Double core-shell structure stabilized porous Si@graphene@TiO₂ microsphere anode with excellent cyclability and high coulombic efficiency

The vast volume expansion of Si anode during lithiation process leads to poor cyclability and low initial coulombic efficiency (ICE), and thus seriously hampers its applications in lithium-ion batteries (LIBs). To overcome these obstacles, in this study, a double core-shell structure stabilized hierarchical porous Si (p -Si) microsphere was synthesized through a graphene-involved electrostatic self-assembly process coupled with a solvent-confined TiO2 (sc-TiO2) monomicelle assembly strategy. The advanced solvent-confined monomicelle assembly process enables the uniform deposition of ultra-thin TiO2 layer on p-Si@graphene (p-Si@G) microsphere. The G/sc-TiO2 hybrid double shell layer can significantly consolidate porous structure of p-Si microsphere and simultaneously improve the ICE value of p-Si@G@sc-TiO2 microsphere. The resulting p-Si@G@sc-TiO2 composite shows a high capacity value of 2597.9 mAh g(-1) at 0.2 A g(-1) with a high ICE value of 80.59%. The p-Si@G@sc-TiO2 composite also demonstrates excellent rate capability with capacity of 802.53 mAh g(-1) at 8 A g(-1) and outstanding cyclability with capacity retention of 68% (1005.1 mAh g(-1)) after 300 cycles at 2 A g(-1), superior to that of p-Si, p-Si@G as well as p-Si@G@TiO2 microsphere preparing by traditional sol-gel TiO2 coating method, suggesting its promising applications in LIBs. (c) 2022 Elsevier Ltd. All rights reserved.