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

• Porous ZnFe2O4/α-Fe2O3 micro-octahedrons are synthesized via a two-step method.
• The porous ZnFe2O4/α-Fe2O3 micro-octahedrons exhibit high capacity and excellent cycling stability and rate performance.
• The outstanding electrochemical performance is attributed to their composition and microstructure.

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 1752 mAh g−1 after 75 cycles at a current density of 200 mA g−1. More importantly, when the current density was increased to as high as 4 A g−1, the ZnFe2O4/α-Fe2O3 electrode can still retain reversible capacity of 1090 mAh g−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.

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