In order to improve the safety of lithium-ion batteries, polyimide (PI) are introduced to be coated on polyethylene (PE) separator to enhance its thermal and mechanical properties simultaneously via electrospray as well as electrospinning methods. Layer- by-layered structure separators were prepared with a layer of E-spray coating firstly and E-spinning coating secondly. Specifically, spray coating is responsible for heat resistance due to its uniformity and high molten point. Meanwhile, fibers produced by electrospinning play an very important role in increasement of mechanical strength. All electrospray conditions were optimized in order to get the best quality of coating and the morphology of the coating surface prepared under different conditions were compared by scanning electron microscope (SEM). At the same time, heat shrinkage test and dynamic mechanical analysis (DMA) test were also conducted to see if PE separator’s thermal as well as properties achieved our goals. What’s more, Fourier- transform infrared spectroscopy (FT-IR) was also applied in my project to make sure there is no structural changes after plasma treatment that is beneficial to combination between spray and fiber coatings. Finally, electrochemical characterization of cells with prepared separators were conducted in order to prove the practicability of lithium-ion batteries.