Abstract: The separator is one of the core inner components of a lithium-ion battery, and its performance directly affects the electrochemical performance, life and safety performance of the battery. The physical and electrochemical properties of polyethylene (PE) separators, polypropylene/polyethylene/polypropylene multilayer (PP/PE/PP) separators polypropylene (PP) separator, and aluminum oxide ceramic-coated polyethylene (PE-Al2O3) separator, which are widely used at present, are analyzed and compared in detail. The results show that the PE-Al2O3 separator has more outstanding performance in puncture strength, thermal stability, wettability and ionic conductivity, except that the tensile strength is slightly lower than that of the PP/PE/PP separator. There are a large number of submicron pores on the surface of the PE separator, PP separator and PP/PE/PP separator. The pores of the PE separator are round, and the pores of the PP separator and PP/PE/PP separator are oval. The alumina particles are evenly distributed on the surface of the PE-Al2O3 separator, and a large number of clear pores are retained between the alumina particles. The tensile strength of the PP/PE/PP separator (247.53 MPa) is higher than that of the PE-Al2O3 (197.58 MPa) in the mechanical direction, and it has the highest tensile strength among the four separators. Among these four separators, the puncture strength of the PE separator was the lowest at 144.26 N?μm-1 and due to the high hardness of alumina nanoparticles, the puncture strength of the PE-Al2O3 separator was the highest at 426.91 N?μm-1. The melting temperature of the PE-Al2O3 separator is 140.9 ℃ lower than that of the PP separator and PP/PE/PP separator but higher than that of the PE separator and no heat shrinkage after heat treatment at 140 ℃ for 1h. The PE-Al2O3 separator is the most comprehensive thermal stability among the four types of separators. The unique hydrophilic properties of alumina nanoparticles improve the wettability between the separator and the electrolyte, and the wetting angle between the PE-Al2O3 separator and the electrolyte is 12.3°, which is significantly smaller than that of the PP separator (35.9°), PE separator (38.3°) and PP/PE/PP separator (35.3°). The excellent electrolyte wettability of the PE-Al2O3 separator effectively reduces the transmission resistance of lithium ions between the anode and cathode, making the separator have excellent ionic conductivity (0.719 mS·cm-1), and the capacity retention rate after 200 cycles is 88.25%, which is significantly better than that of the uncoated PE separator. In conclusion, the PE-Al2O3 separator has the best application prospect in high-power and high-safety lithium-ion batteries compared with the PE separator, PP separator and PP/PE/PP separator.