Polyethylene separator of 300% uni-axial stretching ratio is dip-coated with sol-gel synthesized NiO nanoparticles. The crystalline structure and the porous nature of the synthesized NiOnano particles are confirmed using X-Ray diffractometer (XRD) and field emission scanning electron microscope (FE-SEM). The dip-coated stretched PE separator is to be observed with high ionic conductivity of 2.12 mS cm-1 and lower MacMullin number of 3.9 compared to the uncoated stretched PE separator. With regard to the thermal behavior coated separator has around six times lower enthalpy value, lower weight loss, and lower thermal shrinkage behavior as proven by differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA) and even when exposed to high temperature, respectively. The above characteristics of coated separator enhance the safety of Li-ion batteries. The electrochemical property is tested using electrochemical cycler and Li-ion cells with coated separator possess a similar initial discharge capacity but with enhanced capacity retention ratio of 95.73%. The obtained cycling behavior is well scrutinized by plotting the discharge profile and also by measuring its interfacial stability i.e., charge transfer resistance (R ct) based on cycle numbers using electrochemical impedance spectroscope (EIS). Improved rate capability behavior of Li-ion cells with coated separator is also demonstrated.