LiMn₂O₄–carbon composites composed of 7 nm LiMn₂O₄ nanoparticles homogeneously anchored on conducting carbon nanotubes and graphene nanosheets were fabricated via a self-assembly process combined with solid-state lithiation. Owing to improved Li diffusion kinetics achieved by the small particle size and intimate electrical contact with a porous, conducting carbon matrix, reversible capacities close to the theoretical value with enhanced power capability and cyclability were attained for these highly crystalline LiMn₂O₄–carbon composite cathodes. The facile self-assembly approach can be readily adapted to different carbon supports and could serve as a general synthetic strategy towards controlled fabrication of other functional hybrids for high-performance energy storage devices.