Improved high-rate capability of Li[Ni0.5CoyMn1.5-y]O4-zFz spinel materials for 5 V lithium secondary batteries

Abstract

The effects of substituting cobalt and fluorine for manganese and oxygen on the structural and electrochemical properties of Li[Ni0.5CoyMn1.5-y]O4-zFz cathode materials were studied. The pure phase Li[Ni0.5Coy Mn1.5-y]O4-zFz (y = 0 - 1.0, z = 0 - 0.1) spinel materials were successfully synthesized at 900 degrees C by an ultrasonic spray pyrolysis method. The Li[Ni0.5CoyMn1.5-y]O4-zFz (y = 0 - 1.0, z = 0 - 0.1) powders were characterized by means of X-ray diffraction (XRD), Rietveld refinements, scanning electron microscopy (SEM), energy dispersive spectra (EDS), Brunauer-Emmett-Teller (BET) analysis, and galvanostatic charge/discharge testing. The cobalt and fluorine substitutions were effective for improving the high current discharge capability, even though the electrode was cycled with a discharge current density of 1,350 mA g(-1)(10 C-rate).