Evaluation of electrochemical performances of ZnFe2O4/gamma-Fe2O3 nanoparticles prepared by laser pyrolysis

A ZnFe2O4/gamma-Fe2O3 nanocomposite (theoretical specific capacity: 1002 mA h g(-1)) was successfully synthesized by laser pyrolysis, a very attractive nanosynthesis technique characterized by high versatility and flexibility. The obtained nanopowder was thoroughly characterized by XRD, XPS, Mossbauer spectroscopy and HRTEM, which confirmed the presence of two phases. A bimodal size distribution with small particles (tens of nanometers) and large ones (above 500 nm) was revealed by SEM and TEM. The ZnFe2O4/Fe2O3 nanocomposite was tested as a negative electrode material for lithium-ion batteries, showing significantly improved lithium storage properties with a high reversible capacity and rate capability compared to a pure ZnFe2O4 electrode. A capacity exceeding 1200 mA h g(-1) is sustained after 100 cycles at 100 mA g(-1), with a gradual increase of the capacity during cycling. At 500 mA g(-1) current rate, a reversible and stable capacity of 360 mA h g(-1) is observed after 300 cycles. Electrochemical measurements with several electrolytes and electrode formulations were also conducted in order to explore the origin of the extra capacity and its increase with cycling.