The characteristics of the Li ion battery based on poly(vinyl chloride)/poly(methyl methacrylate) (PVC/PMMA) polymer blend electrolyte are reported. The polymer blend electrolytes exhibited phase-separated structure which consists of a PVC-rich phase and an electrolyte-rich phase. At the constant blend ratio of PVC/PMMA = 6/4, mechanical property and ionic conductivity increase with the increase of the polarity of the liquid electrolyte together with the decrease of domain size of the electrolyte-rich phase. However, these merits obtained by using the liquid electrolyte of high polarity were somewhat contrasted by the low adhesion of the corresponding polymer electrolyte toward electrode. The prototype battery cell, which consists of LiCoO2 cathode, meso-phase carbon fiber anode and the polymer electrolyte based on PVC/PMMA = 6/4 blend and 1M LiPF6 in EC/DMC = 1/1 mixture, showed the discharge capacity of 111 mAh/g (per cathode material) at charge/discharge rate of 2 C and 92% of the initial discharge capacity at 100 cycle upon the repeated charge/discharge at 0.5 C rate (0.5 x complete charge/discharge in 1 h).