Fabrication of flexible conductive items and batteries using modified inks

Abstract

A chemical process to formulate conductive ink with low sintering temperature for inkjet printing is described and shown. The application of fabricated flexible conductive film on lithium ion batteries is also described. This chemical method and composition can remove the oxidation on metallic nanoparticle surface during ink fabrication and sintering processes. Etched metallic ions in the conductive ink are reduced and particles bridged while annealing printed patterns to achieve low temperature sintering at about 350° C. The chemical process can be applied on nickel materials that are excellent current collectors for lithium ion batteries due to high chemical stability especially at high charging-discharging potential of less than 3 Volts. Thermal decomposition and chemical reduction of silver salts are two methods disclosed for particle-free silver ink. Surfactant additive further make silver film more uniform and easier to be sintered.

1 - 12 . (canceled) 
     
     
         13 . A method of making printable conductive pattern, comprising:
 using a silver salt complex solution to formulate a particle-free silver ink;   adding sodium carboxymethyl cellulose (NaCMC) to control final particle shape and size and uniformity of the ink for avoiding nozzle clogging and prone to sintering at lower temperatures and achieving high resolution printing;   thermally treating the ink at a temperature lower than the ink; and   using thermal decomposition or chemical reduction on the silver salt to make a dense silver film, wherein the ink is colorless and transparent.   
     
     
         14 . The method of  claim 13  wherein the printing includes flexo printing and inkjet printing. 
     
     
         15 . The method of  claim 13 , further including reducing the size of the silver particle size by adding a chemical reductant additive. 
     
     
         16 . The method of  claim 15 , wherein the chemical reductant additive includes nickel chloride (NiCl 2 .6H 2 O) and thiourea dioxide (TD). 
     
     
         17 . The method of  claim 13  further including adding ammonia chloride (NH 4 Cl) to etch surface oxidation. 
     
     
         18 . The method of  claim 13  further including adding a thiourea dioxide (TD) additive to reduce sintering process temperature below 400° C. 
     
     
         19 . A method of making printable conductive pattern, comprising:
 using a constantan (copper-nickel alloy) particle suspension of constantan/water/PVP dispersed for ink to manufacture electronic components;   applying a chemical reducing sintering (CRS) to eliminate oxidation layers and sinter the constantan at low temperature below 400° C.;   applying the constantan on a flexible substrate to make a battery by printing layer by layer.   
     
     
         20 . The method of  claim 19  further includes adding ammonia chloride (NH 4 Cl), thiourea dioxide (TD), and potassium hydroxide (KOH) into the constantan suspension to reduce sintering temperature, and the battery is a flexible rechargeable lithium ion battery.