To search for advanced anode materials for Li-ion rechargeable batteries, the structures, stabilities, and electronic properties of crystalline silicon and those of the snowball-type (SB) and core-shell (CS) silicon clusters Sizyubin@icp.ac.ru (n = 2—308) were quantum chemically modeled within the framework of the density functional theory with inclusion of gradient correction and periodic boundary conditions. The formation of SB agglomerates from smaller Sizyubin@icp.ac.ru clusters (n ≤ 7) is energetically preferable. At n ≥ 105 and circumscribed sphere diameters (D) ≥ 17—20 Å, CS isomers comprised of quasi-crystalline cores surrounded by small clusters are energetically more favorable than the SB isomers.