Polysiloxane-coated PI nonwoven separators with higher thermal and electrochemical stability for lithium ion battery application

Polyolefin separators are widely used commercially due to their excellent mechanical properties. However, they are vulnerable to short circuits because of their poor thermal properties at high temperatures. Polyimide-based separators can be a good alternative due to their inherent stability at elevated temperatures, making them suitable separators to prevent thermal failure. Nevertheless, the pore sizes of nonwoven polyimide separators are often too large to provide appropriate electrochemical properties. In this study, we controlled the pore sizes of polyimide (PI) nonwoven separators through polysiloxane coating. We applied the polysiloxane coating to the inner fibers of the PI nonwoven, effectively reducing the size of the pores. Full cell tests demonstrated that the polysiloxane coating enabled a cyclability of 98.6 % after 100 cycles, while the PI nonwoven separators could not be charged due to internal short circuits. The polysiloxane coating effectively controlled pore sizes, showing great potential as a lithium-ion battery (LIB) separator with outstanding thermal stability.