Ultrathin Silicon Nanowires Produced by a Bi-Metal-Assisted Chemical Etching Method for Highly Stable Lithium-Ion Battery Anodes

Silicon is widely studied as a high-capacity lithium-ion battery anode. However, the pulverization of silicon caused by a large volume expansion during lithiation impedes it from being used as a next generation anode for lithium-ion batteries. To overcome this drawback, we synthesized ultrathin silicon nanowires. These nanowires are 1D silicon nanostructures fabricated by a new bi-metal- assisted chemical etching process. We compared the lithium-ion battery properties of silicon nanowires with different average diameters of 100 nm, 30 nm and 10 nm and found that the 30 nm ultrathin silicon nanowire anode has the most stable properties for use in lithium-ion batteries. The above anode demonstrates a discharge capacity of 1066.0 mAh/g at a current density of 300 mA/g when based on the mass of active materials; furthermore, the ultrathin silicon nanowire with average diameter of 30 nm anode retains 87.5% of its capacity after the 50th cycle, which is the best among the three silicon nanowire anodes. The 30 nm ultrathin silicon nanowire anode has a more proper average diameter and more efficient content of SiOx. The above prevents the 30 nm ultrathin silicon nanowires from pulverization and broken during cycling, and helps the 30 nm ultrathin silicon nanowires anode to have a stable SEI layer, which contributes to its high stability.