Silicon is one of the most promising anode material candidates for lithium ion batteries because of its high specific capacity (3579 mAh/g), which is ten times higher than existing graphite anodes. One of the most important issues toward commercialization is the high cost of nanostructured silicon related to the complex fabrication amd expansive raw materials. In this work, we demonstrate the recycling of pure silicon nanoporous particles from rice husks (RHs) directly, which is an abundant agricultural byproduct (10⁸ tons/year) in worldwide. Besides, the massive amount of RHs has unique nanoporous structure on the RHs to preform the function as protection and ventilation. In the first step of our experiment, the metal ions in the RHs by HCl leaching were removed and then incinerate the leached RHs to produce silica with nanostructure. Next step, we convert the silica to silicon by electrochemical reduction method, which is a potential process for large scale reduction in a relative low tempareture compared with conventional carbothermal reduction. Owing to the nanoporous nature, these recovered silicon nano-particles show high performance as lithium ion battery anodes, with high reversible capacity and long cycle life. Recycling RHs as the source of silicon, this work presents a process to produce Si based Li-ion battery with cost effective, energy-efficient, green, and potential of large scale synthesis in industry.

Key words: rice husk, electrochemical reduction, Li-ion battery