Unveiling the Working Mechanism of Graphene Bubble Film/Silicon Composite Anodes in Li-Ion Batteries: From Experiment to Modeling

In spite of the fact that there are plenty of recent studies on Si/graphene composite anodes, the influence of graphene on Li diffusion at the interface and lithiation associated mechanical behavior have not been well-understood. Furthermore, it is still a technical challenge to maintain a high capacity and an ultralong cycle life with high mass loading. Using a simple self-assembly approach, we have developed an all-integrated architecture of Si nanoparticles (SiNPs) encapsulated inside reduced graphene oxide (rGO) bubble films anchored in a 3D rGO macroporous network (encapsulated Si@rGO) as an anode for Li-ion batteries (LIBs). The enhanced electrochemical performance and structural stability of the anode are accomplished by the unique multifunctional rGO bubble film, which smoothly wraps SiNPs with notable void spaces. Its residual functional groups covalently bind with SiNPs, preventing their detachment from the electrode. The bubble wrap together with the outermost 3D framework accommodate the volume change, contributing to a stabilized solid electrolyte interphase (SEI) layer while maintaining ionic and electronic conductive pathways. Density functional theory (DFT) simulations show that the graphene coating boosts the mobility of the Li atoms at the Si–graphene interface. Molecular dynamics (MD) simulations confirm that graphene bubble film can effectively control the stress build-up near the Si surface, maintaining the structural integrity of the anode. The encapsulated Si@rGO anode with a mass loading of 2.6 mg cm–2 demonstrates exceptional cycling stability and superior rate capabilities. The anode demonstrates a high reversible capacity of 1346 mAh g–1 after 200 cycles at 500 mA g–1. Even at a high current density of 2.5 A g–1, a reversible capacity of 998 mAh g–1 is maintained after 1000 cycles with a capacity retention of 97%.