Is Graphite over?, page-2

Elemental silicon has a wide range of traditional applications in metallurgy, synthesis of silicone, and in the semiconductor industry. Nanostructured silicon materials, because of their unique properties and small size, have promising applications in a range of new technologies, such as nanoelectronics11, photonics12, biotechnology13, 14, 15, energy harvesting16, 17, 18, and energy storage19, 20, 21, 22. Among them, nano-Si has attracted considerable attention as a promising anode material in next generation Li-ion batteries for electric vehicles and portable electronics23, 24. This interest is primarily due to the large theoretical specific charge storage capacity of silicon (4,200 mA h g−1), which is more than ten times the theoretical capacity of conventional graphite anodes. However, silicon anode structures experience problems with fracture and pulverization that accompanies the volume changes upon Li insertion and extraction. Recent pioneering works have shown that reducing the size of silicon to the nanoscale in at least one dimension can result in effective accommodation of the strain and can even prevent fracture19, 20, 21, 22, 25, 26, 27. While many guidelines for designing high-performance silicon anodes have been established, the existing methods for producing nano-Si anodes are still limited to high temperature or high energy pyrolysis of silane/polysilane/halosilane precursors28, 29 or laser ablation of bulk Si30, 31 (Fig. 1a). Whereas nano-Si anodes are superior to graphite anodes in terms of performance, alternative fabrication methods that avoid the use of expensive processing are needed to produce Si anodes with comparable cost and scalability to graphite anodes.