Separator Porous Bonding Layer Adhesion Air Permeability

The bonding layer uses a gradient pore structure where pore size and distribution vary through the layer thickness. The surface region has smaller pores for strong adhesion to electrodes, while the bulk region has larger pores for maintaining air permeability. This local variation in pore quality resolves the contradiction between adhesion strength and air permeability.

The bonding layer is formed as a composite structure combining polyvinylidene fluoride-based polymer with inorganic particles (such as alumina or silica). This composite material provides both the adhesive bonding capability through the polymer matrix and the pore structure for ion permeability through the inorganic particles, simultaneously achieving strong adhesion and maintained air permeability.

The separator employs a controlled porous structure with optimized pore size distribution and porosity. The pores are sufficiently large and interconnected to allow rapid ion transfer, while the pore walls maintain adequate thickness and structural integrity to prevent short circuits between electrodes. This porous architecture simultaneously achieves high ion conductivity and safety.

The separator structure utilizes controlled thermal shrinkage parameters where the porous substrate and bonding layer are designed with different thermal contraction characteristics. Upon heating to shutdown temperature, the differential shrinkage causes pore closure to prevent short circuits, while during normal operation the open pore structure maintains high ion transfer efficiency. This parameter-based control resolves the safety-speed contradiction.