Abstract: A new kind of BaSO₄ composite polypropylene (PP) separator for lithium-ion batteries (LIB) was successfully prepared using styrene butadiene rubber (SBR) as binder and carboxymethyl cellulose sodium (CMC) as dispersing agent. Structure, pore size distribution, wettability and absorbency, thermal dimensional stability and ionic conductivity of the composite separator were discussed. Results show that BaSO₄ particles are evenly coated on the surface of PP film. Pores smaller than 200 nm increase because of the existing of the coating layer. Compared with PP membrane, the composite membrane has better thermal stability and good wettability. And the bond strength of SBR is larger than poly(vinylidene fluoride)(PVDF). LIB using the composite membrane shows a higher capacity retention rate with different current densities.