A method for manufacturing slurry for an insulation protective layer of a rechargeable battery includes obtaining an insulation material calibration curve showing a relationship between particle size and compressibility of an insulation material using sets of particle size and compressibility of the insulation material, obtaining a binder calibration curve showing a relationship between particle size and compressibility of a binder using sets of particle size and compressibility of the binder, measuring particle sizes of the insulation material and the binder loaded, determining an optimal mixture weight ratio with reference to the curves so that compressibility of mixture powder of the insulation material and the binder equals a set compressibility based on the measured particle sizes, mixing the insulation material and the binder at the determined mixture weight ratio to form mixture powder, loading the mixture powder into a powder dispenser, and adding a solvent to the mixture powder.