Inward lithium-ion breathing of hollow carbon spheres-encapsulated Fe3O4@C nanodisc with superior lithium ion storage performance

Abstract

A novel hierarchical porous carbon-Fe3O4 composite are fabricated as an anode material for Li-ion batteries. In our design, hollow carbon spheres, HCSs for short, with elasticity are encapsulated in Fe3O4@C nanodisc. During the lithiation process, the out carbon shell confines particle-level outward expansion and ensure the structural integrity and stability. Meanwhile the embedded HCSs can provide void space to tolerate the volumetric expansion inwards. Subsequently, during the delithiation process, the HCSs could push the pulverized particles to contact together, ensuring good electrical contact between the pulverized particles and the outer carbon shell. The unique inward lithium-ion breathing design is helpful to maintain the structural integrity and ensure good inter- and intra-particle electrical contact. Therefore, the HCSs@Fe3O4@C nanodisc delivers an excellent high-rate cycling performance, giving a specific capacity of 595 mAh g−1 after 800 cycles at a current density of 1A g−1, and at a higher rate of 5 A g−1, having a specific capacity of 390 mAh g−1 after 1000 cycles. This work provides a new strategy for the design of high-volume expansion anodes in Li-ion batteries.