Hierarchical Yolk-Shell Silicon/Carbon Anode Materials Enhanced by Vertical Graphene Sheets for Commercial Lithium-Ion Battery Applications

Abstract

Yolk-shell structured silicon/carbon (YS-Si/C) anode materials show promise for commercial lithium-ion batteries (LIBs) because of their high specific capacity and excellent cycling life. However, their commercialization has not been realized despite nearly a decade of research, primarily due to poor mechanical strength, limited rate capability, and low energy density. This study reports a hierarchical YS-Si/C anode material synthesized via thermal chemical vapor deposition for the growth of vertical graphene sheets (VGSs), polymer self-assembly, and one-step carbonization, which establishes connections between the Si core and carbon shell through VGSs, enhancing the electrochemical and mechanical characteristics of the YS-Si/C material. The unique material outperforms VGSs-free composites, which presents a high specific capacity of 1683.2 mAh g⁻¹ at 0.1 C, excellent rate performance of 552.2 mAh g⁻¹ at 10 C, and superior capacity retention of 80.1% after 1000 cycles. When matched with LiNi<inf>0.8</inf>Co<inf>0.1</inf>Mn<inf>0.1</inf>O<inf>2</inf> cathodes, the ampere-hour-level pouch cell delivers high gravimetric and volumetric energy densities of 429.2 Wh kg⁻¹ and 1083 Wh L⁻¹, respectively. Finite element analysis shows that VGSs reduce stress concentration on the carbon shell, helping hollow materials withstand industrial electrode calendaring. This work demonstrates potential for the commercial application of YS-Si/C anode materials in practical LIBs.