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

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.