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

Copper antimonide, Cu{sub 2}Sb, has been investigated as a negative electrode (anode) for rechargeable lithium batteries by in situ X-ray diffraction of Li/Cu{sub 2}Sb cells. The data show that lithium isinserted into Cu{sub 2}Sb with a concomitant extrusion of copper, which initiates a phase transition to a lithiated zinc-blende-type structure, Li{sub x}Cu{sub 2-y}Sb for 0 < x {<=} 2 and 0 {<=} y {<=} 1, yielding Li{sub 2}CuSb at x = 2, y = 1. Further lithiation results in the displacement of the remaining copper to yield Li{sub 2+z}Cu{sub 1-z}Sb compositions (0 < z {<=} 1) with the end member Li{sub 3}Sb. 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{sup 0}, and deliver a steady capacity of approximately 290 mAh/g after one conditioning cycle. The lithium insertion/metal extrusion reactions with the Cu{sub 2}Sb structure bear a resemblance to those observed previously with Cu{sub 6}Sn{sub 5} and InSb.