We report the high-yield preparation of carbon-supported superparamagnetic Fe3O4 nanocomposites (C–Fe3O4-NCs) using a simple evaporation-induced method. The Fe3O4 products consist of 3–10 nm nanocrystals uniformly embedded in a carbon matrix to assemble nanoparticles with a size range from 40 to 80 nm. It is shown that lithium-ion batteries (LIB) assembled from heat-treated C–Fe3O4-NCs present attractive characteristics including a high specific capacity of 752 mA h g−1 at a current rate of 0.2 C for the second discharge cycle as well as good cycling performances with 87% retained capacity after 100 cycles.