Local confinement and alloy/dealloy activation of Sn–Cu nanoarrays for high-performance lithium-ion battery

The practical application of Sn-based anodes are seriously hampered by the dramatic volume expansion (∼300%) during charge/discharge processes, which induces large internal stress that can make the anode materials easily pulverized and cracked to cause the loss of electrical contact and thus severe capacity fading. In order to address this problem, a versatile strategy has been developed for preparing multiple Sn/Cu nanoarrrays including Cu–Sn end-to-end nanowires (NWs), Cu@Sn core-shell NWs and Cu@Sn core-shell semi-nanotubes (NTs) through a two-step successive-electrodeposition process with track-etched polycarbonate (PC) membranes as template: metallic Cu nanowire arrays are first electrodeposited inside the nanopores of the PC membrane on the Cu foil substrate, followed by the deposition of Sn in the second step. The architectures of these samples can be readily tuned by modifying the synthesis conditions or by treating the PC membrane with 3-aminopropyl-triethorxysilane (APTES). The distinct structures of these electrodes provide a high performance in lithium ion batteries. The discharge capacity of Cu–Sn NWs, Cu@Sn NWs, and Cu@Sn NTs after 400 charge-discharge cycles at a specific current of 0.8 A g⁻¹ is 714, 402, and 1193 mA h g⁻¹, respectively. Such a performance can be attributed to a local confinement effect between Sn and Cu maintaining structural integrity and good electrical contact, and an alloy/dealloy activation process achieving high reversible capacities.