To develop next-generation lithium-ion batteries (LIBs) with novel designs, reconsidering traditional materials with enhanced cycle stability and excellent rate performance is crucial. We herein report the successful preparation of three-dimensional (3D) composites in which spilt Sn–Cu alloys are uniformly dispersed in an amorphous carbon nanofiber matrix (Sn–Cu–CNFs) via one-step carbonization-alloying reactions. The spilt Sn–Cu alloys consist of active Cu6Sn5 and inactive Cu3Sn, and are controllable by optimization of the carbonization-alloying reaction temperature. The 3D carbon nanofiber framework allowed the Sn–Cu–CNFs to be used directly as anodes in lithium-ion batteries without the requirement for polymer binders or electrical conductors. These composite electrodes exhibited a stable cyclability with a discharge capacity of 400mA h g−1 at a high current density of 1.0Ag−1 after 1200 cycles, as well as an excellent rate capability, which could be attributed to the improved electrochemical properties of the Sn–Cu–CNFs provided by the buffering effect of Cu3Sn and the 3D carbon nanofiber framework. This one-step synthesis is expected to be widely applicable in the targeted structural design of traditional tin-based anode materials.