Hierarchical Porous Structured Si/C Anode Material for Lithium-Ion Batteries by Dual Encapsulating Layers for Enhanced Lithium-Ion and Electron Transports Rates.

Silicon (Si) is a promising anode material for next-generation lithium-ion batteries (LIBs) due to its high specific capacity and abundance. However, challenges such as significant volume expansion during cycling and poor electrical conductivity hinder its large-scale application. In this study, the multifunction of sodium polyacrylate (PAAS) utilized to develop a hierarchical porous silicon-carbon anode (Si/SiO_x@C) through a simple and efficient method. The hierarchical porous structure successively consists of nano-silicon cores, SiO_x encapsulating layers, surrounding space, and phenolic resin-derived carbon shells with carbon chains connecting the SiO_x layers and carbon shells in the space. The SiO_x nanolayers promote Li⁺ transport, while excess PAAS, removed by washing, generates space for volume expansion, improving cycling performance. Residual carbon chains of PAAS and carbon shells form a conducting carbon network, enhancing electron transport and rate performance. As an anode for LIBs, the composite delivers a high reversible capacity of 685.3 mAh g⁻¹ after 1000 cycles at 1 C with a capacity retention rate of 54.7%. Full cells with the Si/SiO_x@C anode and LiNi_0.8Co_0.1Mn_0.1O₂ cathode exhibit an excellent capacity retention rate of 96.8% after 200 cycles at 1 C. This work provides a novel approach for the rational design and engineering of advanced LIBs.