HYDROCHLORIC ACID WASHING OF CARBON AND GRAPHITE FOR MAKING CONDUCTIVE INK FOR ULTRACAPACITORS

Water-based conductive ink compositions may include acid-washed graphite particles, carbon black particles, at least one polymeric dispersant, at least one acrylic binder, at least one polyvinylpyrrolidone binder, at least one defoamer, and an aqueous carrier. At least 90 wt. % of the acid-washed graphite particles and the carbon black particles, based on the combined weight of the acid-washed graphite particles and the carbon black particles, may have particle sizes less than 10 μm. The water-based conductive ink composition may have a total elemental contaminant level of less than 100 ppm, based on the total weight of the water-based conductive ink composition. Methods for preparing the water-based conductive ink compositions may include preparing a letdown phase from a first premix containing carbon black and a second premix containing acid-washed graphite. The methods may include washing graphite particles in an strong acid such as hydrochloric acid, nitric acid, sulfuric acid, or mixtures thereof.