modifier comprises an alkali-swellable rheology modifier, a hydrophobically modified alkali-swellable rheology modifier. 
     
     
         3 . The method of  claim 2 , wherein a composition of water and the alkali-swellable rheology modifier at 4.25% by weight of the total composition has an increase in viscosity of at least 500 cps over an increase in pH value of 3 pH units within the pH range of 3 to 12, as measured using a Brookfield viscometer using a #4 spindle and operated at 20 RPMs. 
     
     
         4 . The method of  claim 2 , wherein the alkali-swellable rheology modifier comprises a crosslinked alkali-swellable rheology modifier. 
     
     
         5 . The method of  claim 4 , wherein the crosslinked alkali-swellable rheology modifier comprises constitutional units comprising the residue of a monoethylenically unsaturated carboxylic acid, a C 1  to C 6  alkyl (meth)acrylate monomer, and a cros slinking monomer. 
     
     
         6 . The method of  claim 5 , wherein the crosslinked alkali-swellable rheology modifier comprises constitutional units comprising the residue of:
 20 to 65% by weight of the monoethylenically unsaturated carboxylic acid;   20 to 80% by weight of the C 1  to C 6  alkyl (meth)acrylate monomer; and   0.1 to 3% by weight of the crosslinking monomer, based on the total weight of the crosslinked alkali-swellable rheology modifier.   
     
     
         7 . The method of  claim 4 , wherein the crosslinked hydrophobically modified alkali-swellable rheology modifier comprises constitutional units comprising the residue of a monoethylenically unsaturated carboxylic acid, a C 1  to C 6  alkyl (meth)acrylate monomer, and a monoethylenically unsaturated alkyl alkoxylate monomer. 
     
     
         8 . The method of  claim 7 , wherein the hydrophobically modified alkali-swellable rheology modifier comprises constitutional units comprising the residue of:
 2 to 70% by weight of the monoethylenically unsaturated carboxylic acid;   20 to 80% by weight of the C 1  to C 6  alkyl (meth)acrylate monomer; and   0.5 to 60% by weight of the monoethylenically unsaturated alkyl alkoxylate monomer, based on the total weight of the hydrophobically modified alkali-swellable rheology modifier.   
     
     
         9 . The method of  claim 1 , wherein the pH-dependent rheology modifier comprises an acid-swellable rheology modifier. 
     
     
         10 . The method of  claim 1 , wherein the binder further comprises a non-fluorinated organic film-forming polymer. 
     
     
         11 . The method of  claim 10 , wherein the non-fluorinated organic film-forming polymer comprises polysaccharides, polyacrylates, polyethylene, polystyrene, polyvinyl alcohol, poly (methyl acrylate), poly (vinyl acetate), polyacrylonitrile, polyimide, polyurethane, polyvinyl butyral, polyvinyl pyrrolidone, styrene butadiene rubber, xanthan gum, or combinations thereof. 
     
     
         12 . The method of  claim 1 , wherein the electrochemically active material comprises LiCoO 2 , LiNiO 2 , LiFePO 4 , LiFeCoPO 4 , LiCoPO 4 , LiMnO 2 , LiMn 2 O 4 , Li(NiMnCo)O 2 , Li(NiCoAl)O 2 , carbon-coated LiFePO 4 , sulfur, LiO 2 , FeF 2  and FeF 3 , Si, aluminum, tin, SnCo, Fe 3 O 4 , or combinations thereof. 
     
     
         13 . The method of  claim 1 , wherein the electrochemically active material comprises graphite, lithium titanate, lithium vanadium phosphate, silicon, silicon compounds, tin, tin compounds, sulfur, sulfur compounds, lithium metal, graphene, or a combination thereof. 
     
     
         14 . The method of  claim 1 , wherein the electrically conductive agent comprises conductive carbon black, carbon nanotubes, graphene, graphite, carbon fibers, fullerenes, and combinations thereof. 
     
     
         15 . The method of  claim 1 , further comprising a crosslinking agent. 
     
     
         16 . The method of  claim 15 , wherein the crosslinking agent comprises carbodiimide. 
     
     
         17 . The method of  claim 15 , wherein the electrodepositable coating composition comprises:
 (a) 0.1% to 10% by weight of the pH-dependent rheology modifier;   (b) 0.02% to 2% by weight of the crosslinking agent;   (c) 45% to 99% by weight of the electrochemically active material;   (d) optionally 0.5% to 20% by weight of the electrically conductive agent; and   (e) optionally 0.1% to 9.9% by weight of a non-fluorinated organic film-forming polymer; the % by weight based on the total solids weight of the electrodepositable composition.   
     
     
         18 . The method of  claim 1 , wherein the VOC of the electrodepositable coating composition is no more than 500 g/L. 
     
     
         19 . The method of  claim 1 , wherein a coating produced on a substrate by the method of  claim 1  has a 90° peel strength at least 10% greater than a coating produced from a comparative coating composition at a similar mass loading that is not applied by electrodeposition, the 90° peel strength measured according to PEEL STRENGTH TEST METHOD. 
     
     
         20 . The method of  claim 1 , wherein the electrodepositable coating composition is substantially free of fluoropolymer. 
     
     
         21 . The method of  claim 1 , wherein the electrodepositable coating composition is substantially free of cellulose-based materials. 
     
     
         22 . The method of  claim 1 , wherein the pH-dependent rheology modifier is substantially free of amide, glycidyl and hydroxyl groups. 
     
     
         23 . The method of  claim 1 , wherein the pH-dependent rheology modifier is substantially free of the residue of constitutional units comprising aromatic vinyl monomers. 
     
     
         24 . A coated substrate comprising an electrical current collector and a coating formed on at least a portion of the electrical current collector according to the method of  claim 1 . 
     
     
         25 . The coated substrate of  claim 24 , wherein the electrical current collector comprises aluminum, copper, steel, stainless steel, nickel, conductive carbon, a conductive primer coating, or a porous polymer. 
     
     
         26 . The coated substrate of  claim 24 , wherein the coated substrate comprises a positive electrode. 
     
     
         27 . The coated substrate of  claim 24 , wherein the coated substrate comprises a negative electrode. 
     
     
         28 . An electrical storage device comprising:
 (a) an electrode comprising the coated substrate of  claim 24 ;   (b) a counter-electrode, and   (c) an electrolyte.   
     
     
         29 . The electrical storage device of  claim 28 , wherein the electrical storage device comprises a cell, a battery pack, a secondary battery, a capacitor, or a supercapacitor.