Binder-free three-dimensional silicon/carbon nanowire networks for high performance lithium-ion battery anodes

The three-dimensional (3-D) nano-architectures have attracted tremendous attention for applications in lithium-ion (Li-ion) batteries due to their unique structural advantages. In this work, we developed a facile approach to fabricate 3-D Silicon (Si) nanowire networks. By precipitation, Si nanowires spontaneously interwove with one another to form 3-D nanowire networks with large amount of micro/nano gaps, which can not only facilitate Li-ion transport but also effectively accommodate the volume change. Carbon coating was then applied on Si nanowire networks through a chemical vapor deposition (CVD) process, which not only mechanically strengthens the structure but also helps the formation of 3-D electrical conducting network. A Si/C nanowire network with a wire diameter of 75 nm and 12 wt% of carbon coating exhibits a very high specific capacity of 2300 mAh g(-1) at a rate of C/5 and a high specific capacity of around 600 mAh g(-1) at a high rate of 4.5C. Our experimental investigations showed that the cycle life of such Si/C nanowire network can be further prolonged by increasing the carbon coating content, decreasing the diameters of Si nanowires, or reducing the testing voltage window. A Si/C nanowire network with a wire diameter of 37 nm and 17 wt% carbon coating can retain 78% of the initial capacity after 60 cycles in a testing voltage window of 0.1-2 V.