Improved Performance of Si Nanowire Lithium Ion Battery Anodes By Au Catalyst Nanodot Formation on TiN.

Abstract

While silicon (Si) is considered to be an excellent candidate for next-generation lithium ion battery (LIB) anodes due to its abundance and high gravimetric capacity, Si suffers from large volume expansion as a result of lithiation. Nanowires (NWs) allow for radial expansion and strain release. Due to this volume expansion, the formation of bulk-like Si structures during the NWs growth process significantly degrades battery performance. Here we report suppression of bulk-like Si formation by interfacial energy contrast between the NWs nucleation catalysts (spontaneously formed gold (Au) nanodots) and titanium nitride (TiN) films. The TiN film promoted a narrow distribution of Si NWs’ diameters and a direct electrical connection to the stainless steel current collector. The characteristics of the solid electrolyte interphase and lithiation/charge transfer mechanisms in Si NWs were also investigated using electrochemical impedance spectroscopy (EIS). The EIS data suggest that the impedance to lithium diffusion within the NWs is approximately 40 % smaller in the NWs grown on TiN than the NWs grown directly on stainless steel. LIB anodes fabricated with the Au-catalyzed Si NWs on TiN films displayed enhanced specific gravimetric capacities (>30 %) under diverse charge/discharge rates and significantly improved capacity retention over 500 cycles.