Developing eco-friendly ceramic composite separator with competitive electrochemical properties using water-based polymer binder for lithium-ion batteries

The ceramic composite separators used in lithium-ion batteries (LIBs) are conventionally fabricated using a polymeric binder dissolved in an organic solvent, which can have adverse effects on the environment as well as the human body. Additionally, there are limited processes available for the fabrication of these separators owing to the requirement for carbon neutrality, which has attracted considerable attention worldwide to mitigate climate change. To address these issues, we propose an eco-friendly ceramic composite separator with outstanding adhesive strength and low interfacial resistance between the polyethylene (PE) separator and the aqueous polymeric binder with ceramic particles. To fabricate the proposed separator, the hydrophobic surface of the PE separator is preferentially modified into the hydrophilic surface by benzoyl peroxide (BPO) treatment. Following this, the water-soluble binder, that is, polyacrylic acid (PAA), with Al2O3 ceramic particles is coated on the surface of the pre-treated PE separator. The resultant PE separator with the hydrophilic surface and the water-based polymeric coating layer strongly adhere because of the formation of hydrogen bonds between the PAA and functional groups on the BPO pre-treated PE surface; these results in superior adhesive strength, and it reduces the interfacial resistance related with lithium-ion mobility through the separator. Consequently, the LIB half-cell employing the proposed separator displays superior rate performance and outstanding capacity retention.