Silicon–carbon composites with two different morphologies, particulate and fibrous, prepared by NaOH catalyzed polymerization of resorcinol and formaldehyde in presence of Si nanoparticles and cosurfactants, are examined as negative electrodes in lithium-ion batteries. The composites prepared with ca. 33, 50, and 66% Si deliver around 1000, 1500, and 2000 mAh g−1, respectively. Higher silicon content results in higher initial specific charge, but also faster fading during cycling. The composites with the lowest silicon content exhibit the most stable specific charges. The differences in electrochemical behavior for the optimized compositions are investigated by means of microscopy and electrochemical impedance analysis and are discussed in terms of morphology of the different composites.