I am grinding active material, acetylene black and PVDF before adding NMP to the mixture. What should be the weight ratios of PVDF and NMP so that the adhesion of the coating to Cu foil is good?
This depends a lot on your material, its particle size, surface and morphology - I would recommend reading into publications that deal with your material. Usually, between 3 and 10 wt-% PVDF are used (but I have seen much more than that already for applications that require much flexibility) and the NMP amount is regulated in a way that a nice slurry is formed.
sample to PVDF to carbon black...this ratio should be 8:1:1 or 7:2:1 or 7:1:2. Generally 8:1:1 is best. NMP is added as min as possible. For making two single sided electrodes one or two drops were sufficient for me. Then dry off the NMP and u will get perfect slurry for your copper foil as well as mesh.