Effect of Ni/Mn Ordering on Elementary Polarizations of LiNi0.5Mn1.5O4 Spinel and Its Nanostructured Electrode

Elementary polarizations of LiNi0.5Mn1.5O4 spinel materials with disordered structure (space group, Fd -3 m) and ordered structure (space group, P 4(3) 3 2) are quantitatively analyzed in order to clarify how the differences in crystallographic structure affect the rate performance of the cathode materials. A comparative analysis of the disordered and ordered structures disclosed that the nickel and manganese ordering in the spinel-framework would distinctly aggravate the charge-transfer reactions. Furthermore, the ordinary approach to increase the rate performance of an electrode through a reduction of the diffusion lengths and an enlargement of the active surface area with the nano-structured electrode which consists of the disordered spinel revealed that both charge-transfer and solid-state diffusion resistances reduced, but the resistance of lithium migration through the surface films increased significantly. (C) 2013 The Electrochemical Society.