Carbon-coated MnFe2O4 nanoparticle hollow microspheres as high-performance anode for lithium-ion batteries

In this work, carbon-coated MnFe 2 O 4 nanoparticle (NP) hollow microspheres are fabricated by a facile emulsion-based assembly method followed by in situ ligand carbonization . Specifically, MnFe 2 O 4 NPs stabilized by oleic acid (OA) are the primary building blocks to assemble hollow microspheres , while the subsequent carbonization of OA ligands leads to the formation of uniform carbon coatings without degrading the ordering of NPs. As anode materials for lithium-ion batteries, such MnFe 2 O 4 NP hollow composite microspheres exhibit significantly improved electrochemical performance in comparison with their solid counterparts and most MnFe 2 O 4 -based anodes reported to date, retaining a high reversible capacity of 730   mAh   g −1 after 300 cycles at a current density of 2   A   g −1 . Furthermore, even when tested at an ultrahigh rate of 10   A   g −1 , MnFe 2 O 4 NP hollow microspheres can still deliver a high specific capacity of 433   mAh   g −1 . The superior performance of MnFe 2 O 4 NP hollow microspheres is attributable to their hollow superstructure , close-packed configuration of the constituent NPs, and uniform carbon coatings, which facilitate lithium-ion and electron transport while simultaneously alleviating the drastic volumetric change during cycling. Our work establishes that the optimized MnFe 2 O 4 anode material offers great promise for high-performance lithium-ion batteries.