Pomegranate-Like Nano-Confined Silicon Inside Conductive Carbon Black as Anode Materials for Lithium-Ion Batteries

Si materials possess a high theoretical specific capacity when used as anode material in lithium-ion batteries (LIBs). Si/C composites mitigate volume expansion and enhance conductivity, thus achieving improved electrochemical performance in LIBs. Herein, we report a new strategy for preparing pomegranate-like Si/C nanocomposites based on low-cost, readily available conductive carbon black (XC) by using a combination of wet chemical reduction and chemical vapor deposition (CVD) techniques. The preparation first involves a facile wet chemical approach to controlled hydrolysis of SiCl₄ within XC. Subsequently, the obtained SiO₂/XC precursor is reduced to highly crystalline Si particles within XC (Si/XC) using a novel ionic liquid-magnesium reduction system, avoiding unwanted byproducts associated with conventional high-temperature magnesium reduction. Finally, a pomegranate-like Si/XC composite is coated with an outer carbon layer via CVD, forming a nano-confined Si/C structure. The composites exhibit excellent reversible capacity and good cycle stability in LIBs. At 1 A g^-1 after 400 cycles, the Si/XC@C-0.5 composite delivered the highest specific capacity of 835 mA h g^-1, exhibiting a capacity retention rate of 121% compared to the first cycle after activation (688 mA h g^-1). This work provides reproducible and scalable means to prepare high-performance Si/C composites for LIBs.