Electrode compositions containing carbon nanotubes for solid electrolyte capacitors

Abstract

An improved capacitor with an anode with an anode wire and an oxide layer on the surface of the anode. A cathode layer is exterior to the oxide layer. A carbon conductive layer is exterior to the cathode layer wherein the cathode layer comprises 5-75 wt % resin and 25-95 wt % conductor. The conductor has carbon nanotubes. An anode lead is in electrical contact with the anode wire and a cathode lead is in electrical contact with the carbon conductive layer.

1 . A capacitor comprising: 
 an anode comprising an anode body and anode wire;    an oxide layer on a surface of said anode;    a cathode layer exterior to said oxide layer;    a carbon conductive layer exterior to said cathode layer wherein said cathode layer comprises 5-75 wt % resin and 25-95 wt % conductor and said conductor comprises carbon nanotubes;    an anode lead in electrical contact with said anode wire; and    a cathode lead in electrical contact with said cathode layer.    
   
   
       2 . The capacitor of  claim 1  further comprising a silver containing layer between said carbon conductive layer and said cathode lead.  
   
   
       3 . The capacitor of  claim 1  wherein said conductor comprises 0.025-93 wt % carbon nanotubes.  
   
   
       4 . The capacitor of  claim 3  wherein said conductor comprises 1-30 wt % carbon nanotubes.  
   
   
       5 . The capacitor of  claim 3  wherein said conductor comprises about 7 to about 99.975 wt % carbon conductive particles.  
   
   
       6 . The capacitor of  claim 5  wherein said conductor comprises about 15 to about 99 wt % carbon conductive particles.  
   
   
       7 . The capacitor of  claim 6  wherein said conductor comprises about 70 to about 93 wt % carbon conductive particles.  
   
   
       8 . The capacitor of  claim 1  wherein said nanotubes comprise at least one selected from the group consisting of single walled nanotubes; multi-walled nanotubes and combinations thereof.  
   
   
       9 . The capacitor of  claim 1  wherein said carbon nanotubes have a diameter of 1-200 nm.  
   
   
       10 . The capacitor of  claim 9  wherein said carbon nanotubes have a diameter of 1-50 nm.  
   
   
       11 . The capacitor of  claim 10  wherein said carbon nanotubes have a diameter of 1-20 nm.  
   
   
       12 . The capacitor of  claim 11  wherein said carbon nanotubes have a diameter of 1-2 nm.  
   
   
       13 . The capacitor of  claim 9  wherein said carbon nanotubes have a length of at least 5 μm.  
   
   
       14 . The capacitor of  claim 1  wherein said carbon conductive layer further comprises conductive carbon particles selected from carbon black, graphite and carbon fibers.  
   
   
       15 . The capacitor of  claim 14  wherein said carbon conductive layer comprises carbon black.  
   
   
       16 . The capacitor of  claim 15  wherein said conductor has a particle size of 5 nm to 30 μm.  
   
   
       17 . The capacitor of  claim 16  wherein said conductor has a particle size of 5 nm to 200 nm.  
   
   
       18 . The capacitor of  claim 1  wherein said carbon conductive layer comprises 5-25 wt % resin.  
   
   
       19 . The capacitor of  claim 18  wherein said carbon conductive layer comprises 15-20 wt % resin.  
   
   
       20 . The capacitor of  claim 1  wherein said resin comprises at least one material selected from phenolic, phenoxy, epoxy, acrylic, cellulose derivatives, aromatic cyanate esters, diallyl isophthalate, bismaleimide, polyimides, polyamide imides, polysulfones, polyphylenes, polyether sulfones, polyaryl ethers, polyphenylene sulfides, polyarylene ether ketones, polyether imides, polyquinoxalines, polyquinolines, polybenzimidazoles, polybenzoxazoles polybenzothiazoles, silicone polyester, silicone epoxy and silicone.  
   
   
       21 . The capacitor of  claim 20  wherein said resin comprises at least one material selected from cellulose derivatives, aromatic cyanate ester, epoxy, phenolic, acrylic, polyester, diallyl isophthalate and bismaleimide.  
   
