Influences of Supersonic-Wave Treatments on Cycle Performance and Crystal Structure of Li(Mn,M)2O4 as a Cathode Active Material for Li Ion Battery

Co, Ni and Zn) , and found that the partial substitutions improved their thermodynamic and structural stabilities, and both stabilities affected the cathode performances. Moreover, it was reported that the battery characteristic of LiMn2O4 was improved by applying the supersonic-wave treatment in the solution including Zn 2+ 2) . This may be because the treatment induced partial substitution of Zn for Mn and surface-coating by Zn compounds. In this study, we focused on 5V class LiMn1.5Ni0.5O4 with the same spinel structure.This material is promising because of their higher energetic density, i.e., higher operation potential than LiMn2O4. We performed supersonic-wave treatments on the LiMn1.5Ni0.5O4 powder in solutions including Zn or Mg. Taking the results in LiMn2O4 into account, such treatments are expected to result in incorporation of Zn 2+ or Mg 2+ into the crystal structure and/or coating of the particles with Zn or Mg-containing oxides. As for the samples after the treatments, the phase identification, the chemical composition, and the crystal structure analyses were carried out. Based on the results, it was discussed how the treatments affect their cycle performance. EXPERIMENTAL We prepared LiMn1.5Ni0.5O4 by the solid-state reaction method. The obtained powder was immersed into Zn or Mg-containing solution which was prepared by dissolving various content of zinc or magnesium acetate into deionized distilled water, and then supersonic-wave treatments were applied. The treatments were carried out for 10 min at room temperature and various frequencies (28~200kHz). The products were dried at 100℃ for 24h and then heat-treatment at 600℃ for 2h. As for the prepared samples, phase identification and determination of lattice constants were performed with the XRD. The chemical compositions of the materials were evaluated by using the ICP. The SEM-EDX was also applied in order to clarify particle morphologies and dispersion-states of the constituent elements. The LiMn1.5Ni0.5O4 after the supersonic-wave treatments in Zn and Mg-containing solutions were investigated with the CV measurement and charge-discharge cycle tests. In addition, the sample exhibiting excellent cycle performance was studied by powder neutron diffraction (HERMES), and then Rietveld analysis was performed (RIETAN-FP).