“Gradient armor” design of the Si–C anode using biomass-derived porous carbon for high-stability pouch cells

Abstract

To address the issue of structural damage and expansion attenuation caused by the volume expansion of silicon during the cycle, this paper proposes a “core buffer–middle conductivity–outer protection” structure design strategy. Using a biomass natural coconut shell precursor, a biomass-derived porous carbon (BDPC) matrix with a high specific surface area (1776.71 m² g⁻¹), rich micropores (<2 nm), and a high pore volume (0.729 m³ g⁻¹) was prepared after simple treatment. Furthermore, using BDPC as a carrier, the in situ embedding of nano-silicon (Nano-Si) was achieved through chemical vapor deposition (CVD) under a SiH₄ atmosphere, and a carbon-coated, overlapping structure was constructed under a C₂H₂ atmosphere. The “gradient armor” structure effectively reduces the silicon volume effect and improves conductivity, interface stability, and multi-scale structural regulation while significantly improving the electrochemical stability of the composite material. The 2.16 Ah pouch cells were able to achieve a charge capacity of 1.97 Ah and a discharge capacity of 1.68 Ah at a 4C rate, with a capacity retention rate of 75.8% after 500 cycles at 1C. This study's “gradient armor”-structured silicon/carbon composite material has excellent performance, scalability, and cost advantages and offers a new approach for large-scale engineering applications of silicon-based anode electrodes.