Preparation, characteristics and electrochemical properties of surface-modified LiMn2O4 by doped LiNi0.05Mn1.95O4

The surface-modified spinel LiMn2O4 by doped LiNi0.05Mn1.95O4 was prepared by a tartaric acid gel method. Transmission electron microscope (TEM) images indicated that some small particles with 100-200 nm in diameter modified the surface of large particle LiMn2O4. Energy dispersive spectrometry (EDS) showed that the particles were LiNi0.05Mn1.95O4. Electrochemical properties of LiNi0.05Mn1.95O4-modified spinel LiMn2O4 were intensively investigated by the galvanostatic charge-discharge tests, cyclic voltammetry (CV) and AC impedance measurements. The doped LiNi0.05Mn1.95O4-modified LiMn2O4 cathode delivered the same initial discharge capacity as the unmodified LiMn2O4, but its cyclic stability was evidently improved, the capacity retention ratio reached 96% after 20 cycles, being higher than 89% of the unmodified LiMn2O4. Cyclic voltammograms of the LiNi0.05Mn1.95O4-modified LiMn2O4 did not markedly change while the semicircle diameter of AC impedance spectra evidently decreased after 20 cycles, which showed that the surface modification with LiNi0.05Mn1.95O4 improved the electrochemical activity and cycling stability of LiMn2O4.