Cu-Sn alloy microtube assembly fabricated by electroless plating on polyester nonwoven fabric and its lithiation-delithiation performance

The 300-nm-thick Cu6Sn5 microtube assemblies with a Cu inner layer and with a polyester fiber core were fabricated and their lithiation-delithiation performances as the anode of lithium ion batteries were evaluated. The Cu inner layer was obtained by electroless plating on nonwoven polyester fabrics. Cu was uniformly deposited on the fibers in a fabric treated with HNO3-O-3, by which stable hydroxy groups were formed on the fiber surface, and the Pd catalyst adsorption was enhanced. The Cu6Sn5 microtubes were fabricated by the contact immersion deposition process of Sn on the Cu-coated fibers. The deposited Sn formed a dense Cu6Sn5 layer without heat treatment, and its thickness agreed with the theoretical value estimated from the solid-state diffusion coefficient of Sn. Voltage profiles of the microtube assembly electrode during the lithiation-delithiation cycling show the typical features of Cu6Sn5. Capacities were stable during the initial 40 cycles and were paralleled with the Sn loadings. The capacities began to fade after 50 cycles without the removal of Sn, but with the morphological and compositional changes, that is, the trapping of Sn in the degradation products of electrolyte.