Glassy Metal Alloy Nanofiber Anodes Employing Graphene Wrapping Layer: Toward Ultralong-Cycle-Life Lithium-Ion Batteries

Abstract

Amorphous silicon (a-Si) has been intensively explored as one of the most attractive candidates for high-capacity and long-cycle-life anode in Li-ion batteries (LIBs) primarily because of its reduced volume expansion characteristic (∼280%) compared to crystalline Si anodes (∼400%) after full Li⁺ insertion. Here, we report one-dimensional (1-D) electrospun Si-based metallic glass alloy nanofibers (NFs) with an optimized composition of Si₆₀Sn₁₂Ce₁₈Fe₅Al₃Ti₂. On the basis of careful compositional tailoring of Si alloy NFs, we found that Ce plays the most important role as a glass former in the formation of the metallic glass alloy. Moreover, Si-based metallic glass alloy NFs were wrapped by reduced graphene oxide sheets (specifically Si₆₀Sn₁₂Ce₁₈Fe₅Al₃Ti₂ NFs@rGO), which can prevent the direct exposure of a-Si alloy NFs to the liquid electrolyte and stabilize the solid-electrolyte interphase (SEI) layers on the surfaces of rGO sheets while facilitating electron transport. The metallic glass nanofibers exhibited superior electrochemical cell performance as an anode: (i) Si₆₀Sn₁₂Ce₁₈Fe₅Al₃Ti₂ NFs show a high specific capacity of 1017 mAh g^–1 up to 400 cycles at 0.05C with negligible capacity loss as well as superior cycling performance (nearly 99.9% capacity retention even after 2000 cycles at 0.5C); (ii) Si₆₀Sn₁₂Ce₁₈Fe₅Al₃Ti₂ NFs@rGO reveals outstanding rate behavior (569.77 mAh g^–1 after 2000 cycles at 0.5C and a reversible capacity of around 370 mAh g^–1 at 4C). We demonstrate the potential suitability of multicomponent a-Si alloy NFs as a long-cycling anode material