A comparison of sputtered and mechanically milled Cu6Sn5 + C materials for Li-ion battery negative electrodes

Abstract

Sn27Cu33C40 produced by mechanical milling is compared with Sn27Cu31C42 and Sn26Cu31C43 produced by magnetron sputtering for use as anode materials in Li-ion batteries. The sputtered samples were found to be amorphous/nanostructured and had a greater degree of atomic intermixing in comparison to the milled sample, which was more crystalline. Samples were incorporated as electrodes in Li-half cells and had a capacity of about 400 mAh g−1. Significant capacity loss was observed beginning near the 50th cycle for the mechanically milled sample, while little capacity loss was observed for the sputtered samples after 100 cycles. Despite its good cycling performance, amorphous Cu6Sn5 + C was found to crystallize as Li is cycled, resulting in the aggregation of Cu6Sn5 grains. Structural changes during lithiation and delithiation as well as the evolution of the electrochemistry are compared and contrasted for the two materials.