LixCu6Sn5 (0<x<13):: An intermetallic insertion electrode for rechargeable lithium batteries

It has been discovered that lithium can be inserted into the intermetallic compound Cu(6)Sn(5) in a two-phase reaction to yield the product Li(x)Cu(6)Sn(5) (x approximate to 13). This finding has important implications for designing new intermetallic insertion electrodes (anodes) for rechargeable lithium batteries. The theoretical capacity of LixCu(6)Sn(5) derived from the eta-phase, eta-Cu(6)Sn(5), with a NiAs-type structure is 358 mAh/g for x(max) = 13, which corresponds to a fully lithiated composition Li(2.17)CuSn(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 eta-Cu(6)Sn(5). (C) 1999 The Electrochemical Society. S1099-0062(99)01-079-4. All rights reserved.