Improved lithium-ion batteries with coral-like anodes made of recycled spherical porous silicon coated with nitrogen-doped carbon

With the development of the silicon smelting industry, the increase of microsilica waste has become a serious concern calling for methods to recycle silica such as using silicon to improve the anode of lithium-ion batteries. Here we prepared spherical porous silicon by magnesiothermic reduction of microsilica waste from the photovoltaic industry. Spherical porous silicon was further coated with nitrogen-doped carbon to build a material with a coral-like structure. This material displays uniformly interconnected pore channels and nitrogen-doped carbon layers. The material enhances lithium-ion transport, and accommodates extreme volumetric changes of Si during the charge-discharge cycle. The electrodes made of this material delivered a reversible capacity of 803.92 mAh g−1 after 300 cycles at 1000 mA g−1 and exhibited a 18.6% expansion rate.