Electrolytes with high Li + transference number and good electrochemical stability are urgently needed for high-energy-density Li battery. In this paper, we present newly synthesized ionic liquid (IL)-based polymer electrolyte using polymer poly(ethylene oxide) (PEO), salt lithium bis (fluorosulfonly)imide (LiFSI), and IL 1-butyl-3-methylpyridinium bis (trifluoromethylsulfonyl)imide (BMPyTFSI) by solution cast technique. They show high Li + transference number and good electrochemical and thermal stability. Also, nickel-rich layered cathode material LiNi 0.90 Co 0.05 Al 0.05 O 2 (NCA) with good electrochemical performance for lithium secondary battery is successfully synthesized by Co-precipitation method. Using the optimized polymer electrolyte and NCA cathode, Li cell is prepared which shows initial discharge capacity of ~ 137 mAh g −1 at 0.1 C-rate and good Coulombic efficiency ~96.0% upto 125 cycles.