The invention belongs to the technical field of
lithium ion batteries, and particularly relates to a pore-forming method for diaphragms of
lithium ion batteries. The method comprises the following steps: fully dissolving a pore-forming agent into a
solvent so as to prepare a pore-forming agent solution; uniformly
coating the pore-forming agent solution on the surface of a to-be-cold-pressed diaphragm, and carrying out baking on the diaphragm at a temperature lower than the sublimation or
decomposition temperature of the pore-forming agent, so that a
solvent of the pore-forming agent solution is volatilized, and the pore-forming agent is recrystallized in the diaphragm; and carrying out cold pressing on the diaphragm, and then carrying out baking on the diaphragm at a temperature higher than the sublimation or
decomposition temperature of the pore-forming agent, so that the pore-forming agent recrystallized in the diaphragm is sublimated or decomposed, thereby obtaining a porous diaphragm. According to the invention, through regulating the
viscosity of the pore-forming agent solution, a diaphragm with adjustably-distributed pores can be obtained, and the regulating method is simple and flexible, and wide in applicable range; and particularly, according to the invention, an efficient gradient
pore distribution structure that more pores are distributed on the
surface layer of the diaphragm and less pores are distributed on the inner layer of the diaphragm can be realized just through selecting an appropriate
viscosity of the pore-forming agent solution..