Tin (Sn) is one of the best candidates as an anode material for lithium-ion batteries, because of its high capacity and safe working-potential. However, it suffers from degradation due to the large variation in volume (~ 260%) induced by (de)lithiation. Several studies have shown the ability of Sn nanostructures to accommodate this volume change without degradation, but they still suffer from capacity fade as a result of: (1) parasitic reactions to form the solid electrolyte interphase (SEI) that is exacerbated by the high surface area of nanostructures, and (2) “lithium trapping” that results from the difficulty with completely delithiating the nanostructures.

In this context, we reported on the electrochemical performance of three-dimensionally interconnected nickel-tin nanowire network (NiSn 3DNWN) electrodes featuring nanowire diameters of 40 nm, 105 nm, and 230 nm, respectively. The NiSn 3DNWN electrodes were fabricated by template-assisted electrodeposition into polycarbonate membranes with crossed cylindrical nanopores and ~20% porosity. The obtained highly-packed 3DNWN architecture, as well as the nanowire diameters, allowed for volume variation on (de)lithiation with no observable degradation.

To mitigate the surface parasitic reactions, the effects of fluoroethylene carbonate (FEC) and vinylene carbonate (VC) additive were also investigated as a function of nanowire diameter and additive concentration. The results show that FEC and VC of all concentrations improve the capacity retentions and coulombic efficiencies (CEs) of the NiSn 3DNWN electrodes. Moreover, the impact of electrolyte concentration on capacity retention and rate performance reduces as the nanowires diameter increases (i.e., as electrode surface area decreases). However, the NiSn 3DNWN electrode with intermediate nanowire size displays the highest average CE. Electrochemical impedance spectroscopy and post-cycling morphological investigations reveal that FEC has the most profound effect on the interfacial resistances, which is reflected in the rate performances of the electrodes. The data suggest that the effects of additives and nanowire diameter on the performance of lithium-alloying nanowire-based anode materials may result from the different capacity fade mechanisms as the nanowire diameter varies.