At present, graphite (LiC6: 372mAhg−1, 840mAhcm−3) is used as the anode material for lithium-ion batteries. However, methods to enhance the energy density, cyclability, initial Coulombic efficiency, and rate capability of lithium-ion batteries are still actively being researched. Here, we report a simple, fast, and novel method for transforming micron-sized Sn and Sb powders into ca. 10nm- and 2–3nm-sized SnSb crystallites by mechanochemical synthesis and electrochemical reactions, respectively. These nanocrystallites are uniformly distributed in an amorphous carbon matrix, resulting in a SnSb/C nanocomposite structure. The fabricated SnSb/C nanocomposite showed excellent electrochemical properties, such as a high energy density (1st charge: 706mAhg−1), long cyclability (ca. 550mAhg−1 over 300 cycles), good initial Coulombic efficiency (ca. 81%), and a fast rate capability (1C: 590mAhg−1, 2C: 550mAhg−1).