Hydrangea-like microspheres as anodes toward long-life and high-capacity lithium storage

Transition metal oxides show great promise as high-energy anodes for lithium-ion batteries (LIBs), thanks to appealing combination of high theoretical specific capacity and low cost. However, they still undergo dramatic volumetric expansion and low electronic/ionic conductivities, which leads to numerous problems, for instance, rapid capacity degradation and electrode pulverization, thus severely hindering their practical applications. In this paper, a designed hydrangea-like microstructure consisting of MnO₂ nanosheets and ZnFe₂O₄ microspheres is achieved by a hydrothermal route. When evaluated as an anode material for LIBs, ZnFe₂O₄@MnO₂ electrode displays a high specific capacity of 2707 mA h g⁻¹ after 100 cycles at 0.2 A g⁻¹. Even at a higher current density of 2 A g⁻¹, the electrode has a long lifespan with a specific capacity of 1458 mA h g⁻¹ after 800 cycles and outperforms the previously reported zinc ferrite composite electrodes. These excellent electrochemical properties are ascribed to the hydrangea-like structure, which buffers the volume variation of ZnFe₂O₄ during charging/discharging process and decreases the internal resistance significantly due to excellent contact between ZnFe₂O₄ microparticles and MnO₂ nanosheets. Consequently, the facile synthesis strategy and superior Li-storage performance make the hydrangea-like ZnFe₂O₄@MnO₂ microspheres the promising candidate for next-generation high-performance LIBs in the future.