Characteristics and Electrochemical Performance of Hydroxyl-Functionalized Graphene Quantum Dot-Coated Si Nanoparticles/Reduced Graphene Hybrid Anodes for Advanced Li-Ion Batteries

Abstract

By powering sophisticated lithium-ion batteries (LIBs), silicon/carbon (Si/C) composites have the potential to accelerate the sustainable energy transition. This is a first-of-its-kind Si/C hybrid with hydroxyl-functionalized graphene quantum dots (OH-GQD) electrostatically assembled within interconnected reduced graphene oxide networks (OH-GQD@Si/rGO) prepared through solution-phase ultrasonication and subsequent one-step, low-temperature annealing and thermal reduction. The OH-GQD@Si/rGO hybrid utilized as the LIB anode delivered a high initial specific capacity of 2,229.16, 1,303.21, and 1,090.13 mAh g-1 reversible capacities at 100 mA g-1 after 50 and 100 cycles, and recovered 1,473.28 mAh g-1 at rates as high as 5 A g-1. The synergistic benefits of the OH-GQD/rGO interface give dual, conductive carbon protection to silicon nanoparticles. Consecutive Si surface modifications improved Si-rGO contact modes. The initial OH-GQD carbon coating increased storage capacity through vacancy defects changing the electron density in the lattice, whereas hydroxyl functionality at the edges acted as active storage sites. Secondary protection through rGO encapsulation improved Si conductivity and usage by providing continuous electron/ion routes while minimizing Si volume variations. The proposed OH-GQD/rGO hybridization as a dual-carbon protection strategy to Si stabilized the solid electrolyte interface leading to electrode stability. This work is expected to advance the development of next-generation Si-based LIB anodes. © 2023 Angelica Martino et al.