Carbon-Coated Si Nanosheets as Anode Materials for High-Performance Lithium-Ion Batteries

Silicon (Si) and Si-based compounds have been considered by many researchers as one of the anode materials for the next-generation lithium-ion batteries (LIBs) due to their extraordinarily large theoretical capacity, moderate operating voltage, and abundant resources. However, silicon's poor conductivity and significant volume changes during charge and discharge, compared to conventional carbon materials, severely restrict its widespread use in LIBs. In this study, a two-dimensional (2D) mesoporous Si nanosheet/carbon (pSi@C) composite is designed using cetrimonium bromide-disodium edetate dihydrate (CTAB-EDTA) as a template via a sol-gel method, magnesium thermal reduction method, and thermal decomposition method. The vertical diffusion distance of Li+ is significantly reduced by the 2D Si nanosheets. Additionally, the carbon coating on the Si surface provides a protective layer to limit the volume expansion of Si and form a stable solid electrolyte interface (SEI). This enhances the structural integrity and cycle stability of the pSi@C anode material during Li+ insertion and extraction. At a current density of 1 A g(-1), the reversible capacity of the pSi@C composite after 150 cycles is 2236 mAh g(-1), with a capacity retention rate of 71.5%. The electrode's capacity is 467.8 mAh g(-1) after 500 cycles at a current density of 5 A g(-1). Therefore, this unique template and technology can be used to design 2D anode composites with excellent properties, thereby providing an effective strategy for commercial application of LIBs.