3D binder-free nanoarchitecture design of porous silicon/graphene fibers for ultrastable lithium storage

Enhancing the stability and fast-charging capability of battery electrodes is of paramount importance in the field of battery technology. Silicon (Si), renowned for its high specific capacity, has emerged as a promising candidate for anodes. However, the limited structural stability and electron/ion conductivity of silicon-based anodes have raised significant concerns, including fractures and the continuous formation of unstable solid-electrolyte interphase (SEI) layers, leading to rapid capacity decay. In this study, we introduce a comprehensive approach to fabricating a binder-free and free-standing anode electrode paper using a combination technique of employing electrospinning, magnetron sputtering, and chemical vapor deposition (CVD) techniques. This developed paper electrode incorporates a 3D interconnected network of nitrogen-doped vertical graphene nanosheets (VGs) that connect porous carbon fibers (PCFs) with uniformly distributed Si nanoparticles (VGs@Si@PCFs). The as-fabricated VGs@Si@PCFs paper effectively addresses the mechanical and chemical stability issues commonly associated with Si anodes. The VGs@Si@PCFs anode demonstrates a remarkable reversible capacity of 2205 mAh g at 0.1 A g and exhibits exceptional cycling performance with 83.5% capacity retention at 1.0 A g after 3000 cycles. This design leverages the nanoporous carbon fibers and nitrogen-doped vertical graphene nanosheets as flexible and conductive supports, enhancing the robustness and flexibility of the electrode. Additionally, mechanical modeling reveals that the overall Mises strain in the porous VGs@Si@PCFs structure is significantly lower compared to nonporous cases, potentially minimizing low-cycle fatigue. Our free-standing Si/C composite anode introduces a new class of low-strain Si-based materials, showcasing significantly improved stabilities and fast-charging capabilities.