Ultra-high lithium storage capacity achieved by porous ZnFe₂O₄/α-Fe₂O₃ micro-octahedrons

Transition metal oxide-based hybrid material systems have been demonstrated to exhibit significantly improved electrochemical performance as anode materials for lithium ion batteries (LIBs). In this work, porous ZnFe₂O₄/α-Fe₂O₃ micro-octahedrons have been designed and fabricated by a facile solvothermal method followed by thermal treatment. The unique structures including the heterojunctions between ZnFe₂O₄ and α-Fe₂O₃ NPs and the open inter-connected pores are beneficial for the electrochemical performance. When evaluated as an anode material for LIBs, the as-prepared porous ZnFe₂O₄/α-Fe₂O₃ micro-octahedrons show an excellent lithium storage performance. The discharge capacity could reach 1752mAhg^-1 after 75 cycles at a current density of 200mAg^-1. More importantly, when the current density was increased to as high as 4Ag^-1, the ZnFe₂O₄/α-Fe₂O₃ electrode can still retain reversible capacity of 1090mAhg^-1. The capability and rate performance of the porous ZnFe₂O₄/α-Fe₂O₃ micro-octahedrons both are better than those of bare ZnFe₂O₄ and α-Fe₂O₃. The superior lithium storage performance of the porous ZnFe₂O₄/α-Fe₂O₃ micro-octahedrons is mainly attributed to their unique composition and microstructure, which not only could provide high conductivity, good Li⁺ diffusion, and large electrode-electrolyte contact area, but also could reduce volume change during charge/discharge process.