Simple preparation of Cu6Sn5/Sn composites as anode materials for lithium-ion batteries

Abstract

Cu₆Sn₅/Sn composites are directly fabricated by a high energy mechanical milling technique and subsequent heat treatment. In particular, the effects of the ratios of Sn to Cu₆Sn₅ (Cu_xSn_y, x = 10 − y, y = 4.5, 7 and 9) on the lithium-ion batteries performances are investigated. The results show that the sample with y = 4.5 is a single-phase Cu₆Sn₅, the sample with y = 7 is slightly Sn rich in the Cu₆Sn₅ (Sn < Cu₆Sn₅), and the sample with y = 9 is excessively Sn rich in the Cu₆Sn₅ (Sn > Cu₆Sn₅). Furthermore, the Cu₆Sn₅/Sn composite has an obvious structure of a core–shell, only when y = 7. As an anode material for lithium-ion batteries, the Cu₆Sn₅/Sn composite with y = 7 exhibits a discharge capacity of 761.6 mA h g⁻¹ after the first cycle, 457.8 mA h g⁻¹ after 20th cycles, and an initial coulombic efficiency of 91.37%, which shows a better electrochemical performance than that of y = 4.5 or 9. In addition, after adding 15 wt% of graphite, the sample with y = 7 maintains a discharge capacity of 605.8 mA h g⁻¹ after 100 repeated cycles, higher than many reported Cu–Sn-based anode materials.