N-rich porous Si@SiOx/NC composites derived from in situ polymerisation of acrylic acid as anode for Li-ion batteries

Si possesses a high theoretical specific capacity as anode material for Li-ion batteries. However, it has poor electrical conductivity and severe volume effect during charge-discharge processes, resulting in substantial internal resistance and significantly reduced available capacity. These issues can be greatly mitigated by encapsulating Si nanoparticles within a carbonous material. Hence, network precursors are synthesised herein to encapsulate Si nanoparticles by in situ polymerisation of acrylic acid and melamine. After freeze-drying, the precursors are pyrolysed under Ar atmosphere to obtain homogeneous N-rich porous Si@SiOx/NC composites. A fibrous network structure is acquired by using appropriate amounts of polyacrylic acid and Si. Such a structure provides an outstanding electron transmission network and effectively buffers the volume change of Si to maintain a stable electrode structure. The results show that when the content of Si nanoparticles in the composite is 35.2 wt%, the prepared Si@SiOx/NC−2 composite has abundant micropores (267.90 m2 g−1) and mesopores (17.48 m2 g−1). The material shows an initial discharge-specific capacity of 1833.6 mAh g−1 and Coulombic efficiency of 65%. After 150 cycles at 0.1 A g−1, the discharge-specific capacity is still as high as 922.8 mAh g−1. The excellent electrochemical performance of the Si@SiOx/NC composites is due to the three-dimensional conductive structure. The unique construction could play an important role in expanding the commercial application of Si-based anode materials in Li-ion batteries.