Phase transitions in lithiated Cu2Sb anodes for lithium batteries:: an in situ X-ray diffraction study

Copper antimonide, Cu(2)sb, has been investigated as a negative electrode (anode) for rechargeable lithium batteries by in situ X-ray diffraction of Li/Cu2Sb cells. The data show that lithium is inserted into Cu2Sb with a concomitant extrusion of copper, which initiates a phase transition to a lithiated zinc-blende-type structure, LixCu2-ySb for 02 and 0 less than or equal toy less than or equal to1, yielding Li2CuSb at x = 2, y = 1. Further lithiation results in the displacement of the remaining copper to yield Liz(2+z)Cu(1-z)Sb compositions (0 < z 1) with the end member Li3Sb. The Sb array remains intact in a face-centred arrangement throughout these reactions, despite a 42% expansion of the array. The reactions are reversible; they occur between 1.0 and 0 V vs. Li-0, and deliver a steady capacity of approximately 290 mAh/g after one conditioning cycle. The lithium insertion/metal extrusion reactions with the Cu2Sb structure bear a resemblance to those observed previously with Cu6Sn5 and InSb. (C) 2001 Elsevier Science B.V. All rights reserved.