Polymer electrolytes have received extensive attention in the realm of lithium based batteries due to their mechanical flexibility and superior thermal stability. However, further improvement of ionic conductivity and electrochemical performance is highly necessary to make it commercially viable. Here, we report a novel nano-silica doped composite polymer chitosan/poly(ethylene oxide)-based electrolyte. The polymer electrolyte prepared by the addition of nano-silica has an excellent ionic conductivity of 0.92 mS cm at room temperature, a superior lithium-ion migration number of 0.7, and exceptional thermal stability. The lithium-metal/LiFePO quasi solid-state lithium battery using this composite polymer electrolyte can be operated at room temperature maintaining a high initial cathode capacity of 134 mA h g at a current density of 0.2C for 300 cycles, and the coulombic efficiency is above 95%. The composite polymer electrolyte doped by nano-silica has high ionic conductivity and excellent electrochemical performance, which clearly indicates this electrolyte can be a suitable candidate for commercially available batteries.