Improved Electrochemical Performance of the 5 V Spinel Cathode LiMn1.5Ni0.42Zn0.08O4 by Surface Modification

The 5 V spinel LiMn1.5Ni0.42Zn0.08O4 with a cation-disordered structure has been surface modified with 2 wt % nanosize Al2O3, ZnO, and Bi2O3 by an electrostatic self-assembly method and characterized by X-ray diffraction, Fourier transform IR spectroscopy, high-resolution transmission electron microscopy, and electrochemical measurements. Although the modifications do not change the crystallographic structure of the spinel sample, the surface-modified samples exhibit better cyclability, rate capability, and rate capability retention on cycling compared to the bare LiMn1.5Ni0.42Zn0.08O4. Among the various samples investigated, the surface modification with Al2O3 gives the best electrochemical performance. Electrochemical impedance spectroscopy measurements demonstrate that the improved performance on surface modification is due to a suppression of both the surface layer resistance and charge transfer resistance.