Rice Husk-Derived Porous Silicon with High Purity As Anode for Lithium Ion Batteries

Abstract

Recently, social concerns and the importance of ‘green growth’ and ‘renewed energy technology’ have increased, which resulted from the increase in the cost of fossil fuels and climate change. One of the critical technologies for accomplishing ‘green growth’ is the recycle of waste products generated through manufacturing processes. One of the largest wastes is rice husks, which are generated from the production of rice. Rice is cultivated in more than 75 countries in the world and the worldwide annual rice production amounts to approx. 422 million metric tons, of which about 20% is rice husk. However, its utilization has been limited to low-value applications in the agriculture area, such as stockbreeding rugs, bed soil, fertilization and lagging materials etc., which is the case because of their tough, woody and abrasive properties. Thus, many researchers have attempted to increase their added value, including the development of rice husks activated carbon, rice husk gasification and electricity generation. Some research groups have studied the potential of using rice husks as a fiber resource. Ah et al. reported the preparation of packing materials and Lee et al. developed a rice husk board. Rice husks contain approximately 20 wt% silica and because of ‘natural selectivity’ of rice plants, it has a lower level of metallic impurities than other representative silica sources, such as quartz, bentonite and diatomaceous earth etc.. Therefore, a significant effort has been directed at the production of high purity silicon-based materials from rice husks, such as SiC, Si3N4, SiO2 and high grade silicon. However, most of these studies are based on using rice husk ash (RHA), which is generated after the combustion of rice husk and very few studies have examined the potential of using the organic part of rice husks. Thus, we developed a refinery process to integrate the use of rice husks and increase of the value of rice husks. This process has the combined benefit of producing valuable silicon-based materials and cellulose-based materials. The rice husks are divided into fiber and inorganic components during the refinery process. In this work, we investigated the chemical composition and morphological characteristics of the rice-husk derived silica obtained from the refinery process. The conditions for preparing SiO2 with high purity and high surface area were optimized and highly porous nano-structured silicon (Si) with high purity was prepared from rice husk-derived silica. We also examined the potential of using the rice husk derived silicon as an anode material in Li-ion batteries.