We prepared polyacrylonitrile (PAN) nanofibrous membranes via electrospinning and investigated the effects of the oven-drying and thermal-pressing conditions on their porosity and tensile strength. A total of 27 different samples were prepared via the Taguchi design method (based on an L-27 orthogonal array) using Minitab to optimize the process parameters for the porosity and tensile strength of the samples. PAN 1 (porosity of 56.75% and tensile strength of 36.21 MPa), PAN 2 (porosity of 60.80% and tensile strength of 32.66 MPa), and PAN 3 (porosity of 67.26% and tensile strength of 20.62 MPa) exhibited high porosity and tensile strength. The optimized PAN nanofibrous membranes were used as lithium-ion coin-cell separators. The coin cell with the PAN 2 membrane as the separator exhibited the highest specific capacity of 117.92 mAhg(-1) at a C-rate of 1 C. Additionally, this coin cell showed a Coulombic efficiency of up to 99.6% and retained 89.36% of its initial capacity at the 1 C rate. The results indicate that the PAN membranes prepared in this study can be used as separators in lithium-ion batteries.