Diameter dependent performance of silicon nanowire anodes grown on 3D current collectors for lithium-ion batteries

Si nanowires (Si NWs) with diameters tuned from similar to 35 to 100 nm were directly grown on large-area (30 cm2) stainless-steel mesh (SSM) substrates via a facile vapour-liquid-solid approach. The 3-dimensional open mesh and interwoven structure of SSM allow for the dense growth of well-anchored Si NWs and a sufficient buffer space for repeating volume changes during electrochemical cycling. In this study, the controlled synthesis of silicon nanowires with different diameters and the influence of nanowire diameter on electrochemical performance were investigated for the first time. We demonstrate that the diameter of Si NWs has a significant influence on their electrochemical performance as anode materials for lithium-ion batteries. Through systematic electrochemical testing, we observed that rate capability, specific capacities and capacity retention obtained for Si NWs samples are inversely proportional to nanowire diameter, demonstrating a diameter-dependent performance of silicon nanowires anodes. Si NWs with an average size of 100 nm exhibited specific capacities of similar to 800 mA h g-1. Reducing the diameters to 55 nm gave similar to 1200 mA h g-1 whereas Si NWs with an average diameter of similar to 35 nm demonstrated a specific capacity of similar to 1500 mA h g-1 when cycled with an applied specific current of 1 A g-1. The phase transition and structure evolution of Si NWs before and after cycling were investigated by Raman spectroscopy and electron microscopy.