   
       22 . The capacitor of  claim 1  wherein said anode comprises niobium, aluminum, tantalum, titanium, zirconium, hafnium, tungsten and alloys or combinations thereof.  
   
   
       23 . A method for forming a capacitor comprising: 
 forming an anode from a valve metal with an anode wire extending therefrom;    exposing a surface of said anode to an oxidizing solution to form an oxide layer thereon;    forming a cathode layer on at least a portion of said oxide layer;    applying a carbon coating layer on at least a portion of said cathode layer wherein said carbon coating layer comprises solvent, resin and carbon nanotubes;    removing said solvent from said carbon coating layer to form a carbon conductive layer;    attaching an anode lead into electrical contact with said anode wire; and    attaching a cathode lead into electrical contact with said cathode layer.    
   
   
       24 . The method for forming a capacitor of  claim 23  further comprising applying a silver conductive layer between said applying a carbon coating layer and said attaching an anode lead.  
   
   
       25 . The method for forming a capacitor of  claim 23  wherein said carbon conductive layer comprises 5-75 wt % resin.  
   
   
       26 . The method for forming a capacitor of  claim 25  wherein said carbon conductive layer comprises 15-20 wt % resin.  
   
   
       27 . The method for forming a capacitor of  claim 23  wherein said resin comprises at least one material selected from phenolic, phenoxy, epoxy, acrylic, cellulose derivatives, aromatic cyanate esters, diallyl isophthalate, bismaleimide, polyimides, polyamide imides, polysulfones, polyphylenes, polyether sulfones, polyaryl ethers, polyphenylene sulfides, polyarylene ether ketones, polyether imides, polyquinoxalines, polyquinolines, polybenzimidazoles, polybenzoxazoles polybenzothiazoles, silicone polyester, silicone epoxy and silicone  
   
   
       28 . The method of forming a capacitor of  claim 23  wherein said carbon conductive layer further comprises conductive carbon particles.  
   
   
       29 . The method of forming a capacitor of  claim 28  wherein said conductive carbon particles comprise carbon black.  
   
   
       30 . The method of forming a capacitor of  claim 23  wherein said carbon conductive layer comprises 0.025-93 wt % carbon nanotubes.  
   
   
       31 . The method of forming a capacitor of  claim 30  wherein said carbon conductive layer comprises 1-30 wt % carbon nanotubes.  
   
   
       32 . The method of forming a capacitor of  claim 23  wherein said carbon conductive layer comprises 7-99.975 wt % carbon.  
   
   
       33 . The method of forming a capacitor of  claim 23  wherein said carbon nanotubes comprise at least one selected from the group consisting of single wall carbon nanotubes, multiple wall carbon nanotubes and combinations thereof.  
   
   
       34 . The method of forming a capacitor of  claim 23  wherein said carbon nanotubes have a diameter of 1-200 nm.  
   
   
       35 . The method of forming a capacitor of  claim 34  wherein said carbon nanotubes have a diameter of 1-100 nm.  
   
   
       36 . The method of forming a capacitor of  claim 35  wherein said carbon nanotubes have a diameter of 1-2 nm.  
   
   
       37 . The method of forming a capacitor of  claim 23  wherein said carbon nanotubes have a length of at least 5 μm.  
   
   
       38 . The method of forming a capacitor of  claim 23  further comprising applying said carbon coating layer by dipping.  
   
   
       39 . The method of forming a capacitor of  claim 23  wherein said carbon coating solution comprises 20-90 wt % solvent.  
   
   
       40 . The method of forming a capacitor of  claim 23  wherein said solvent is selected from glycol ethers, glycol ester ethers, N-methyl pyrrolidone, dimethyl formamide and xylene.  
   
   
       41 . The method of forming a capacitor of  claim 40  wherein said solvent is selected from glycol ester ethers.  
   
   
       42 . A capacitor formed by the method of  claim 23 .  
   
   
       43 . A capacitor comprising: 
 an anode comprising an anode body and anode wire;    an oxide layer on a surface of said anode;    a cathode layer exterior to said oxide layer; and    a carbon conductive layer exterior to said cathode layer wherein said cathode layer comprises 5-75 wt % resin and 25-95 wt % conductor and said conductor comprises carbon nanofibers.