“Gradient Armor” Design of Si-C Anode by 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 biomass natural coconut shell precursor, a biomass-derived porous carbon (BDPC) matrix with high specific surface area (1614.23 m2 g-1), rich micropores (< 2 nm), and high pore volume (0.745 m3 g-1) was prepared after simple treatment. Furthermore, by using BDPC as a carrier, the in-situ embedding of nano-silicon (Nano-Si) was achieved through chemical vapor deposition (CVD) under the SiH4 atmosphere, and a carbon-coated, overlapping structure was constructed in C2H2 atmosphere. The "gradient armor" structure effectively reduces the silicon volume effect, 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 to large-scale engineering applications of silicon-based anode electrodes.