Dual carbon-network armored silicon anode: Graphene-CNT reinforced pomegranate architecture enabling long-cycle lithium-ion battery

Abstract

Silicon (Si) anode materials have garnered significant attention owing to their exceptional theoretical specific capacity. However, their practical application is hindered by severe volume expansion and particle disintegration. This study introduces a silicon/carbon composite anode material with distinct advantages through rational structural design and straightforward synthesis techniques. A three-dimensional carbon skeleton is developed using the sheet structure of graphene. Specifically, nanosilicon, carbon nanotubes, binders, and graphene nanosheets (GNs) are initially fabricated into spherical composites through spray drying. Subsequently, these graphene-based spheres are encapsulated with pyrolytic carbon via chemical vapour deposition to yield the final product (GBs@SiNPs@CNTs-2). In this composite material, the three-dimensional carbon skeleton, comprising carbon nanotubes and graphene sheets, acts as a conductive matrix and provides buffer space to accommodate the volume changes of silicon nanoparticles during charge and discharge processes. The binder effectively contracts the loose three-dimensional structure during carbonisation and pyrolysis. Additionally, the three-dimensional material particles are coated with a layer of amorphous carbon, which prevents direct contact between the composite Si particles and the electrolyte. Experimental results indicate that the GBs@SiNPs@CNTs-2 composite material achieves an initial coulombic efficiency of 79.2 %, a reversible capacity of 1186.87 mA h g⁻¹, and retains a specific charging capacity of 406.72 mA h g⁻¹ after 500 cycles at 1.0C.