Polyimide-based separator containing aluminum oxide, method for manufacturing the same, and lithium secondary battery comprising the same

Low-Shrinkage Polyimide Separator Based on Al2O3-EPP Radical Scavenging Composite Dip-Coating

This technology involves coating the surface of a polyimide (PI) separator with a composite of nano-sized aluminum oxide (Al2O3) and the free radical scavenger ethylene bis(diphenylphosphine) (EPP) to close large pores and ensure safety.

While conventional polyimide (PI) separators offer excellent heat resistance, their macroscopic porous structure often fails to sufficiently separate the anode and cathode during cell assembly, leading to internal short circuits and current leakage.

This technology involves dispersing Al2O3 and EPP in a PVdF-HFP binder solution and dip-coating it at a loading of 2.8 mg/cm² or more to seal the pores on the polyimide separator surface. EPP scavenges free radicals to enhance thermal stability and electrochemical performance, maintaining lower shrinkage at 550°C compared to Al2O3-only coatings. Applicable to EV, electric ship, and military batteries requiring extreme high-temperature safety, it preserves separator integrity during rapid temperature spikes, reducing the risk of chain ignition.

‍

‍

Key Features:

• Aluminum oxide and EPP composite coated onto a polyimide-based separator at a loading of 2.8 mg cm-2 or more
• Lithium secondary battery separator with lower tensile strength and lower shrinkage at 550 °C compared to aluminum oxide-only coated polyimide separators
• Step of preparing a composite by dispersing aluminum oxide and EPP in a binder solution of PVdF-HFP dissolved in acetone
• Step of dip-coating a polyimide-based separator in the composite dispersion solution to coat the composite onto the separator surface

‍