Engineering carbon-coated hollow hematite spheres for stable lithium-ion batteries

Metal oxides with hollow structure provide improved cycling performance, superior rate capability, and high specific capacity when used as anode materials for lithium-ion batteries (LIBs). In this work, the as-prepared sample named H–Fe2O3@N–C was synthesized by simple polypyrrole (PPY) coating on hollow Fe2O3 and subsequent carbonization under N2 and air. Interestingly, the thermal treatment of hollow Fe2O3 under air at 500 ​°C induces a phase transition of Fe2O3 from maghemite to hematite which is beneficial for the PPY-coated process. The lithium-storage performance of the resulting materials used as anodes was evaluated. The as-prepared H–Fe2O3@N–C anode shows a high specific capacity (1093.1 ​mA ​h ​g−1 at a current density of 0.1 ​A ​g−1) and high cyclic stability (the specific capacity of 501.3 ​mA ​h g−1 was maintained at a current density of 2.0 A g−1 after 700 cycles). The high specific capacity and superior cyclic stability of the prepared anode are attributed to the hollow structure and N-doped carbon coatings that can alleviate the volume variation and reduce the charge-transfer resistance.