High-Yield Synthesis of Battery-Grade Silicon from Halloysite Through HF-Free Metallothermic Reduction
Year: 2026
Type: article
Abstract: Magnesiothermic reduction is a promising route for synthesizing nanostructured silicon for battery anodes, yet commercial scalability is hindered by highly exothermic reaction conditions and reliance on hydrofluoric acid (HF) for purification. Here, it is demonstrated that intrinsic thermal accumulation during bulk synthesis drives the formation of magnesium silicate. To counteract this effect, a binary calcium chloride–magnesium chloride salt mixture was used as an intrinsic heat sink. By tuning its liquidus temperature to 675 °C, the reaction exotherm was absorbed via latent heat of fusion, preventing byproduct formation without microreactor geometries. Furthermore, an optimized ethanol-based purification protocol was developed to suppress surface silicon oxidation. This suppression circumvented the need for HF etching to remove unreacted surface oxides, resulting in a final silicon yield of approximately 93%. Additionally, powder X-ray diffraction is established as a predictive, high-throughput screening tool; the intensity of the amorphous scattering peak reliably correlates with surface oxide thickness and subsequent electrochemical failure. Ultimately, the fully optimized, HF-free silicon demonstrated sustained cyclability and capacity retention comparable to traditional HF-etched baselines. By resolving thermal scaling limits and surface oxide formation, this work establishes a high-yield and HF-free pathway for the commercial manufacturing of silicon anode active material.
Source: Batteries
Institution: Brigham Young University
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,258
OpenAlex ID: W7221151785