This study presents the preparation of a composite polymer electrolyte (CPE), polyindole-based CuO dispersed CPE containing lithium perchlorate by sol–gel method. Morphology and the structural studies were conducted by scanning electron microscopy and X-ray diffraction. The ionic conductivity of CPE was measured for different concentration of the monomer by impedance spectroscopy. CPE containing CuO/indole (2:1 w/w ratio) (CPE3) exhibited enhanced conductivity of 1.9498 × 10−5 S/cm at RT. This CPE showed a linear relationship between the ionic conductivity and the reciprocal of the temperature, indicative of the system decoupled from the segmental motion of the polymer.