Measuring moisture in a CNT based fluid or paste
The present disclosure relates to pastes and methods of making a moisture determination of the paste during manufacture; optionally, the pastes comprise carbon nanotubes. The instant invention provides a simple and repeatable measurement protocol to determine the moisture or water content in paste comprising a non-aqueous solvent and a solid component, optionally, carbon nanotubes, CNT, and subsequently provide a method to monitor and control moisture level during electrode preparation and battery manufacturing.
1. A method for measuring the water content of a fluid or paste comprising multi-walled carbon nanotube agglomerates, dispersant and polymeric binder, the method comprising the steps:
selecting the fluid or paste comprising the multi-walled carbon nanotube agglomerates, the dispersant and the polymeric binders and further comprising a first solvent, wherein the multi-walled carbon nanotube agglomerates, the dispersant and the polymeric binder of the fluid or paste are dispersed in the first solvent;
adding a second solvent to the fluid or paste such that the second solvent is more than about 25% by volume or weight ratio of the total solvent mixture of the first solvent and the second solvent and wherein the multi-walled carbon nanotube agglomerates do not disperse in the total solvent mixture and the second solvent is miscible with the first solvent;
precipitating the multi-walled carbon nanotube agglomerates from the total solvent mixture, thereby leaving a supernatant;
taking a sample of the supernatant; and
measuring the water content of the sample.
2. The method of claim 1 wherein the weight ratio of the first solvent to the second solvent in the total solvent mixture is between about 2:1 and about 1:10.
3. The method of claim 1 wherein the measuring of the water content is done by one or more of the techniques consisting of solvent evaporation, Karl-Fischer titration, coulometric titration, and volumetric titration.
4. The method of claim 1 wherein the second solvent is chosen from a group consisting of ethers, alcohols, ketones, esters and mixtures thereof.
5. The method of claim 4 wherein the ketones include acetone and the esters include ethyl acetate.
6. The method of claim 1 wherein the first solvent is chosen from a group consisting of poly(vinylpyrrolidone) (PVP), poly(styrene sulfonate) (PSS), poly(phenylacetylene) (PAA), poly(meta-phenylenevinylene) (PmPV), polypyrrole (PPy), poly(p-phenylene benzobisoxazole) (PBO), natural polymers, amphiphilic materials in aqueous solutions, anionic aliphatic surfactant, sodium dodecyl sulfate (SDS), cyclic lipopeptide bio surfactant, surfactin, water-soluble polymers, carboxyl methyl cellulose, hydroxyl ethyl cellulose, poly(vinyl alcohol), (PVA), n-methylpyrrolidone, polyoxyethylene surfactant, poly(vinylidene fluoride), (PVdF), carboxyl methyl cellulose (CMC), hydroxyl ethyl cellulose (HEC), polyacrylic acid (PAA), polyvinyl chloride (PVC) and combinations thereof.
7. The method of claim 1 wherein the tap density of the carbon nanotube agglomerates is greater than about 0.02g/cm 3 .
8. The method of claim 1 wherein the a polymeric binder is chosen from a group consisting of polyethylene, polypropylene, polyamide, polyurethane, polyvinyl chloride, polyvinylidene fluoride, thermoplastic polyester resins, and mixtures thereof and the polymeric binder is less than about 5% by weight of the fluid or paste.
9. The method of claim 1 wherein the multi-walled carbon nanotube agglomerates are present in the fluid or paste in the range of about 1 to 15% by weight of the fluid or paste.
10. The method of claim 1 wherein the multi-walled carbon nanotube agglomerates are present in the fluid or paste in the range of about 0.2 to 5% by weight of the fluid or paste.