Preparation of nanostructured silicon by low-temperature aluminothermic reduction of clay minerals as anode material for high-performance lithium-ion batteries

Abstract

Silicon has been widely recognized as one of the most attractive anode candidates in the next generation of lithium-ion batteries due to its excellent theoretical specific capacity, low operating voltage, and extensive sources. Herein, one-dimensional tubular silicon and two-dimensional lamellar silicon with porous structures have been successfully synthesized from low-cost and resource-rich clay minerals (halloysite, kaolin, chlorite and dickite) as raw materials through the low-temperature aluminothermic molten salt reduction process. The results show that the morphology and microstructure of nanostructured silicon depend largely on the morphology and microstructure of its precursor, i.e., one-dimensional tubular silicon from halloysite, two-dimensional lamellar silicon from kaolin, chlorite and dickite. When used as an anode for lithium-ion batteries, one-dimensional tubular Si derived from natural halloysite exhibits superior electrochemical performance, with an initial discharge capacity of 2675 mAh g⁻¹ and an initial coulombic efficiency of 86 %. It yields a high reversible capacity of 1418 mAh g⁻¹ at 0.2 A g⁻¹ after 400 cycles with a capacity retention of 53 %. The voltage and SiLi chemical bond state of elemental silicon during charge and discharge were studied through molecular dynamics and first-principles calculations. It was found that electrons from Li atoms transferred to nearby Si atoms, and with the increase of Li content, the ionic bond properties of SiLi bonds increased, resulting in a decrease in Young's modulus and an increase in tensile fracture. This work provides a facile and cost-effective approach for the preparation of nanostructured silicon from natural clay minerals as high-performance silicon anode materials.