Electric arc synthesis enables the fabrication of materials in the form of metal nanoparticles packed into a carbon matrix, which separates the nanoparticles, preventing them from contacting each other, merging, coagulating, or contacting possible reactive environments, thereby stabilizing the nanoparticles. This paper presents the results of studies of the effect of tin on the structure of a composite tin–carbon nanomaterial synthesized by the electric arc method. The concentration of tin affects both the formed carbon structure, changing it from amorphous to graphene-like, and the size of the formed tin nanoparticles. In turn, these structural features affect the electrochemical properties of the synthesized materials used as anodes in lithium-ion batteries. Increasing the tin content increased the specific capacity, but increasing the size of the tin nanoparticles and the rigidity of the carbon matrix decreased the anode material’s stability.