Two-Step Graphene Strategy Enabling Long-Cycle Stability of Silicon Anodes

A two-step graphene-reinforced hierarchical structure to address the poor cycle stability due to significant volume fluctuations in silicon anodes for lithium-ion batteries (LIBs) is introduced in this study. Fine composite granules (1-2 μm), SiNPs@rGO where silicon nanoparticles (SiNPs) were fully encapsulated by reduced graphene oxide (rGO) flakes, were synthesized by a high-power planetary ball milling technique. The compact structure of the SiNPs@rGO granules effectively suppressed the dispersion loss of Si and Li_xSi fragments from the granules. To accommodate the large volume fluctuation of Si in lithiation and delithiation cycles, a hierarchical structure using mechanically flexible and stretchable holey reduced graphene oxide (HrGO) 2D layers was developed. The hierarchical structure of HrGO/SiNPs@rGO composite anode successfully accommodated the volume fluctuations of SiNPs@rGO, thereby markedly enhancing long-cycle stability. Systematic analyses of the characteristic electrochemical properties and morphological evolution of these 2D material-based anodes are reported.