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.

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH[0001]This invention was made with government support under Agreement No. W15QKN-10-D-0503 awarded by the U.S. Department of Army. The government has certain rights in the invention.FIELD[0002]The present application discloses inks and printing technology used to fabricate, among other things, thin films for electronic components, antennas, and batteries. More particularly, the present application relates to an ink composition and new method using particle free silver ink, constantan particle suspension ink, and nickel ink to manufacture conductive flexible components and thin designable batteries.BACKGROUND[0003]Currently there is a great interest in manufacturing printed circuits, sensors, electronics and radio frequency identification tags via liquid based “ink”. Generally, the functional ink is made of metallic nanoparticles (NPs) dispersed in organic / inorganic solvents. By using the functional fluid, inkjet printing technology is ...

AI Technical Summary

Benefits of technology

[0008]Particle-free silver ink has been developed to avoid nozzle clogging and achieve high resolution printing. Silver salt complex solution is used as a particle free ink. After printing and curing, the organic silver complex is transformed into a highly conductive silver thin film. The thermal treating temperature is usually lower than nanoparticle based ink. Thermal decomposition and chemical reduction of silver salts are two methods disclosed for particle-free silver ink. Chemical reduction makes denser silver film than thermal decomposition caused by volume shrinkage of silver precursor decomposition after thermal sintering. The resistivity of silver patterns made by chemical reduction is also lower than made by thermal decomposition because of less porosity. Addition of a surfactant additive further makes the silver film more uniform and easier to be sintered.

[0009]Both the thermal decomposition of silver salts and chemical reduction of silver complex can produce pure silver without impurity. The synthesized silver film has excellent electronic conductivity and adhesion. It has been discovered that sodium carboxymethyl cellulose (NaCMC) plays a crucial role in the final particle size and uniformity. No peeling off and cracking of the printed silver patterns occurred when the film was bent with a large radius. The ink made by chemical reduction is qualified for the flexible electronics fabrication.

[0013]Constantan particle suspension ink may be used to make constantan sensors and resistors and metallic conductive tracks. A new chemical reducing sintering (CRS) is used to eliminate oxidation layers and sinter the constantan at low temperature. CRS is much safer and easier than other current methods.

[0014]Nickel ink and Nickel conductive film is made by CRS and used as the current collectors for the lithium ion batteries, which is cheaper than the traditional gold current collectors and more conductive than conventional carbon serious current collectors. Nickel ink particle size could be reduced with a certain amount of chemical reductant additive such as nickel chloride (NiCl2.6H2O) and thiourea dioxide (TD). Flexible rechargeable lithium ion batteries are made by inkjet printing layer by layer. Inkjet printing, among other methods such as but not limited to flexo printing, screen printing, pad printing and the like, is used to fabricate thin film designable batteries and provides high resolution of the printed image due to the reduction of nozzle clogging.

Problems solved by technology

However, due to their small size, metallic nanoparticles form an oxide layer on the surface during the nanoparticle fabrication process.

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