MnFe2O4–graphene nanocomposites with enhanced performances as anode materials for Li-ion batteries

Abstract

MnFe₂O₄–graphene nanocomposites (MnFe₂O₄–GNSs) with enhanced electrochemical performances have been successfully prepared through an ultrasonic method, e.g., approximate 1017 mA h g⁻¹ and 767 mA h g⁻¹ reversible capacities are retained even after 90 cycles at a current density of 0.1 A g⁻¹ and 1 A g⁻¹, respectively. The remarkable improvement in the reversible capacity, cyclic stability and rate capability of the obtained MnFe₂O₄–GNSs nanocomposites can be attributed to the good electrical conductivity and special structure of the graphene nanosheets. On the other hand, MnFe₂O₄ also plays an important role because it transforms into a nanosized hybrid of Fe₃O₄–MnO with a particle size of about 20 nm during discharge–charge process, and the in situ formed hybrid of Fe₃O₄–MnO can be combined with GNSs to form a spongy porous structure. Furthermore, the formed hybrid can also act as the matrix of MnO or Fe₃O₄ to prevent the aggregation of Fe₃O₄ or MnO, and accommodate the volume change of the active materials during the discharge–charge processes, which is also beneficial to improve the electrochemical performances of the MnFe₂O₄–GNSs nanocomposites.