Li xCu 6Sn 5 (0

Electrochemical and Solid-State Letters, Volume 2, No. 7, Year 1999

It has been discovered that lithium can be inserted into the intermetallic compound Cu 6Sn 5 in a two-phase reaction to yield the product Li xCu 6Sn 5 (x≈13). This finding has important implications for designing new intermetallic insertion electrodes (anodes) for rechargeable lithium batteries. The theoretical capacity of Li xCu 6Sn 5 derived from the eta-phase, η-Cu 6Sn 5, with a NiAs-type structure is 358 mAh/g for x max = 13, which corresponds to a fully lithiated composition Li 2.17CuSn 0.83; this capacity is close to the theoretical capacity of lithiated graphite LiC 6 (372 mAh/g). The reaction occurs at approximately 0.4 V vs. lithium metal. The best cycling efficiency is obtained when the end voltage is restricted to 200 mV above the potential of lithium metal. A mechanism is proposed for the insertion of lithium into η-Cu 6Sn 5.