Uniform NiCo2O4/NiFe2O4 hollow nanospheres with excellent properties for Li-ion batteries and supercapacitors

Designing mixed metal oxides with uniform nanostructures as a significant electrode material in energy storage devices is a vital concern for the whole world. But achieving this goal is plagued by many problems such as tedious procedures, hard morphology control and poor conductivities. The NiCo2O4/NiFe2O4 hollow nanospheres (NSs) are prepared for the first time through a novel one-pot approach. The introduced NiFe2O4 has amazingly improved the electrochemical performance of NiCo2O4 hollow NSs in both Li-ion batteries (LIBs) and supercapacitors (SCs). And the ratio of Fe to Ni plays an important role for the improvement of electrochemical performance. The NiCo2O4/NiFe2O4 hollow NSs exhibit superior capacity/capacitance values (3795 F g−1 at a current density of 1 A g−1) and fine cycling performances (11.0% specific capacitance decay after 6000 cycles) which can be attributed to the larger specific surface area of hollow NSs and the synergistic effect of two components. This provides a feasible preview of their practical applications.