Abstract: The surfaces of commercial polypropylene (PP) separator, a Li-ion battery material, were modified with composite coatings of carbon/lanthanum zirconate lithium (C/LLZO) grown by magnetron co-sputtering. The influence of the C/LLZO coatings on the separator's properties, including but not limited to the microstructures, interfacial adhesion, electrolyte affinity, electrochemical characteristics, polysulfide diffusion and initial capacity, was investigated. The results show that the C/LLZO coating had a major positive impact. For example, highly conductive carbon significantly decreased sulfur anode resistivity and increased polysulfide adsorption; LLZO increased Li-ion conductivity 2. 63 times, up to 5. 26 m S/cm, and considerably chemisorbed polysulfide. Importantly, the capacity of the modified separator decreased from 902. 73 m Ah/g to 704. 96 m Ah/g after 200 cycles at 0. 2 C. Moreover, magnetron sputtering outperforms conventional spray coating because of more uniform, stronger interfacial adhesion, and greater porosity of the separator.