High-Performance Core-Shell Structured SiOx@Si-Silicide Nanocomposite Anode Material for Lithium-Ion Rechargeable Batteries

Abstract

Si-based materials are the most promising anode candidates for high-performance and safe lithium-ion batteries (LIBs). However, their successful practical utilization is hampered due to the large volume variations during the alloying/dealloying process, structural instability, and poor conductivity. To address these issues, herein, we report a novel double-protection strategy for Si with a mechanically strengthen and conductive FeSi2 phase and SiOx core–shell structure (SiOx@Si-FeSi2 nanocomposite) synthesized via induction melting followed by high-energy mechanical milling and thermal oxidation. A high initial cycle coulombic efficiency (∼79%) and high reversible capacity of ∼843 mAh/g@220th cycle (under 1C-rate = 0.5 A g−1) is achieved for the SiOx@Si-FeSi2 nanocomposite. Moreover, high average coulombic efficiency of ∼99.1% and high reversible capacity retention of ∼80% (at 1C-rate) over 200 cycles; and excellent rate capability is obtained. The outstanding electrochemical performance of the SiOx@Si-FeSi2 nanocomposite is attributed to the synergistic effect of well dispersed active Si in the FeSi2 phase. Additionally, an amorphous SiOx core–shell structure significantly reduces the mechanical stresses/strains experienced by Si during lithiation/delithiation. It also provides a stable solid electrolyte interface and good conductivity. Subsequently, this facile, cost-effective synthetic approach providing excellent electrochemical performance makes the SiOx@Si-FeSi2 nanocomposite a promising anode material for high-performance LIBs.