A high capacity and cycle-stable organic molecule/polymer composite is synthesized by physical doping of redox-active perylene-3,4,9,10-tetracarboxydiimide (PTCDI) in polypyrrole (PPy). The as-prepared PTCDI/PPy composite demonstrates a synergistic electrochemical activation, in which the insoluble large PTCDI anions act as a redox-active dopant to activate the PPy backbones, while the activated PPy backbones form a conductive network to promote the redox activity of PTCDI molecules for Li insertion/extraction reactions. As a result, the PTCDI/PPy composite demonstrated a considerably high reversible capacity of >100 mAh g−1 and a stable cyclability with 92% capacity retention over 200 cycles, possibly serving as a low cost and renewable alternative to the inorganic cathode materials for Li-ion batteries. Since such a physical doping method is simple and easily adoptable for different organic molecules and polymers, it may offer a new route for developing low cost and electrochemically active organic electrode materials.