Si nanoparticles enclosed in hierarchically structured dual-component porous carbon as superior anode for lithium-ion batteries: Structure formation and properties investigation

The volume effect of Si hinders its application as anode for lithium-ion batteries. To address these challenges, composites consisting of Si nanoparticles enclosed in a hierarchically structured carbon matrix are constructed. Firstly, Si nanoparticles are embedded in the metal-organic framework of ZIF-67 with a surface modification directed epitaxial growth. Subsequently, the Si embedded ZIF-67 are further integrated into microspheres of polysaccharide using spray drying, achieving encapsulation of the Si nanoparticles in a hierarchically structured carbon sphere after calcination. Metallic cobalt nanoparticles are derived from the decomposition of ZIF-67, which act as a catalyst and facilitate in turn the decomposition of the organic ligands along with the extensive growth of carbon nanotubes (CNTs). The CNTs formed in-situ act as reinforcing and conductive networks, providing the compact and robust interfaces between the Si and the carbon matrix. The dual-component carbon substrates induce a thinner and inorganic carbonate-rich solid electrolyte interface (SEI) during cycling. The novel structure endows the composite a specific capacity of 1018 mAh g−1 after 1200 cycles at a current density of 1000 mA g−1 for half-cell and exhibits a high capacity retention rate of 76.9 % after 200 cycles for full cell paired with lithium iron phosphate as cathode.