Microwave assisted crystalline and morphology evolution of flower-like Fe2O3@ iron doped K-birnessite composite and its application for lithium ion storage

Manganese oxides (MnOx) and derivations are considered as one of the most attractive anode materials for lithium-ion batteries (LIBs) due to their earth-abundant, cost-effective and low-toxic specialties. Herein, we report a flower-like composite consisting of internal Fe2O3 nanocrystals and outer hierarchal iron doped K-birnessite type MnOx layers (Fe2O3@Fe doped K-birnessite), which is synthesized by a facile one-pot microwave-assisted heating synthesis (MAHS). The crystalline and morphology evolution of Fe2O3@Fe doped K-birnessite composite are studied by checking the products at various reaction durations, using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning & transmission electron microscopy (SEM & TEM). Key factors affecting the morphology such as reactive temperature and stoichiometric ratio are systematically investigated. When tested for LIBs, the optimized hybrid Fe2O3@Fe doped K-birnessite composite exhibits a high reversible capacity of 758 mA h g(-1) at 500 mA g(-1) after 200 cycles, outperforming the pure K-birnessite (203 mA h g(-1)). The excellent electrochemical performance is assigned to the efficient utilization of the merits of the flower-like structure and strong interaction between MnOx and Fe2O3. Further, crucial factors associated with structural stability of Fe2O3@Fe doped K-birnessite composite during cycling are identified.