Separator with Hydrophilic Resin Layer for Battery Impregnation

The patent applies different porosity characteristics to different regions and layers of the separator structure. The base polyolefin microporous film maintains high porosity for ion conductivity, while the heat-resistant resin coating layer has controlled porosity optimized for electrolyte retention. This local differentiation allows each layer to perform its specific function optimally without compromising overall structural integrity.

The composite structure combines a highly porous polyolefin base layer for ion transport with a less porous but still permeable heat-resistant coating layer for structural support and electrolyte retention. The inorganic filler particles within the coating create a porous network that balances ion conductivity with mechanical strength and liquid-holding capacity.

The heat-resistant resin coating layer is designed with controlled porosity to maintain electrolyte penetration capability. The porous structure of the coating layer, combined with hydrophilic inorganic filler particles, creates capillary channels that facilitate electrolyte impregnation while the heat-resistant resin matrix provides thermal stability. The pore size and distribution are optimized to balance thermal resistance with electrolyte access.

The patent modifies the chemical and physical parameters of the coating layer by incorporating inorganic fillers with different surface properties and controlling the resin composition and crosslinking degree. These parameter changes enhance both thermal stability and electrolyte wettability, as the inorganic filler surfaces provide hydrophilic sites that improve electrolyte impregnation while the resin matrix maintains thermal resistance.