An Al2O3 inorganic separator is prepared by a double sintering process. The Al2O3 separator has a high porosity and good mechanical strength. After the liquid electrolyte is infiltrated, the separator exhibits quite high ionic conductivities, and even the conductivity reaches 0.78mScm−1 at −20°C. Furthermore, the inorganic separator has an advantage over the polymer separator in the electrolyte retention. The LiFePO4/graphite cell using the Al2O3 inorganic separator shows higher discharge capacity and rate capability, and better low-temperature performance than that using the commercial polymer separator, which indicates that the Al2O3 separator is very promising to be applied in the lithium-ion batteries.