Co-Sn Alloys as Negative Electrode Materials for Rechargeable Lithium Batteries

We have prepared the intermetallic compound Cu 6 Sn 5 using mechanical-alloying, gas-atomizing, and melt-spinning techniques, The electrochemical performance of the compound is critically dependent on its morphology due to different preparation methods. The Cu 6 Sn 5 alloy created by mechanical alloying, consisting of < I μm thick flake powder has the best battery performance of all compounds. It delivers a rechargeable capacity of 200 mAh/g (2000 Ah/L) over 50 cycles when the cycled voltage range is restricted to 0.2-1.5 V. The effect of the mechanical-alloying lime and Cu/Sn ratio on its battery performance was further investigated. The presence of excess Cu in alloy, relative to Cu 6 Sn 5 , showed improved cyclability at the expense of capacity, whereas an excess of Sn resulted in poor cyclability. A lithium-ion cell based on a flaked Cu-Sn mierocomposite alloy negative electrode and a 5 V LiNi x Mn 2-x O 4 positive electrode was assembled. The cell showed an average working voltage at 4.0 V and cycled well with a reversible capacity of ca. 200 mAh/g based on the pure Cu-Sn alloy when a cell was cycled between 3.5 and 4.6 V.