A Yolk–Shell Structured Silicon Anode with Superior Conductivity and High Tap Density for Full Lithium-Ion Batteries

The poor cycling stability resulting from the large volume expansion caused by lithiation is a critical issue for Si-based anodes. Herein, we report for the first time of a new yolk–shell structured high tap density composite made of a carbon-coated rigid SiO₂ outer shell to confine multiple Si NPs (yolks) and carbon nanotubes (CNTs) with embedded Fe₂O₃ nanoparticles (NPs). The high tap density achieved and superior conductivity can be attributed to the efficiently utilised inner void containing multiple Si yolks, Fe₂O₃ NPs, and CNTs Li⁺ storage materials, and the bridged spaces between the inner Si yolks and outer shell through a conductive CNTs “highway”. Half cells can achieve a high area capacity of 3.6 mAh cm⁻² and 95 % reversible capacity retention after 450 cycles. The full cell constructed using a Li-rich Li₂V₂O₅ cathode can achieve a high reversible capacity of 260 mAh g⁻¹ after 300 cycles.