A Stress-Buffering Hierarchically Porous Silicon/Carbon Composite for High-Energy Lithium-Ion Batteries

Abstract

The electrochemical performance of Si anodes for lithium-ion batteries (LIBs) is primarily influenced by the stress–strain and transport dynamics. However, traditional Si/carbon composites often fail to well balance these two factors. Herein, a hierarchically porous silicon/carbon composite (denoted as pSi@void@NMC) with high lithium storage capacity is developed under the guidance of finite element analysis, where porous Si (pSi) and nitrogen-doped mesoporous carbon (NMC) is used as the yolk and shell, respectively. The internal and external cultivation design endows the pSi@void@NMC composite with fast transfer kinetics, effective stress-buffering, low volume expansion, and superior mechanical stability. Compared with core–shell pSi@NMC and bare pSi electrodes, the resulting pSi@void@NMC anode demonstrates a high reversible capacity of 1769.8 mAh g⁻¹ after 300 cycles at 0.2 A g⁻¹ and exceptional cycling stability only with 0.016% capacity decay rate per cycle. In situ and ex situ characterization results further confirm its high reversibility of Li⁺ insertion/extraction during electrochemical reactions benefiting from the formation of inorganic LiF-rich SEI film. Moreover, the developed pSi@void@NMC composite also shows a good potential for full-cell applications. These findings provide a facile design concept and research strategy for addressing stress fractures and inadequate transport kinetics of Si-based anode materials for high-performance LIBs.