Constructing a multi-dimensional hierarchical structure to improve the cycling stability of silicon nanowires

Abstract

Despite its exceptionally high theoretical capacity, silicon faces significant challenges as an anode material for lithium-ion batteries (LIBs) due to its intrinsically low electrical conductivity and substantial volume variation (∼300%) during repeated (de)lithiation processes. To address these issues, silicon nanowires (SiNWs) featuring a 0D–1D–3D hierarchical structure are constructed by employing carbon nanotubes (CNTs) as structural templates, via a sol–gel process followed by magnesiothermic reduction. The nanowire morphology effectively shortens the Li⁺ diffusion distance and enhances Li⁺ transport kinetics. Besides, the internal voids between nanoparticles accommodate the large volume expansion of silicon, effectively mitigating mechanical strain and reducing electrode pulverization. Consequently, the electrode exhibits a remarkably low volume expansion of only 73.7% after 200 cycles. Furthermore, the interconnected 3D network established by the nanowires provides continuous pathways for both electron transport and ion diffusion, which reduces interparticle contact resistance. This architecture results in a 44.5% enhancement in the lithium-ion diffusion coefficient compared to conventional silicon nanoparticles. Additionally, the robust 3D framework effectively distributes localized stress, greatly improving cycling stability. As a result, the SiNW-based anode delivers a high specific capacity of 997.3 mA h g⁻¹ after 200 cycles at 0.1C. This synthesis strategy, centered on stress-management engineering, demonstrates considerable potential for the practical application of Si-based anodes in high-energy-density LIBs.