Alleviating the volume expansion of silicon anodes by constructing a high-strength ordered multidimensional encapsulation structure

Abstract

The application of silicon-based nanomaterials in fast-charging scenarios is hindered by volume expansion during lithiation and side reactions induced by surface effects. Constructing a robust encapsulation structure with high mechanical strength and conductivity is pivotal for optimizing the electrochemical performance of nanostructured silicon anodes. Herein, we propose a multifaceted hierarchical encapsulation structure featuring excellent mechanical strength and high conductivity by sequentially incorporating SiO_x, hard carbon, and closed-pore carbon layers around silicon quantum dots, thereby enabling stable cycling at high current densities. In this structure, the ultra-thin SiO_x layer strengthens the Si–C interface, while the outermost carbon matrix with closed pores functions both as a conductive network and a barrier against electrolyte intrusion. Notably, the synthesized material exhibits a specific capacity of 1506 mA h g⁻¹ with 90.17% retention after 300 cycles at 1.0 A g⁻¹. After 500 cycles at 5.0 A g⁻¹, it retains 640.4 mA h g⁻¹, over 70% of its initial capacity.