Silicon sources: collection and characterization

Abstract

SILICON IS a promising anode material in lithium-ion batteries due to its high theoretical capacity of 3579 mAh g-1. Compared to the conventional graphite anode (372 mAh g-1) it is significantly higher (Obrovac, Chevrier 2014). The rising demand for sustainable and efficient battery technologies has driven advancements in exploring alternative silicon sources, especially those obtained from renewable and environmentally friendly materials (Muraleedharan Pillai, Kalidas, Zhao, Lehto 2022). Traditional silicon extraction processes usually rely on high-purity silica (SiO2) derived from non-renewable quartz. Such processes are energy-intensive and environmentally taxing (Nawaz, Zakharenko, Zemchenko, Haider, Ali, Imtiaz, Chung, Tsatsakis, Sun, Golokhvast 2019). Identifying and utilizing biomass-based silicon sources presents a compelling alternative to potentially reduce the carbon footprint of silicon production and provide a sustainable approach to silicon sourcing. This study aims to investigate various biomass materials and their potential as sustainable silicon sources. A range of biomasses, including barley husk, horsetail, ferns, reed canary grass, diatoms and brewer’s spent grain, together with geothermal brine, were systematically evaluated for their efficacy in producing high-quality silicon for advanced applications. Study began with a comprehensive collection and preparation, followed by silicon dioxide (SiO2) extraction using specialized methods tailored to each material’s unique properties. Once SiO2 is extracted, it undergoes a reduction process to yield elemental silicon, an essential step in preparing silicon anode for lithium-ion batteries. The relevent data on reed canary grass are sourced from the literature. To accurately assess quality of the silicon and its potential suitability for energy storage, we employ a range of material characterization methods, including X-ray diffraction (XRD), X-ray Fluorescence analysis (XRF), scanning electron microscopy (SEM)/ energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), and N2 sorption analysis. These techniques allow in-depth analysis of the purity of silicon, structural properties, and morphological features obtained from each biomass source. Electrochemical characterization further evaluates the performance of silicon in half cells, evaluating its potential for lithiumion storage. This process provides insights into lithium activity, lithiation reversibility, and capacity retention, which are crucial for determining the material’s applicability in lithium-ion battery anodes. The results section thoroughly examines each biomass source, with a detailed discussion of each material’s SiO2 yield, purity and morphology. Each biomass source is explored individually to highlight unique attributes, advantages, and potential challenges. Barley husk, horsetail, fern, reed canary grass, diatoms and brewer’s spent grain are natural sources known for their SiO2 content, while geothermal brine provides an alternative silicon source with distinct extraction challenges. This study compares these SiO2 sources, offering a perspective on their relative usefulness in silicon production. This study aims to expand the knowledge on biobased silicon sources by comparing silica from various origins and providing data to advance sustainability. By assessing the electrochemical performance of silicon derived from Geosilica, it seeks to promote environmentally friendly, locally sourced materials. This approach could reduce the battery industry’s dependence on conventional quartz-derived silicon, enhancing the overall sustainability of the energy storage sector.