Partially Reduced Si/SiOx via High Energy Mechanical Milling and Magnesiothermic Reduction for Lithium Storage Materials

Abstract

Lithium ion battery is widely used as a power source for many applications including smart phones and laptops as well as energy storage system (ESS) and electric vehicles due to its high energy density and high power. Currently commercialized anode material is graphite that have some advantages, uch as low reduction potential and high stability. Nowadays, the demand for high-capacity batteries has increased with the expansion of the electric vehicle market and the development of renewable energy, silicon has been considered as a next generation anode material to replace graphite anode because it has 10 times higher theoretical capacity than that of graphite. However, the main problem is severe volume changes during cycling, resulting in pulverization of silicon particles, loss of electrical contact and finally poor cycle performance. As an effective strategy to improve these problems, Si/SiOx material was introduced because the less active SiOx matrix in the Si/SiOx which can alleviate Si volume expansion so that Si/SiOx material shows excellent cycle performance. However, it suffers from low initial coulombic efficiency caused by the formation of irreversible products such as Li4SiO4 and Li2O for the first charging process. In this study, I propose a partial reduction of Si/SiOx to suppress the formation of irreversible phases by decreasing oxygen contents in Si/SiOx. Moreover, this research demonstrates that high energy mechanical milling with Mg, and magnesiothermic reduction are effective way to partially reduce the Si/SiOx. As a result, reduced Si/SiOx has an improved initial coulombic efficiency as well as initial reversible capacity compare to that of pristine Si/SiOx.